Systematic Review and Meta-Analysis of the Impact of Computed Tomography-Assessed Skeletal Muscle Mass on Outcome in Patients Awaiting or Undergoing Liver Transplantation

Frailty and sarcopenia in patients with cirrhosis awaiting liver transplantation: evidence from a single-centre, prospective cohort study

Sarcopenia and frailty are common complications in patients with cirrhosis evaluated for liver transplantation (LT). Although the negative impact of sarcopenia on patient's outcome has been well studied, the prognostic role of frailty is not as clear. We assessed the prevalence of sarcopenia and frailty and the clinical impact of frailty in a prospective cohort of cirrhosis patients with and without hepatocellular carcinoma (HCC) listed for LT. Patients with cirrhosis were prospectively recruited at the time of admission into the waiting list. Clinical and lab values were collected. Physical frailty was assessed by liver frailty index (LFI) and patients were categorized into robust (< 3.2); pre-frail (between 3.2 and 4.5), and frail (> 4.5). Skeletal muscle mass was evaluated via skeletal muscle index (SMI) obtained from last CT scan before LT; sarcopenia was defined by SMI < 50 cm2/m2 in males and < 39 cm2/m2 in females. 105 patients were included, of which 42 (40%) had hepatocellular carcinoma (HCC). In patients without HCC (63.5% males, median age 61 years), 36.5% were frail, 50.8% were pre-frail and 12.7% were robust. Frail patients were older than non-frail patients (63 vs. 56; p = 0.008) and had more severe liver disease (Child C: 65% vs. 37.5%; p = 0.02). Prevalence of sarcopenia in patients without HCC was 63%, with similar value of median SMI between frail and not frail patients (p = 0.454). Patients with HCC (78.6% males, 65 years old) were 21.4% frail, 61.9% pre-frail, and 16.7% robust. Frail patients had more severe liver disease (Child C: 77% vs. 18.2%; p = 0.004), whereas age was comparable to non-frail patients; among patients without HCC, during a median follow-up of 263 days, 17% died (of which 72% were frail) and 10 patients were delisted due to clinical improvement (none of whom were frail). Among those with HCC, during a median follow-up of 289 days, 4 (9%) patients died of which 50% were frail. Frailty and sarcopenia are common complications in patients with cirrhosis awaiting LT. Frailty appears to be associated with an increased risk of mortality during wait-list time especially in those with decompensated cirrhosis. At univariate analysis Meld score, Child score and presence of frailty were found to be associated with shorter survival, however, at multivariate analysis presence of frailty and Child C vs. A/B were the only independent predictor of death. Larger cohorts are required to confirm these results.

Comparison between AWGC-cachexia and GLIM-malnutrition in patients with gastric cancer

BACKGROUND

The newly released Asian Working Group for Cachexia (AWGC) criteria share similar diagnostic items with the Global Leadership Initiative on Malnutrition (GLIM) criteria. This study aims to compare the AWGC cachexia and GLIM malnutrition in patients with gastric cancer and investigate whether one diagnosis continues to be a prognostic factor in individuals diagnosed with the other condition.

METHODS

Data of patients who underwent radical gastrectomy for gastric adenocarcinoma were prospectively collected from 2013 to 2019. The AWGC and GLIM criteria were applied to diagnosis cachexia and malnutrition, respectively. Univariate and multivariate logistic and Cox regression were used to verify the effect of relevant factors on postoperative complications and overall survival.

RESULTS

A total of 1420 patients were included, among whom 174 (12.3 %) were diagnosed with AWGC-cachexia alone, 85 (6.0 %) were diagnosed with GLIM-malnutrition alone, and 324 (22.8 %) had both AWGC-cachexia and GLIM-malnutrition. Both AWGC-cachexia and GLIM-malnutrition were independent risk factors for complications and overall survival. When they coexisted, the odds ratios (OR) and hazard ratios (HR) tended to be higher. In the AWGC-cachexia subset, GLIM-malnutrition remained an independent risk factor (HR = 1.544, 95 % CI = 1.098-2.171, P = 0.012) for overall survival after the adjustment of confounding factors. Similarly, in the GLIM-malnutrition subset, AWGC-cachexia remained an independent risk factor for overall survival (HR = 1.697, 95 % CI = 1.087-2.650, P = 0.020). Patients with both cachexia and malnutrition had the worst overall survival.

CONCLUSION

AWGC-cachexia and GLIM-malnutrition criteria were two non-redundancy tools in reflecting mortality risk in preoperative nutritional assessment.

Sarcopenia evaluated by EASL/AASLD computed tomography-based criteria predicts mortality in patients with cirrhosis: A systematic review and meta-analysis

Background & Aims

Sarcopenia is associated with increased morbidity and mortality in patients with cirrhosis, but its definition in current literature is very heterogeneous. We performed a systematic review and meta-analysis to assess the association between mortality and sarcopenia evaluated by computed tomography (CT) in patients with cirrhosis, both overall and stratified for the criteria used to define sarcopenia.

Methods

Medline, Embase, Scopus, and Cochrane Library were searched up to January 2023. We included studies assessing sarcopenia presence with CT scans and providing data on the risk of mortality. Adjusted hazard ratios (HRs) and 95% CIs were pooled using a random-effects model.

Results

Thirty-nine studies comprising 12,827 patients were included in the meta-analysis. The summary prevalence of sarcopenia was 44% (95% CI 38-50%). The presence of sarcopenia (any definition) was an independent predictor of mortality with an adjusted HR of 2.07 (95% CI 1.81-2.36), and the result was consistent in all subgroup analyses. The prognostic role of the EASL/AASLD criteria was confirmed for the first time with an HR of 1.86 (95% CI 1.53-2.26) (n = 14 studies). The cut-offs used to define sarcopenia based on psoas muscle parameters varied among studies, thus, a subgroup analysis was not feasible. There was no substantial heterogeneity for the main estimates and no significant risk of publication bias.

Conclusions

Sarcopenia on CT is associated with a 2-fold higher risk of mortality in patients with cirrhosis. The cut-offs proposed by EASL/AASLD are prognostically relevant and should be the recommended criteria used to define sarcopenia in clinical practice.

Impact and implications

Sarcopenia assessed by the reference standard (computed tomography scan) is an independent predictor of mortality in patients with cirrhosis, with a 2-fold increase in the risk of death in all sensitivity analyses. This finding is particularly valid in patients from Europe and North America, and in transplant candidates. Stratifying for the parameters and cut-offs used, we confirmed for the first time the prognostic impact of the definition proposed by EASL/AASLD, supporting their use in clinical practice. Psoas muscle assessment is promising, but data are still limited and too heterogeneous to recommend its routine use at present.

Sarcopenia is an independent risk factor for short-term mortality in patients undergoing transjugular intrahepatic portosystemic shunt

BACKGROUND

Sarcopenia is common in patients with cirrhosis and is a risk factor for increased mortality. Transjugular intrahepatic portosystemic shunt (TIPS) placement has been utilized in cirrhosis patients with decompensation . We investigated the role of sarcopenia in predicting mortality in patients undergoing TIPS.

METHODS

We conducted a single-center retrospective study of 232 patients with cirrhosis who underwent TIPS between January 2010 and December 2015. Sarcopenia was defined by the psoas muscle index (PMI) cutoff value, calculated based on dynamic time-dependent outcomes using X-tile software. Kaplan-Meier analysis demonstrated the difference in survival in the sarcopenia group versus the non-sarcopenia group. . Univariate and multivariate analyses were used to identify the relationship between sarcopenia and post-TIPS mortality during a follow-up period of 1 year.

RESULTS

For TIPS indications, 111 (47.84%) patients had refractory ascites, 69 (29.74%) patients had variceal bleeding, 12 (5.17%) patients had ascites, and 40 (17.24%) for other indications. The mean PMI was 4.40 ± 1.55. Sarcopenia was defined as a PMI value of <4.36 in males, and <3.23 in females. Sarcopenia was present in 96 (41.38%) of patients. . Kaplan-Meier analysis showed thatsarcopenia is associated with worse survival (log-rank P  < 0.01). Multivariate Cox regression analysis showed that sarcopenia is independently associated with worse survival during the 1-year follow-up period with an hazard ratio of 2.435 (95% CI 1.346-4.403) ( P  < 0.01), after adjusting for age, BMI, indications for TIPS, etiology for cirrhosis, and MELD score and stratified by sex.

CONCLUSION

Sarcopenia is an independent risk factor for 1-year mortality in patients undergoing TIPS and should be considered when patients are evaluated as a candidate for TIPS.

Shining a spotlight on sarcopenia and myosteatosis in liver disease and liver transplantation: Potentially modifiable risk factors with major clinical impact

Muscle-wasting and disease-related malnutrition are highly prevalent in patients with chronic liver diseases (CLD) as well as in liver transplant (LT) candidates. Alterations of body composition (BC) such as sarcopenia, myosteatosis and sarcopenic obesity and associated clinical frailty were tied to inferior clinical outcomes including hospital admissions, length of stay, complications, mortality and healthcare costs in various patient cohorts and clinical scenarios. In contrast to other inherent detrimental individual characteristics often observed in these complex patients, such as comorbidities or genetic risk, alterations of the skeletal muscle and malnutrition are considered as potentially modifiable risk factors with a major clinical impact. Even so, there is only limited high-level evidence to show how these pathologies should be addressed in the clinical setting. This review discusses the current state-of-the-art on the role of BC assessment in clinical outcomes in the setting of CLD and LT focusing mainly on sarcopenia and myosteatosis. We focus on the disease-related pathophysiology of BC alterations. Based on these, we address potential therapeutic interventions including nutritional regimens, physical activity, hormone and targeted therapies. In addition to summarizing existing knowledge, this review highlights novel trends, and future perspectives and identifies persisting challenges in addressing BC pathologies in a holistic way, aiming to improve outcomes and quality of life of patients with CLD awaiting or undergoing LT.

