Functional elements associated with hepatic regeneration in living donors after right hepatic lobectomy

A Validated LC-MS/MS Assay for the Quantification of Cholate Isotopes in Human Serum

BACKGROUND

Current methods for evaluating liver health rely on nonspecific blood tests, elastography surrogates for fibrosis, and invasive procedures, none of which directly measure liver function and physiology. Herein we present the analytical validation of a unique, highly sensitive LC-MS/MS assay and dual-sample oral (DuO) cholate challenge test to reliably quantify serial serum concentrations of cholate isotopes administered to patients with liver diseases. The clearance of administered cholate isotopes measured by the assay provides information about liver function and physiology.

METHODS

Analytical method validation of the cholate assay analytes (endogenous unlabeled cholic acid, 24-13C-cholic acid, and 2,2,4,4-D4-cholic acid) in terms of accuracy, precision, analytical sensitivity, analytical specificity, and range of reliable response was completed in human serum samples spiked with quality controls and calibrators in accordance with applicable guidelines. DuO test parameters were validated using samples from 48 subjects representing various liver disease etiologies.

RESULTS

Accuracy (mean biases) for all analytes ranged from 0.1% to 3.7%. Using a nested components-of-variance design (20 days, 2 runs per day, 2 replicates per sample), total imprecision for all analytes ranged from 2.3% to 8.4%. Lower and upper limits of quantitation were established and validated at 0.1 to 10.0 µM. Matrix effects and potential interferents did not affect assay performance. DuO test validation met all prespecified acceptance criteria.

CONCLUSIONS

The method validation studies described herein established the performance characteristics in terms of accuracy, precision, analytical sensitivity, analytical specificity, reportable ranges, and reference intervals of the LC-MS/MS cholate assay and DuO test.

Hepatic improvement within 27 days of avenciguat treatment in Child-Pugh A cirrhosis detected by an oral cholate challenge test

New methods for measuring hepatic improvement in clinical trials and the clinic are needed. One new method, HepQuant SHUNT, detected dose-dependent improvements in hepatic function and portal physiology in the phase 1b study (NCT03842761) of avenciguat, an activator of soluble guanylyl cyclase that is being developed for the treatment of portal hypertension. Herein, we examined whether HepQuant Duo, an easy-to-administer test version, could similarly detect the effects of avenciguat. Twenty-three patients with Child-Pugh A cirrhosis and liver stiffness >15 kPa received either a placebo (n = 5) or a maximum twice-daily avenciguat dose of 1, 2, or 3 mg (n = 6 per group) for 28 days. The DuO test was performed at baseline and on days 11 and 27 in each subject. The test involved administering 40 mg of d4-cholate orally, measuring d4-cholate concentrations in serum at 20 and 60 minutes, and calculating portal hepatic filtration rate, disease severity index, portal-systemic shunting (SHUNT%), and hepatic reserve (HR%). Avenciguat demonstrated dose-dependent improvement in all test parameters. Changes from baseline in SHUNT% after 27 days' treatment were 0.1 ± 9.0% for placebo, 1.7 ± 5.5% for 1 mg twice-daily, -3.2 ± 2.7% for 2 mg twice-daily, and -6.1 ± 5.0% for 3 mg twice-daily (paired t test for change from baseline p = 0.98, 0.48, 0.04, and 0.03, respectively). The changes detected by HepQuant DuO were similar to those previously observed and reported for HepQuant SHUNT. The results support further study of avenciguat in treating portal hypertension and spotlight the utility of HepQuant DuO in the development of drug therapy for liver disease. HepQuant DuO facilitates the use of function testing to measure hepatic improvement in clinical trials and the clinic.

New insights into the regulation of bile acids synthesis during the early stages of liver regeneration: A human and experimental study

BACKGROUND AND AIMS

Liver regeneration is essential for the preservation of homeostasis and survival. Bile acids (BAs)-mediated signaling is necessary for liver regeneration, but BAs levels need to be carefully controlled to avoid hepatotoxicity. We studied the early response of the BAs-fibroblast growth factor 19 (FGF19) axis in healthy individuals undergoing hepatectomy for living donor liver transplant. We also evaluated BAs synthesis in mice upon partial hepatectomy (PH) and acute inflammation, focusing on the regulation of cytochrome-7A1 (CYP7A1), a key enzyme in BAs synthesis from cholesterol.

