Understanding the meaning of fat in the liver

Heme Oxygenase-1-Modified BMMSCs Activate AMPK-Nrf2-FTH1 to Reduce Severe Steatotic Liver Ischemia-Reperfusion Injury

BACKGROUND

Ischemia-reperfusion injury (IRI) is an important cause of graft dysfunction post-liver transplantation, where donor liver with severe steatosis is more sensitive to IRI. Liver IRI involves ferroptosis and can be alleviated by heme oxygenase-1-modified bone marrow mesenchymal stem cells (HO-1/BMMSCs).

AIMS

To explore the role and mechanism of HO-1/BMMSCs in severe steatotic liver IRI.

METHODS

A severe steatotic liver IRI rat model and a hypoxia/reoxygenation (H/R) of severe steatosis hepatocyte model were established. Liver and hepatocyte damage was evaluated via liver histopathology and cell activity. Ferroptosis was evaluated through ferroptosis indexes. Nuclear factor erythroid 2-related factor 2 (Nrf2) was knocked down in severe steatotic hepatocytes. The role of Nrf2 and AMPK in HO-1/BMMSC inhibition of ferroptosis was examined using the AMP-activated protein kinase (AMPK) pathway inhibitor Compound C.

RESULTS

The HO-1/BMMSCs alleviated severe steatotic liver IRI and ferroptosis. HO-1/BMMSCs promoted ferritin heavy chain 1(FTH1), Nrf2, and phosphorylated (p)-AMPK expression in the H/R severe steatotic hepatocytes. Nrf2 knockdown decreased FTH1 expression levels but did not significantly affect p-AMPK expression levels. The protective effect of HO-1/BMMSCs against H/R injury in severe steatotic hepatocytes and the inhibitory effect on ferroptosis were reduced. Compound C decreased p-AMPK, Nrf2, and FTH1 expression levels, weakened the HO-1/BMMSC protective effect against severe steatotic liver IRI and H/R-injured severe steatotic hepatocytes, and reduced the inhibition of ferroptosis.

CONCLUSIONS

Ferroptosis was involved in HO-1/BMMSC reduction of severe steatotic liver IRI. HO-1/BMMSCs protected against severe steatotic liver IRI by inhibiting ferroptosis through the AMPK-Nrf2-FTH1 pathway. HO-1/BMMSCs activate AMPK, which activates Nrf2, promotes its nuclear transcription, then promotes the expression of its downstream protein FTH1, thereby inhibiting ferroptosis and attenuating severe steatotic liver IRI in rats. Glu: glutamic acid; Cys: cystine; GSH: glutathione; GPX4: glutathione peroxidase 4; HO-1/BMMSCs: HO-1-modified BMMSCs; Fer-1: ferrostatin-1; DFO: deferoxamine; FTH1: ferritin heavy chain1; p-AMPK: phosphorylated AMP-activated protein kinase; Nrf2: nuclear factor erythroid 2-related factor 2; IRI: ischemia-reperfusion injury; MCD: methionine-choline deficiency.

Abrogation of greater graft failure risk of female-to-male liver transplantation with donors older than 40 years or graft macrosteatosis greater than 5

Greater graft-failure-risk of female-to-male liver transplantation (LT) is thought to be due to acute decrease in hepatic-estrogen-signaling. Our previous research found evidence that female hepatic-estrogen-signaling decreases after 40 years or with macrosteatosis. Thus, we hypothesized that inferiority of female-to-male LT changes according to donor-age and macrosteatosis. We stratified 780 recipients of grafts from living-donors into four subgroups by donor-age and macrosteatosis and compared graft-failure-risk between female-to-male LT and other LTs within each subgroup using Cox model. In recipients with ≤ 40 years non-macrosteatotic donors, graft-failure-risk was significantly greater in female-to-male LT than others (HR 2.03 [1.18-3.49], P = 0.011). Within the subgroup of recipients without hepatocellular carcinoma, the inferiority of female-to-male LT became greater (HR 4.75 [2.02-11.21], P < 0.001). Despite good graft quality, 1y-graft-failure-probability was 37.9% (23.1%-57.9%) in female-to-male LT within this subgroup while such exceptionally high probability was not shown in any other subgroups even with worse graft quality. When donor was > 40 years or macrosteatotic, graft-failure-risk was not significantly different between female-to-male LT and others (P > 0.60). These results were in agreement with the estrogen receptor immunohistochemistry evaluation of donor liver. In conclusion, we found that the inferiority of female-to-male LT was only found when donor was ≤ 40 years and non-macrosteatotic. Abrogation of the inferiority when donor was > 40 years or macrosteatotic suggests the presence of dominant contributors for post-transplant graft-failure other than graft quality/quantity and supports the role of hepatic-estrogen-signaling mismatch on graft-failure after female-to-male LT.

Gallstone and Gallbladder Disease: Biliary Tract and Cholangiopathies

Cholestatic liver diseases are named primarily due to the blockage of bile flow and buildup of bile acids in the liver. Cholestasis can occur in cholangiopathies, fatty liver diseases, and during COVID-19 infection. Most literature evaluates damage occurring to the intrahepatic biliary tree during cholestasis; however, there may be associations between liver damage and gallbladder damage. Gallbladder damage can manifest as acute or chronic inflammation, perforation, polyps, cancer, and most commonly gallstones. Considering the gallbladder is an extension of the intrahepatic biliary network, and both tissues are lined by biliary epithelial cells that share common mechanisms and properties, it is worth further evaluation to understand the association between bile duct and gallbladder damage. In this comprehensive article, we discuss background information of the biliary tree and gallbladder, from function, damage, and therapeutic approaches. We then discuss published findings that identify gallbladder disorders in various liver diseases. Lastly, we provide the clinical aspect of gallbladder disorders in liver diseases and ways to enhance diagnostic and therapeutic approaches for congruent diagnosis. © 2023 American Physiological Society. Compr Physiol 13:4909-4943, 2023.