Sarcopenia in cirrhosis: Unraveling the prevalence and relationships with liver disease severity and complications

BACKGROUND AND OBJECTIVES

Sarcopenia in cirrhosis is associated with poor survival and adverse pre and post-transplant outcomes. The study aimed at determining the prevalence of sarcopenia and its association with the severity, complications and etiology of liver disease.

METHODS

As many as 416 cirrhotic patients who met the inclusion criteria underwent muscle strength testing using a dynamometer. As many as 109 probable sarcopenia patients underwent computed tomography (CT) scan to measure skeletal muscle index (SMI) at the L3 vertebral level and gait-speed testing. The gender-specific cut-offs used to define sarcopenia were an SMI of 36.54 cm2/m2 in males and 30.21 cm2/m2 in females. A gait speed ≤ 0.8 m/s was taken as a cut-off to define severe sarcopenia in both genders.

RESULTS

The mean age was 54.7 ± 9.51 years and male:female ratio was 2.2:1.The mean body mass index (BMI) was 24.2 ± 1.34 kg/m2. Alcohol and non-alcoholic steatohepatitis (NASH) were the two most common etiologies (45.9% and 31.2%). The proportion of patients belonging to Child-Pugh class A, B and C was 26.6%, 48.6% and 24.8%, respectively. Forty out of 109 (36.7%) patients had a model for end-stage liver disease (MELD) > 14. Ascites, upper gastrointestinal bleeding and hepatic encephalopathy (HE) were present in 59 (54.1%), 60 (55.0%) and 24 (22.0%) patients, respectively. The prevalence of probable sarcopenia, sarcopenia and severe sarcopenia was found to be 26.20%, 10.09% and 6.73%, respectively. Sarcopenia and severe sarcopenia were associated with Child-Pugh class (p < 0.001, p < 0.001), MELD (p = 0.007, 0.002), upper gastrointestinal bleed (p = 0.007, 0.004), ascites (p = 0.038, 0.025) and HE (0.001, < 0.001).

CONCLUSION

The prevalence of sarcopenia and severe sarcopenia was found to be 10.09% and 6.73%, respectively. Sarcopenia and severe sarcopenia had a significant association with the severity and complications of cirrhosis. However, no association was observed with etiology of liver disease.

Emerging drugs for the treatment of sarcopenia in cirrhosis of the liver

INTRODUCTION

Malnutrition and sarcopenia are common and impact the prognosis in patients with liver cirrhosis. The etiology is multifactorial and includes periods of reduced caloric intake, increased catabolism and direct molecular mechanisms that inhibit muscle synthesis. Although these conditions are widely acknowledged, and there is a growing interest in their diagnosis, robust evidence regarding the treatment and reversibility of these conditions is still lacking.

AREAS COVERED

We have explored the current evidence on the pharmacological treatment of sarcopenia in patients with cirrhosis. Additionally, we have searched for drugs already in use and ongoing trials for other chronic diseases.

EXPERT OPINION

The current guidelines recommend the use of a protein-adequate diet and moderate physical activity for treating sarcopenia in patients with cirrhosis. Currently, robust evidence is derived only from the supplementation of Branched-Chain Amino Acids, capable of increasing muscle mass and function. There are many drugs targeting various pathways that contribute to sarcopenia. However, evidence is sporadic and insufficient to suggest their use in clinical practice.Novel drugs specifically designed to enhance muscle mass and function should be developed. Finally, gender significantly influences the type of muscle alteration and therapeutic mechanisms; therefore, future studies should be designed taking gender differences into consideration.

Preoperative DLCO predicts severe early complications after liver transplantation

BACKGROUND

Severe early complications are common after liver transplantation (LT) and are a key determinant of LT-related morbidity and mortality. The aim of this study was to assess whether lung function measured in the pre-operative period predicted complicated outcomes in the first month after LT.

MATERIAL AND METHODS

Patients with mild-to-moderate liver disease (Model for End stage Liver Disease-MELD score≤30) who underwent LT between October 2015 and May 2020 in a single centre were retrospectively included. The primary endpoint was the occurrence of severe early complications after LT defined by mechanical ventilation duration > 2 days or length of ICU stay > 7 days or reintubation or death < 1 month after LT.

RESULTS

One hundred and twenty patients were included (age 59 [53-64] years, 72 % men). Forty patients (33 %) had early complications after LT. Measured and%predicted hemoglobin-corrected lung transfer capacity for carbon monoxide (DLCOc) were significantly lower in patients with severe early complications after LT. DLCOc was the only variable that associated independently with severe early complications by multivariate analysis. DLCOc under 16.3 ml.min-1.mmHg-1 predicted respiratory complications with a sensitivity of 67.5 % and a specificity of 62.9 %. DLCOc%pred under 61.5 % had a sensitivity of 56.8 % and a specificity of 72 %. DLCOc independently associated with forced vital capacity (FVC), pulmonary emphysema, and the muscle mass index.

CONCLUSION

A decrease in DLCOc indicated an increased risk of severe early complications after LT.

Longitudinal changes in sarcopenia was associated with survival among cirrhotic patients

Background

Sarcopenia is common in patients with liver cirrhosis and is an independent predictor of multiple clinical outcomes. Most studies to date have used a static assessment of sarcopenia. However, there is very limited data evaluating the temporal course of muscle area in cirrhosis. To bridge this gap in clinical studies, we performed a longitudinal analysis to evaluate the impact of changes in sarcopenia for cirrhotic patients.

Methods

Adult patients with clinically diagnosed liver cirrhosis who underwent at least 2 abdominal computed tomography (CT) scans in the hospital were enrolled. The interval between the two abdominal scans was 6 ± 1 months. Patients were categorized into persistent non-sarcopenia, new-onset sarcopenia, sarcopenia to non-sarcopenia, and persistent sarcopenia based on changes in sarcopenia. Kaplan-Meier method and Log-rank tests were used to separately compare unadjusted survival curves by different statuses of sarcopenia. Cox regression analysis was performed to assess the associations between different states of sarcopenia and overall mortality. The association between persistent non-sarcopenia and new-onset sarcopenia was analyzed by multivariate logistic regression analysis.

Results

A total of 307 patients were included for analysis. At the second assessment, 10.10% (31/307) patients were new-onset sarcopenia, 27.69% (85/307) with persistent sarcopenia status, while 13.03% (40/307) patients with sarcopenia developed non-sarcopenia and 49.19% (151/307) with persistent non-sarcopenia status. The overall survival rate was significantly lower in the persistent sarcopenia and new-onset sarcopenia than in the non-sarcopenia group and sarcopenia to non-sarcopenia group (p < 0.001). Persistent sarcopenia (HR 5.799, 95%CI 1.563-21.521, p = 0.009) and new onset sarcopenia (HR 5.205, 95%CI 1.482-18.282, p = 0.010) were identified as poor prognostic factors for cirrhotic patients. The etiology of cirrhosis and the initial skeletal muscle mass were independent risk factors for new-onset sarcopenia.

Conclusion

Sarcopenia is a dynamically changing process in patients with cirrhosis. Persistent and new-onset sarcopenia were independently and robustly associated with overall survival.

Perioperative Considerations in Older Kidney and Liver Transplant Recipients: A Review

With the growth of the older adult population, the number of older adults waitlisted for and undergoing kidney and liver transplantation has increased. Transplantation is an important and definitive treatment for this population. We present a contemporary review of the unique preoperative, intraoperative, and postoperative issues that patients older than 65 y face when they undergo kidney or liver transplantation. We focus on geriatric syndromes that are common in older patients listed for kidney or liver transplantation including frailty, sarcopenia, and cognitive dysfunction; discuss important considerations for older transplant recipients, which may impact preoperative risk stratification; and describe unique challenges in intraoperative and postoperative management for older patients. Intraoperative challenges in the older adult include using evidence-based best anesthetic practices, maintaining adequate perfusion pressure, and using minimally invasive surgical techniques. Postoperative concerns include controlling acute postoperative pain; preventing cardiovascular complications and delirium; optimizing immunosuppression; preventing perioperative kidney injury; and avoiding nephrotoxicity and rehabilitation. Future studies are needed throughout the perioperative period to identify interventions that will improve patients' preoperative physiologic status, prevent postoperative medical complications, and improve medical and patient-centered outcomes in this vulnerable patient population.

Sarcopenia Affects Liver Regeneration and Long-Term Survival Rate After Living-Donor Liver Transplantation in Patients With Hepatocellular Carcinoma

PURPOSE

Despite technological and immunologic innovations, some living-donor liver transplant (LDLT) recipients still face poor liver regeneration. Sarcopenia is often recognized as a biomarker for poor outcomes in surgical patients. This study aimed to evaluate associations between sarcopenia and liver regeneration in LDLT recipients.

MATERIALS AND METHODS

This retrospective review included consecutive patients who had received LDLT at Chang Gung Memorial Hospital between 2005 and 2017. Sarcopenia was assessed using the psoas muscle index (PMI) in cross-sectional images. Receiver operating characteristic curve analysis was used to determine the ability of PMI to predict relatively poor survival rates. Correlations between liver regeneration and sarcopenia were evaluated using regression analysis.

