Biopsy-proven Hepatocellular Carcinoma in a 53-year-old Woman With Arginase Deficiency.

Arginase 1 deficiency, the least common urea cycle disorder, commonly presents with childhood-onset spastic paraplegia, progressive neurologic impairment, epilepsy, and developmental delay or regression. Biopsy-proven cirrhosis and hepatocellular carcinoma diagnosed via clinical and imaging studies (but without biopsy confirmation) have been previously reported. We report, herein, a case of a 53-year-old woman with arginase 1 deficiency who developed symptoms of "abdominal bloating." Imaging studies (ultrasound and magnetic resonance imaging) demonstrated 2 dominant hepatic masses, measuring 5.9 cm and 5.7 cm in greatest dimensions and located in hepatic segments 5 and 6, respectively. Core biopsies of the lesions demonstrated well-differentiated hepatocellular carcinoma. Immunohistochemistry performed on the segment 5 lesion was negative for arginase 1. This report represents, to the best of our knowledge, the first case of biopsy-proven hepatocellular carcinoma in an individual with arginase 1 deficiency.

Irreversible Electroporation: Defining the MRI Appearance of the Ablation Zone With Histopathologic Correlation in a Porcine Liver Model.

OBJECTIVE: The purpose of this study is to evaluate the MRI appearance of the irreversible electroporation zone in porcine liver, with histopathologic correlation. MATERIALS AND METHODS: Nine irreversible electroporation ablations were percutaneously created in two Yorkshire pigs. Irreversible electroporation was performed with a bipolar 16-gauge electrode with 3-cm exposure tip and fixed 8-mm interpolar distance. Gadoxetate disodium-enhanced 3-T MRI was performed 50 hours after irreversible electroporation. Livers were harvested immediately after MRI for histopathologic analysis. Ablation zone size was measured on each pulse sequence and correlated with pathologic ablation zone size. Qualitative MRI features of the ablation zone were assessed, and contrast-to-noise ratios (CNRs) were calculated. Statistical analysis included Pearson correlation and t tests. RESULTS: Histopathologically, three distinct layers were present in the irreversible electroporation ablation zone: an inner layer of coagulative necrosis (hyperintense at T1- and T2-weighted imaging and nonenhancing), a middle layer of congestion and hemorrhage (hypointense at T1-weighted imaging, hyperintense at T2-weighted imaging and DWI, and progressively enhancing but hypointense at the hepatobiliary phase), and a peripheral layer of inflammation (hyperintense at the arterial phase but isointense at all other sequences). The hepatobiliary phase ablation zone size showed the highest correlation with the pathologic ablation zone size (r = 0.973). This correlation was significant (p < 0.001). T2-weighted imaging had the highest lesion-to-normal tissue CNR. CONCLUSION: The irreversible electroporation ablation zone contains three distinct histopathologic zones, each with unique MRI features. T2-weighted imaging had the highest CNR, and the hepatobiliary phase had the strongest correlation with ablation zone size.

Bruton Tyrosine Kinase Inhibition Attenuates Liver Damage in a Mouse Warm Ischemia and Reperfusion Model.