METHODS

Serum was obtained from twelve human liver donors. Mice underwent 2/3-PH or sham-operation. Acute inflammation was induced with bacterial lipopolysaccharide (LPS) in mice fed control or antoxidant-supplemented diets. BAs and 7α-hydroxy-4-cholesten-3-one (C4) levels were measured by HPLC-MS/MS; serum FGF19 by ELISA. Gene expression and protein levels were analyzed by RT-qPCR and western-blot.

RESULTS

Serum BAs levels increased after PH. In patients with more pronounced hypercholanemia, FGF19 concentrations transiently rose, while C4 levels (a readout of CYP7A1 activity) dropped 2 h post-resection in all cases. Serum BAs and C4 followed the same pattern in mice 1 h after PH, but C4 levels also dropped in sham-operated and LPS-treated animals, without marked changes in CYP7A1 protein levels. LPS-induced serum C4 decline was attenuated in mice fed an antioxidant-supplemented diet.

CONCLUSIONS

In human liver regeneration FGF19 upregulation may constitute a protective response from BAs excess during liver regeneration. Our findings suggest the existence of post-translational mechanisms regulating CYP7A1 activity, and therefore BAs synthesis, independent from CYP7A1/Cyp7a1 gene transcription.

Within-individual reproducibility of a dual sample oral cholate challenge test (DuO) and simplified versions of the HepQuant SHUNT test

Current noninvasive liver tests measure fibrosis, inflammation, or steatosis and do not measure function. The HepQuant platform of noninvasive tests uniquely assesses both liver function and physiology through the hepatic uptake of stable isotopes of cholate. However, the prototypical HepQuant SHUNT test (SHUNT V1.0) is cumbersome to administer, requiring intravenous and oral administration of cholate and six peripheral venous blood samples over 90 min. To alleviate the burden of test administration, we explored whether an oral only (DuO) version, and other simplified versions, of the test could provide reproducible measurements of liver function. DuO requires only oral dosing and two blood samples over 60 min. The simplified SHUNT test versions were SHUNT V1.1 (oral and IV dosing but four blood samples) and SHUNT V2.0 (oral and IV dosing but only two blood samples over 60 min). In this paper, we describe the reproducibility of DuO and the simplified SHUNT tests relative to that of SHUNT V1.0; equivalency is described in a separate paper. Data from two studies comprising 236 SHUNT tests in 94 subjects were analyzed retrospectively by each method. All simplified methods were highly reproducible across test parameters with intraclass correlation coefficients >0.93 for test parameters Disease Severity Index (DSI) and Hepatic Reserve. DuO and SHUNT V2.0 improved reproducibility in measuring portal-systemic shunting (SHUNT%). These simplified tests, particularly DuO and SHUNT V2.0, are easier to administer and less invasive, thus, having the potential to be more widely accepted by care providers administering the test and by patients receiving the test.

Advances in noninvasive measurement of liver function and physiology: The HepQuant DuO test

Current noninvasive liver tests are surrogates for fibrosis and lack ability to directly measure liver function. HepQuant tests measure liver function and physiology through hepatic uptake of stable cholate isotopes. HepQuant SHUNT (V1.0) involves oral and intravenous dosing and six blood samples over 90 min. We developed simplified test versions: SHUNT V2.0 (oral and intravenous dosing, two blood samples over 60 min) and DuO (oral dosing only, two blood samples over 60 min). The aim of this study was to evaluate equivalency of the simplified tests to the original SHUNT test. Data from three studies comprising 930 SHUNT tests were retrospectively analysed by each method. Equivalence was evaluated in terms of proportion of tests in which the difference between methods was less than any clinically meaningful difference and additionally by two one-sided t-test and bioequivalence methods. DuO and SHUNT V2.0 were equivalent to the original SHUNT test for Disease Severity Index, with >99% and >96% of tests falling within equivalence bounds. DuO and SHUNT V2.0 met equivalency criteria by two one-sided t-tests and bioequivalence. DuO and SHUNT V2.0 are easier to administer, are less invasive than the original SHUNT test and have potential to be more accepted by patients and providers.

