Kidney allocation to liver transplant candidates with renal failure of undetermined etiology: role of percutaneous renal biopsy

Improved outcomes of kidney after liver transplantation after the implementation of the safety net policy

The number of kidney after liver transplants (KALT) increased after the implementation of the United Network of Organ Sharing (UNOS) safety net policy, but the effects of the policy on KALT outcomes remain unknown. Using the UNOS database, we identified KALT between 60 and 365 days from liver transplant from January 1, 2010, to December 31, 2020. The main outcome was 1- and 3-year patient, liver, and kidney graft survival. Secondary outcomes included 6-month and 1-year acute rejection (AR) of liver and kidney, and 1-year kidney allograft function. Of the 256 KALT, 90 were pre-policy and 166 post-policy. Compared to pre-policy, post-policy 1- and 3-year liver graft survival was higher (54% and 54% vs. 86% and 81%, respectively, p <0.001), while 1- and 3-year kidney graft survival (99% and 75% vs. 92% and 79%, respectively, p =0.19), and 1- and 3-year patient survival (99% and 99% vs. 95% and 89%, respectively, p =0.11) were not significantly different. Subgroup analysis revealed similar trends in patients with and without renal failure at liver transplant. Liver AR at 6 months was lower post-policy (6.3% vs. 18.3%, p =0.006) but was similar (10.5% vs. 13%, p =0.63) at 1 year. Kidney AR was unchanged post-policy at 6 months and 1 year. Creatinine at 1 year did not differ post-policy versus pre-policy (1.4 vs. 1.3 mg/dL, p =0.07) despite a higher proportion of deceased donors, higher Kidney Donor Profile Index, and longer kidney cold ischemia time post-policy ( p <0.05 for all). This 3-year follow-up after the 2017 UNOS policy revision demonstrated that the safety net implementation has resulted in improved liver outcomes for patients who underwent KALT with no increased AR of the liver or the kidney allografts.

Applying Metabolomics and Aptamer-based Proteomics to Determine Pathophysiologic Differences in Decompensated Cirrhosis Patients Hospitalized with Acute Kidney Injury

A case-control study of 97 patients hospitalized at our institution. We performed aptamer-based proteomics and metabolomics on serum biospecimens obtained within 72 hours of admission. We compared the proteome and metabolome by the AKI phenotype (i.e., HRS-AKI, ATN) and by AKI recovery (decrease in sCr within 0.3 mg/dL of baseline) using ANCOVA analyses adjusting for demographics and clinical characteristics. We completed Random Forest (RF) analyses to identify metabolites and proteins associated with AKI phenotype and recovery. Lasso regression models were developed to highlight metabolites and proteins could improve diagnostic accuracy. Results: ANCOVA analyses showed no metabolomic or proteomic differences by AKI phenotype while identifying differences by AKI recovery status. Our RF and Lasso analyses showed that metabolomics can improve the diagnostic accuracy of both AKI diagnosis and recovery, and aptamer-based proteomics can enhance the diagnostic accuracy of AKI recovery. Discussion: Our analyses provide novel insight into pathophysiologic pathways, highlighting the metabolomic and proteomic similarities between patients with cirrhosis with HRS-AKI and ATN while also identifying differences between those with and without AKI recovery.

Hepatorenal Syndrome-Acute Kidney Injury in Liver Transplantation

Hepatorenal syndrome (HRS) is a serious complication of cirrhosis. HRS nomenclature has recently changed to HRS-AKI (acute kidney injury). HRS is a complex response to chronic vasodilatory changes brought about by portal hypertension and exacerbated by inflammatory responses that portends poor prognosis to patients with cirrhosis. This syndrome is commonly seen in the setting of infections, particularly spontaneous bacterial peritonitis. Because of the frequency of renal injury in the patient with cirrhosis, HRS-AKI has to be considered high in the differential diagnosis of AKI. Discontinuation of potential triggering agents and elimination of pre-renal AKI, intrinsic renal disease, and structural uropathy as causes of injury are imperative on presentation. Volume expansion with albumin and vasoconstrictive drugs to counteract the underlying splanchnic vasodilation constitutes the most effective medical modality to manage this process. Although the most effective therapy is generally considered to be liver transplantation (LT), the logistic barriers of offering this life-saving therapy on time to all needing it is a major limitation. Terlipressin has been shown to reverse HRS-AKI in a significant proportion of those treated and consequently can lead to increased LT patient survival and freedom from renal replacement therapy. We will review the impact of HRS on the management of patients awaiting LT, present strategies to prevent this significant complication, and discuss major implications of recent therapeutic advances in the setting of LT.

The Renal Histological Correlates of Refractory Renal Dysfunction After Liver Transplantation

Background

Kidney dysfunction is common after liver transplantation (LT) and is often attributed to calcineurin inhibitors (CNIs). Very few studies have looked at histological causes.

Material and methods

The study is a retrospective analysis of histological findings and diagnosis in all patients who underwent a kidney biopsy after LT from 2010 to 2020. Data are shown as mean ± standard deviation or medians (25-75 interquartile range).

Results

The study cohort consisted of 26 patients (25 males, 1 female), aged 55 ± 7 years at the time of the kidney biopsy. Kidney biopsies were done at 27.5 (6.7-60.7) months after LT. At the time of the kidney biopsy, the median serum creatinine was 2.10 (1.50-2.86) mg/dl and proteinuria was 3.8 (1.8-5.9) gm/day. Twenty-four (92%) patients were on CNIs. The diagnoses on kidney biopsies were diabetic nephropathy (n = 7), focal segmental glomerulosclerosis (n = 4), CNI nephrotoxicity (n = 3), IgA nephropathy (n = 4), chronic glomerulonephritis (n = 3), hypertensive nephropathy (n = 1), membranous glomerulonephritis (n = 1), acute on chronic interstitial nephritis (n = 1), and C1q nephropathy (n = 1), and the sample was inadequate in one patient. A total of sixteen patients had progression of kidney disease. The kidney function remained stable/improved in 6 (23%) patients, follow-up data were not available for 4 patients. Fourteen (53.8%) patients (including one with CNI nephrotoxicity) required hemodialysis at 13.5 (5.7-29) months after the kidney biopsy.

Conclusion

Although the kidney biopsy diagnosed the cause of unexplained renal insufficiency in LT recipients, the majority of patients progressed to end-stage renal disease despite treatment modifications. The use of CNIs was an uncommon cause of renal impairment.