BACKGROUND: Bruton tyrosine kinase (Btk) is a central player in multiple signaling pathways of lymphoid and myeloid cells. Myeloid cells are crucial early effectors in organ ischemia-reperfusion (IR) injury. BTKB66 is a selective, irreversible inhibitor of Btk. In this study, we hypothesized that Btk inhibition would reduce hepatocellular injury in a murine model of liver warm hepatic IR. METHODS: First, BTKB66 was tested in in vitro models of lipopolysaccharide-mediated neutrophil and macrophage activation. Then, to assess its efficacy in vivo, BTKB66 was administered orally to mice for 7 days before subjecting them to 90 minutes of warm hepatic ischemia followed by reperfusion for 6 or 24 hours. Clinical and pathologic features in the livers, including AST, ALT, and a panel of cytokines and chemokines, were examined. RESULTS: BTKB66 potently inhibited lipopolysaccharide-mediated activation of bone marrow-derived neutrophils and macrophages in vitro. It also reduced the severity of IR injury as determined by AST and ALT levels, as well as immune cell infiltrates. BTKB66 significantly decreased hepatic markers of sterile inflammation, such as C-X-C motif chemokine 1, C-X-C motif chemokine 2, and C-X-C motif chemokine 10, in parallel with depression of serum markers of the myeloid cell activation, such as CCL5, CCL11, and C-X-C motif chemokine 5. CONCLUSIONS: BTKB66 treatment ameliorated hepatocellular injury in a well-established model of liver partial warm ischemia and in situ reperfusion. These findings confirm that neutrophil recruitment and activation play an essential role in IR stress, and that targeting Btk activity may provide a useful approach for preventing hepatocellular damage and improving outcomes in liver transplantation.

Early cytokine signatures of ischemia/reperfusion injury in human orthotopic liver transplantation.

BACKGROUND. Orthotopic liver transplant (OLT) is the primary therapy for end-stage liver disease and acute liver failure. However, ischemia/reperfusion injury (IRI) can severely compromise allograft survival. To understand the evolution of immune responses underlying OLT-IRI, we evaluated longitudinal cytokine expression profiles from adult OLT recipients before transplant through 1 month after transplant. METHODS. We measured the expression of 38 cytokines, chemokines, and growth factors in preoperative and postoperative recipient circulating systemic blood (before transplant and 1 day, 1 week, and 1 month after transplant) and intraoperative portal blood (before and after reperfusion) of 53 OLT patients and analyzed this expression in relation to biopsy-proven IRI (n = 26 IRI+; 27 IRI-), clinical liver function tests early (days 1-7) after transplant, and expression of genes encoding cytokine receptors in biopsies of donor allograft taken before and after reperfusion. RESULTS. Bilirubin and arginine transaminase levels early after transplant correlated with IRI. Fourteen cytokines were significantly increased in the systemic and/or portal blood of IRI+ recipients that shifted from innate to adaptive-immune responses over time. Additionally, expression of cognate receptors for 10 of these cytokines was detected in donor organ biopsies by RNAseq. CONCLUSION. These results provide a mechanistic roadmap of the early immunological events both before and after IRI and suggest several candidates for patient stratification, monitoring, and treatment. FUNDING. Ruth L. Kirschstein National Research Service Award T32CA009120, Keck Foundation award 986722, and a Quantitative & Computational Biosciences Collaboratory Postdoctoral Fellowship.

Contrast Enhancement Patterns after Irreversible Electroporation: Experimental Study of CT Perfusion Correlated to Histopathology in Normal Porcine Liver.

PURPOSE: To analyze ablated tissue zones after irreversible electroporation (IRE) of porcine liver using computed tomography (CT) perfusion imaging with histopathologic correlation. MATERIALS AND METHODS: Under ultrasound and CT guidance, 10 IRE ablations were performed percutaneously in three Yorkshire pigs using a single bipolar electrode. CT perfusion imaging was performed in all pigs immediately after ablation and on day 2. Pathologic sections were prepared for correlation with histopathology (hematoxylin-eosin and terminal deoxynucleotidyl transferase dUTP nick end labeling stains, 5-mm-thick slices). The short diameter of different enhancing zones on CT was correlated with the gross specimen. RESULTS: CT perfusion images showed three differently enhancing zones: zone 1, inner nonenhancing zone; zone 2, middle well-defined progressive internal enhancement zone; and zone 3, outer ill-defined arterial enhancement zone with rapid washout. On histopathology, zone 1 showed a strong correlation with a pale zone, and zone 2 correlated with a red zone, together accounting for the extent of cell death. Zone 3 was outside of the ablation zone and contained inflammatory cells. Each enhancing zone had different perfusion parameters. CONCLUSIONS: CT perfusion imaging in the acute setting effectively demonstrates histopathologic tissue zones after IRE ablation. Zone 2 is unique to IRE not seen in thermal ablation, characterized by progressive intra-zonal enhancement, and its outer boundary defines the extent of cell death.