Biomechanics in liver regeneration after partial hepatectomy

The liver is a complicated organ within the body that performs wide-ranging and vital functions and also has a unique regenerative capacity after hepatic tissue injury and cell loss. Liver regeneration from acute injury is always beneficial and has been extensively studied. Experimental models including partial hepatectomy (PHx) reveal that extracellular and intracellular signaling pathways can help the liver recover to its equivalent size and weight prior to an injury. In this process, mechanical cues possess immediate and drastic changes in liver regeneration after PHx and also serve as main triggering factors and significant driving forces. This review summarized the biomechanics progress in liver regeneration after PHx, mainly focusing on PHx-based hemodynamics changes in liver regeneration and the decoupling of mechanical forces in hepatic sinusoids including shear stress, mechanical stretch, blood pressure, and tissue stiffness. Also discussed were the potential mechanosensors, mechanotransductive pathways, and mechanocrine responses under varied mechanical loading in vitro. Further elucidating these mechanical concepts in liver regeneration helps establish a comprehensive understanding of the biochemical factors and mechanical cues in this process. Proper adjustment of mechanical loading within the liver might preserve and restore liver functions in clinical settings, serving as an effective therapy for liver injury and diseases.

Compartmental model describing the physiological basis for the HepQuant SHUNT test

The HepQuant SHUNT test quantifies hepatic functional impairment from the simultaneous clearance of cholate from the systemic and portal circulations for the purpose of monitoring treatment effects or for predicting risk for clinical outcome. Compartmental models are defined by distribution volumes and transfer rates between volumes to estimate parameters not defined by noncompartmental analyses. Previously, a noncompartmental analysis method, called the minimal model (MM), demonstrated reproducible and reliable measures of liver function (Translational Research 2021). The aim of this study was to compare the reproducibility and reliability of a new physiologically based compartmental model (CM) vs the MM. Data were analyzed from 16 control, 16 nonalcoholic steatohepatitis (NASH), and 16 hepatitis C virus (HCV) subjects, each with 3 replicate tests conducted on 3 separate days. The CM describes transfer of cholates between systemic, portal, and liver compartments with assumptions from measured or literature-derived values and unknown parameters estimated by nonlinear least-squares regression. The CM was compared to the MM for 6 key indices of hepatic disease in terms of intraclass correlation coefficient (ICC) with a lower acceptable limit of 0.7. The CM correlated well with the MM for disease severity index (DSI) with R² (95% confidence interval) of 0.96 (0.94-0.98, P < 0.001). Acceptable reproducibility (ICC > 0.7) was observed for 6/6 and 5/6 hepatic disease indices for CM and MM, respectively. SHUNT, a measure of the absolute bioavailability, had ICC of 0.73 (0.60-0.83, P = 0.3095) for MM and 0.84 (0.76-0.90, P = 0.0012) for CM. The CM, but not the MM, allowed determination of anatomic shunt and hepatic extraction and improved the within individual reproducibility.

Perioperative management of living donor liver transplantation: Part 2 - Donors

Living donor liver transplantation was first developed to mitigate the limited access to deceased donor organs in Asia in the 1990s. This alternative liver transplantation method has become a widely practiced and established transplantation option for adult patients suffering with end-stage liver disease, and it has successfully helped address the shortage of deceased donors. The Society for the Advancement of Transplant Anesthesia and the Korean Society of Transplantation Anesthesiologists jointly reviewed published studies on the perioperative management of adult live liver donors undergoing donor hemi-hepatectomy. The goal of the review is to offer transplant anesthesiologists and critical care physicians a comprehensive overview of the perioperative management of adult live donors. We featured the current status, donor selection process, outcomes and complications, surgical procedure, anesthetic management, Enhanced Recovery After Surgery protocols, avoidance of blood transfusion, and considerations for emergency donation. Recent surgical advances, including laparoscopic donor hemi-hepatectomy and robotic laparoscopic donor surgery, are also addressed.