Essentials of Liver Transplantation in the Setting of Acute Kidney Injury and Chronic Kidney Disease

Kidney dysfunction is common among liver transplant candidates with decompensated cirrhosis and has a major impact on pre- and post-liver transplant survival. Updated definitions of acute kidney injury and criteria for the diagnosis of hepatorenal syndrome allow for early recognition and intervention, including early initiation of vasoconstrictor therapy for hepatorenal syndrome. The rise of the metabolic syndrome and nonalcoholic fatty liver disease as a cause of cirrhosis has coincided with an increase in intrinsic chronic kidney disease recognized in transplant candidates and recipients. Ultimately, the ability to accurately assess kidney function and associated risk is essential to decision-making in the context of transplantation, including selection of candidates for simultaneous liver and kidney transplantation.

Kidney Allocation Issues in Liver Transplantation Candidates with Chronic Kidney Disease and Severe Kidney Liver Injury

The number of liver transplant candidates with concomitant renal disease has been steadily rising since the implementation of MELD-based allocation in 2002. Consequently, the number of simultaneous liver-kidney (SLK) transplants being performed each year has also increased. However, the establishment of well-defined criteria for when to choose SLK over liver transplant alone has lagged behind. The lack of clear guidelines has worsened an already large shortage of transplantable kidneys. This article further explores the rationale for and outlines the implementation of the SLK allocation policy.

Hepatorenal Syndrome Type 1: From Diagnosis Ascertainment to Goal-Oriented Pharmacologic Therapy

Hepatorenal syndrome type 1 (HRS-1) is a serious form of AKI that affects individuals with advanced cirrhosis with ascites. Prompt and accurate diagnosis is essential for effective implementation of therapeutic measures that can favorably alter its clinical course. Despite decades of investigation, HRS-1 continues to be primarily a diagnosis of exclusion. Although the diagnostic criteria dictated by the International Club of Ascites provide a useful framework to approach the diagnosis of HRS-1, they do not fully reflect the complexity of clinical scenarios that is often encountered in patients with cirrhosis and AKI. Thus, diagnostic uncertainty is often faced. In particular, the distinction between HRS-1 and acute tubular injury is challenging with the currently available clinical tools. Because treatment of HRS-1 differs from that of acute tubular injury, distinguishing these two causes of AKI has direct implications in management. Therefore, the use of the International Club of Ascites criteria should be enhanced with a more individualized approach and attention to the other phenotypic aspects of HRS-1 and other types of AKI. Liver transplantation is the most effective treatment for HRS-1, but it is only available to a small fraction of the affected patients worldwide. Thus, pharmacologic therapy is necessary. Vasoconstrictors aimed to increase mean arterial pressure constitute the most effective approach. Administration of intravenous albumin is an established co-adjuvant therapy. However, the risk for fluid overload in patients with cirrhosis with AKI is not negligible, and interventions intended to expand or remove volume should be tailored to the specific needs of the patient. Norepinephrine and terlipressin are the most effective vasoconstrictors, and their use should be determined by availability, ease of administration, and attention to optimal risk-benefit balance for each clinical scenario.

Current knowledge about biomarkers of acute kidney injury in liver cirrhosis

Acute kidney injury (AKI) is common in advanced cirrhosis. Prerenal azotemia, hepatorenal syndrome, and acute tubular necrosis are the main causes of AKI in patients with cirrhosis. Evaluation of renal function and differentiation between functional and structural kidney injury are important issues in the management of cirrhosis. However, AKI in cirrhosis exists as a complex clinical spectrum rather than concrete clinical entity. Based on current evidence, changes in serum creatinine (Cr) levels remain the most appropriate standard for defining AKI in cirrhosis. However, serum Cr has a limited role in assessing renal function in this population. This review examines previous studies that investigated the ability of recent biomarkers for AKI in cirrhosis from the perspective of earlier and accurate diagnosis, classification of AKI phenotype, and prediction of clinical outcomes. Serum cystatin C and urine neutrophil gelatinase-associated lipocalin have been extensively studied in cirrhosis, and have facilitated improved diagnosis and prognosis prediction in patients with AKI. In addition, urine N-acetyl-β-D-glucosaminidase, interleukin 18, and kidney injury molecule 1 are other promising biomarkers for advanced cirrhosis. However, the clinical significance of these markers remains unclear because there are no cut-off values defining the normal range and differentiating phenotypes of AKI. In addition, AKI has been defined in terms of serum Cr, and renal biopsy-the gold standard-has not been carried out in most studies. Further discovery of innovate biomarkers and incorporation of various markers could improve the diagnosis and prognosis prediction of AKI, and will translate into meaningful improvements in patient outcomes.

KDOQI US Commentary on the 2020 KDIGO Clinical Practice Guideline on the Evaluation and Management of Candidates for Kidney Transplantation

Evaluation of patients for kidney transplant candidacy is a comprehensive process that involves a detailed assessment of medical and surgical issues, psychosocial factors, and patients' physical and cognitive abilities with an aim of balancing the benefits of transplantation and potential risks of surgery and long-term immunosuppression. There is considerable variability among transplant centers in their approach to evaluation and decision-making regarding transplant candidacy. The 2020 KDIGO (Kidney Disease: Improving Guidelines Outcome) clinical practice guideline on the evaluation and management of candidates for kidney transplantation provides practice recommendations that can serve as a useful reference guide to transplant professionals. The guideline, covering a broad range of topics, was developed by an international group of experts from transplant and nephrology through a review of literature published until May 2019. A work group of US transplant nephrologists convened by NKF-KDOQI (National Kidney Foundation-Kidney Disease Quality Initiative) chose key topics for this commentary with a goal of presenting a broad discussion to the US transplant community. Each section of this article has a summary of the key KDIGO guideline recommendations, followed by a brief commentary on the recommendations, their clinical utility, and potential implementation challenges. The KDOQI work group agrees broadly with the KDIGO recommendations but also recognizes and highlights the decision-making challenges that arise from lack of high-quality evidence and the need to balance equity with utility of organ transplantation.

Clinical Relevance of Kidney Biopsy in Patients Qualified for Liver Transplantation and After This Procedure in the Model for End-stage Liver Disease (MELD) Era: Where Are We Today?