Characterization of hepatic steatosis using controlled attenuation parameter and MRI-derived proton density fat fraction in living donor liver transplantation

BACKGROUND

The increasingly favorable outcomes of live donor liver transplant warrant development of screening techniques to expand current donor pool. Transient elastography (TE) with controlled attenuation parameter (CAP) is accessible and has promising diagnostic performance in non-obese individuals. Here, we demonstrate its utility in grading donor steatosis for risk assessment in living liver donors (LLD).

STUDY DESIGN

In a prospective study of LLD and recipients, accuracy was determined using MRI-derived proton density fat fraction (PDFF) as reference.

RESULTS

One hundred and one LLD underwent TE, 95 of whom had available PDFF. Median CAP and MRI-PDFF were 233 dB/m (206-270) and 2.9% (2.3-4.0), respectively. A CAP threshold of 270 dB/m captured all steatosis which was present in 13 (13%) LLD (AUROC .942, 100% sensitivity and 83% specificity). Performance further improved when excluding obese LLD and limiting analysis to M-probe (AUROC .971 and .974, respectively, with 87% specificity). There was no difference in CAP and MRI-PDFF between LLD and nondonors (P = .26 and .21, respectively). Early allograft dysfunction was observed in one recipient (CAP 316, PDFF 9.5%), zero underwent retransplant, and one died from sepsis.

CONCLUSION

The specific role of CAP in living liver donation warrants further study, beginning with its use as screening tool across peripheral clinics.

Analysis of outcomes and renal recovery after adult living-donor liver transplantation among recipients with hepatorenal syndrome

When timely access to deceased-donor livers is not feasible, living-donor liver transplantation (LDLT) is an attractive option for patients with hepatorenal syndrome (HRS). This study's primary objective was to describe outcomes after LDLT among HRS recipients, and the secondary objective was to determine predictors of poor renal recovery after LDLT. This single-center, retrospective study included 2185 LDLT recipients divided into HRS (n = 126, 5.8%) and non-HRS (n = 2059, 94.2%) groups. The study outcomes were survival and post-LT renal recovery. The HRS group had a higher death rate than the non-HRS group (17.5% vs. 8.6%, p < 0.001). In the HRS group, post-LT renal recovery occurred in 69.0%, and the death rate was significantly lower in association with HRS recovery compared with non-recovery (5.7% vs. 43.6%, p < 0.001). Multivariable analysis indicated that post-LT sepsis (p < 0.001) and non-recovery of HRS (p < 0.001) were independent negative prognostic factors for survival. Diabetes mellitus (p = 0.01), pre-LT peak serum creatinine ≥3.2 mg/dl (p = 0.002), time interval from HRS diagnosis to LDLT ≥38 days (p = 0.01), and post-LT sepsis (p = 0.03) were important negative prognostic factors for renal recovery after LDLT. In conclusion, post-LT renal recovery was important for survival, and the interval from HRS to LDLT was significantly associated with post-LT renal recovery.

Long-term cold storage preservation does not affect fatty livers from rats fed with a methionine and choline deficient diet

BACKGROUND

Waiting lists that continue to grow and the lack of organs available for transplantation necessitate the use of marginal livers, such as fatty livers. Since steatotic livers are more susceptible to damage from ischemia and reperfusion, it was investigated whether fatty livers with different lipidomic profiles show a different outcome when subjected to long-term cold storage preservation.

METHODS

Eight-week-old male Wistar rats fed for 2 weeks by a methionine-choline-deficient (MCD) diet or control diet were employed in this study. Livers were preserved in a University of Wisconsin (UW) solution at 4 °C for 6, 12 or 24 h and, after washout, reperfused for 2 h with a Krebs-Henseleit buffer at 37 °C. Hepatic enzyme release, bile production, O2-uptake, and portal venous pressure (PVP) were evaluated. The liver fatty acid profile was evaluated by a gas chromatography-mass spectrometry (GC/MS).

RESULTS

MCD rats showed higher LDH and AST levels with respect to the control group. When comparing MCD livers preserved for 6, 12 or 24 h, no differences in enzyme release were found during both the washout or the reperfusion period. The same trend occurred for O2-uptake, PVP, and bile flow. A general decrease in SFA and MUFA, except for oleic acid, and a decrease in PUFA, except for arachidonic, eicosadienoic, and docosahexanaeoic acids, were found in MCD rats when compared with control rats. Moreover, the ratio between SFA and the various types of unsaturated fatty acids (UFA) was significantly lower in MCD rats.

CONCLUSIONS

Although prolonged cold ischemia negatively affects the graft outcome, our data suggest that the quality of lipid constituents could influence liver injury during cold storage: the lack of an increased hepatic injury in MCD may be justified by low SFA, which likely reduces the deleterious tendency toward lipid crystallization occurring under cold ischemia.

Magnetic resonance imaging-derived proton density fat fraction (MRI-PDFF) is a viable alternative to liver biopsy for steatosis quantification in living liver donor transplantation

This study aimed to investigate whether magnetic resonance imaging-derived proton density fat fraction (MRI-PDFF) can be a viable noninvasive alternative to liver biopsy for the quantification of living liver donor steatosis. Hepatic steatosis for 143 donors was graded by MRI-PDFF. Study endpoints included liver volume regeneration in donors, recipient outcomes including length of hospital stay, deaths, primary non-function (PNF), early allograft dysfunction (EAD), and small for size syndrome (SFSS). Correlation between MRI-PDFF determined donor steatosis and endpoints were analyzed. Donors had lower steatosis grade than non-donors. Donor remnant liver regenerated to an average of 82% of pre-donation volume by 101 ± 24 days with no complications. There was no correlation between percent liver regeneration and steatosis severity. Among recipients, 4 underwent redo-transplantation and 6 died, with no association with degree of steatosis. 52 recipients (36%) fulfilled criteria for EAD (driven by INR), with no difference in hepatic steatosis between groups. MRI-PDFF reliably predicted donor outcomes. Living donors with no or mild steatosis based on MRI-PDFF (ie, <20%) and meeting other criteria for donation can expect favorable post-surgical outcomes, including liver regeneration. Recipients had a low rate of death or retransplantation with no association between mild hepatic steatosis and EAD.