Pregnancy Outcomes After Living Liver Donation: A Multi-Institutional Study

Nearly half of living liver donors in North America are women of child-bearing age. Fetal and maternal outcomes after donation are unknown. We conducted a retrospective cohort study of female living liver donors (aged 18-50 years at donation) from 6 transplant centers. Participants were surveyed about their pregnancies and fertility. Outcomes were compared between predonation and postdonation pregnancies. Generalized estimating equations were clustered on donor and adjusted for age at pregnancy, parity, and pregnancy year. Among the 276 donors surveyed, 151 donors responded (54.7% response rate) and reported 313 pregnancies; 168/199 (68.8%) of the predonation pregnancies and 82/114 (71.9%) of the postdonation pregnancies resulted in live births, whereas 16.6% and 24.6% resulted in miscarriage, respectively. Women with postdonation pregnancies were older (32.0 versus 26.7 years; P < 0.001) and more frequently reported abnormal liver enzymes during pregnancy (3.5% versus 0.0%; P = 0.02) and delivery via cesarean delivery (35.4% versus 19.7%; P = 0.01). On adjusted analysis, there was no difference in cesarean delivery (odds ratio [OR], 2.44; 95% confidence interval [95% CI], 0.98-6.08), miscarriage (OR, 1.59; 95% CI, 0.78-3.24), combined endpoints of pregnancy-induced hypertension and preeclampsia (OR, 1.27; 95% CI, 0.36-4.49), or intrauterine growth restriction and preterm birth (OR, 0.91; 95% CI, 0.19-4.3). Of the 49 women who attempted pregnancy after donation, 11 (22.5%) self-reported infertility; however, 8/11 (72.7%) eventually had live births. Aside from increased reporting of abnormal liver enzymes and cesarean deliveries, there was no significant difference in pregnancy outcomes before and after living liver donation. One-fifth of women who attempt pregnancy after liver donation reported infertility, and although the majority went on to successful live births, further exploration is needed to understand the contributing factors. Future research should continue to monitor this patient-centered outcome across a large cohort of donors.

The within-individual reproducibility of the disease severity index from the HepQuant SHUNT test of liver function and physiology

The HepQuant SHUNT test quantifies liver function and blood flow using systemic and portal clearances of cholate. The test can identify the risk of well-compensated patients to develop complications of cirrhosis. To confirm the reliability of a single HepQuant SHUNT test we defined its within-individual reproducibility. Healthy subjects (n = 16), 16 with nonalcoholic steatohepatitis (NASH), and 16 with chronic hepatitis C virus (HCV) underwent 3 HepQuant SHUNT tests on 3 separate days within 30 days. The test involves simultaneous administration of 20 mg 13C-cholate IV and 40 mg d4-cholate PO, and subsequent collection of 3 mL blood samples at 5, 20, 45, 60, and 90 minutes. Clearances are expressed as systemic and portal hepatic filtration rate. Portal-systemic shunting (SHUNT), a disease severity index (DSI), and an estimate of DSI (STAT) are calculated from the clearances. Reproducibility was determined by the intraclass correlation coefficient (ICC > 0.70) and Bland-Altman analysis. Equal numbers of NASH and HCV patients had either early (F0-F2) or advanced (F3/F4) stages of fibrosis. All F3/F4 subjects were clinically compensated. The intraclass correlation coefficient (ICC) for DSI was 0.94 (0.90-0.96 95% confidence interval) indicating excellent reproducibility. The other test parameters had ICCs ranging from 0.74 (SHUNT) to 0.90 (STAT). In Bland-Altman analysis, the mean of differences between measurements of DSI was 0.13 with standard deviation 2.12. The excellent reproducibility of the HepQuant SHUNT test, particularly DSI, supports the use this minimally invasive, blood-based test as a reliable test of liver function and physiology.

Hepatic regeneration following radiation-induced liver injury is associated with increased hepatobiliary secretion measured by PET in Göttingen minipigs

Normal liver tissue is highly vulnerable towards irradiation, which remains a challenge in radiotherapy of hepatic tumours. Here, we examined the effects of radiation-induced liver injury on two specific liver functions and hepatocellular regeneration in a minipig model. Five Göttingen minipigs were exposed to whole-liver stereotactic body radiation therapy (SBRT) in one fraction (14 Gy) and examined 4–5 weeks after; five pigs were used as controls. All pigs underwent in vivo positron emission tomography (PET) studies of the liver using the conjugated bile acid tracer [N-methyl-¹¹C]cholylsarcosine ([¹¹C]CSar) and the galactose-analogue tracer [¹⁸F]fluoro-2-deoxy-d-galactose ([¹⁸F]FDGal). Liver tissue samples were evaluated histopathologically and by immunohistochemical assessment of hepatocellular mitosis, proliferation and apoptosis. Compared with controls, both the rate constant for secretion of [¹¹C]CSar from hepatocytes into intrahepatic bile ducts as well as back into blood were doubled in irradiated pigs, which resulted in reduced residence time of [¹¹C]CSar inside the hepatocytes. Also, the hepatic systemic clearance of [¹⁸F]FDGal in irradiated pigs was slightly increased, and hepatocellular regeneration was increased by a threefold. In conclusion, parenchymal injury and increased regeneration after whole-liver irradiation was associated with enhanced hepatobiliary secretion of bile acids. Whole-liver SBRT in minipigs ultimately represents a potential large animal model of radiation-induced liver injury and for testing of normal tissue protection methods.