Chronic kidney disease (CKD) has been recognized as an increasingly common complication of liver transplantation (OLTx). Post-transplant renal dysfunction contributes to long-term morbidity and mortality following OLTx and is a very important issue in the management of liver transplant recipients. Its etiology is multifactorial and can be determined by kidney biopsy, which is too rarely done in this patient group. In the clinical context of patients with liver cirrhosis, accurate and reliable evaluation of the renal injury is crucial. We performed a review of kidney biopsies in patients with symptoms of CKD (proteinuria/hematuria/elevated creatinine) before and after liver transplantation in the published literature. Kidney biopsies were performed either before or after liver transplantation using percutaneous technique. There are few reports on transjugular kidney biopsy. Biopsy results prevented unnecessary modification of immunosuppressive therapy or selection of candidates for liver transplantation. In our opinion, kidney biopsy is a clinically relevant diagnostic approach to recognize kidney disease before and after liver transplantation, it also helps with the management of kidney disease in this population, and it is safe. Kidney biopsy should be offered more often in liver transplant patients to ensure appropriate therapy in concomitant CKD in this population. Our decisions today will impact clinical outcomes in the future.

Renal disease in the allograft recipient

Chronic renal failure after liver transplantation (LT) is significantly more frequent than after lung or heart transplantation and it results in an increased short and long-term mortality. Renal impairment may occur before LT (functional or due to preexisting parenchymal kidney disease), in the peri-operative period or later after LT. The number of patients with renal failure after LT has increased due to the liver allocation based on MELD and to the more liberal use of higher risk grafts. Calcineurin inhibitor (CNI) nephrotoxicity is the most important cause of renal dysfunction but is a modifiable factor. Strategy to prevent CNI-associated nephrotoxicity is post-op CNI minimization by induction therapy and reduced dose and/or delayed introduction of CNI in combination with mycophenolate mofetil (MMF) or everolimus with no penalty in term of rejection. With everolimus, usually started one month after LT, a drastic minimization of CNI is possible and this results in superior kidney function until at least 3 years follow up. At the moment of renal impairment a drastic reduction of CNI dose together with the introduction of MMF results in an improvement in GFR at 6 to 2 years with a low rate of acute rejection. However, secondary prevention fails to normalize renal function in most of the patients once e GFR <60 ml/min/1.73m²ml.

Arterial Blood Pressure at Liver Transplant Evaluation Predicts Renal Histology in Candidates With Renal Dysfunction

Renal dysfunction is common in liver transplantation (LT) candidates, but differentiating between reversible and irreversible renal injury can be difficult. Kidney biopsy might be helpful in differentiating reversible from irreversible renal injury, but it is associated with significant complications. We aimed to identify pre-LT predictors of potentially reversible renal injury using histological information obtained on pre-LT renal biopsy. Data on 128 LT candidates who underwent pre-LT kidney biopsy were retrospectively collected and correlated with renal histological findings. Indications for kidney biopsy were iothalamate glomerular filtration rate (iGFR) ≤40 mL/minute, proteinuria >500 mg/day, and/or hematuria. According to the biopsy diagnosis, patients were grouped into the following categories: normal (n = 13); acute tubular necrosis (ATN; n = 25); membranoproliferative glomerulonephritis (n = 19); minimal histological changes (n = 24); and advanced interstitial fibrosis (IF) and glomerulosclerosis (GS) (n = 47). Compared with patients having advanced IF/GS, patients with normal biopsies and those with ATN had lower systolic blood pressure (SBP) and diastolic blood pressure (DBP) and higher international normalized ratio and total bilirubin levels (<0.05 for all). Both SBP and DBP directly correlated with the degree of IF and GS (R = 0.3, P ≤ 0.02 for all). SBP ≤90 mm Hg was 100% sensitive and 98% specific in correlating with normal biopsies or ATN, whereas SBP ≥140 mm Hg was 22% sensitive and 90% specific in correlating with advanced IF/GS. Model for End-Stage Liver Disease score, serum creatinine, iGFR, urinary sodium excretion, and renal size did not correlate with biopsy diagnosis or degree of IF or GS. In conclusion, SBP at the time of LT evaluation correlates with renal histology, and it should be included along with other clinical and laboratory markers in the decision-making process to list patients with renal dysfunction for LT alone versus simultaneous liver-kidney transplantation.

Reappraising the spectrum of AKI and hepatorenal syndrome in patients with cirrhosis

The occurrence of acute kidney injury (AKI) in patients with end-stage liver disease constitutes one of the most challenging clinical scenarios in in-hospital and critical care medicine. Hepatorenal syndrome type 1 (HRS-1), which is a specific type of AKI that occurs in the context of advanced cirrhosis and portal hypertension, is associated with particularly high mortality. The pathogenesis of HRS-1 is largely viewed as a functional derangement that ultimately affects renal vasculature tone. However, new insights suggest that non-haemodynamic tubulo-toxic factors, such as endotoxins and bile acids, might mediate parenchymal renal injury in patients with cirrhosis, suggesting that concurrent mechanisms, including those traditionally associated with HRS-1 and non-traditional factors, might contribute to the development of AKI in patients with cirrhosis. Moreover, histological evidence of morphological abnormalities in the kidneys of patients with cirrhosis and renal dysfunction has prompted the functional nature of HRS-1 to be re-examined. From a clinical perspective, a diagnosis of HRS-1 guides utilization of vasoconstrictive therapy and decisions regarding renal replacement therapy. Patients with cirrhosis are at risk of AKI owing to a wide range of factors. However, the tools currently available to ascertain the diagnosis of HRS-1 and guide therapy are suboptimal. Short of liver transplantation, goal-directed haemodynamically targeted pharmacotherapy remains the cornerstone of treatment for this condition; improved understanding of the underlying pathogenic mechanisms might lead to better clinical outcomes. Here, we examine our current understanding of the pathophysiology of HRS-1 and existing challenges in its diagnosis and treatment.