Sex difference in the tolerance of hepatic ischemia-reperfusion injury and hepatic estrogen receptor expression according to age and macrosteatosis in healthy living liver donors

BACKGROUND

Hepatic estrogen signaling, which is important in liver injury/recovery, is determined by the level of systemic estrogen and hepatic estrogen receptor. We aimed to evaluate whether female's advantage in the tolerance of hepatic ischemia-reperfusion injury decreases according to the age of 40 y (systemic estrogen decrease) and macrosteatosis (hepatic estrogen receptor decrease).

METHODS

We included 358 living liver donors (128 females and 230 males). The tolerance of hepatic ischemia-reperfusion injury was determined by the slope of the linear regression line modeling the relationship between the duration of intraoperative hepatic ischemia and the peak postoperative transaminase level. Estrogen receptor content was measured in the biopsied liver samples using immunohistochemistry.

RESULTS

In the whole cohort, the regression slope for aspartate transaminase was comparable between females and males (P=0.940). Within the subgroup of ≤40 y donors, the regression slope was significantly smaller in females (P=0.031), whereas it was comparable within >40 y donors (P=0.867). Within the subgroup of ≤40 y non-macrosteatotic donors, the regression slope was significantly smaller in females in univariable (P=0.002) and multivariable analysis (P=0.006), whereas the sex difference was not found within ≤40 y macrosteatotic donors (P=0.685). Estrogen receptor content was significantly greater in females within ≤40 y non-macrosteatotic donors (P=0.021), whereas it was not different in others of >40 y or with macrosteatosis (P=0.450).

CONCLUSIONS

The tolerance of hepatic ischemia-reperfusion injury was greater in females than in males only when they were <40 y and without macrosteatosis. The results were in agreement with hepatic estrogen receptor immunohistochemistry study.

Effect of Donor Hepatic Steatosis on Ischemia Reperfusion Injury in Liver Transplant Recipient

INTRODUCTION

Ischemia reperfusion injury (IRI) is an important complication of liver transplant (LT). The donor risk index, which does not incorporate steatosis, includes several variables known to impact on allograft survival. The purpose of this study was to report on donor liver allograft steatosis and its association with severity of IRI.

AIM

The aim of this study was to determine the effect of type and grade of donor liver steatosis on the occurrence and severity of IRI in LT recipients.

METHODS

This was an observational study conducted at a single center over a period of 37 months from July 2013 to August 2016. Liver biopsy was performed twice, initially at the time of procurement before graft perfusion for steatosis assessment. Steatosis was classified as microsteatosis (MiS) or macrosteatosis (MaS) with mild, moderate, or severe grade. Second biopsy for IRI assessment was taken before skin closure in death donor LT (DDLT) and at the time of transaminitis in postoperative period (<72 hrs) in living donor LT (LDLT). IRI was graded as per neutrophil infiltrate, apoptosis, and hepatocyte cell dropout. Prevalence of IRI and association steatosis was studied along with other factors.

RESULTS

Among 53 subjects, 35 were DDLTs and 18 were LDLTs. All live donor grafts were restricted to <15% MaS and the deceased liver grafts had different type and degree of steatosis. In DDLTs, the association between occurrence of IRI and MaS was not statistically significant (P = 0.201). In DDLTs, the mild steatosis was not significantly associated with IRI. Death donor and ischemic time were significantly associated with IRI. Child's stage and MELD scores, gender, and age were not associated with risk of IRI. Severity of IRI is significantly associated with 3-month mortality (P = 0.001).

CONCLUSION

In patients with mild steatosis, IRI does not correlate with steatosis. However, more patients with moderate and severe steatosis are needed to define the relationship of the two in this group of patients.

Comparison of CT methods for determining graft steatosis in living donor liver transplantation

PURPOSE

To evaluate and compare the diagnostic performance of non-enhanced computed tomography (NECT) and contrast-enhanced CT (CECT) attenuation indices in the assessment of hepatic steatosis by using biopsy as the reference standard.

MATERIALS AND METHODS

This retrospective study was approved by our Institutional Review Board. 55 Potential donors who underwent both NECT and triphasic CECT and core liver biopsy, were included the study. Average attenuation measurements that were obtained from multiple regions in liver, spleen, and psoas muscle on both unenhanced and CECT were used for analysis. Hepatic attenuation measurements were analyzed with and without normalization with the spleen and psoas muscle. Linear regression and receiver operating characteristic (ROC) curve analysis were used to evaluate the statistical association between CT indices and steatosis at histology.

RESULTS

Linear regression analysis confirmed the strongest correlation between steatosis and normalized measurements of hepatic attenuation with splenic attenuations on hepatic venous phase of CECT scan (R 0.821; R² 0.674 and R 0.816; R² 0.665, respectively). The use of ROC curve analysis also demonstrated that normalized measurements of hepatic attenuation with splenic attenuations on hepatic venous phase of CECT showed high diagnostic performance regarding the qualitative distinction of steatosis (AUC values greater than 0.9).

CONCLUSION

Attenuation measurements of liver normalized with spleen on hepatic venous phase may be useful in evaluating steatosis in donor candidates with moderate to severe steatosis who are unacceptable for liver donation. In this manner unnecessary liver biopsy may be avoided in those donor candidates.