Sex differences in postsurgical skeletal muscle depletion after donation of living-donor liver transplantation, although minimal, should not be ignored

Background

Donor safety is the top priority in living-donor liver transplantation. Splenic hypertrophy and platelet count decrease after donor surgery are reported to correlate with the extent of hepatectomy, but other aftereffects of donor surgeries are unclear. In this study, we evaluated the surgical effects of donor hepatectomy on skeletal muscle depletion and their potential sex differences.

Methods

Among a total of 450 consecutive donor hepatectomies performed from April 2001 through March 2017, 277 donors who completed both preoperative and postoperative (60–119 days postsurgery) evaluation by computed tomography were the subjects of this study. Donors aged 45 years or older were considered elderly donors. Postoperative skeletal muscle depletion was assessed on the basis of the cross-sectional area of the psoas major muscle. Postoperative changes in the spleen volume and platelet count ratios were also analysed to evaluate the effects of major hepatectomy.

Results

The decrease in the postoperative skeletal muscle mass in the overall donor population was slight (99.4 ± 6.3%). Of the 277 donors, 59 (21.3%) exhibited skeletal muscle depletion (i.e., < 95% of the preoperative value). Multivariate analysis revealed that elderly donor (OR:2.30, 95% C.I.: 1.27–4.24) and female donor (OR: 1.94, 95% C.I. 1.04–3.59) were independent risk factors for postoperative skeletal muscle depletion. Stratification of the subjects into four groups by age and sex revealed that the elderly female donor group had significantly less skeletal muscle mass postoperatively compared with the preoperative values (95.6 ± 6.8%), while the other three groups showed no significant decrease. Due to their smaller physical characteristics, right liver donation was significantly more prevalent in the female groups than in the male groups (112/144, 77.8% vs 65/133, 48.9%; p < 0.001). The estimated liver resection rate correlated significantly with the splenic hypertrophy ratio (r = 0.528, p < 0.001) and the extent of the platelet count decrease (r = − 0.314, p < 0.001), but donor age and sex did not affect these parameters.

Conclusion

Elderly female donors have a higher risk of postoperative skeletal muscle depletion. Additionally, female donors are more likely to donate a right liver graft, whose potential subclinical risks include postoperative splenic enlargement and a platelet count decrease.

Looking Into the Crystal Ball: Predicting the Future Challenges of Fibrotic NASH Treatment

Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease worldwide, and its aggressive form of nonalcoholic steatohepatitis (NASH) is becoming a leading cause for end-stage liver disease and liver transplantation in the United States. In patients with NASH, the presence of advanced fibrosis is considered the most important prognostic factor in predicting liver-related morbidity and mortality. Unfortunately, there are no US Food and Drug Administration (FDA)-approved medications to treat patients with NASH-induced advanced fibrosis. However, the field of drug development to treat NASH and fibrosis has witnessed major advances over the past 5 years with several medications in phase III trials. Results from some of these trials are expected in 2019 with potential FDA approval in 2020. Clinicians who treat patients with NAFLD are likely to face several challenges over the next few years related to identifying patients with advanced fibrosis who may derive most benefit from pharmacologic treatment, the requirement for liver biopsy to assess histologic severity and response to treatment, and the urgent need to validate noninvasive tests to replace liver biopsy-to determine treatment initiation, response, futility, and the need for combination therapy with multiple drugs. Conclusion: In this review, we aim to dissect each of these challenges and attempt to provide suggested solutions while fully realizing that knowledge gaps still exist where future research is likely to provide urgently needed answers.