Gadoxetate Disodium-Enhanced MRI to Differentiate Dysplastic Nodules and Grade of Hepatocellular Carcinoma: Correlation With Histopathology.

OBJECTIVE: The objective of our study was to determine quantitative differences to differentiate low-grade from high-grade dysplastic nodules (DNs) and low-grade from high-grade hepatocellular carcinomas (HCCs) using gadoxetate disodium-enhanced MRI. MATERIALS AND METHODS: A retrospective study of 149 hepatic nodules in 127 consecutive patients who underwent gadoxetic acid-enhanced MRI was performed. MRI signal intensities (SIs) of the representative lesion ROI and of ROIs in liver parenchyma adjacent to the lesion were measured on unenhanced T1-weighted imaging and on dynamic contrast-enhanced MRI in the arterial, portal venous, delayed, and hepatobiliary phases. The relative SI of the lesion was calculated for each phase as the relative intensity ratio as follows: [mass SI / liver SI]. RESULTS: Of the 149 liver lesions, nine (6.0%) were low-grade DNs, 21 (14.1%) were high-grade DNs, 83 (55.7%) were low-grade HCCs, and 36 (24.2%) were high-grade HCCs. The optimal cutoffs for differentiating low-grade DNs from high-grade DNs and HCCs were an unenhanced to arterial SI of ≥ 0 or a relative SI on T2-weighted imaging of ≤ 1.5, with a positive predictive value (PPV) of 99.2% and accuracy of 88.6%. The optimal cutoffs for differentiating low-grade HCCs from high-grade HCCs were a relative hepatobiliary SI of ≤ 0.5 or a relative T2 SI of ≥ 1.5, with a PPV of 81.0% and an accuracy of 60.5%. CONCLUSION: Gadoxetate disodium-enhanced MRI allows quantitative differentiation of low-grade DNs from high-grade DNs and HCCs, but significant overlap was seen between low-grade HCCs and high-grade HCCs.

Novel liver findings in ornithine transcarbamylase deficiency due to Xp11.4-p21.1 microdeletion.

Ornithine transcarbamylase deficiency (OTCD, OMIM 311250), the most common urea cycle disorder, results in impaired synthesis of citrulline from carbamoyl phosphate and ornithine. Individuals have been identified with OTCD due to a contiguous gene deletion at Xp11.4-p21.1 and unique clinical features, described as the "extended OTCD phenotype". We present a male with neonatal-lethal OTCD due to a 1.87Mb microdeletion at Xp11.4-p21.1 (37126841-38998991 hg18). Autopsy revealed a novel histological finding of hepatocyte globular and granular inclusions. Such inclusions have not been described in OTCD or other metabolic disorders and are not an associated finding in neonatal liver failure due to other causes. The deleted region includes the gene SYTL5, potentially involved in RAB27A-dependent membrane trafficking in the liver and placenta. We propose that the contiguous gene deletion could contribute to the severity of the clinical presentation here and hypothesize that deletion of SYTL5 could contribute to the liver findings.

Splenic hamartomas in Alagille syndrome: case report and literature review.

Alagille syndrome is a rare autosomal dominant disorder with characteristic findings of paucity of intrahepatic bile ducts, congenital heart disease, and vertebral, ocular, and renal abnormalities. We present a unique autopsy case of an 18-year-old female with Alagille syndrome and splenic hamartomas. Autopsy findings included growth restriction, Tetralogy of Fallot, paucity of intrahepatic bile ducts, end-stage renal disease with mesangiolipidosis, and splenomegaly with two well-circumscribed, splenic tumors. Histologic findings of the splenic tumors revealed disorganized vascular channels lined by cells without cytologic atypia. Immunohistochemical analysis demonstrated CD8(+)CD31(+) endothelial cells, consistent with splenic hamartomas. In summary, Alagille syndrome is a rare genetic disorder characterized by JAG1 mutations and disrupted Notch signaling. Review of the literature highlights the importance of Notch signaling in vascular development and disorders. However, to our knowledge this is the first description of splenic hamartomas in Alagille syndrome.