Retraction: "Safety limitations of fatty liver transplantation can be extended to 40%: Experience of a single centre in China", by Yu Z., Yu S., Zhang L., Feng X., Zhang M., et al

The above article, published online on 13 October 2016 in Wiley OnlineLibrary (wileyonlinelibrary.com), has been retracted by agreement between the journal Editor in Chief, Mario U. Mondelli, and John Wiley & Sons Ltd. see accompanying Editorial Note It has come to the attention of the Editors that the article may have contained data referring to the use of organs retrieved from executed prisoners and not from donors after cardiac death (DCD), thus breaching international organ donation ethical standards. Further information is contained in the accompanying Editorial link. REFERENCE Yu Z, Sun Z, Yu S, et al. Safety limitations of fatty liver transplantation can be extended to 40%: experience of a single centre in China. Liver Int. 2016; doi: 10.1111/liv.13244.

Noninvasive assessment of macrovesicular liver steatosis in cadaveric donors based on computed tomography liver-to-spleen attenuation ratio

Fatty liver disease, including liver steatosis, is a major health problem worldwide. In liver transplantation, macrovesicular steatosis in donor livers is a major cause of graft failure and remains difficult to assess. On one hand, several imaging modalities can be used for the assessment of liver fat, but liver biopsy, which is still considered the gold standard, may be difficult to perform in this context. On the other hand, computed tomography (CT) is commonly used by teams managing cadaveric donors to assess donors and to minimize the risk of complications in recipients. The purpose of our study was to validate the use of CT as a semiquantitative method for assessing macrovesicular steatosis in cadaveric donors with liver biopsy as a reference standard. A total of 109 consecutive cadaveric donors were included between October 2009 and May 2011. Brain death was diagnosed according to French legislation. Liver biopsy and then CT were performed on the same day to determine the degree of macrovesicular steatosis. All liver biopsies and CT scans were analyzed in a double-blinded fashion by a senior pathologist and a senior radiologist, respectively. For CT, we used the liver-to-spleen (L/S) attenuation ratio, which is a validated method for determining 30% or greater steatosis in living liver donors. Fourteen of 109 biopsies exhibited macrovesicular steatosis > 30% upon histologic analysis. A receiver operating characteristic curve was generated for the L/S ratio to identify its ability to predict significant steatosis, which was defined as >30%. A cutoff value of 0.9 for the CT L/S ratio provided a sensitivity of 79% and a specificity of 97% to detect significant steatosis.

Magnetic resonance fat quantification in living donor liver transplantation

OBJECTIVE

Hepatic steatosis can cause substantial problems for both donors and recipients in living donor liver transplantation (LDLT). The aim of this study is to evaluate the accuracy of the magnetic resonance IDEAL (iterative decomposition of water and fat with echo asymmetry and least squares estimation) sequence in quantifying the liver fat during LDLT.

MATERIALS AND METHODS

A total of 63 liver donors (29 men and 34 women ranging from 18 to 47 years old with a mean age of 30) who received both magnetic resonance imaging (MRI) and intraoperative liver biopsy were enrolled in this study. MR IDEAL IQ sequences were performed by 1.5-T MRI (Discovery 450; GE Healthcare, Milwaukee, Wis, United States) to estimate the liver fatty content. Accuracy was assessed through linear regression between fat fraction image and pathology grading. Sensitivity and specificity of MR IDEAL IQ fat fractions were also calculated.

RESULTS

A total of 63 LDLTs were performed and with pathology grading. No fatty content was found in 48 donors (76.2%; group 1), 5% to 10% fatty liver in 11 donors (17.4%; group 2), 11% to 15% fatty liver in 2 donors (3.2%; group 3), and >16% fatty change in 2 donors (3.2%; group 4). MR IDEAL fat fraction results were excellent in prediction of the normal and fatty content and with good correlation with the pathology grading (2.9 ± 0.9, 8.3 ± 4.2, P < .0001). Linear regression between IDEAL image and pathology grading indicated a high accuracy rate (R(2) = 0.813, R(2) = 0.9286) for all 4 groups. The sensitivity and specificity for detection of liver steatosis in MRI fat fraction image were 100% and 77.1% (P < .0001, 95% confidence interval 0.000-1.000).

CONCLUSION

MR IDEAL IQ sequencing is a highly precise and accurate method in quantifying hepatic steatosis for the living donor.

Comparison of the tolerance of hepatic ischemia/reperfusion injury in living donors: macrosteatosis versus microsteatosis

A safe use of intermittent hepatic inflow occlusion (IHIO) has been reported for living donor hepatectomy. However, it remains unclear whether the maneuver is safe in steatotic donors. In addition, the respective importance of macrosteatosis (MaS) and microsteatosis (MiS) is an important issue. Thus, we compared MiS and MaS with respect to the tolerance of hepatic ischemia/reperfusion (IR) injury induced by IHIO. One hundred forty-four donors who underwent a right hepatectomy were grouped according to the presence of MaS and MiS: a non-MaS group (n = 68) versus an MaS group (n = 76) and a non-MiS group (n = 51) versus an MiS group (n = 93). The coefficients of the regression lines between the cumulative IHIO time and the peak postoperative transaminase concentrations were used as surrogate parameters indicating the tolerance of hepatic IR injury. The coefficients were significantly greater for the MaS group versus the non-MaS group (4.12 ± 0.59 versus 2.22 ± 0.46 for alanine aminotransferase, P = 0.01). Conversely, the MiS and non-MiS groups were comparable. A subgroup analysis of donors who underwent IHIO for >30 minutes showed that MaS significantly increased the transaminase concentrations, whereas MiS had no impact. Also, IHIO for >30 minutes significantly increased the biliary complication rate for MaS donors (12.1% for ≤ 30 minutes versus 32.6% for >30 minutes, P = 0.04), whereas MiS donors were not affected. In conclusion, the tolerance of hepatic IR injury might differ between MaS livers and MiS livers. It would be rational to assign more clinical importance to MaS versus MiS. We further recommend limiting the cumulative IHIO time to 30 minutes or less for MaS donors undergoing right hepatectomy.