News in pathophysiology, definition and classification of hepatorenal syndrome: A step beyond the International Club of Ascites (ICA) consensus document

Renal dysfunction is a common, life-threatening complication occurring in patients with liver disease. Hepatorenal syndrome (HRS) has been defined as a purely "functional" type of renal failure that often occurs in patients with cirrhosis in the setting of marked abnormalities in arterial circulation, as well as overactivity of the endogenous vasoactive systems.^4,5 In 2007, the International Club of Ascites (ICA) classified HRS into types 1 and 2 (HRS-1 and HRS-2).⁵ HRS-1 is characterised by a rapid deterioration of renal function that often occurs because of a precipitating event, while HRS-2 is a moderate and stable or slowly progressive renal dysfunction that often occurs without an obvious precipitant. Clinically, HRS-1 is characterised by acute renal failure while HRS-2 is mainly characterised by refractory ascites. Nevertheless, after these two entities were first described, new concepts, definitions, and diagnostic criteria have been developed by nephrologists for renal dysfunction in the general population and hospitalised patients. In particular, the definitions and characterisation of acute kidney injury (AKI), acute kidney disease and chronic kidney disease have been introduced/refined.⁶ Accordingly, a debate among hepatologists of the ICA led to a complete revision of the nomenclature and diagnosistic criteria for HRS-1, which was renamed HRS-AKI.⁷ Additionally, over recent years, greater granularity has been gained regarding the pathogenesis of HRS; it is now increasingly recognised that it is not a purely "functional" entity with haemodynamic derangements, but that systemic inflammation, oxidative stress and bile salt-related tubular damage may contribute significantly to its development. That is, HRS has an additional structural component that would not only make traditional diagnostic criteria less reliable, but would explain the lack of response to pharmacological treatment with vasoconstrictors plus albumin that correlates with a progressive increase in inflammation. Because classification, nomenclature, diagnostic criteria and pathogenic theories have evolved over the years since the traditional classification of HRS-1 and HRS-2 was first described, it was considered that all these novel aspects be reviewed and summarised in a position paper. The aim of this position paper authored by two hepatologists (members of ICA) and two nephrologists involved in the study of renal dysfunction in cirrhosis, is to complete the re-classification of HRS initiated by the ICA in 2012 and to provide an update on the definition, classification, diagnosis, pathophysiology and treatment of HRS.

Kidney-liver pathophysiological crosstalk: its characteristics and importance

The kidney plays a crucial role in controlling the blood volume and pressure, electrolyte and acid-base balance, erythropoietin secretion, as well as renin-angiotensin-aldosterone system activity. All these renal activities have important repercussion in the organism, explaining why morbidity and mortality rates are high in patients with significant renal dysfunction. In this sense, there are renal-induced liver damages in acute kidney injury, as well as liver-induced renal damages in hepatic disease. Ischemia, reperfusion, cytokine outflow, pro-inflammatory cascades, metabolic acidosis, oxidative stress, and changes in enzymatic and metabolic pathways provide the bases for this bidirectional kidney-liver damage. In conclusion, knowing the characteristics of this kidney-liver crosstalk is crucial for handling the complications induced by this vicious circle.

Perioperative Management of the Liver Transplant Recipient

Perioperative management of the liver transplant recipient is a team effort that requires close collaboration between intensivist, surgeon, anesthesiologist, hepatologist, nephrologist, other specialists, and hospital staff before and after surgery. Transplant viability must be reassessed regularly and particularly with each donor organ. Regular discussions with patient and family facilitate realistic determinations of goals based on patient aspirations and clinical realities. Early attention to hemodynamics with optimal resuscitation and judicious vasopressor support, respiratory care designed to minimize iatrogenic injury, and early renal support is key. Preoperative and postoperative nutritional support and physical rehabilitation should remain a focus.

Fractional excretion of urea: A simple tool for the differential diagnosis of acute kidney injury in cirrhosis

Current approaches to determine the cause of acute kidney injury (AKI) in patients with cirrhosis are suboptimal. The aim of this study was to determine the utility of fractional excretion of urea (FEUrea) for the differential diagnosis of AKI in patients with cirrhosis. A retrospective analysis was performed in patients (n = 50) with cirrhosis and ascites admitted with AKI. Using adjudicated etiology assessment as the reference standard, receiver operating curves and optimal cutoff, sensitivity (Sn), and specificity (Sp) for the diagnosis of prerenal azotemia (PRA), type 1 hepatorenal syndrome (HRS), and acute tubular necrosis (ATN) were derived. Validation was performed in an independent cohort (n = 50) and by bootstrap analysis. The causes of AKI (derivation:validation cohorts) were: PRA 21:21, HRS 18:15, and ATN 11:14. Median FEUrea was statistically different across all etiologies of AKI in the derivation cohort (PRA 30.1 vs. HRS 20.2 vs. ATN 43.6; P < 0.001) and validation cohort (PRA 23.1 vs. HRS 13.3 vs. ATN 44.7; P < 0.001). The area underneath the curve (cutoff, Sn/Sp) for FEUrea was 0.96 (33.4, 85/100) for ATN versus non-ATN, 0.87 (28.7, 75/83) for HRS versus non-HRS, and 0.81 (21.6, 90/61) for PRA versus HRS. When applied to the validation cohort, Sn/Sp were maintained for ATN versus non-ATN (93/97), HRS versus non-HRS (100/63), and for PRA versus HRS (67/80). After bootstrapping, Sn/Sp for FEUrea in the ATN versus non-ATN, HRS versus non-HRS, and PRA versus HRS was 88/96, 63/97, and 55/87, respectively.

CONCLUSION

FEUrea is a promising tool for the differential diagnosis of AKI in patients with cirrhosis. (Hepatology 2018;68:224-233).

Perioperative Care of the Liver Transplant Patient

With the evolution of surgical and anesthetic techniques, liver transplantation has become "routine," allowing for modifications of practice to decrease perioperative complications and costs. There is debate over the necessity for intensive care unit admission for patients with satisfactory preoperative status and a smooth intraoperative course. Postoperative care is made easier when the liver graft performs optimally. Assessment of graft function, vigilance for complications after the major surgical insult, and optimization of multiple systems affected by liver disease are essential aspects of postoperative care. The intensivist plays a vital role in an integrated multidisciplinary transplant team.

Kidney Injury in Liver Disease

Acute kidney injury (AKI) occurs frequently in patients with liver disease and increases morbidity and mortality. Hepatorenal syndrome is a common cause of AKI in patients with decompensated cirrhosis and is due to alterations in systemic and renal hemodynamics. Serum creatinine-based estimation of kidney function is a key component of the Model for End-stage Liver Disease score in liver transplant candidates. Continuous renal replacement therapy is used in critically ill patients with liver failure and AKI. Simultaneous liver-kidney transplantation (SLK) may be required in patients with liver failure and prolonged AKI. Identification of appropriate candidates for SLK remains controversial.