Assessment of chronological effects of irreversible electroporation on hilar bile ducts in a porcine model.

PURPOSE: To evaluate the chronological effects of irreversible electroporation (IRE) on large hilar bile ducts in an in vivo porcine model correlated with computed tomography (CT) cholangiography and histopathology. MATERIALS AND METHODS: Twelve IRE zones were made along hilar bile ducts intraoperatively under ultrasound (US)-guidance in 11 pigs. Paired electrodes were placed either on opposing sides of the bile duct (straddle [STR]) or both on one side of the bile duct (one-sided [OSD]). The shortest electrode-to-duct distance was classified as periductal (≤ 2 mm) or nonperiductal (>2 mm). CT cholangiography and laboratory tests were performed before IRE and again at 2 days, 4 weeks, and 8 weeks after IRE. Degree of bile duct injury were graded as follows: grade 0 = no narrowing; grade 1 = ≤ 50 % duct narrowing; grade 2 = >50 % narrowing without proximal duct dilatation; grade 3 = grade 2 with proximal duct dilatation; and grade 4 = grade 3 with enzyme elevation. Pigs were selected for killing and histopathology at 2 days, 4, and 8 weeks. RESULTS: Nonperiductal electrode placement produced no long-term strictures in 5 of 5 ducts. Periductal electrode placement produced mild narrowing in 6 of 7 ducts: 5 grade 1 and 1 grade 2. None showed increased enzymes. There was no significant difference between STR versus OSD electrode placement. Histopathology showed minor but relatively greater ductal mural changes in narrowed ducts. CONCLUSION: In the larger hilar ducts, long-term patency and mural integrity appear resistant to IRE damage with the energy deposition used, especially if the electrode is not immediately periductal in position.

Chromophobe hepatocellular carcinoma with abrupt anaplasia: a proposal for a new subtype of hepatocellular carcinoma with unique morphological and molecular features.

Hepatocellular carcinomas exhibit heterogeneous morphologies by routine light microscopy. Although some morphologies represent insignificant variations in growth patterns, others may represent unrecognized subtypes of hepatocellular carcinoma. Identification of these subtypes could lead to separation of hepatocellular carcinomas into discrete groups with unique underlying genetic changes, prognosis, or therapeutic responses. In order to identify potential subtypes, two pathologists independently screened a cohort of 219 unselected hepatocellular carcinoma resection specimens and divided cases into potential subtypes. One of these promising candidate subtypes was further evaluated using histological and molecular techniques. This subtype was characterized by a unique and consistent set of histological features: smooth chromophobic cytoplasm, abrupt focal nuclear anaplasia (small clusters of tumor cells with marked nuclear anaplasia in a background of tumor cells with bland nuclear cytology), and scattered microscopic pseudocysts--we designate this variant as 'chromophobe hepatocellular carcinoma with abrupt anaplasia'. Thirteen cases were identified (6% of all hepatocellular carcinomas), including 6 men and 7 women with an average age of 61 years. Six cases occurred in cirrhotic livers. Serum AFP was elevated in 6 out of 10 cases. There were a variety of underlying liver diseases, but cases were enrichment for chronic hepatitis B, P=0.006. Interestingly, at the molecular level, this variant was strongly associated with the alternative lengthening of telomere (ALT) phenotype by telomere FISH. ALT is a telomerase-independent mechanism of telomere maintenance and is found in approximately 8% of unselected hepatocellular carcinomas. In contrast, 11/12 (92%) of the cases of chromophobe hepatocellular carcinoma with abrupt anaplasia were ALT-positive. In summary, we propose that chromophobe hepatocellular carcinoma with abrupt anaplasia represents a new subtype of hepatocellular carcinoma with unique morphological and molecular features.