Early postoperative hypoalbuminaemia is associated with pleural effusion after donor hepatectomy: A propensity score analysis of 2316 donors

Pleural effusion and hypoalbuminaemia frequently occur after hepatectomy. Despite the emphasis on the safety of donors, little is known about the impact of postoperative albumin level on pleural effusion in liver donors. We retrospectively assessed 2316 consecutive liver donors from 2004 to 2014. The analysis of donors from 2004 to 2012 showed that postoperative pleural effusion occurred in 47.4% (970/2046), and serum albumin levels decreased until postoperative day 2 (POD2) and increased thereafter. In multivariable analysis, the lowest albumin level within POD2 (POD2ALB) was inversely associated with pleural effusion (OR 0.28, 95% CI 0.20-0.38; P < 0.001). POD2ALB ≤3.0 g/dL, the cutoff value at the 75th percentile, was associated with increased incidence of pleural effusion after propensity score (PS) matching (431 pairs; OR 1.69, 95% CI 1.30-2.21; P < 0.001). When we further analysed data from 2010 to 2014, intraoperative albumin infusion was associated with higher POD2ALB (P < 0.001) and lower incidence of pleural effusion (P = 0.024), compared with synthetic colloid infusion after PS matching (193 pairs). In conclusion, our data showed that POD2ALB is inversely associated with pleural effusion, and that intraoperative albumin infusion is associated with a lower incidence of pleural effusion when compared to synthetic colloid infusion in liver donors.

Current Status of Living Donor Liver Transplantation in the United States

Adult-to-adult living donor liver transplantation (LDLT) was introduced in response to the shortage of deceased donor liver grafts. The number of adult living donor transplants is increasing due to improved outcomes and increasing need. Advantages of LDLT include optimization of the timing of transplant, better organ quality, and lower rates of recipient mortality compared to staying on the wait list for deceased donor liver transplant. Donor safety remains the major focus when considering LDLT. Recent advancements have supported the increased use of LDLT to help decrease wait list death and improve long-term survival of transplant recipients.

Status of Adult Living Donor Liver Transplantation in the United States: Results from the Adult-To-Adult Living Donor Liver Transplantation Cohort Study

This article reviews the Adult-to-Adult Living Donor Liver Transplant Cohort Study (A2ALL). The findings show that the number of adult-to-adult living donor liver transplants is consistently increasing. Living donor liver transplantation has an important benefit for patients with acute liver failure, does not compromise donor safety, and has lower rates of acute cellular rejection in biologically related donor and recipient. The conclusions from the A2ALL consortium have been critical in transplant advancement, supporting increased use to help decrease waitlist death and improve long-term survival of transplant recipients.

Potential use of metabolic breath tests to assess liver disease and prognosis: has the time arrived for routine use in the clinic?

The progression of liver disease may be unique among organ system diseases in that progressive fibrosis compromises not only the sufficiency of hepatocyte mass but also impairs blood flow to the liver, resulting in porto-systemic shunting. Although liver biopsy as an assessment of fibrosis has become the key biomarker of and target for new therapies, it is invasive and subject to sampling error, and cannot quantify metabolic function or porto-systemic shunting. Measurement of the hepatic venous pressure gradient accommodates some of the deficiencies of biopsy but requires expertise not widely available and misses minor changes in hepatocellular mass and thereby information about metabolic function. Thus, an unmet need in clinical hepatology remains unfulfilled: a noninvasive biomarker which quantitates both the hepatocellular insufficiency and porto-systemic shunting inherent in progressive hepatic fibrosis. Ideally, such a biomarker should correlate with clinical endpoints including liver-related survival and cirrhotic complications, be performed at the point-of-care, and be affordable and easy to use. This review, an expert opinion, summarizes background and recent data suggesting that metabolic breath tests may now meet these requirements and have a valid place in clinical hepatology to supplant the time-honoured assessment of hepatic fibrosis.

Surgical planning for living donor liver transplant using 4D flow MRI, computational fluid dynamics and in vitro experiments

This study used magnetic resonance imaging (MRI), computational fluid dynamics (CFD) modeling, and in vitro experiments to predict patient-specific alterations in hepatic hemodynamics in response to partial hepatectomy in living liver donors. 4D Flow MRI was performed on three donors before and after hepatectomy and models of the portal venous system were created. Virtual surgery was performed to simulate (1) surgical resection and (2) post-surgery vessel dilation. CFD simulations were conducted using in vivo flow data for boundary conditions. CFD results showed good agreement with in vivo data, and in vitro experimental values agreed well with imaging and simulation results. The post-surgery models predicted an increase in all measured hemodynamic parameters, and the dilated virtual surgery model predicted post-surgery conditions better than the model that only simulated resection. The methods used in this study have potential significant value for the surgical planning process for the liver and other vascular territories.