Fractional excretion of sodium in hepatorenal syndrome: Clinical and pathological correlation

AIM

To determine the accuracy of fractional excretion of sodium (FeNa) in the diagnosis of hepatorenal syndrome (HRS).

METHODS

Eighty-eight liver transplantation candidates with renal dysfunction and/or proteinuria were included in the study sample. The baseline characteristics of the patients were obtained. All the 88 patients underwent iothalamate glomerular filtration rate testing, 24-h urine collection for urinary sodium and protein excretions, random urine for sodium and creatinine testing, and percutaneous kidney biopsy. FeNa was calculated using the equation [(urine sodium × serum creatinine)/(serum sodium × urine creatinine)] × 100%. Diuretic use was recorded among the participants. Patients on renal replacement therapy were not included in the original sample.

RESULTS

Seventy-seven (87%) of the 88 patients had FeNa < 1%. FeNa < 1% was present in 10/10, 10/12, 11/13, 12/15 and 34/38 in patients with HRS, acute tubular necrosis, membranoproliferative glomerulonephritis, minimal histological findings (≤ 30%) and advanced (≥ 30%-40%) interstitial fibrosis and/or glomerulosclerosis, respectively (P = 0.4). FeNa < 1% was 100% sensitive and 14% specific in diagnosing HRS. Receiver operating characteristic curve confirmed the poor accuracy of FeNa < 1% in diagnosing HRS (area under the curve = 0.58, P = 0.47). Calculated positive predictive value and negative predictive value for FeNa < 1% in HRS diagnosis were 46% and 100%, respectively. When used as a continuous variable, FeNa did not correlate with kidney biopsy findings (P = 0.41).

CONCLUSION

FeNa < 1% was common in cirrhotic patients with renal dysfunction and it did not differentiate between HRS and other causes of renal pathologies. HRS diagnosis should be avoided in patients with FeNa > 1%.

Kidney biomarkers in cirrhosis

Impaired renal function due to acute kidney injury (AKI) and/or chronic kidney diseases (CKD) is frequent in cirrhosis. Recurrent episodes of AKI may occur in end-stage cirrhosis. Differential diagnosis between functional (prerenal and hepatorenal syndrome) and acute tubular necrosis (ATN) is crucial. The concept that AKI and CKD represent a continuum rather than distinct entities, is now emerging. Not all patients with AKI have a potential for full recovery. Precise evaluation of kidney function and identification of kidney changes in patients with cirrhosis is central in predicting reversibility. This review examines current biomarkers for assessing renal function and identifying the cause and mechanisms of impaired renal function. When CKD is suspected, clearance of exogenous markers is the reference to assess glomerular filtration rate, as creatinine is inaccurate and cystatin C needs further evaluation. Recent biomarkers may help differentiate ATN from hepatorenal syndrome. Neutrophil gelatinase-associated lipocalin has been the most extensively studied biomarker yet, however, there are no clear-cut values that differentiate each of these conditions. Studies comparing ATN and hepatorenal syndrome in cirrhosis, do not include a gold standard. Combinations of innovative biomarkers are attractive to identify patients justifying simultaneous liver and kidney transplantation. Accurate biomarkers of underlying CKD are lacking and kidney biopsy is often contraindicated in this population. Urinary microRNAs are attractive although not definitely validated. Efforts should be made to develop biomarkers of kidney fibrosis, a common and irreversible feature of CKD, whatever the cause. Biomarkers of maladaptative repair leading to irreversible changes and CKD after AKI are also promising.

Renal Function and Transplantation in Liver Disease

Kidney injury is associated with increased morbidity and mortality in liver transplant recipients. Since the introduction of the model for end-stage liver disease for the allocation of organs for liver transplantation in 2002, the heavy weighting of serum creatinine in the model for end-stage liver disease score has significantly increased the incidence of renal dysfunction seen among patients undergoing liver transplantation. As a result, the frequency of simultaneous liver-kidney (SLK) transplantation compared to liver transplantation alone (LTA) has also increased. The decision to perform SLK rather than LTA is an important one because the benefits to the liver transplant recipient receiving a kidney transplant must be balanced with the benefits of using that organ for a patient with end-stage renal disease. However, predicting whether or not a patient with liver failure has reversible kidney disease, and therefore does not also need a kidney transplant, is difficult. The severity and duration of pretransplant renal dysfunction, hepatitis c, diabetes, and other risk factors for kidney disease are associated with an increased risk of posttransplant end-stage renal disease. However, there are currently no clinical findings that accurately predict renal recovery post liver transplant. As a result, the rate of SLK versus LTA differs significantly between transplant centers. To increase consistency across centers, multiple guidelines have been proposed to guide the decision between SLK and LTA, but their poor predictive value has limited their uniform adoption. Nevertheless, adoption of uniform rules for the allocation of kidneys would reduce the variability between centers in rates of SLK transplant.

Acute Kidney Injury in Patients with Cirrhosis

Acute kidney injury (AKI) occurs commonly in patients with advanced cirrhosis and negatively impacts pre- and post-transplant outcomes. Physiologic changes that occur in patients with decompensated cirrhosis with ascites, place these patients at high risk of AKI. The most common causes of AKI in cirrhosis include prerenal injury, acute tubular necrosis (ATN), and the hepatorenal syndrome (HRS), accounting for more than 80% of AKI in this population. Distinguishing between these causes is particularly important for prognostication and treatment. Treatment of Type 1 HRS with vasoconstrictors and albumin improves short term survival and renal function in some patients while awaiting liver transplantation. Patients with HRS who fail to respond to medical therapy or those with severe renal failure of other etiology may require renal replacement therapy. Simultaneous liver kidney transplant (SLK) is needed in many of these patients to improve their post-transplant outcomes. However, the criteria to select patients who would benefit from SLK transplantation are based on consensus and lack strong evidence to support them. In this regard, novel serum and/or urinary biomarkers such as neutrophil gelatinase-associated lipocalin, interleukins-6 and 18, kidney injury molecule-1, fatty acid binding protein, and endothelin-1 are emerging with a potential for accurately differentiating common causes of AKI. Prospective studies are needed on the use of these biomarkers to predict accurately renal function recovery after liver transplantation alone in order to optimize personalized use of SLK.