Abdominal imaging can misdiagnose submassive hepatic necrosis as cirrhosis in acute liver failure.

Patients with acute liver failure (ALF) can be listed status I for liver transplantation (LT) whereas patients with cirrhosis must follow the MELD scoring system. Liver imaging can mistakenly diagnose submassive hepatic necrosis in ALF as cirrhosis. The purpose of our study was to assess the accuracy of ultrasound (US) and computed tomography (CT) in distinguishing cirrhosis from ALF. All patients listed for ALF and transplanted during the study period were included. Controls were age- and gender-matched cirrhotic patients who underwent LT during the same period. Abdominal US or CT scans obtained on all patients were independently reviewed by three blinded abdominal radiologists. Explants from all patients were reviewed by two blinded pathologists, and histological diagnosis was correlated with radiological diagnosis. Forty-one patients with ALF and 42 patients with cirrhosis were analyzed. Univariate and multivariate analyses both revealed overall accuracy of 85% for ultrasound and 93% for CT. US and CT scans both provide high levels of accuracy in terms of discriminating ALF from cirrhosis but measures taken to determine whether a patient has ALF vs. cirrhosis needs to approach 100% accuracy. Thus, imaging studies alone should not definitively diagnosis one etiology of liver failure over the other.

Hepatitis C-associated cryoglobulinemic glomerulonephritis with crystalline deposits.

Infection with hepatitis C virus has been associated with a number of extrahepatic manifestations, including kidney disease. Of the glomerular pathologic states described with hepatitis C virus infection, cryoglobulinemic glomerulonephritis is the most prevalent. On kidney biopsy, cryoglobulinemic glomerulonephritis has a variable appearance, with a membranoproliferative pattern of injury as the most common light microscopic finding. Ultrastructurally, curved and paired microtubules are the most characteristic finding, but these also can be variable. We present a case of cryoglobulinemic glomerulonephritis with distinct and highly unusual ultrastructural findings.

Irreversible electroporation in porcine liver: acute computed tomography appearance of ablation zone with histopathologic correlation.

OBJECTIVE: The objective of this study was to define acute computed tomography (CT) characteristics of ablation zone created by irreversible electroporation (IRE) in porcine liver, with histopathologic correlation. METHODS: Twenty-three IRE ablation zones were created in 4 Yorkshire pig livers percutaneously under image guidance. A prototype generator was used (Ethicon Endo-surgery, Cincinnati, Ohio). Variable spacing of paired electrodes between 1 and 2.0 cm was used. Contrast-enhanced multiphasic CT scans were obtained. Pigs were killed after 5 to 6 hours for gross pathology sectioning with routine and vital histological stains. Computed tomography images were analyzed using 3-dimensional software, and ablation zone size measured on CT was correlated with pathologically determined size. RESULTS: Nineteen of 19 ablation zones created with up to 1.5-cm spacing showed fusion between individual ablation zones generated by each electrode. Ablation zones were isodense precontrast and hypodense to liver postcontrast, with best delineation in the portal phase. Nine of these had nondistorted circumferential margins on both CT and gross pathology suitable for correlation, and among these, size measurements on CT were closely correlated with pathologically determined ablation zone size. Most importantly, on the delayed venous phase, there is internal enhancement within the ablation zone itself, except for small perielectrode zones that remained hypodense. On histopathology, IRE ablation zones showed preserved microvasculature with congestion of sinusoids, except for small perielectrode zones where coagulative changes were suggested. CONCLUSION: Portal phase contrast-enhanced CT scans correlate well with liver IRE ablation size and shape on histopathology.