RESULTS

A total of 109 LDLT recipients were included. The 1-, 3-, 5, 10-, and 15-year survival rates were 93.7%, 84.8%, 79.7%, 74.7%, and 73.3% in males and 93.3%, 83.3%, 83.3%, 71.4%, and 71.4% in females. PMIs were significantly different based on 10- and 15-year overall survival rates (P = .001 and P = .000) in male patients. Receiver operating characteristic curve analysis revealed the PMI cutoff point at 6.7 cm2/m2 (sensitivity = 48.3%, specificity = 81%, AUC (area under the ROC curve) = 0.685) based on 10-year survival. Linear regression analysis revealed that PMI was significantly associated with liver regeneration in males (P = .013).

CONCLUSIONS

Sarcopenia and low PMI are associated with poor liver regeneration and long-term survival after LDLT in male patients. Further studies, including sarcopenia with conventional scores, may help to more reliably predict liver regeneration and mortality among LDLT patients with hepatocellular carcinoma.

Effect of pretransplant sarcopenia on patient and graft outcomes in solid organ transplant recipients: A systematic review and meta-analysis

The relationship between sarcopenia and prognosis in solid organ transplantation recipients (SOTr) remains unverified. We aimed to quantify the prevalence of pretransplant sarcopenia and its effect on patient and graft survival in SOTr. We used PubMed, EMBASE, Cochrane Library and Web of Science to search relevant studies published in English (from inception to December 31, 2021). Prospective and retrospective cohort studies that reported the prevalence of sarcopenia before transplant or the association between sarcopenia and clinical outcomes in SOTr were included. Primary outcomes were the prevalence of sarcopenia and its impact on patient and graft survival. Secondary outcomes included perioperative complications, acute rejection, length of hospital stay, length of intensive care unit stay (ICU LOS) and early readmission. Thirty-nine studies involving 5792 patients were included. Pooled prevalence of sarcopenia amongst SOTr candidates was 40 % (95 % confidence interval [CI]: 34%-47 % and I2 = 97 %). Sarcopenia was associated with increased risk of death (hazard ratio [HR] = 1.87, 95 % CI: 1.46-2.41 and I2 = 60 %), poor graft survival (HR = 1.71, 95 % CI: 1.16-2.54 and I2 = 57 %) and increased liver graft loss (HR = 1.43, 95 % CI: 1.03-1.99 and I2 = 38 %). Patients with sarcopenia demonstrated increased incidence of perioperative complications (risk ratio [RR] = 1.34, 95 % CI: 1.17-1.53 and I2 = 40 %), long ICU LOS (mean difference = 2.31 days, 95 % CI: 0.58-4.04 and I2 = 97 %) and decreased risk of acute rejection (RR = 0.61, 95 % CI: 0.42-0.89 and I2 = 0 %). In Conclusion, sarcopenia is prevalent in SOTr candidates and associated with death and graft loss. Identifying sarcopenia before transplantation and intervening may improve long-term outcomes.

Sarcopenia increases mortality risk in liver transplantation: a systematic review and meta-analysis

INTRODUCTION

Liver transplantation is an efficacious treatment option for those with liver cirrhosis. However, the prognostic role of sarcopenia in these patients is unknown. Given this background, we conducted a systematic review and meta-analysis of the impact of sarcopenia on mortality in patients listed, evaluated and undergoing liver transplantation.

EVIDENCE ACQUISITION

Several databases were searched from the inception to December 2022 for observational studies regarding sarcopenia in liver transplant and mortality. We calculated the risk of mortality in sarcopenia vs. no sarcopenia using the most adjusted estimate available and summarizing the data as risk ratios (RRs) with their 95% confidence intervals (CIs). A random-effect model was considered for all analyses.

EVIDENCE SYNTHESIS

Among 1135 studies initially considered, 33 articles were included for a total of 12,137 patients (mean age: 55.3 years; 39.4% females). Over a median of 2.6 years and after adjusting for a median of 3 covariates, sarcopenia increased the risk of mortality approximately 2-fold (RR: 2.01; 95% CI: 1.70-2.36). After accounting for publication bias, the re-calculated RR was 1.75 (95% CI: 1.49-2.06). The quality of the studies was generally low, as determined by the Newcastle Ottawa Scale.

CONCLUSIONS

Sarcopenia was significantly linked with an increased risk of mortality in patients listed, evaluated, and undergoing a liver transplantation, indicating the need of interventional studies in this special population with the main aim to reverse this potential reversible condition and decrease mortality risk.

Prevalence and clinical impact of sarcopenia in liver transplant recipients: A meta-analysis

BACKGROUND

The prevalence of sarcopenia in patients undergoing liver transplantation (LT) remains to be determined partly because of different diagnostic criteria. Sarcopenia has recently been recognized as a new prognostic factor for predicting outcomes in LT candidates.

AIM

To estimate the prevalence of sarcopenia and evaluate its clinical effect on LT candidates.

METHODS

This systematic search was conducted in PubMed, Web of Science, Embase, and Cochrane Library for original English-language articles that investigated the prevalence and influence of sarcopenia in patients undergoing LT from database inception to November 30, 2022. Cohort studies of the definition of sarcopenia that estimate sarcopenia prevalence and evaluate its effect on clinical outcomes and the risk of mortality were included.

RESULTS

Twenty-five studies involving 7760 patients undergoing LT were included. The pooled prevalence of sarcopenia in patients undergoing LT was 40.7% [95% confidence intervals (95%CI): 32.1-49.6]. The 1-, 3-, and 5-year cumulative probabilities of post-LT survival in patients with preoperative sarcopenia were all lower than those without sarcopenia (P < 0.05). Sarcopenia was associated with an increased risk of post-LT mortality in patients undergoing LT (adjusted hazard ratio: 1.58; 95%CI: 1.21-2.07). Patients with preoperative sarcopenia had a longer intensive care unit stay, a high risk ratio of sepsis, and serious post-LT complications than those without sarcopenia.

CONCLUSION

Sarcopenia is prevalent in a substantial proportion of patients undergoing LT and is strongly and independently associated with higher a risk of mortality risk.

Nutrition support management of organ transplant recipients in the acute posttransplant phase

Patients who undergo solid organ transplant can have an extensive and challenging postoperative course. The chronicity of the disease state prior to transplant in combination with transplant-specific complications and immunosuppressant medications can lead to distinct challenges that are not observed in other critically ill patients. Although the manifestation of posttransplant complications may be specific to the organ being transplanted, there are common transplant challenges that affect nutrition therapy in these patients. Effects of malnutrition, metabolic aberrations, and posttransplant organ dysfunction should be considered when developing a nutrition care plan for patients in the immediate posttransplant phase. This article addresses the various complications that can arise in the immediate posttransplant phase among patients undergoing solid organ transplant and the appropriate nutrition interventions or considerations for this specialized patient population.

Imaging of Sarcopenia in Type 2 Diabetes Mellitus

Sarcopenia is an age-related condition characterized by the loss of skeletal muscle mass, muscular strength, and muscle function. In older adults, type 2 diabetes mellitus (T2DM) constitutes a significant health burden. Skeletal muscle damage and deterioration have emerged as novel chronic complications in patients with diabetes, often linked to their increased longevity. Diabetic sarcopenia has been associated with increased rates of hospitalization, cardiovascular events, and mortality. Nevertheless, effectively managing metabolic disorders in patients with T2DM through appropriate therapeutic interventions could potentially mitigate the risk of sarcopenia. Utilizing imaging technologies holds substantial clinical significance in the early detection of skeletal muscle mass alterations associated with sarcopenia. Such detection is pivotal for arresting disease progression and preserving patients' quality of life. These imaging modalities offer reproducible and consistent patterns over time, as they all provide varying degrees of quantitative data. This review primarily delves into the application of dual-energy X-ray absorptiometry, computed tomography, magnetic resonance imaging, and ultrasound for both qualitative and quantitative assessments of muscle mass in patients with T2DM. It also juxtaposes the merits and limitations of these four techniques. By understanding the nuances of each method, clinicians can discern how best to apply them in diverse clinical scenarios.

Preoperative low muscle mass and early postoperative outcomes in children undergoing living donor liver transplantation: A retrospective study

Low skeletal muscle mass may develop in children with end-stage liver disease, affecting postoperative outcomes. We retrospectively investigated whether preoperative low muscle mass was associated with early postoperative outcomes in pediatric patients undergoing living donor liver transplantation (LDLT). Electronic medical records of children (age below 12 y) who underwent LDLT between February 1, 2007, and January 31, 2018, were reviewed. The cross-sectional areas of psoas, quadratus lumborum, and erector spinae muscles at the level of fourth-fifth lumbar intervertebral disks were measured using abdominal CT images, divided by the square of the height and were added to obtain the total skeletal muscle index (TSMI). The patients were divided into two groups according to the median TSMI in the second quintile (1859.1 mm 2 /m 2 ). Complications in the early postoperative period (within 30 d after surgery) classified as Clavien-Dindo grade 3 or higher were considered major complications. Logistic regression analyses were performed to determine the association between preoperative low muscle mass and early postoperative outcomes. In the study population of 123 patients (median age, 14 mo; range, 8-38 mo) who underwent LDLT, 29% and 71% were classified in the low (mean TSMI, 1642.5 ± 187.0 mm 2 /m 2 ) and high (mean TSMI 2188.1 ± 273.5 mm 2 /m 2 ) muscle mass groups, respectively. The rates of major complications, mechanical ventilation >96 hours, intensive care unit stay >14 days, hospital stay >30 days, and in-hospital mortality were not significantly different between the 2 groups. Additionally, adverse outcomes according to pediatric end-stage liver disease scores and sex were not significantly different between the 2 groups. In conclusion, preoperative low muscle mass defined by TSMI was not associated with early postoperative outcomes in pediatric patients undergoing LDLT.