Outcomes of liver transplantation alone after listing for simultaneous kidney: comparison to simultaneous liver kidney transplantation

BACKGROUND

Data on patient and liver graft survival comparing liver transplantation alone after listing for kidney with simultaneous liver kidney (SLK) transplantation are scanty.

METHODS

United Network Organ Sharing network database (1994-2011) queried for liver transplantation alone after being listed for kidney and SLK transplants.

RESULTS

Of 65,206 first liver transplants, 3549 were listed for simultaneous kidney. Of these, 422 (12%) received only liver (LIST) and differed from SLK recipients for the white race (64% vs. 57%; 0.005), diabetes (27% vs. 37%; P = 0.02), model for end-stage liver disease era (68% vs. 82%; P = 0.0001), serum creatinine (2.9±1.9 vs. 4.3±2.5; P < 0.0001), dialysis (35% vs. 64%; P < 0.0001), and donor risk index (1.6±0.4 vs. 1.5±0.3; P < 0.0001). Overall survival was poorer in the LIST group (55% vs. 76%; P < 0.0001). A higher proportion of patients died within 2 days of transplantation in LIST group (11% vs. 0.5%; P < 0.0001), mostly from cardiovascular causes. After excluding these patients, odds of patient mortality and liver graft loss were about 1.2-fold and twofold higher in the LIST group. A total of 103 (24%) patients needed a renal transplantation in the LIST group with 16 (4%) receiving kidney within first year after transplantation. After excluding patients receiving kidney within first year, about 33% recovered renal function to above estimated GFR of greater than 60 mL per min.

CONCLUSION

Guidelines are needed for patient selection to list for and receipt of simultaneous liver kidney transplantation.

Kidney biomarkers and differential diagnosis of patients with cirrhosis and acute kidney injury

Acute kidney injury (AKI) is common in patients with cirrhosis and associated with significant mortality. The most common etiologies of AKI in this setting are prerenal azotemia (PRA), acute tubular necrosis (ATN), and hepatorenal syndrome (HRS). Accurately distinguishing the etiology of AKI is critical, as treatments differ markedly. However, establishing an accurate differential diagnosis is extremely challenging. Urinary biomarkers of kidney injury distinguish structural from functional causes of AKI and may facilitate more accurate and rapid diagnoses. We conducted a multicenter, prospective cohort study of patients with cirrhosis and AKI assessing multiple biomarkers for differential diagnosis of clinically adjudicated AKI. Patients (n = 36) whose creatinine returned to within 25% of their baseline within 48 hours were diagnosed with PRA. In addition, 76 patients with progressive AKI were diagnosed by way of blinded retrospective adjudication. Of these progressors, 39 (53%) patients were diagnosed with ATN, 19 (26%) with PRA, and 16 (22%) with HRS. Median values for neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), kidney injury molecule-1 (KIM-1), liver-type fatty acid binding protein (L-FABP), and albumin differed between etiologies and were significantly higher in patients adjudicated with ATN. The fractional excretion of sodium (FENa) was lowest in patients with HRS, 0.10%, but did not differ between those with PRA, 0.27%, or ATN, 0.31%, P = 0.54. The likelihood of being diagnosed with ATN increased step-wise with the number of biomarkers above optimal diagnostic cutoffs.

CONCLUSION

Urinary biomarkers of kidney injury are elevated in patients with cirrhosis and AKI due to ATN. Incorporating biomarkers into clinical decision making has the potential to more accurately guide treatment by establishing which patients have structural injury underlying their AKI. Further research is required to document biomarkers specific to HRS.

First successful case of simultaneous liver and kidney transplantation for patients with chronic liver and renal failure in Japan

Establishment of a preferential liver allocation rule for simultaneous liver and kidney transplantation (SLK) and revisions of laws regarding organ transplants from deceased donors have paved the way for SLK in Japan. Very few cases of SLK have been attempted in Japan, and no such recipients have survived for longer than 40 days. The present report describes a case of a 50-year-old woman who had undergone living donor liver transplantation at the age of 38 years for management of post-partum liver failure. After the first transplant surgery, she developed hepatic vein stenosis and severe hypersplenism requiring splenectomy. She was then initiated on hemodialysis (HD) due to the deterioration of renal function after insertion of a hepatic vein stent. She was listed as a candidate for SLK in 2011 because she required frequent plasma exchange for hepatic coma. When her Model for End-stage Liver Disease score reached 46, the new liver was donated 46 days after registration. The reduced trisegment liver and the kidney grafts were simultaneously transplanted under veno-venous bypass and intraoperative HD. The hepatic artery was reconstructed prior to portal reconstruction in order to shorten anhepatic time. Although she developed subcapsular bleeding caused by hepatic contusion on the next day, subsequent hemostasis was obtained by transcatheter embolization. Thereafter, her recovery was uneventful, except for mild rejection and renal tubular acidosis of the kidney graft. This case highlights the need to establish Japanese criteria for SLK.

Predictors of renal recovery in patients with pre-orthotopic liver transplant (OLT) renal dysfunction

BACKGROUND

Renal dysfunction occurs commonly in patients awaiting orthotopic liver transplantation (OLT) for end-stage liver disease. The use of simultaneous liver-kidney transplantation has increased in the MELD scoring era. As patients may recover renal function after OLT, identifying factors predictive of renal recovery is a critical issue, especially given the scarcity of available organs.

METHODS

Employing the UNOS database, we sought to identify donor- and patient-related predictors of renal recovery among 1720 patients with pre-OLT renal dysfunction and transplanted from 1989 to 2005. Recovery of renal function post-OLT was defined as a composite endpoint of serum creatinine (SCr) ≤1.5 mg/dL at discharge and survival ≥29 days. Pre-OLT renal dysfunction was defined as any of the following: SCr ≥2 mg/dL at any time while awaiting OLT or need for renal replacement therapy (RRT) at the time of registration and/or OLT.

RESULTS

Independent predictors of recovery of renal function post-OLT were absence of hepatic allograft dysfunction, transplantation during MELD era, recipient female sex, decreased donor age, decreased recipient ALT at time of OLT, decreased recipient body mass index at registration, use of anti-thymocyte globulin as induction therapy, and longer wait time from registration. Contrary to popular belief, a requirement for RRT, even for prolonged periods in excess of 8 weeks, was not an independent predictor of failure to recover renal function post-OLT.