Assessment of hepatic steatosis by transplant surgeon and expert pathologist: a prospective, double-blind evaluation of 201 donor livers.

An accurate clinical assessment of hepatic steatosis before transplantation is critical for successful outcomes after liver transplantation, especially if a pathologist is not available at the time of procurement. This prospective study investigated the surgeon's accuracy in predicting hepatic steatosis and organ quality in 201 adult donor livers. A steatosis assessment by a blinded expert pathologist served as the reference gold standard. The surgeon's steatosis estimate correlated more strongly with large-droplet macrovesicular steatosis [ld-MaS; nonparametric Spearman correlation coefficient (rS ) = 0.504] versus small-droplet macrovesicular steatosis (sd-MaS; rS = 0.398). True microvesicular steatosis was present in only 2 donors (1%). Liver texture criteria (yellowness, absence of scratch marks, and round edges) were mainly associated with ld-MaS (variance = 0.619) and were less associated with sd-MaS (variance = 0.264). The prediction of ≥30% ld-MaS versus <30% ld-MaS was excellent when liver texture criteria were used (accuracy = 86.2%), but it was less accurate when the surgeon's direct estimation of the steatosis percentage was used (accuracy = 75.5%). The surgeon's quality grading correlated with the degree of ld-MaS and the surgeon's steatosis estimate as well as the incidence of poor initial function and primary nonfunction. In conclusion, the precise estimation of steatosis remains challenging even in experienced hands. Liver texture characteristics are more helpful in identifying macrosteatotic organs than the surgeon's actual perception of steatosis. These findings are especially important when histological assessment is not available at the donor's hospital.

Liver Transplant Pathology: Review of Challenging Diagnostic Situations.

Histopathologic assessment of allograft liver biopsies has an important role in managing patients who have undergone liver transplantation. In this review, several topics are discussed that create diagnostic problems in transplant pathology, with emphasis on pathologic features and differential diagnosis. The topics discussed are acute cellular rejection, late acute rejection (centrizonal/parenchymal rejection), chronic rejection, plasma cell hepatitis, idiopathic posttransplant chronic hepatitis, fibrosing cholestatic hepatitis, selected viral infections (cytomegalovirus, Epstein-Barr virus, and hepatitis E), and acute antibody-mediated rejection.

Irreversible electroporation in porcine liver: short- and long-term effect on the hepatic veins and adjacent tissue by CT with pathological correlation.

OBJECTIVE: The objective of the study was to determine the short- and long-term effects of irreversible electroporation (IRE) on the hepatic veins and the perivascular tissue through serial computed tomography (CT) with pathological correlation. MATERIALS AND METHODS: Multiple IRE lesions were created percutaneously by ultrasound guidance in livers of 11 Yorkshire pigs using a prototype IRE generator. Paired electrodes were used. Three pigs were killed at the same day; 2 pigs, at 2 days; 2 pigs, at 2 weeks; 2 pigs, at 4 weeks; and 2 pigs, at 8 weeks. Contrast-enhanced CT was performed in all pigs initially and thereafter at selected intervals. Pathological sections were performed for correlation. Initial CT scans were analyzed for lesions for degree of circumferential contact (< 25%, 26%-50%, 51%-75%, and 76%-100%) to the hepatic veins for analysis of any contour deformity. The hepatic veins were also analyzed for any thrombus and for any narrowing. Those lesions with follow-up scans were also analyzed for changes over time. RESULTS: Twenty-three lesions showed contiguity to the hepatic veins between 3 to 9 mm in size at the initial CT. No contour deformity due to perivascular tissue sparing is detected for any lesion. There was no thrombus detected in any vessel at any time point. Vessel narrowing was seen in 9 of 23 veins on the initial CT, all less than 50% in diameter and all with lesion contact of greater than 25% in circumference, but 2 of 3 veins with follow-up scans showed return-to-normal caliber. No late narrowing of any hepatic vein was seen on the long-term follow-up. CONCLUSION: Irreversible electroporation creates uniform tissue ablation around the hepatic veins without perivascular tissue sparing. Vessel narrowing may occur acutely but without long-term sequela.