Effect of pure microsteatosis on transplant outcomes after living donor liver transplantation: a matched case-control study

Liver steatosis mostly exists in a mixed form of macrosteatosis (MaS) and microsteatosis (MiS). This coexistence is responsible for previous conflicting results regarding the importance of MiS in liver transplantation. We aimed to evaluate the independent effect of MiS on posttransplant outcomes with the exclusion of the confounding effect of MaS. Seventy-one living donors who had pure MiS (defined as an MiS degree > 5% without MaS) were matched 1:1 with control donors, and 66 recipients who received pure MiS grafts were matched 1:1 with control recipients on the basis of propensity scores. Matched variables included the donor age, remnant liver volume, cold ischemia time, graft-to-recipient weight ratio and Model for End-Stage Liver Disease score. The degree of pure MiS ranged from 5% to 50%. Donors in the control and pure MiS groups were comparable with respect to peak postoperative transaminase concentrations [alanine aminotransferase (ALT): 194 versus 176 IU/L, P = 0.61] and postoperative complications. Recipients in the control and pure MiS groups were comparable with respect to recipient (P = 0.15) and graft survival rates (P = 0.56) as well as peak postoperative transaminase concentrations (ALT: 266 versus 281 IU/L, P = 0.88), and graft regeneration rates at 2 weeks (61% versus 59%, P = 0.73). The 2 groups were also comparable with respect to major complications, primary graft dysfunction/nonfunction, intensive care unit/hospital stays, and metabolic diseases. In conclusion, MiS alone does not seem to impair the posttransplant outcomes of living donors and their recipients. The interaction between MiS and MaS, and the effect of a greater degree of MiS are the next important topics to be further evaluated in the mixed steatosis population.

Quantification of hepatic steatosis: a comparison of computed tomography and magnetic resonance indices in candidates for living liver donation

RATIONALE AND OBJECTIVES

To evaluate, in a group of candidates for liver donation, the role of unenhanced computed tomography (CT) and magnetic resonance (MR) as noninvasive means to measure hepatic steatosis (HS).

MATERIALS AND METHODS

Sixty-one consecutive candidates underwent CT and MR evaluation for liver donation within 3 weeks of liver biopsy. On CT, three methods of HS quantification were evaluated: the measurement of hepatic attenuation (CT L), the ratio of hepatic attenuation to splenic attenuation (CT L/S), and the difference between the hepatic and splenic attenuation (CT L-S). On MR, HS was reported in terms of fat signal fraction (FSF) using in-phase/opposed-phase and fat/non-fat- saturated images, with and without normalization with the spleen (T1W IP/OP FSF, T1W IP/OP FSF spleen and T2W ± FS FSF, TW2 ± FS FSF spleen). The accuracy of each imaging index in the diagnosis of HS, according to various thresholds, was assessed using receiver operating characteristic analysis.

RESULTS

On biopsy, 35 donors showed no significant HS (<5%); the remaining 26 showed HS ranging from 5% to 40%. With all CT and MR indices, there was a trend toward increasing diagnostic accuracy as the threshold levels of HS increased. When comparing all the indices, TW2 ± FS FSF(spl) showed higher accuracy at threshold levels of 5% and 10% of steatosis but without reaching statistical significance.

CONCLUSIONS

In candidates for living donation, MR and CT indices are similar in estimating liver-fat content; however, MR with T2W ± FS FSF(spl) sequences shows higher accuracy when low threshold levels of steatosis (≤5% and ≤10% HS) are selected.

Liver-specific deceased donor risk indices

In order to assess the quality of the donor liver, procuring surgeons should accurately evaluate not only general donor risk indices, such as donor age, causes of brain death and cold ischemic time, but also consider the specific donor risk indices. In this review, we focus on liver-specific deceased donor risk indices, including liver steatosis, anti-hepatitis B core (HBc) positive or hepatitis C virus (HCV) positive donors, hypernatremia and anatomical variations. Liver steatosis is strongly associated with poor graft function after liver transplantation. Liver with more than 40-50% macrosteatosis should not be used. However, at present the quantity of fatty livers lack accepted standards. The computerized image analysis programs should be used to automate the determination of fat content in liver biopsy specimens. Liver grafts from anti-HBc positive donors can be safely used, preferentially in hepatitis B surface antigen (HBsAg) positive or anti-HBc/anti-HBs positive recipients. HCV positive allografts free from fibrosis or severe inflammation are a safe option for HCV positive recipients. The procurement team should consider liver biopsy to evaluate these HCV positive allografts. Donor serum sodium over 150 mm may predict a higher rate of graft primary non-functions. Recently, however, some investigators reported the sodium level likely has little clinical impact on post-transplant liver function. The incidence of hepatic artery variations has been reported to be approximately 30%. To avoid injuries, it is very important to know and identify these variations with precision at the time of organ procurement.

Safe use of highly steatotic livers by utilizing a donor/recipient clinical algorithm

The aim of this study was to assess the long-term safety and clinical outcomes associated with the utilization of highly steatotic donor livers utilizing a specific donor/recipient matching algorithm. This was a prospective, observational, single-center, 10-yr follow-up study. Highly steatotic livers were utilized according to a donor/recipient algorithm that guided the surgeon to use highly steatotic donor organs judiciously in low-risk recipients. This study initially compared fat assessment based on frozen-section Ehrlich's hematoxylin and eosin (H&E) to reperfusion biopsy fat assessment and demonstrated that H&E is an insensitive analysis to determine degree of steatosis. Patients were divided into three groups based on donor steatosis (group 1: <30% steatosis, group 2: 30-60% steatosis, group 3: >60% steatosis), and clinical outcomes were assessed. One hundred and sixteen patients were included in the analysis. Patients that received severely steatotic livers (>60% fat) showed increased reperfusion liver injury and delayed return of liver function in the early postoperative period, demonstrated by biochemical markers. However, there were no differences in primary non-function, postoperative complications, length of stay, and patient and graft survival. Using rigorous donor/recipient matching through a detailed algorithm, these data demonstrate that normal liver allograft outcomes are not superior to those in highly steatotic grafts.