Diagnosis of Sarcopenia Using the L3 Skeletal Muscle Index Estimated From the L1 Skeletal Muscle Index on MR Images in Patients With Cirrhosis

BACKGROUND

Cirrhotic patients with sarcopenia have poor prognoses and higher mortality. The third lumbar vertebra (L3) skeletal muscle index (SMI) is widely used to assess sarcopenia. However, L3 is generally outside the scanning volume on standard liver MRI.

PURPOSE

To investigate SMIs change between slices in cirrhotic patients and the relationships between SMI at the 12th thoracic vertebra (T12), the first lumbar vertebra (L1) and the second lumbar vertebra (L2) levels and L3-SMI and assess the accuracy of the estimated L3-SMIs in diagnosing sarcopenia.

STUDY TYPE

Prospective.

SUBJECTS

A total of 155 cirrhotic patients (109 with sarcopenia, 67 male; 46 without sarcopenia, 18 male).

FIELD STRENGTH/SEQUENCE

A 3.0 T, 3D dual-echo T1-weighted gradient echo sequence (T1WI).

ASSESSMENT

Two observers analyzed T12 to L3 skeletal muscle area (SMA) in each patient based on T1W water images and calculated the SMI (SMA/height2 ). Reference standard was L3-SMI.

STATISTICAL TESTS

Intraclass correlation coefficient (ICC), Pearson correlation coefficients (r), and Bland-Altman plots. Models relating L3-SMI to the SMI at T12, L1, and L2 levels were constructed using 10-fold cross-validation. Accuracy, sensitivity, and specificity were calculated for the estimated L3-SMIs for diagnosing sarcopenia. P < 0.05 was considered statistically significant.

RESULTS

Intraobserver and interobserver ICCs were 0.998-0.999. The L3-SMA/L3-SMI were correlated with the T12 to L2 SMA/SMI (r = 0.852-0.977). T12-L2 models had mean-adjusted R2 values of 0.75-0.95. The estimated L3-SMI from T12 to L2 levels to diagnose sarcopenia had good accuracy (81.4%-95.3%), sensitivity (88.1%-97.0%), and specificity (71.4%-92.9%). The recommended L1-SMI threshold of 43.24 cm2 /m2 in males and 33.73 cm2 /m2 in females.

DATA CONCLUSION

The estimated L3-SMI from T12, L1 and L2 levels had good diagnostic accuracy in assessing sarcopenia in cirrhotic patients. Although L2 was best associated with L3-SMI, L2 is generally not included in standard liver MRI. L3-SMI estimate from L1 may therefore be most clinically applicable.

EVIDENCE LEVEL

1.

TECHNICAL EFFICACY

Stage 2.

Malnutrition in solid organ transplant patients: A review of the literature

Screening for malnutrition is of vital importance for solid organ transplant candidates to optimize nutrition status before transplant, to improve clinical outcomes and to inform selection committees of nutritional contraindications and risks. There are multiple criteria and screening tools available for determining malnutrition diagnosis and risk. Registered Dietitian Nutritionists use these tools for nutrition assessments to quantify the severity of malnutrition, provide patient-centered interventions, and monitor progression. Many transplant centers in the United States utilize the American Society of Parenteral and Enteral Nutrition and the Academy of Nutrition and Dietetics' Adult Malnutrition Criteria, though there is limited research using these criteria specifically in the transplant population. Malnutrition, utilizing other diagnostic and screening tools, has been associated with important complications, including longer length of hospital stay, increased mortality, decreased quality of life, worsened end-stage organ progression, and decreased functional status. Malnutrition typically results from sarcopenia and cachexia, and can ultimately lead to frailty, causing further negative impacts on transplant outcomes. This literature review summarizes the current research on malnutrition in solid organ transplant candidates and provides recommendations for future research and current practice implications.

Sarcopenia is associated with osteopenia and impaired quality of life in children with genetic intrahepatic cholestatic liver disease

BACKGROUND

Sarcopenia occurs in pediatric chronic liver disease, although the prevalence and contributing factors in genetic intrahepatic cholestasis are not well-described. The objective of this study was to measure muscle mass in school-aged children with genetic intrahepatic cholestasis and assess relationships between sarcopenia, clinical variables, and outcomes.

METHODS

Estimated skeletal muscle mass (eSMM) was calculated on dual-energy x-ray absorptiometry obtained in a Childhood Liver Disease Research Network study of children with bile acid synthesis disorders(BASD) alpha-1 antitrypsin deficiency (a1ATd), chronic intrahepatic cholestasis (CIC), and Alagille syndrome (ALGS). Relationships between eSMM, liver disease, and transplant-free survival were assessed.

RESULTS

eSMM was calculated in 127 participants (5-18 y): 12 BASD, 41 a1ATd, 33 CIC, and 41 ALGS. eSMM z-score was lower in CIC (-1.6 ± 1.3) and ALGS (-2.1 ± 1.0) than BASD (-0.1 ± 1.1) and a1ATd (-0.5 ± 0.8, p < 0.001). Sarcopenia (defined as eSMM z-score ≤- 2) was present in 33.3% of CIC and 41.5% of ALGS participants. eSMM correlated with bone mineral density in the 4 disease groups (r=0.52-0.55, p < 0.001-0.07), but not serum bile acids, bilirubin, aspartate aminotransferase/platelet ratio index, or clinically evident portal hypertension. Of the 2 patients who died (1 with sarcopenia) and 18 who underwent liver transplant (LT, 4 with sarcopenia), eSMM z-score did not predict transplant-free survival. eSMM z-score correlated with the Physical Pediatric Quality of Life Inventory score (r=0.38-0.53, p = 0.007-0.04) in CIC and a1ATd.

CONCLUSION

Severe sarcopenia occurs in some children with ALGS and CIC. The lack of correlation between eSMM and biochemical cholestasis suggests mechanisms beyond cholestasis contribute to sarcopenia. While sarcopenia did not predict transplant-free survival, LT and death were infrequent events. Future studies may define mechanisms of sarcopenia in genetic intrahepatic cholestasis.

Cirrhosis-related sarcopenia may not resolve after liver transplantation

Background & Aims

Sarcopenia has significant burden in cirrhosis and has been shown to worsen short-term post-liver transplantation (LT). This study aims to evaluate the long-term change in sarcopenia post-LT along with its associations and predictors.

Methods

A retrospective study of adult patients who underwent LT at a tertiary centre between 1/1/2009 and 12/31/2018. Relevant demographic and clinical data were collected. Skeletal muscle index (SMI) was calculated using standard of care computerised tomography (CT) scans pre- and post-LT. Sarcopenia was defined using previously established cut-points. The primary outcome was SMI change post-LT and secondary outcome was post-LT mortality.

Results

Out of 1165 patients, 401 met inclusion criteria (1,205 CT scans reviewed). The average age at transplant was 57 years; 63% were male. The average BMI was 28 kg/m2. Thirteen percent of females and 32% of males had sarcopenia pre-LT. Post-LT SMI declined by 4.7 cm2/m2 in the first year then by 0.39 cm2/m2 per year thereafter. Females had greater rate of decline in SMI after the first year compared with males (0.87 cm2/m2 per year vs. 0.17 cm2/m2 per year, respectively, p = 0.02). Post-LT physical rehabilitation, infection, and readmissions were not associated with SMI trajectory. At 3 years post-LT, 31% of females and 48% of males had sarcopenia. Baseline sarcopenia was the only predictor of long-term post-LT sarcopenia on multivariable analysis, but it was not associated with mortality.

Conclusions

Sarcopenia does not appear to resolve post-LT and likely worsens leading to nearly doubling its prevalence in those with long-term follow-up. Immediate post-LT physical rehabilitation was not associated with SMI trajectory in our cohort.

Impact and implications

The prevalence of sarcopenia is high among patients with cirrhosis; however, data are mixed on the impact of sarcopenia on post-liver transplant (LT) course and there have been no studies evaluating the long-term evolution of sarcopenia post-LT beyond 1 year. In this study, we analysed changes in muscle mass up to 3 years after transplant in 401 patients and found that sarcopenia did not resolve in most liver transplant recipients and skeletal muscle mass tended to worsen after transplant with the greatest decline in muscle mass in the first year post-LT. Interestingly, sarcopenia did not influence post-transplant outcomes. Future prospective studies are needed to further understand the natural course of sarcopenia post-LT to guide interventions aiming at reversing post-LT sarcopenia.

Upper thigh skeletal muscle index predicts outcomes in liver transplant recipients

Purpose

The skeletal muscle index (SMI) at the L3 level is widely used to diagnose sarcopenia. The upper thigh (UT) also reflects changes in whole-body muscle mass, but no study has examined this using the UT to diagnose sarcopenia in liver transplantation (LT). This study aimed to determine an optimal cut-off value for UT-SMI and investigate how sarcopenia diagnosed by UT-SMI correlates with outcomes in LT recipients.

Methods

In this retrospective study of 332 LT patients from 2018 to 2020, we investigated the association between sarcopenia diagnosed by UT-SMI and patient outcomes after LT.