CONCLUSION

These data indicate that the duration of renal dysfunction, even among those requiring RRT, is a poor way to discriminate reversible from irreversible renal dysfunction.

Renal dysfunction in liver transplant recipients: evaluation of the critical issues

Major progress has been made in the field of liver transplantation since the first procedure was performed nearly 50 years ago. Despite these improvements, renal dysfunction before and after liver transplantation remains a major complicating factor associated with increased health care costs, morbidity, and mortality. Creatinine-based estimates of renal function are inaccurate in the setting of end-stage liver disease and often lead to underdiagnosis and late intervention. This issue is critical in that it is important to understand both the etiology and chronicity of renal dysfunction before liver transplantation because the treatment clearly varies, especially with respect to simultaneous liver-kidney (SLK) transplantation. Because of the scarcity of available grafts, identifying appropriate candidates for SLK transplantation is crucial. Hepatorenal syndrome is common in liver transplant candidates; however, other etiologies of renal dysfunction need to be considered. Renal dysfunction after liver transplantation is common and may have an acute or chronic presentation. Although calcineurin inhibitors (CNIs) have been associated with post-liver transplant nephrotoxicity, their role may be overestimated, and other contributing etiologies should remain in a clinician's differential diagnosis. Alternatives to CNIs have been evaluated; however, a safe immunosuppressive regimen that achieves the preservation of renal function in liver transplant recipients remains to be established. In this review of the literature, renal dysfunction in the setting of liver transplantation is evaluated, and the critical issues that are barriers to improved outcomes are highlighted.

Combined liver-kidney transplantation is preferable to liver transplant alone for cirrhotic patients with renal failure

BACKGROUND

The role of combined liver-kidney transplantation (CLKT) for cirrhotic patients with renal failure (RF) is controversial. Since the model for end-stage liver disease era, there has been a rise in the number of CLKT. Using the Organ Procurement Transplant Network/United Network for Organ Sharing database, this study was undertaken to compare outcomes of cirrhotic patients with RF who received either liver transplant alone (LTA) or CLKT between 2002 and 2008.

METHODS

Analysis was limited to cirrhotic patients 18 years old or older, with serum creatinine level 2.5 mg/dL or higher at the time of orthotopic liver transplantation (OLT) or who received dialysis at least twice during the week before OLT. Patients who received CLKT were categorized based on the cause of their underlying RF.

RESULTS

Overall liver allograft and patient survival rates of LTA patients were significantly lower compared with CLKT patients (P<0.001). CLKT patients with hepatorenal syndrome showed significantly higher patient and liver allograft survival rates. Liver allograft survival was superior among CLKT patients irrespective of whether they received dialysis. Prevalence of posttransplantation RF was higher for LTA patients at 6 months and 3 years of follow-up (P<0.001). LTA was a significant risk factor both for graft loss and mortality. Recipient hepatitis C virus seropositivity, donor age, donor cause of death, and life support at the time of OLT were also risk factors for graft loss and death.

CONCLUSIONS

Cirrhotic patients with RF, in particular with hepatorenal syndrome, CLKT is preferable to LTA because it improves liver allograft and patient survival.

Impact of the etiology of acute kidney injury on outcomes following liver transplantation: acute tubular necrosis versus hepatorenal syndrome

Acute kidney injury (AKI) at the time of liver transplantation (LT) has been associated with increased morbidity and mortality. In patients with potentially reversible renal dysfunction, predicting whether there will be sufficient return of native kidney function is sometimes difficult. Previous studies have focused mainly on the effect of the severity of renal dysfunction or the duration of pretransplant dialysis on posttransplant outcomes. We performed a retrospective analysis of patients who underwent LT at our center after Model for End-Stage Liver Disease-based allocation so that we could determine the impact of the etiology of AKI [acute tubular necrosis (ATN) versus hepatorenal syndrome (HRS)] on post-LT outcomes. The patients were stratified according to the severity of AKI at the time of LT as described by the Risk, Injury, Failure, Loss, and End-Stage Kidney Disease (RIFLE) classification: risk, injury, or failure. The RIFLE failure group was further subdivided according to the etiology of AKI: HRS or ATN. The patient survival and renal outcomes 1 and 5 years after LT were significantly worse for those with ATN. At 5 years, the incidence of chronic kidney disease (stage 4 or 5) was statistically higher in the ATN group versus the HRS group (56% versus 16%, P < 0.001). A multivariate analysis revealed that the presence of ATN at the time of LT was the only variable associated with higher mortality 1 year after LT (P < 0.001). Our study is the first to demonstrate that the etiology of AKI has the greatest impact on patient and renal outcomes after LT.

The challenges of providing renal replacement therapy in decompensated liver cirrhosis

Development of renal failure requiring renal replacement therapy (RRT) in the cirrhotic patient is a devastating complication. Survival without RRT is less than 10% on average at 6 months. However, it is now appreciated that all renal failure in this group of patients is not due solely to hepatorenal syndrome, and the cause of the renal failure affects the prognosis. This paper reviews the prognosis depending on cause and points out the difficulty in making the correct diagnosis. Provision of RRT is difficult in this group of patients due to hypotension and coagulopathy which is highly prevalent. Survival with RRT is still poor with only 30-60% of patients surviving to liver transplant. Provision of RRT should be offered as a bridge to patients awaiting liver transplant or those undergoing liver transplant evaluation. Provision of long-term RRT is usually not indicated in other cirrhotic patients who develop a need for RRT except as a trial to see if renal function will return. The decision between intermittent hemodialysis or continuous renal replacement therapy (CRRT) is usually based on the clinical characteristics of the patient. Neither has been demonstrated to be superior to the other, although CRRT may be better tolerated in the unstable patient. CRRT is clearly indicated in cases of fulminant hepatic failure as it does not raise intracranial pressure. Provision of intraoperative CRRT during liver transplant may be indicated to help control volume and electrolytes in those patients presenting for liver transplant with renal failure. Newer extracorporeal support systems, such as extracorporeal albumin dialysis (MARS) and fractional plasma separation and adsorption with hemodialysis (Prometheus), have recently been developed to provide both renal and liver support in this group of patients. These are still considered experimental, although the MARS system has been utilized to treat patients with hepatorenal syndrome, and is available outside the United States.