Value of the ultrasound attenuation index for noninvasive quantitative estimation of hepatic steatosis

OBJECTIVES

To assess the value of the ultrasound (US) attenuation index for noninvasive estimation of hepatic steatosis and determine its optimal cutoff value for severe steatosis in potential living liver donors.

METHODS

Two hundred forty potential donors underwent US-guided biopsy. The target site was scanned at 4 and 8 MHz. On the sonogram, the observer drew 3 × 3-mm square regions of interest in superficial (3-cm) and deep (5-cm) areas. The attenuation index was defined as the difference between superficial and deep echogenicity/superficial echogenicity × 100. On biopsy specimens, replacement of hepatic parenchyma was evaluated on a percentage scale. Severe steatosis was defined as macrovesicular fatty change of 30% or greater. Spearman rank correlation (ρ) was used to determine correlation coefficients between the attenuation index and steatosis degree; receiver operating characteristic analysis was performed to determine the optimal attenuation index cutoff value for severe steatosis.

RESULTS

The median steatosis degree was 3% (interquartile range [IQR], 0%-10%). Severe steatosis was found in 10 donors. The attenuation index ranged from -27.4 to 36.6 (median, 4.0; IQR, -1.6-10.4) at 4 MHz and -18.0 to 78.1 (median, 14.5; IQR, 7.2-21.9) at 8 MHz. There was a minimal positive correlation between steatosis and the attenuation index at 4 MHz (total steatosis: ρ = 0.339; P < .001; macrovesicular steatosis: ρ = 0.360; P < .001). However, there was a significant moderate correlation between steatosis and the attenuation index at 8 MHz (total steatosis: ρ = 0.669; P < .001; macrovesicular steatosis: ρ = 0.645; P < .001). The optimal attenuation index cutoff value for severe steatosis at 8 MHz was 31.0.

CONCLUSIONS

The US attenuation index at 8 MHz is a useful indicator for noninvasive quantitative estimation of hepatic steatosis and diagnosis of severe steatosis in potential living liver donors.

The use of fatty liver grafts in modern allocation systems: risk assessment by the balance of risk (BAR) score

OBJECTIVE

To integrate the amount of hepatic steatosis in modern liver allocation models.

BACKGROUND

The aim of this study was to combine the 2 largest liver transplant databases (United States and Europe) in 1 comprehensive model to predict outcome after liver transplantation, with a novel focus on the impact of the presence of steatosis in the graft.

METHODS

We adjusted the balance of risk (BAR) score for its application to the European Liver Transplant Registry (ELTR) database containing 11,942 patients. All liver transplants from ELTR and United Network for Organ Sharing with recorded liver biopsies were then combined in one survival analysis in relation to the presence of graft micro- (n = 9,677) and macrosteatosis (n = 11,516).

RESULTS

Microsteatosis, regardless of the amount, was associated with a similar relationship between mortality and BAR score as nonsteatotic livers. Low-grade macrosteatotic liver grafts (≤30% macrosteatosis) resulted in 5-year graft-survival rates of 60% or more up to BAR 18, comparable to nonsteatotic grafts. However, use of moderate or severely steatotic liver grafts (>30% macrosteatosis) resulted in acceptable outcome only if the cumulative risk at transplant was low, that is, BAR score of 9 or less.

CONCLUSIONS

Microsteatotic or 30% or less macrosteatotic liver grafts can be used safely up to BAR score of 18 or less, but liver grafts with more than 30% macrosteatotis should be used with risk adjustment, that is, up to BAR score of 9 or less.

Is it time to extend liver acceptance criteria for controlled donors after cardiac death?

BACKGROUND

Donation after cardiac death (DCD) has reemerged as potential way to increase donor liver availability. Earlier, programs with DCD liver transplantation used conservative donor criteria to allow safe results. Successful initial outcomes allowed extended DCD criteria to address transplant demand.

METHODS

A total of 63 DCD liver grafts were used during the study period in carefully selected recipients. These were divided into two groups: "Standard" DCD within conservative criteria (n=33; age ≤60 years, body mass index <30 kg/m(2), donor warm ischemia time ≤30 min, and cold ischemia time ≤8 hr) and "Extended" DCD beyond these criteria (n=30). We compared donor and recipient characteristics and postoperative outcomes, including patient and graft survival.

RESULTS

Both groups had satisfactory initial function; liver graft function at 1, 7, and 30 days after liver transplantation were similar. Median follow-up period was 25 and 18.5 months for Standard and Extended criteria DCD grafts, respectively, with 1-year patient and graft survival of 88% and 82% for the Standard group vs. 90% and 90% for the Extended. Overall, 8 of 63 (13%) patients developed biliary complications; however, the incidence was not different between the Standard and Extended groups. Seven early deaths occurred, four and three in the Standard and Extended groups, respectively.

CONCLUSIONS

Recipients of DCDs beyond conventional acceptance criteria have equivalent early outcomes to standard DCD grafts. With careful selection of donors and recipients, these grafts can be safely used to expand the donor pool.

Liver transplantation using fatty livers: always feasible?

Steatotic liver grafts represent the most common type of "extended criteria" organs that have been introduced during the last two decades due to the disparity between liver transplant candidates and the number available organs. A precise definition and reliable and reproducible method for steatosis quantification is currently lacking and the potential influence of the chemical composition of hepatic lipids has not been addressed. In our view, these shortcomings appear to contribute significantly to the inconsistent results of studies reporting on graft steatosis and the outcome of liver transplantation. In this review, various definitions, prevalence and methods of quantification of liver steatosis will be covered. Ischemia/reperfusion injury of the steatotic liver and its consequences on post-transplant outcome will be discussed. Selection criteria for organ allocation and a number of emerging protective strategies are suggested.