Metabolic scaling predicts posthepatectomy liver regeneration after accounting for hepatocyte hypertrophy

We adapted a mathematical model of posthepatectomy liver regeneration using data from a subset of patients in the Adult-to-Adult Living Donor Liver Transplantation Cohort Study. The original model addressed changes in the number of quiescent, primed, and proliferating cells. Our adapted model takes into account hypertrophy of primed and replicating cells, and it is better able to predict liver volume. In addition, by building off the hypothesis that cell cycle parameters are approximately the same across all mammals, we found that changing only a single parameter characterizing metabolic load could model liver regeneration in 5 species of mammals. In conclusion, we improved a mathematical model of liver regeneration, predicted mammalian liver regeneration based on metabolism, and found correlations between model parameters and physiological measurements from liver donors.

Serial changes of cytokines and growth factors in peripheral circulation after right lobe donor hepatectomy

Cytokines and growth factors have prominent roles in liver regeneration. The aim of this study was to evaluate the biological markers of liver regeneration in healthy donors undergoing right lobe donor hepatectomy for living donor liver transplantation. Twenty-five voluntary liver donors were enrolled. Peripheral blood samples were taken a day before the operation and on postoperative days (PODs) 1, 3, 7, 14, and 42. Levels of hepatocyte growth factor (HGF), interleukin (IL) 6, tumor necrosis factor α (TNF-α), thrombopoietin (TPO), transforming growth factor β1 (TGF-β1), interferon (IFN) α, and IFNγ were monitored. The remnant liver volume (RLV) before surgery and regeneration liver volume (RgV) on POD 14 were calculated on computed tomography (CT). RgV/RLV ratio was correlated with the remnant-liver-volume-to-body-weight ratio (RLVBWR). Inverse correlation was observed between RgV/RLV and RLVBWR (r(2) = 0.61; P < 0.001). There was a significant rise of HGF on POD 1 (P = 0.001), POD 7 (P = 0.049), and POD 14 (P = 0.04). TNF-α was elevated on POD 1 (P = 0.004). The levels of IL 6 (P < 0.001) and TPO (P < 0.001) were higher from POD 1 to POD 42. IFNα was higher on POD 14 (P = 0.003) and POD 42 (P = 0.001). There was a significant fall of IFNγ on POD 1 (P = 0.01) and increase on POD 14 (P = 0.04). The levels of TGF-β1 were higher on POD 14 (P = 0.008) and on POD 42 (P = 0.002). In conclusion, HGF, IL 6, TNF-α, and TPO are involved in the early phase, whereas TGF-β1 and IFN are involved in the termination phase of liver regeneration. Liver regeneration was observed to be higher in donors with low RLVBWR.

Pharmacokinetics of drugs in adult living donor liver transplant patients: regulatory factors and observations based on studies in animals and humans

INTRODUCTION

Limited information is available on the pharmacokinetics of drugs in the donors and recipients following adult living donor liver transplantation (LDLT). Given that both the donors and recipients receive multiple drug therapies, it is important to assess the pharmacokinetics of drugs used in these patients.

AREAS COVERED

Pathophysiological changes that occur post-surgery and regulatory factors that may influence pharmacokinetics of drugs, especially hepatic drug metabolism and transport in both LDLT donors and the recipients are discussed. Pharmacokinetic data in animals with partial hepatectomy are presented. Clinical pharmacokinetic data of certain drugs in LDLT recipients are further reviewed.

EXPERT OPINION

It takes up to six months for the liver volume to return to normal after LDLT surgery. In the LDLT recipients, drug exposure generally is higher with lower clearance during early period post-transplant; lower initial dosages of immunosuppressants are used than deceased donor liver transplant recipients during the first six months post-transplantation. In animals, the activities of hepatic drug metabolizing enzymes and transporters are known to be altered differentially during liver regeneration. Future studies on the actual hepatic function with reference to drug metabolism, drug transport, and biliary secretion in both LDLT donors and recipients are required.

Ad Integrum Functional and Volumetric Recovery in Right Lobe Living Donors: Is It Really Complete 1 Year After Donor Hepatectomy?