Results

The cut-off values for UT-SMI were 38.3 cm2/m2 for females (area under the curve [AUC], 0.927; P < 0.001) and 46.7 cm2/m2 for males (AUC, 0.898; P < 0.001). The prevalence of sarcopenia diagnosed by UT-SMI was 33.4% in our cohort. Patient and graft survival rates in the UT-SMI sarcopenia group were significantly poorer than those in the UT-SMI non-sarcopenia group (P < 0.001 and P < 0.001). UT-SMI was an independent prognostic factor for patient survival (hazard ratio [HR], 2.182; 95% confidence interval [CI], 1.183-4.025; P = 0.012) and graft survival (HR, 2.227; 95% CI, 1.054-4704; P = 0.036) in our multivariable Cox analysis.

Conclusion

We confirmed that sarcopenia diagnosed by UT-SMI is associated with outcomes in LT recipients. In addition, UT-SMI was identified as an independent prognostic factor for patient survival and graft survival. Therefore, UT-SMI could be a good option for CT-based evaluations of sarcopenia in LT recipients.

Global Leadership Initiative on Malnutrition criteria for the diagnosis of malnutrition and prediction of mortality in patients awaiting liver transplant: A validation study

OBJECTIVES

The Global Leadership Initiative on Malnutrition (GLIM) is a framework aiming to standardize malnutrition diagnosis. However, it still needs to be validated, in particular for patients with chronic liver disease. This study aimed to validate the GLIM criteria in patients with liver cirrhosis awaiting liver transplant (LTx).

METHODS

This was a retrospective observational study carried out with adult patients on the waiting list for LTx, consecutively evaluated between 2006 and 2021. The phenotypic criteria were unintentional weight loss, low body mass index, and reduced muscle mass (midarm muscle circumference [MAMC]). The etiologic criteria were high Model for End-Stage Liver Disease (MELD) and MELD adjusted for serum sodium (MELD-Na) scores, the Child-Pugh score, low serum albumin, and low food intake and/or assimilation. Forty-three GLIM combinations were tested. Sensitivity (SE), specificity (SP), positive and negative predictive values, and machine learning (ML) techniques were used. Survival analysis with Cox regression was carried out.

RESULTS

A total of 419 patients with advanced liver cirrhosis were included (median age, 52.0 y [46-59 y]; 69.2% male; 68.8% malnourished according to the Subjective Global Assessment [SGA]). The prevalence of malnutrition by the GLIM criteria ranged from 3.1% to 58.2%, and five combinations had SE or SP >80%. The MAMC as a phenotypic criterion with MELD and MELD-Na as etiologic criteria were predictors of mortality. The MAMC and the presence of any phenotypic criteria associated with liver disease parameters and low food intake or assimilation were associated with malnutrition prediction in ML analysis.

CONCLUSIONS

The MAMC and liver disease parameters were associated with malnutrition diagnosis by SGA and were also predictors of 1-y mortality in patients with liver cirrhosis awaiting LTx.

Correcting Posterior Paraspinal Muscle Computed Tomography Density for Intravenous Contrast Material Independent of Sex and Vascular Phase

PURPOSE

Intravenous contrast poses challenges to computed tomography (CT) muscle density analysis. We developed and tested corrections for contrast-enhanced CT muscle density to improve muscle analysis and the utility of CT scans for the assessment of myosteatosis.

MATERIALS AND METHODS

Using retrospective images from 240 adults who received routine abdominal CT imaging from March to November 2020 with weight-based iodine contrast, we obtained paraspinal muscle density measurements from noncontrast (NC), arterial, and venous-phase images. We used a calibration sample to develop 9 different mean and regression-based corrections for the effect of contrast. We applied the corrections in a validation sample and conducted equivalence testing.

RESULTS

We evaluated 140 patients (mean age 52.0 y [SD: 18.3]; 60% female) in the calibration sample and 100 patients (mean age 54.8 y [SD: 18.9]; 60% female) in the validation sample. Contrast-enhanced muscle density was higher than NC by 8.6 HU (SD: 6.2) for the arterial phase (female, 10.4 HU [SD: 5.7]; male, 6.0 HU [SD:6.0]) and by 6.4 HU [SD:8.1] for the venous phase (female, 8.0 HU [SD: 8.6]; male, 4.0 HU [SD: 6.6]). Corrected contrast-enhanced and NC muscle density was equivalent within 3 HU for all correctionns. The -7.5 HU correction, independent of sex and phase, performed well for arterial (95% CI: -0.18, 1.80 HU) and venous-phase data (95% CI: -0.88, 1.41 HU).

CONCLUSIONS

Our validated correction factor of -7.5 HU renders contrast-enhanced muscle density statistically similar to NC density and is a feasible rule-of-thumb for clinicians to implement.

Transjugular intrahepatic portosystemic shunt insertion improves muscle mass but not muscle function or frailty measures

INTRODUCTION

Sarcopenia in cirrhosis is associated with poor outcomes. While transjugular intrahepatic portosystemic shunt (TIPS) insertion improves radiological measures of muscle mass, its impact on muscle function, performance and frailty has not been evaluated.

METHODS

Patients with cirrhosis referred for TIPS were prospectively recruited and followed for 6 months. L3 CT scans were used to calculate skeletal muscle and adipose tissue parameters. Handgrip strength, Liver Frailty Index and short physical performance battery were serially monitored. Dietary intake, insulin resistance, insulin-like growth factor (IGF)-1, and immune function using QuantiFERON Monitor (QFM) were measured.

RESULTS

Twelve patients completed the study with a mean age of 58 ± 9 years and model for end-stage liver disease score of 16 ± 5. At 6 months post-TIPS, skeletal muscle area increased from 139.33 cm 2  ± 22.72 to 154.64 ± 27.42 ( P  = 0.012). Significant increases were observed in the subcutaneous fat area ( P  = 0.0076) and intermuscular adipose tissue ( P  = 0.041), but not muscle attenuation or visceral fat. Despite marked changes in muscle mass, no improvements were observed in handgrip strength, frailty, or physical performance. At 6 months post-TIPS, IGF-1 ( P  = 0.0076) and QFM ( P  = 0.006) increased compared to baseline. Nutritional intake, hepatic encephalopathy measures, insulin resistance and liver biochemistry were not significantly impacted.

CONCLUSION

Muscle mass increased following TIPS insertion as did IGF-1, a known driver of muscle anabolism. The lack of improvement in muscle function was unexpected and may relate to impairment in muscle quality and the effects of hyperammonaemia on muscle contractile function. Improvements in QFM, a marker of immune function, may suggest a reduction in infection susceptibility in this at-risk population and requires further evaluation.

Association between skeletal muscle index prior to liver transplantation and 1-year mortality posttransplant

BACKGROUND

Liver transplantation is the only curative therapy for end-stage liver disease (ESLD). Sarcopenia is often defined as the loss of muscle quantity (skeletal muscle index [SMI]), but muscle attenuation (MA), a surrogate marker of muscle quality, is also decreased in ESLD. We assessed pre-liver transplant SMI and MA and their association with posttransplant mortality, complications, and length of intensive care unit (ICU) and hospital stay.

METHODS

In 169 consecutive patients with ESLD who underwent a liver transplantation between 2007 and 2014, SMI and MA were measured on computed tomography scans at time of placement on the waiting list for liver transplantation. The primary outcome of interest was 1-year posttransplant mortality. Secondary posttransplantation outcomes of interest were complications within 30 days and length of stay in the ICU > 3 days and in the hospital >3 weeks. Logistic and Cox regression analyses were performed.

RESULTS

MA was associated with 1-year posttransplant mortality rate (hazard ratio=0.656, 95% CI=0.464-0.921, P = 0.015). The highest quartile of SMI had a lower odds for the total length of stay in the hospital lasting >3 weeks (odds ratio=0.211, 95% CI=0.061-0.733, P = 0.014). MA was associated with a prolonged ICU stay; this was, however, not statistically significant after adjustment for age, sex, and Model for ESLD score.

CONCLUSION

Lower MA is associated with a longer length of ICU stay and 1-year mortality after liver transplantation, whereas low SMI was associated with a total length of hospital stay.

Advances and Controversies in Acute Alcohol-Related Hepatitis: From Medical Therapy to Liver Transplantation

Alcohol-related hepatitis (AH) is a clinical syndrome characterized by recent-onset jaundice in the context of alcohol consumption. In patients with severe AH "unresponsive" to steroid therapy, mortality rates exceed 70% within six months. According to European and American guidelines, liver transplantation (LT) may be considered in highly selected patients who do not respond to medical therapy. The aim of this narrative review is to summarize current knowledge from medical therapy to liver transplantation in acute alcohol-related hepatitis. Due to the impossibility to guarantee six-month abstinence, LT for AH is controversial. Principal concerns are related to organ scarcity in the subset of stigma of "alcohol use disorder" (AUD) and the risk of relapse to alcohol use after LT. Return to alcohol use after LT is a complex issue that cannot be assessed as a yes/no variable with heterogeneous results among studies. In conclusion, present data indicate that well-selected patients have excellent outcomes, with survival rates of up to 100% at 24 and 36 months after LT. Behavioral therapy, ongoing psychological support, and strong family support seem essential to improve long-term outcomes after LT and reduce the risk in relapse of alcohol use.

Nutritional Support for Liver Diseases

The liver is a key organ that is responsible for the metabolism of proteins, fats, and carbohydrates and the absorption and storage of micronutrients. Unfortunately, the prevalence of chronic liver diseases at various stages of advancement in the world population is significant. Due to the physiological function of the liver, its dysfunction can lead to malnutrition and sarcopenia, and the patient's nutritional status is an important prognostic factor. This review discusses key issues related to the diet therapy of patients with chronic liver diseases, as well as those qualified for liver transplantation and in the postoperative period.