Renal Dysfunction in Liver Transplant Candidates: Evaluation, Classification and Management in Contemporary Practice

Renal dysfunction is a common comorbidity in patients with liver failure and is a well-established predictor of both morbidity and mortality among patients awaiting liver transplantation. The etiology of renal failure in patients with cirrhosis can be functional, structural, or represent a combination of potentially reversible physiologic changes and permanent histologic damage. Diagnostic criteria for acute and chronic kidney disease have been established, but cirrhosis poses challenges for accurate assessment of renal function with conventional clinical methods such as serum creatinine and creatinine-based estimating equations. Renal biopsies can have an important role for defining permanent structural damage as part of the pre-transplant evaluation of patients with liver disease; however, coagulopathy, portal hypertension and ascites increase the risk of biopsy-associated complications in cirrhotic patients. While renal dysfunction due to hepatorenal physiology is potentially reversible after liver transplantation, simultaneous kidney liver transplantation and kidney after liver transplant can also improve outcomes in a subset of patients with irreversible renal injury.

Hepatorenal syndrome in the intensive care unit

Hepatorenal syndrome (HRS) is a functional form of acute kidney injury (AKI) associated with advanced liver cirrhosis or fulminant hepatic failure. Various new concepts have emerged since the initial diagnostic criteria and definition of HRS was initially published. These include better understanding of the pathophysiological mechanisms involved in HRS, identification of bacterial infection (especially spontaneous bacterial peritonitis) as the most important HRS-precipitating event, recognition that insufficient cardiac output plays a role in the occurrence of HRS, and evidence that renal failure reverses with pharmacotherapy. Patients with HRS are often critically ill and, by definition, have multiorgan failure. The purpose of this review is to provide an update on novel advances in HRS, with emphasis on the different aspects of management of these patients in the intensive care unit.

Simultaneous liver and kidney transplants: optimizing use of this double resource

Simultaneous liver and kidney transplantation is a life saving procedure for patients with combined liver and kidney failure; however, it remains controversial because of the need to balance individual patient need versus resource allocation. As waiting lists for transplantation become longer and patients become increasingly ill, there will be greater numbers of patients referred for liver and kidney transplantation. Acute kidney injury even requiring dialysis may potentially be reversible making combined transplant decisions difficult. Similarly, selected compensated cirrhotic patients with renal failure may be managed with renal transplant alone. Shared multicenter experience or clinical trials or both will be required to refine our ability to optimally manage these patients with combined liver and kidney dysfunction.

Critical care of the end-stage liver disease patient awaiting liver transplantation

Patients with end-stage liver disease awaiting liver transplantation frequently require intensive care admission and management due to either complications of liver failure or to intercurrent illness, particularly infection. Mortality in such patients is high and the development of an illness necessitating intensive care unit management can influence transplant candidacy. Specialized support frequently requires hemodynamic support, mechanical ventilation, and renal support. In this review, areas of management of particular importance to patients with end-stage liver disease in the intensive care unit are discussed. These areas are hepatic encephalopathy, infectious diseases, cardiovascular support, mechanical ventilation, renal support and combined transplantation, and decisions regarding delisting. Current knowledge specific to these patients, when available, is discussed, current practice is described, and areas of uncertainty in the evidence are discussed.

The spectrum of renal lesions in patients with cirrhosis: a clinicopathological study

BACKGROUND/OBJECTIVE

Little is known on the morphological changes in the kidneys of cirrhotic patients with abnormal urinalysis and/or high serum creatinine levels. This retrospective, one-point-in-time study aimed to report the results of the analysis of renal biopsy specimens obtained in patients with cirrhosis.

METHODS

We retrieved information on 65 patients who underwent transvenous renal biopsy for proteinuria >0.5 g/day and/or microscopic haematuria and/or unexplained renal impairment (defined by serum creatinine levels >1.5 mg/dl).

RESULTS

Fifty-one per cent of the patients had proteinuria >0.5 g/day, 58% had haematuria and 83% had renal impairment. Renal biopsy disclosed injury to glomeruli in 77% of the patients, to vessels in 69% and to the tubulointerstitium system in 94% (chronic in 77%; acute in 75%). Fibrous endarteritis was the most common renal vascular lesion. Injuries to different structures were frequently combined. Isolated glomerular alterations were found in only two patients. Acute tubular necrosis was significantly more common in patients with fibrous endarteritis than in those without. Among 18 patients with renal impairment, proteinuria <0.5 mg/day and no haematuria, 10 had glomerular lesions, 13 had chronic tubulointerstitial lesions and 12 acute tubulointerstitial lesions.

CONCLUSION

In patients with cirrhosis, various types of renal injuries are frequently combined. Chronic lesions (vascular or tubulointerstitial) may influence the outcome, in particular in patients who subsequently undergo liver transplantation and receive anticalcineurins. Renal vascular lesions may increase the risk of acute tubular necrosis. In patients with renal impairment, the absence of significant proteinuria and haematuria do not rule out the presence of renal lesions.

The evaluation of renal function and disease in patients with cirrhosis

The MELD score has shown that, besides markers of liver function, serum creatinine has a strong prognostic value in cirrhosis. However, even though creatinine has a good prognostic value, it is an inaccurate marker of renal function in cirrhosis. Creatinine and creatinine-based equations tend to overestimate glomerular filtration rate (GFR), and creatinine clearance from timed urine collection also overestimates GFR. Hence, clearance of exogenous markers such as iohexol remains the only reliable method for assessing precisely GFR in cirrhosis. Whereas these investigations are limited by their costs and complexity, and they can hardly be repeated at short intervals, serum cystatin C could be an alternative, although it needs further validation. Accurate markers and/or specific equations are therefore still needed to assess GFR in cirrhotic patients. Pre-renal failure and hepatorenal syndrome (HRS) are the main causes of acute renal failure in cirrhosis. Both result from decreased renal blood flow and both can result in acute tubular necrosis. HRS is not always fully reversible with liver transplantation possibly due to underlying chronic kidney damage. A number of cirrhotic patients with acute renal failure may also have chronic kidney damage ("acute-on-chronic renal failure"); furthermore, cirrhotic patients frequently have co-morbidities such as diabetes that may result in chronic impairment in renal function. Since conventional urinary markers are biased in cirrhosis, a biopsy is the only way to document and quantify renal lesions; moreover, transvenous route should be preferred to percutaneous route. In candidates for transplantation, attention should therefore be focused on vascular lesions which may represent a risk factor for nephrotoxicities induced by calcineurin-inhibitors.