Assessment of hepatic steatosis by expert pathologists: the end of a gold standard

BACKGROUND

The presence of fat in the liver is considered a major risk for postoperative complication after liver surgery and transplantation. The current standard of quantification of hepatic steatosis is microscopic evaluation by pathologists, although consistency in such assessment remains unclear. Computerized image analysis is an alternative method for objective assessment of the degree of hepatic steatosis.

METHODS

High resolution images of hematoxylin and eosin stained liver sections from 46 consecutive patients, initially diagnosed with liver steatosis, were blindly assessed by 4 established expert pathologists from different institutions. Computerized analysis was carried out simultaneously on the same sections. Interobserver agreement and correlation between the pathologists' and computerized assessment were evaluated using intraclass correlation coefficients (ICC), Spearman rank correlation coefficients, or descriptive statistics.

RESULTS

Poor agreement among pathologists (ICC: 0.57) was found regarding the assessment of total steatosis, (ICC >0.7 indicates acceptable agreement). Pathologists' estimation of micro- and macrosteatosis disclosed also poor correlation (ICC: 0.22, 0.55, respectively). Inconsistent assessment of histological features of steatohepatitis (lobular inflammation, portal inflammation, hepatocyte ballooning, and Mallory hyaline) was documented. Poor conformity was also shown between the computerized quantification and ratings of 3 pathologists (Spearman rank correlation coefficients: 0.22, 0.82, 0.28, and 0.38).

CONCLUSION

Quantification of hepatic steatosis in histological sections is strongly observer-dependent, not reproducible, and does not correlate with the computerized estimation. Current standards of assessment, previously published data and the clinical relevance of hepatic steatosis for liver surgery and transplantation must be challenged.

Quantification of liver fat content: comparison of triple-echo chemical shift gradient-echo imaging and in vivo proton MR spectroscopy

PURPOSE

To validate a triple-echo gradient-echo sequence for measuring the fat content of the liver, by using hydrogen 1((1)H) magnetic resonance (MR) spectroscopy as the reference standard.

MATERIALS AND METHODS

This prospective study was approved by the appropriate ethics committee, and written informed consent was obtained from all patients. In 37 patients with type 2 diabetes (31 men, six women; mean age, 56 years), 3.0-T single-voxel point-resolved (1)H MR spectroscopy of the liver (Couinaud segment VII) was performed to calculate the liver fat fraction from the water (4.7 ppm) and methylene (1.3 ppm) peaks, corrected for T1 and T2 decay. Liver fat fraction was also computed from triple-echo (consecutive in-phase, opposed-phase, and in-phase echo times) breath-hold spoiled gradient-echo sequence (flip angle, 20 degrees), by estimating T2* and relative signal intensity loss between in- and opposed-phase values, corrected for T2* decay. Pearson correlation coefficient, Bland-Altman 95% limit of agreement, and Lin concordance coefficient were calculated.

RESULTS

Mean fat fractions calculated from the triple-echo sequence and (1)H MR spectroscopy were 10% (range, 0.7%-35.6%) and 9.7% (range, 0.2%-34.1%), respectively. Mean T2* time was 14.7 msec (range, 5.4-25.4 msec). Pearson correlation coefficient was 0.989 (P < .0001) and Lin concordance coefficient was 0.988 (P < .0001). With the Bland-Altman method, all data points were within the limits of agreement.

CONCLUSION

A breath-hold triple-echo gradient-echo sequence with a low flip angle and correction for T2* decay is accurate for quantifying fat in segment VII of the liver. Given its excellent correlation and concordance with (1)H MR spectroscopy, this triple-echo sequence could replace (1)H MR spectroscopy in longitudinal studies.

Unenhanced CT for assessment of macrovesicular hepatic steatosis in living liver donors: comparison of visual grading with liver attenuation index

PURPOSE

To retrospectively compare the accuracy of visual grading and the liver attenuation index in the computed tomographic (CT) diagnosis of 30% or higher macrovesicular steatosis in living hepatic donors, by using histologic analysis as the reference standard.

MATERIALS AND METHODS

Institutional review board approval was obtained with waiver of informed consent. Of 703 consecutive hepatic donor candidates, 24 patients (22 men and two women; mean age +/- standard deviation, 36.3 years +/- 9.7) who had 30% or higher macrovesicular steatosis at histologic analysis and same-day CT with subsequent needle biopsy in the right hepatic lobe (at least two samples per patient) were evaluated. An age- and sex-matched control group of 24 subjects included those who had less than 30% macrovesicular steatosis but otherwise met the same criteria as the patient group. A diagnostically difficult setting was made by selecting those with the highest degree of macrovesicular steatosis when there were multiple control subjects matched for a particular subject in the patient group. Two independent radiologists assessed steatosis of the right hepatic lobe by using two methods: a five-point visual grading system that used attenuation comparison between the liver and hepatic vessels and the liver attenuation index (CT(L-S)), defined as hepatic attenuation minus splenic attenuation and calculated with region of interest measurements of hepatic attenuation. Interobserver agreement was assessed. Accuracy in the diagnosis of 30% or higher macrovesicular steatosis was compared by using a multireader, multicase receiver operating characteristic (ROC) analysis.

RESULTS

For visual grading, kappa = 0.905 (95% confidence interval [CI]: 0.834, 0.976). Intraclass correlation coefficient for CT(L-S) was 0.962 (95% CI: 0.893, 0.983). The area under the ROC curve of visual grading and CT(L-S) were 0.927 (95% CI: 0.822, 1) and 0.929 (95% CI: 0.874, 0.983), respectively, indicating no statistically significant difference (P = .975).

CONCLUSION

Both visual grading and CT(L-S) are highly reliable and similarly accurate in the diagnosis of 30% or higher macrovesicular steatosis in living hepatic donor candidates.