Evaluation and Management of Nutritional Consequences of Chronic Liver Diseases

Liver diseases are the major predisposing conditions for the development of malnutrition, sarcopenia, and frailty. Recently, the mechanism of the onset of these complications has been better established. Regardless of the etiology of the underlying liver disease, the clinical manifestations are common. The main consequences are impaired dietary intake, altered macro- and micronutrient metabolism, energy metabolism disturbances, an increase in energy expenditure, nutrient malabsorption, sarcopenia, frailty, and osteopathy. These complications have direct effects on clinical outcomes, survival, and quality of life. The nutritional status should be assessed systematically and periodically during follow-up in these patients. Maintaining and preserving an adequate nutritional status is crucial and should be a mainstay of treatment. Although general nutritional interventions have been established, special considerations are needed in specific settings such as decompensated cirrhosis, alcohol-related liver disease, and metabolic-dysfunction-associated fatty liver disease. In this review, we summarize the physiopathology and factors that impact the nutritional status of liver disease. We review how to assess malnutrition and sarcopenia and how to prevent and manage these complications in this setting.

A pilot feasibility study of an ultrasound-based tool to assess muscle mass in children with liver disease

BACKGROUND

Sarcopenia is associated with adverse outcomes following liver transplantation, and at-risk children must be identified and prehabilitated. The gold standard for assessing sarcopenia in end-stage liver disease (ESLD) is CT assessment of the total Psoas Muscle Area (tPMA). However, radiation exposure and sedation requirements make this approach impractical for children. The bilateral anterior thigh thickness (BATT) is the cumulative measurement of the rectus femoris and vastus intermedius muscles by ultrasound and has been used to identify sarcopenia in adults. There are no studies assessing muscle mass in children using ultrasound. We hypothesized that measuring BATT with ultrasound in children with ESLD is feasible and is associated with sarcopenia.

METHODS

A prospective pilot feasibility study of patients with ESLD on the liver transplantation waitlist and age-matched healthy controls. BATT was measured by a single operator using ultrasound. tPMA indices were determined by CT imaging, along with clinical and anthropometric data.

RESULTS

Thirty children were studied between September 2021 and December 2022, 15 listed patients aged 4-30 months, and 15 controls aged 4-32 months. No major technical challenges or complications were encountered while performing the ultrasounds. Median BATTs of 30.8 mm (interquartile range: 27.9-32.8 mm) versus 32.7 mm (interquartile range: 31.8-36.9 mm) were demonstrated in the ESLD and control groups, respectively, and p = 0.01. A positive correlation (R = 0.603) was demonstrated between BATT and tPMA at the L4-5 level among patients with ESLD. No correlation was observed between BATT and anthropometrics.

CONCLUSIONS

This study yields novel data on the feasibility of ultrasound to measure mid-thigh thickness in children with ESLD and suggests a correlation between BATT and tPMA, the gold standard for diagnosing sarcopenia. It sets the stage for ultrasound as a simple, noninvasive, and easily repeatable tool for assessing sarcopenia in children.

Detection of Sarcopenia in Patients with Liver Cirrhosis Using the Bioelectrical Impedance Analysis

Bioelectrical impedance analysis (BIA) is a body composition assessment method. We aimed to determine its accuracy in the detection of sarcopenia in patients with liver cirrhosis (LC), using skeletal muscle index (SMI) at the level of third lumbar vertebra (L3-SMI) obtained using multislice computed tomography as the reference method. Patients with LC were enrolled in the period October 2019-March 2022 and follow-ups were conducted until January 2023. Their BIA parameters were compared against L3-SMI, and BIA cut-off values were proposed using AUROC analysis. Patients underwent outcome analysis based on obtained clinical characteristics. A total of 106 patients were included. We found a fair correlation between BIA parameters with the L3-SMI. We determined cut-off values of ≤11.1 kg/m2 for BIA-SMI (Se 73%, Sp 66%, AUROC 0.737, p < 0.001) and ≤5.05° for phase angle (PA) (Se 79%, Sp 60%, AUROC 0.762, p < 0.001) in the detection of sarcopenia. The relative risk of death was 2.2 times higher in patients with skeletal muscle mass (SMM) ≤ 36.5 kg. SMM was significantly associated with outcome in Kaplan-Meier analysis. This non-invasive and simple method that showed fair performances and a very good outcome prediction could provide for the unmet need for fast and affordable detection of sarcopenia in patients with LC and should be further evaluated.

From Listing to Recovery: A Review of Nutritional Status Assessment and Management in Liver Transplant Patients

Liver transplantation (LT) is a complex surgical procedure requiring thorough pre- and post-operative planning and care. The nutritional status of the patient before, during, and after LT is crucial to surgical success and long-term prognosis. This review aims to assess nutritional status assessment and management before, during, and after LT, with a focus on patients who have undergone bariatric surgery. We performed a comprehensive topic search on MEDLINE, Ovid, In-Process, Cochrane Library, EMBASE, and PubMed up to March 2023. It identifies key factors influencing the nutritional status of liver transplant patients, such as pre-existing malnutrition, the type and severity of liver disease, comorbidities, and immunosuppressive medications. The review highlights the importance of pre-operative nutritional assessment and intervention, close nutritional status monitoring, individualised nutrition care plans, and ongoing nutritional support and monitoring after LT. The review concludes by examining the effect of bariatric surgery on the nutritional status of liver transplant recipients. The review offers valuable insights into the challenges and opportunities for optimising nutritional status before, during, and after LT.

CT-derived psoas muscle area and density are associated with length of stay and discharge disposition after liver transplantation

BACKGROUND & AIMS

Prolonged length of stay (LOS) and discharge disposition following liver transplantation are associated with postoperative complications and increased healthcare utilization. This study evaluated the relationship between CT-derived psoas muscle measurements and hospital LOS, intensive care unit (ICU) LOS, and discharge disposition after liver transplant. The psoas muscle was chosen given its ease of measurement with any radiological software. A secondary analysis assessed the relationship between the American Society for Parenteral and Enteral Nutrition and the Academy of Nutrition and Dietetics (ASPEN/AND) malnutrition diagnosis criteria and CT-derived psoas muscle measures.

METHODS

CT-derived measures of psoas muscle density (mHU) and cross-sectional area at the level of the third lumbar vertebrae were obtained from preoperative CT scans of liver transplant recipients. Cross-sectional area measures were corrected for body size to generate a psoas area index variable (cm²/m²; PAI).

RESULTS

Each 1-unit increase in PAI was associated with a reduced hospital LOS of 4 days (R² = 0.07). Each 5-unit increase in mean Hounsfield units (mHU) was associated with a reduced hospital and ICU LOS of 5 and 1.6 days, respectively (R² = 0.22 and 0.14, respectively). Mean PAI and mHU were higher in patients who discharged to home. PAI was reasonably identified through ASPEN/AND malnutrition criteria, but there was no difference in mHU between those with and without malnutrition.

CONCLUSION

Measures of psoas density were associated with both hospital and ICU LOS and discharge disposition. PAI was associated with hospital LOS and discharge disposition. CT-derived measures of psoas density may be a valuable complement to preoperative liver transplant nutrition assessment using traditional ASPEN/AND malnutrition criteria.

Liver transplantation in the patient with physical frailty

Frailty is a decline in functional reserve across multiple physiological systems. A key component of frailty is sarcopenia, which denotes a loss of skeletal muscle mass and impaired contractile function that ultimately result in physical frailty. Physical frailty/sarcopenia are frequent and contribute to adverse clinical outcomes before and after liver transplantation. Frailty indices, including the liver frailty index, focus on contractile dysfunction (physical frailty), while cross-sectional image analysis of muscle area is the most accepted and reproducible measure to define sarcopenia. Thus, physical frailty and sarcopenia are interrelated. The prevalence of physical frailty/sarcopenia is high in liver transplant candidates and these conditions have been shown to adversely impact clinical outcomes including mortality, hospitalisations, infections, and cost of care both before and after transplantation. Data on the prevalence of frailty/sarcopenia and their sex- and age-dependent impact on outcomes are not consistent in patients on the liver transplant waitlist. Physical frailty and sarcopenic obesity are frequent in the obese patient with cirrhosis, and adversely affect outcomes after liver transplantation. Nutritional interventions and physical activity remain the mainstay of management before and after transplantation, despite limited data from large scale trials. In addition to physical frailty, there is recognition that a global evaluation including a multidisciplinary approach to other components of frailty (e.g., cognition, emotional, psychosocial) also need to be addressed in patients on the transplant waitlist. Recent advances in our understanding of the underlying mechanisms of sarcopenia and contractile dysfunction have helped identify novel therapeutic targets.

Radiological assessment of skeletal muscle index and myosteatosis and their impact postoperative outcomes after liver transplantation

BACKGROUND

Liver transplantation offers curative treatment to patients with acute and chronic end-stage liver disease. The impact of nutritional status on postoperative outcomes after liver transplantation remains poorly understood. The present study investigated the predictive value of radiologically assessed skeletal muscle index (SMI) and myosteatosis (MI) on postoperative outcomes.

PATIENTS AND METHODS

Data of 138 adult patients who underwent their first orthotopic liver transplantation were retrospectively analysed. SMI and MI in computer tomography (CT) scan at the third lumbar vertebra level were calculated. Results were analyzed for the length of hospitalisation and postoperative outcomes.