Histopathology of de novo autoimmune hepatitis.

De novo autoimmune hepatitis (DAIH) is a well-recognized complication of pediatric liver transplantation (LT). The diagnosis is largely based on elevated liver function test results and the development of autoimmune antibodies. The histology of DAIH was first described in 1998. We present detailed histological data from the largest series to date of pretreatment and posttreatment biopsy samples from pediatric LT patients with DAIH. The histological evaluation included first an assessment of the predominant pattern of injury (hepatitis, rejection, or bile duct obstruction). Then, the necroinflammatory activity (interface, lobular, and perivenular), plasma cell density, rejection activity index, and fibrosis were scored. Seventy of 685 pediatric patients (10.2%) who underwent LT developed DAIH according to clinical and biopsy findings. Fifty-one pretreatment biopsy samples and 38 posttreatment biopsy samples were available for a retrospective review. The predominant pattern of injury (hepatitis, rejection, or bile duct obstruction) was determined, and biopsy samples were scored for the necroinflammatory activity (interface, lobular, and perivenular), plasma cell density, rejection activity index, and fibrosis. The most common pattern of injury was lobular hepatitis, which was frequently unaccompanied by interface necroinflammatory activity or prominent plasma cell infiltrates. Seven of the 51 cases had features strongly suggestive of acute rejection. Posttreatment biopsy samples showed a reduction in the degree of necroinflammatory activity and plasma cell infiltrates. In most patients, the degree of fibrosis was stable or had regressed. Because the histological features of DAIH are variable and nonspecific, a high index of suspicion and correlation with autoimmune antibodies are necessary to establish the diagnosis. In the majority of patients with DAIH, treatment appears to yield good clinical outcomes and histological improvements.

Regulated hepatic reperfusion mitigates ischemia-reperfusion injury and improves survival after prolonged liver warm ischemia: a pilot study on a novel concept of organ resuscitation in a large animal model.

BACKGROUND: Ischemia-reperfusion injury (IRI) can occur during hepatic surgery and transplantation. IRI causes hepatic mitochondrial and microcirculatory impairment, resulting in acute liver dysfunction and failure. We proposed a novel strategy of regulated hepatic reperfusion (RHR) to reverse the cellular metabolic deficit that incurred during organ ischemia by using a substrate-enriched, oxygen-saturated, and leukocyte-depleted perfusate delivered under regulated reperfusion pressure, temperature, and pH. We investigate the use of RHR in mitigating IRI after a prolonged period of warm ischemia. METHODS: Using a 2-hour liver warm ischemia swine model, 2 methods of liver reperfusion were compared. The control group (n = 6) received conventional reperfusion with unmodified portal venous blood under unregulated reperfusion pressure, temperature, and pH. The experimental group (n = 6) received RHR. We analyzed the effects of RHR on post-reperfusion hemodynamic changes, liver function, and 7-day animal survival. RESULTS: RHR resulted in 100% survival compared with 50% in the control group (p = 0.05). Post-reperfusion syndrome was not observed in the RHR group, but it occurred in 83% of the control group. RHR resulted in a lesser degree of change from baseline serum alanine aminotransferase levels, aspartate aminotransferase, and lactate dehydrogenase after reperfusion compared with the control group. Histopathologic evaluation showed minimal ischemic changes in the RHR group, whereas a considerable degree of coagulative hepatocellular necrosis was observed in the control group. CONCLUSIONS: Regulated hepatic reperfusion mitigates IRI, facilitates liver function recovery, and improves survival after a prolonged period of hepatic warm ischemia. This novel strategy has potential applicability to clinical hepatic surgery and liver transplantation when marginal grafts are used.