Diseases Associated with Childhood Obesity

OBJECTIVE

Radiologists can play an active role in children's health by increasing awareness of diseases associated with obesity. This article reviews key imaging findings in obesity-related diseases, current issues in imaging obese children, and treatment strategies.

CONCLUSION

There has been a well-documented pediatric obesity epidemic and a dramatic increase in clinical diseases associated with it. These serious health consequences affect nearly every organ system. Despite the increasing prevalence of obesity and the associated health hazards, pediatric obesity as a diagnosis is often overlooked by health care providers.

Heat shock proteins and mitogen-activated protein kinases in steatotic livers undergoing ischemia-reperfusion: some answers

Ischemic preconditioning protects steatotic livers against ischemia-reperfusion (I/R) injury, but just how this is achieved is poorly understood. Here, I/R or preconditioning plus I/R was induced in steatotic and nonsteatotic livers followed by investigating the effect of pharmacological treatments that modulate heat shock proteins (HSPs) and mitogen-activated protein kinases (MAPKs). MAPKs, HSPs, protein kinase C, and transaminase levels were measured after reperfusion. We report that preconditioning increased HSP72 and heme-oxygenase-1 (HO-1) at 6 and 24 hours of reperfusion, respectively. Unlike nonsteatotic livers, steatotic livers benefited from HSP72 activators (geranylgeranylacetone) throughout reperfusion. This protection seemed attributable to HO-1 induction. In steatotic livers, preconditioning and geranylgeranylacetone treatment (which are responsible for HO-1 induction) increased protein kinase C activity. HO-1 activators (cobalt(III) protoporphyrin IX) protected both liver types. Preconditioning reduced p38 MAPK and c-Jun N-terminal kinase (JNK), resulting in HSP72 induction though HO-1 remained unmodified. Like HSP72, both p38 and JNK appeared not to be crucial in preconditioning, and inhibitors of p38 (SB203580) and JNK (SP600125) were less effective against hepatic injury than HO-1 activators. These results provide new data regarding the mechanisms of preconditioning and may pave the way to the development of new pharmacological strategies in liver surgery.

Mild hepatic steatosis is not a major risk factor for hepatectomy and regenerative power is not impaired

BACKGROUND

An understanding of the regeneration power and operative risk of steatotic livers after hepatectomy is still unclear. We evaluated the volume regeneration and outcome of steatotic livers after donor hepatectomy.

METHODS

Fifty-four, consecutive living liver donors from September 2002 to December 2003 were evaluated prospectively by volumetric analysis, liver-spleen ratio, and liver attenuation index; the latter has been shown by serial computed tomographic scanning to be correlated strongly with histologic steatosis. Donors were followed up completely for at least 1 year (460-915 days) and were allocated according to histologic degree of macrovesicular steatosis: group 1, <5% (n = 36); group 2, 5%-30% (n = 18).

RESULTS

No mortality or hepatic failure was observed, and no donor required reoperation or intraoperative transfusion. The results of serial liver function tests, and major and minor morbidities were comparable between groups. Liver-spleen ratio and liver attenuation index remained at a constant level above normal values postoperatively in group 1, but increased rapidly above normal values in group 2. No difference in the rate of liver regeneration at 10 days after hepatectomy was found between the groups (P = .487), but the liver regeneration rate at 3 months after hepatectomy in group 1 was slightly higher than that in group 2 (P < .044). However, no difference was observed between the 2 groups at 1 year after hepatectomy (P = .4).

CONCLUSIONS

Mild hepatic steatosis is cleared immediately after hepatectomy, and early regeneration power is impaired, but the long-term regenerative power is comparable. Hepatectomy in donors with mild steatosis can be performed with low morbidity.

Macrovesicular hepatic steatosis in living liver donors: use of CT for quantitative and qualitative assessment

PURPOSE

To determine prospectively the diagnostic performance of unenhanced computed tomography (CT) in the assessment of macrovesicular steatosis in potential donors for living donor liver transplantation by using same-day biopsy as a reference standard.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. A total of 154 candidates, including 104 men (mean age, 30.2 years +/- 10.3 [standard deviation]) and 50 women (mean age, 31.8 years +/- 11.2), underwent same-day unenhanced CT and ultrasonography-guided liver biopsy. Histologic degree of macrovesicular steatosis was determined. Three liver attenuation indices were derived: liver-to-spleen attenuation ratio (CT(L)(/S)), difference between hepatic and splenic attenuation (CT(L)(-S)), and blood-free hepatic parenchymal attenuation (CT(LP)). Regression equations were used to quantitatively estimate the degree of macrovesicular steatosis. Limits of agreement between estimated macrovesicular steatosis and the reference standard were calculated. Receiver operating characteristic analyses were used to determine the performance of each index for qualitative diagnosis of macrovesicular steatosis of 30% or greater. The cutoff value that provided a balance between sensitivity and specificity and the highest cutoff value that yielded 100% specificity were determined.

RESULTS

Limits of agreement were -14% to 14% for CT(L)(/S) and CT(L)(-S) and -13% to 13% for CT(LP). Performance in diagnosing macrovesicular steatosis of 30% or greater was not significantly different among indices (P > .05). Cutoff values of 0.9, -7, and 58 were determined for CT(L)(/S), CT(L)(-S), and CT(LP), respectively, and provided a balance between sensitivity and specificity. Cutoff values of 0.8, -9, and 42 were determined for CT(L)(/S), CT(L)(-S), and CT(LP), respectively, and yielded 100% specificity for all indices, with corresponding sensitivities of 82%, 82%, and 73% for CT(L)(/S), CT(L)(-S), and CT(LP), respectively.

CONCLUSION

Diagnostic performance of unenhanced CT for quantitative assessment of macrovesicular steatosis is not clinically acceptable. Unenhanced CT, however, provides high performance in qualitative diagnosis of macrovesicular steatosis of 30% or greater.