RESULTS

In 63% of male and 28.9% of female recipients, low SMI was found. High MI was found in 45(32.6%) patients. Male patients with high SMI had longer intensive care unit (ICU) stay (P < 0.025). Low SMI had no influence on ICU stay in female patients (P = 0.544), length of hospitalisation (male, P > 0.05; female, P = 0.843), postoperative complication rates (males, P = 0.883; females, P = 0.113), infection rate (males, P = 0.293, females, P = 0.285) and graft rejection (males, P = 0.875; females, P = 0.135). The presence of MI did not influence ICU stay (P = 0.161), hospitalization (P = 0.771), postoperative complication rates (P = 0.467), infection rate (P = 0.173) or graft rejection rate (P = 0.173).

CONCLUSIONS

In our study, changes in body composition of liver transplant recipients observed with SMI and MI had no impact on postoperative course after liver transplantation. CT body composition analysis of recipients and uniformly accepted cut-off points are crucial to producing reliable data in the future.

Muscle quality determined by computed tomography predicts short-term and long-term survival after liver transplantation

Sarcopenia, the loss of muscle mass and quality, contributes to worse clinical outcome in patients with end-stage liver disease, but its impact on short- and long-term survival remains insufficiently understood. The aim of this study was to evaluate the development of computed tomography (CT) muscle parameters and their impact on short-term and long-term survival after liver transplantation. This retrospective study included patients with liver transplantation between 2011 and 2015 and a pre-transplant CT scan. Clinical characteristics, CT muscle mass and density were assessed pre-transplant, and in available CT scans at short-term (11 months) and long-term follow-up (56 months). Overall, 93/152 (61%) patients (109 male, 55 ± 10 years) suffered from sarcopenia pre-transplant. In short- (n = 50) and long-term follow-up (n = 52) the muscle mass (- 2.65 cm²/m² 95% CI [- 4.52, - 0.77], p = 0.007; - 2.96 cm²/m² [- 4.7, - 1.23], p = 0.001, respectively), and muscle density (- 3 HU [- 6, - 1], p = 0.007; - 2 HU [- 4, 0], p = 0.069) decreased. Myosteatosis was associated with a higher post-transplant mortality (survival probability: 3 months 72% vs. 95%, 1 year 63% vs. 90%, 5 years 54% vs. 84%, p = 0.001), while muscle mass was not. In conclusion, muscle mass and quality did not improve after transplant. Muscle quality predicts short- and long-term survival and could help to identify a patient's risk profile.

Liver Transplant in Patients with Hepatocarcinoma: Imaging Guidelines and Future Perspectives Using Artificial Intelligence

Hepatocellular carcinoma is the most common primary malignant hepatic tumor and occurs most often in the setting of chronic liver disease. Liver transplantation is a curative treatment option and is an ideal solution because it solves the chronic underlying liver disorder while removing the malignant lesion. However, due to organ shortages, this treatment can only be applied to carefully selected patients according to clinical guidelines. Artificial intelligence is an emerging technology with multiple applications in medicine with a predilection for domains that work with medical imaging, like radiology. With the help of these technologies, laborious tasks can be automated, and new lesion imaging criteria can be developed based on pixel-level analysis. Our objectives are to review the developing AI applications that could be implemented to better stratify liver transplant candidates. The papers analysed applied AI for liver segmentation, evaluation of steatosis, sarcopenia assessment, lesion detection, segmentation, and characterization. A liver transplant is an optimal treatment for patients with hepatocellular carcinoma in the setting of chronic liver disease. Furthermore, AI could provide solutions for improving the management of liver transplant candidates to improve survival.

The interplay between sarcopenia and portal hypertension predicts ascites and mortality in cirrhosis

BACKGROUND

The role of sarcopenia in predicting decompensation other than hepatic encephalopathy is unclear. We aimed to evaluate the prognostic role of sarcopenia, assessed by computed tomography (CT), in the development of ascites and mortality in patients with advanced chronic liver disease (ACLD) outside the liver transplantation (LT) setting.

MATERIAL AND METHODS

We retrospectively evaluated ACLD patients with liver stiffness measurement (LSM) >10 kPa and an available CT scan within 6 months. Sarcopenia was defined as skeletal muscle index (SMI) <50 and <39 cm²/m², respectively, in men and women. Competing risk regression models were used to assess the variables associated with the main outcomes.

RESULTS

209 patients were included in the final analysis and sarcopenia was present in 134 (64.1%). During a median follow-up of 37 (20-63) months, 52 patients developed ascites, 24 underwent LT, and 30 died. Sarcopenia was found a predictive factor of decompensation with ascites (SHR 2.083, 95%-CI: 1.091-3.978), independently from the features of clinically significant portal hypertension (LSM≥21 kPa or portosystemic shunts). Sarcopenia (SHR: 2.744, 95%-CI: 1.105-6.816) and LSM≥21 kPa (SHR: 3.973, 95%-CI: 1.548-10.197) were independent risk factors for increased mortality.

CONCLUSIONS

Sarcopenia and portal hypertension are two major and independent risk factors for decompensation with ascites and mortality in cirrhotic patients outside the LT context.

Sarcopenia in cirrhosis: epidemiology, diagnosis, management and prognosis

PURPOSE OF REVIEW

With the development of many international guidelines, research on sarcopenia has increased rapidly, showing that sarcopenia is predictive of adverse outcomes, including increased mortality and impaired mobility, in patients with cirrhosis. The purpose of this article is to review the current evidence concerning the epidemiology, diagnosis, management and predictive value of sarcopenia on the prognosis of patients with cirrhosis.

RECENT FINDINGS

Sarcopenia is a frequent and lethal complication of cirrhosis. Currently, abdominal computed tomography imaging is the most commonly used method to diagnose sarcopenia. In clinical practice, assessing muscle strength and physical performance, such as by measuring handgrip strength and gait speed, is of increasing interest. In addition to the necessary pharmacological therapy, adequate intake of protein, energy and micronutrients, as well as regular moderate-intensity exercise, can help to minimize sarcopenia. Sarcopenia has been shown to be a strong predictor of prognosis in patients with severe liver disease.

SUMMARY

A global consensus is needed on the definition and operational parameters for the diagnosis of sarcopenia. Further research should focus on developing standardized screening, management and treatment protocols for sarcopenia. Adding sarcopenia to existing models may better exploit the effect of sarcopenia on prognosis in patients with cirrhosis, which should be investigated further.

CT analysis of thoracolumbar body composition for estimating whole-body composition

BACKGROUND

To evaluate the correlation between single- and multi-slice cross-sectional thoracolumbar and whole-body compositions.

METHODS

We retrospectively included patients who underwent whole-body PET-CT scans from January 2016 to December 2019 at multiple institutions. A priori-developed, deep learning-based commercially available 3D U-Net segmentation provided whole-body 3D reference volumes and 2D areas of muscle, visceral fat, and subcutaneous fat at the upper, middle, and lower endplate of the individual T1-L5 vertebrae. In the derivation set, we analyzed the Pearson correlation coefficients of single-slice and multi-slice averaged 2D areas (waist and T12-L1) with the reference values. We then built prediction models using the top three correlated levels and tested the models in the validation set.

RESULTS

The derivation and validation datasets included 203 (mean age 58.2 years; 101 men) and 239 patients (mean age 57.8 years; 80 men). The coefficients were distributed bimodally, with the first peak at T4 (coefficient, 0.78) and the second peak at L2-3 (coefficient 0.90). The top three correlations in the abdominal scan range were found for multi-slice waist averaging (0.92) and single-slice L3 and L2 (0.90, each), while those in the chest scan range were multi-slice T12-L1 averaging (0.89), single-slice L1 (0.89), and T12 (0.86). The model performance at the top three levels for estimating whole-body composition was similar in the derivation and validation datasets.

CONCLUSIONS

Single-slice L2-3 (abdominal CT range) and L1 (chest CT range) analysis best correlated with whole-body composition around 0.90 (coefficient). Multi-slice waist averaging provided a slightly higher correlation of 0.92.

Osteosarcopenia in NAFLD/MAFLD: An Underappreciated Clinical Problem in Chronic Liver Disease

Chronic liver disease (CLD), including non-alcoholic fatty liver disease (NAFLD) and its advanced form, non-alcoholic steatohepatitis (NASH), affects a significant portion of the population worldwide. NAFLD is characterised by fat accumulation in the liver, while NASH is associated with inflammation and liver damage. Osteosarcopenia, which combines muscle and bone mass loss, is an emerging clinical problem in chronic liver disease that is often underappreciated. The reductions in muscle and bone mass share several common pathophysiological pathways; insulin resistance and chronic systemic inflammation are the most crucial predisposing factors and are related to the presence and gravity of NAFLD and to the worsening of the outcome of liver disease. This article explores the relationship between osteosarcopenia and NAFLD/MAFLD, focusing on the diagnosis, prevention and treatment of this condition in patients with CLD.

Computed tomography body composition and clinical outcomes following lung transplantation in cystic fibrosis

BACKGROUND

Low muscle mass is common in patients approaching lung transplantation and may be linked to worse post-transplant outcomes. Existing studies assessing muscle mass and post-transplant outcomes include few patients with cystic fibrosis (CF).

METHODS

Between May 1993 and December 2018, 152 adults with CF received lung transplants at our institution. Of these, 83 met inclusion criteria and had usable computed tomography (CT) scans. Using Cox proportional hazards regression, we evaluated the association between pre-transplant thoracic skeletal muscle index (SMI) and our primary outcome of death after lung transplantation. Secondary outcomes, including days to post-transplant extubation and post-transplant hospital and intensive care unit (ICU) length of stay, were assessed using linear regression. We also examined associations between thoracic SMI and pre-transplant pulmonary function and 6-min walk distance.