The partial liver's ability to regenerate both as a graft and remnant justifies right lobe (RL) living donor liver transplantation. We studied (using biochemical and radiological parameters) the rate, extent of, and predictors of functional and volumetric recovery of the remnant left liver (RLL) during the first year in 91 consecutive RL donors. Recovery of normal liver function (prothrombin time [PT] ≥70% of normal and total bilirubin [TB] ≤20 µmol/L), liver volumetric recovery, and percentage RLL growth were analyzed. Normal liver function was regained by postoperative day's 7, 30, and 365 in 52%, 86%, and 96% donors, respectively. Similarly, mean liver volumetric recovery was 64%, 71%, and 85%; whereas the percentage liver growth was 85%, 105%, and 146%, respectively. Preoperative PT value (p = 0.01), RLL/total liver volume (TLV) ratio (p = 0.03), middle hepatic vein harvesting (p = 0.02), and postoperative peak TB (p < 0.01) were predictors of early functional recovery, whereas donor age (p = 0.03), RLL/TLV ratio (p = 0.004), and TLV/ body weight ratio (p = 0.02) predicted early volumetric recuperation. One-year post-RL donor hepatectomy, though functional recovery occurs in almost all (96%), donors had incomplete restoration (85%) of preoperative total liver volume. Modifiable predictors of regeneration could help in better and safer donor selection, while continuing to ensure successful recipient outcomes.

Noninvasive assessment of liver function

PURPOSE OF REVIEW

It is our opinion that there is an unmet need in hepatology for a minimally or noninvasive test of liver function and physiology. Quantitative liver function tests define the severity and prognosis of liver disease by measuring the clearance of substrates whose uptake or metabolism is dependent upon liver perfusion or hepatocyte function. Substrates with high-affinity hepatic transporters exhibit high 'first-pass' hepatic extraction and their clearance measures hepatic perfusion. In contrast, substrates metabolized by the liver have low first-pass extraction and their clearance measures specific drug metabolizing pathways.

RECENT FINDINGS

We highlight one quantitative liver function test, the dual cholate test, and introduce the concept of a disease severity index linked to clinical outcome that quantifies the simultaneous processes of hepatocyte uptake, clearance from the systemic circulation, clearance from the portal circulation, and portal-systemic shunting.

SUMMARY

It is our opinion that dual cholate is a relevant test for defining disease severity, monitoring the natural course of disease progression, and quantifying the response to therapy.

Changes in liver and spleen volumes after living liver donation: a report from the Adult-to-Adult Living Donor Liver Transplantation Cohort Study (A2ALL)

Previous reports have drawn attention to persistently decreased platelet counts among liver donors. We hypothesized an etiologic association between altered platelet counts and postdonation splenomegaly and sought to explore this relationship. This study analyzed de-identified computed tomography/magnetic resonance scans of 388 donors from 9 Adult-to-Adult Living Donor Liver Transplantation Cohort Study centers read at a central computational image analysis laboratory. Resulting liver and spleen volumes were correlated with time-matched clinical laboratory values. Predonation liver volumes varied 2-fold in healthy subjects, even when they were normalized by the body surface area (BSA; range = 522-1887 cc/m(2) , n = 346). At month 3 (M3), postdonation liver volumes were, on average, 79% of predonation volumes [interquartile range (IQR) = 73%-86%, n = 165] and approached 88% at year 1 (Y1; IQR = 80%-93%, n = 75). The mean spleen volume before donation was 245 cc (n = 346). Spleen volumes greater than 100% of the predonation volume occurred in 92% of donors at M3 (n = 165) and in 88% at Y1 after donation (n = 75). We sought to develop a standard spleen volume (SSV) model to predict normal spleen volumes in donors before donation and found that decreased platelet counts, a younger age, a higher predonation liver volume, higher hemoglobin levels, and a higher BSA predicted a larger spleen volume (n = 344, R(2)  = 0.52). When this was applied to postdonation values, some large volumes were underpredicted by the SSV model. Models developed on the basis of the reduced sample of postdonation volumes yielded smaller underpredictions. These findings confirm previous observations of thrombocytopenia being associated with splenomegaly after donation. The results of the SSV model suggest that the biology of this phenomenon is complex. This merits further long-term mechanistic studies of liver donors with an investigation of the role of other factors such as thrombopoietin and exposure to viral infections to better understand the evolution of the spleen volume after liver donation.

Challenges in living donor liver transplantation

Living donor liver transplantation is a procedure that has waned in its application over the past decade but remains a beneficial procedure for properly selected candidates. This review discusses some of the newer, relevant studies in the field, focusing on outcomes with hepatocellular carcinoma, ABO-incompatible transplant, and issues in donor complications and safety.