RESULTS

Median thoracic SMI was 26.95 cm²/m² (IQR 23.97, 31.32) for men and 22.83 cm²/m² (IQR 21.27, 26.92) for women. There was no association between pre-transplant thoracic SMI and death after transplant (HR 1.03; 95% CI 0.95, 1.11), days to post-transplant extubation, or post-transplant hospital or ICU length of stay. There was an association between pre-transplant thoracic SMI and pre-transplant FEV1% predicted (b = 0.39; 95% CI 0.14, 0.63), with higher SMI associated with higher FEV1% predicted.

CONCLUSIONS

Skeletal muscle index was low for men and women. We did not identify a significant relationship between pre-transplant thoracic SMI and post-transplant outcomes. There was an association between thoracic SMI and pre-transplant pulmonary function, confirming the potential value of sarcopenia as a marker of disease severity.

Association between Abdominal CT Measurements of Body Composition before Deceased Donor Liver Transplant with Posttransplant Outcomes

Background Pre-liver transplant (LT) sarcopenia is associated with poor survival. Methods exist for measuring body composition with use of CT scans; however, it is unclear which components best predict post-LT outcomes. Purpose To quantify the association between abdominal CT-based body composition measurements and post-LT mortality in a large North American cohort. Materials and Methods This was a retrospective cohort of adult first-time deceased-donor LT recipients from 2009 to 2018 who underwent pre-LT abdominal CT scans, including at the L3 vertebral level, at Johns Hopkins Hospital. Measurements included sarcopenia (skeletal muscle index [SMI] <50 in men and <39 in women), sarcopenic obesity, myosteatosis (skeletal muscle CT attenuation <41 mean HU for body mass index [BMI] <25 and <33 mean HU for BMI ≥25), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and VAT/SAT ratio. Covariates in the adjusted models were selected with use of least absolute shrinkage and selection operator regression with lambda chosen by means of 10-fold cross-validation. Cox proportional hazards models were used to quantify associations with post-LT mortality. Model discrimination was quantified using the Harrell C-statistic. Results A total of 454 recipients (median age, 57 years [IQR, 50-62 years]; 294 men) were evaluated. In the adjusted model, pre-LT sarcopenia was associated with a higher hazard ratio (HR) of post-LT mortality (HR, 1.6 [95% CI: 1.1, 2.4]; C-statistic, 0.64; P = .02). SMI was significantly negatively associated with survival after adjustment for covariates. There was no evidence that myosteatosis was associated with mortality (HR, 1.3 [95% CI: 0.86, 2.1]; C-statistic, 0.64; P = .21). There was no evidence that BMI (HR, 1.2 [95% CI: 0.95, 1.4]), VAT (HR, 1.0 [95% CI: 0.98, 1.1]), SAT (HR, 1.0 [95% CI: 0.97, 1.0]), and VAT/SAT ratio (HR, 1.1 [95% CI: 0.90, 1.4]) were associated with mortality (P = .15-.77). Conclusions Sarcopenia, as assessed on routine pre-liver transplant (LT) abdominal CT scans, was the only factor significantly associated with post-LT mortality. © RSNA, 2022 See also the editorial by Ruehm in this issue.

Waitlist and posttransplantation outcomes of lean individuals with nonalcoholic fatty liver disease

Lean individuals with nonalcoholic fatty liver disease (NAFLD) represent a subset of patients with a distinct risk factor profile. We assessed the association between body mass index (BMI) on waitlist and postliver transplantation (LT) outcomes among these patients. We retrospectively analyzed the United Network for Organ Sharing data, including adult patients with NAFLD listed for LT between February 27, 2002, and June 30, 2020. We first used competing risk analyses to estimate the association of BMI with waitlist removal due to death or clinical deterioration. We then conducted Kaplan-Meier estimates and Cox regression models to determine the impact of weight change during the waiting list on all-cause mortality and graft failure after LT. Patients with normal weight (BMI 18.5-24.9 kg/m 2 ) suffered higher waitlist removal (adjusted subdistribution hazard ratio 1.26, 95% confidence interval [CI] 1.10-1.43; p = 0.001) compared with patients with obesity class I (BMI 30-34.9 kg/m 2 ). Those who remained at normal weight had higher all-cause mortality (adjusted hazard ratio [aHR] 1.61, 95% CI 1.32-1.96; p  <0.001) and graft failure (aHR 1.57, 95% CI 1.32-1.88; p  <0.001) than patients with stable obesity. Among patients with normal weight, those with the greatest weight increase (BMI gain ≥3 kg/m 2 ) had lower all-cause mortality (aHR 0.55, 95% CI 0.33-0.93; p = 0.03) and graft failure (aHR 0.49, 95% CI 0.30-0.81; p = 0.01) compared with patients with stable weight (BMI change ≤1 kg/m 2 ). Patients with NAFLD with normal weight have increased waitlist removal and those who remained at normal weight during the waitlist period have worse posttransplantation outcomes. Identifying and addressing factors influencing apparent healthy weight prior to LT are crucial to mitigate poor outcomes.

Elevated intramuscular adipose tissue content with a high Ishak fibrosis stage (>3) had a negative effect on liver regeneration in cirrhotic patients undergoing portal vein embolization

This study investigated the relationship between body composition parameters and changes in future liver remnant volume (FLRV) in hepatocellular carcinoma (HCC) patients undergoing portal vein embolization (PVE) in preparation for right hepatectomy. This retrospective study enrolled 21 patients between May 2013 and October 2020. Body composition parameters, including skeletal muscle attenuation (SMA), skeletal muscle mass index (SMI), intramuscular adipose tissue content (IMAC), and visceral-to-subcutaneous adipose tissue area ratio (VSR), were measured by computed tomography (CT) prior to PVE. Liver volumetry was measured before and at least 5 weeks after PVE. The mean interval between two CT volumetries was 9.1 ± 4.9 weeks, the mean value of increase in FLRV (ΔFLRV) was 236.0 ± 118.3 cm³ , the ratio of increased FLRV (ΔFLRV%) was 55.7 ± 29.4%, and the rate of increased FLRV was 31.0 ± 18.8 (cm³ /week). Subjects with high IMAC showed significantly lower (p = 0.044) ΔFLRV% than those with normal IMAC. Furthermore, ΔFLRV% was linearly reduced (p for trend = 0.043) among those with low Ishak fibrosis stage (<3) + normal IMAC (76.1 ± 36.8%), those with low Ishak fibrosis stage (<3) + high IMAC or high Ishak fibrosis stage (>3) + normal IMAC (54.0 ± 24.1%), and those with high Ishak fibrosis stage (>3) + low IMAC (28.7 ± 1.6%) (p for trend = 0.043). Our data indicated that high IMAC with a high Ishak fibrosis stage (>3) had a significant negative effect on ΔFLRV%.

Cirrhosis and Sarcopenia

Sarcopenia is a progressive muscle wasting syndrome involving loss in skeletal muscle mass, strength, and function. It is closely associated with cirrhosis and its complications with up to more than half of cirrhotic patients demonstrating imaging findings of sarcopenia. The pathogenesis of this syndrome remains complex, including multiple factors involved in skeletal muscle homeostasis, systemic inflammation, and energy dysregulation. Many modalities exist in assessing and measuring sarcopenia. The use of cross-sectional imaging, such as computed tomography and magnetic resonance imaging, with accurate and clinically proven assessment software should be considered the gold standard. Sarcopenia has become the focus of ongoing extensive research with initial findings highlighting increased mortality and complication rates in patient with cirrhosis and hepatocellular carcinoma. Additional studies have demonstrated reversal and improved survival in sarcopenic patients who have undergone transjugular intrahepatic portosystemic shunt placement. Thus, accounting for sarcopenia can help risk stratify patients prior to interventional procedures to allow for better outcomes and improved survival.

The effect of computed tomography parameters on sarcopenia and myosteatosis assessment: a scoping review

Computed tomography (CT) is a valuable assessment method for muscle pathologies such as sarcopenia, cachexia, and myosteatosis. However, several key underappreciated scan imaging parameters need consideration for both research and clinical use, specifically CT kilovoltage and the use of contrast material. We conducted a scoping review to assess these effects on CT muscle measures. We reviewed articles from PubMed, Scopus, and Web of Science from 1970 to 2020 on the effect of intravenous contrast material and variation in CT kilovoltage on muscle mass and density. We identified 971 articles on contrast and 277 articles on kilovoltage. The number of articles that met inclusion criteria for contrast and kilovoltage was 11 and 7, respectively. Ten studies evaluated the effect of contrast on muscle density of which nine found that contrast significantly increases CT muscle density (arterial phase 6-23% increase, venous phase 19-57% increase, and delayed phase 23-43% increase). Seven out of 10 studies evaluating the effect of contrast on muscle area found significant increases in area due to contrast (≤2.58%). Six studies evaluating kilovoltage on muscle density found that lower kilovoltage resulted in a higher muscle density (14-40% increase). One study reported a significant decrease in muscle area when reducing kilovoltage (2.9%). The use of contrast and kilovoltage variations can have dramatic effects on skeletal muscle analysis and should be considered and reported in CT muscle analysis research. These significant factors in CT skeletal muscle analysis can alter clinical and research outcomes and are therefore a barrier to clinical application unless better appreciated.