Central venulitis in the allograft liver: a clinicopathologic study

Banff 2016 Global Assessment and Quantitative Scoring for T Cell-Mediated Liver Transplant Rejection are Interchangeable

Introduction. Histopathological assessment of liver biopsies is the current “gold standard” for diagnosing graft dysfunction after liver transplantation (LT), as graft dysfunction can have nonspecific clinical presentations and inconsistent patterns of liver biochemical dysfunction. Most commonly, post-LT, graft dysfunction within the first year, is due to acute T-cell mediated rejection (TCMR) which is characterised histologically by the degree of portal inflammation (PI), bile duct damage (BDD), and venous endothelial inflammation (VEI). This study aimed to establish the relationship between global assessment, which is the global grading of rejection using a “gestalt” approach, and the rejection activity index (RAI) of each component of TCMR as described in revised Banff 2016 guidelines. Methods. Liver biopsies (n = 90) taken from patients who underwent LT in 2015 and 2016 at the Australian National Liver Transplant Unit were identified from the electronic medical records. All biopsy slides were microscopically graded by at least two assessors independently using the revised 2016 Banff criteria. Data were analysed using IBM SPSS v21. A Fisher–Freeman–Halton test was performed to assess the correlation between the global assessment and the RAI scores for each TCMR biopsy. Results. Within the cohort, 60 (37%, n = 164) patients underwent at least 1 biopsy within 12 months after LT. The most common biopsy outcome (total n = 90) was acute TCMR (64, 71.1%). Global assessment of TCMR slides strongly positively correlated with PI ( $p$ value <0.001), BDD ( $p$ value <0.001), VEI ( $p$ value <0.001), and total RAI ( $p$ value <0.001). Liver biochemistry of patients with TCMR significantly improved within 4 to 6 weeks post-biopsy compared to the day of the biopsy. Conclusion. In acute TCMR, global assessment and total RAI are strongly correlated and can be used interchangeably to describe the severity of TCMR.

Ultrastructural changes of donor livers in liver transplantation indicate hepatocytes injury

The use of electron microscopy (EM) can provide details about cells and tissue down to the nanometer level. We aim to observe ultrastructural changes in the donor liver by EM and analyze the relationship with prognosis. Data from 89 liver transplant recipients were collected and analyzed for recovery of graft function. The results revealed significantly higher organelle injury scores in the primary liver graft nonfunction (PNF) group. High-score group had higher peak alanine aminotransferases, peak aspartate aminotransferases, and peak international normalized ratio (p = .041, .006 and .036, respectively). Warm ischemia time, score of rough endoplasmic reticulum and nucleus was larger in low-score group (p = .007, .006, and .025, respectively). Patients in high-score group had a significantly short survival time (60.0% vs. 92.9%, p = .0039). No significant difference was found in the analysis of 3-year survival rate (60% vs. 84.5%, p = .07). EM is one of feasible and effective strategy for evaluating the quality of donor liver and the patient's prognosis. Ultrastructural changes under EM indicate hepatocytes injury and a high score indicates a worse outcome in early period but does not affect long-term survival.

Centrizonal hepatocyte dropout in allograft liver biopsies: A clinicopathologic study

BACKGROUND

Centrizonal hepatocyte dropout has been described in diverse liver pathologies, including viral hepatitis, venous outflow obstruction, and allograft cellular rejection. However, its clinical significance remains uncertain.

METHODS AND RESULTS

We designed a clinicopathologic study of 206 allograft liver biopsies with centrizonal hepatocyte dropout. Centrizonal hepatocyte dropout was associated most frequently cellular rejection (n=62), asymptomatic/protocol biopsies (n=56), immediate post-transplantation biopsies (n=21), biliary obstruction (n=14), and viral hepatitis (n=13). The differential diagnosis is informed by timing post-transplantation, biliary imaging, and laboratory test results. "Cholestatic" and "hepatocytic" laboratory patterns were associated with biliary obstruction and cellular rejection, respectively. A mixed pattern peaking after biopsy was observed in viral hepatitis. In the context of cellular rejection, dropout was not associated with time interval to normalization of serum ALT but was associated with shorter transplant-free survival (hazard ratio 4, p = 0.01) compared to histologic severity-matched controls. In time zero allograft biopsies, time to ALT normalization was prolonged (median 15 versus 11 days, p=0.002) in allografts with centrizonal dropout, with no effect on re-transplant free survival.

CONCLUSIONS

Centrizonal hepatocyte dropout has low clinicopathologic diagnostic specificity. However, it correlates with adverse clinical outcomes in allograft cellular rejection and time zero biopsies.

Clinicopathologic Characteristics of Centrilobular Injury in Pediatric Liver Transplantation

Centrilobular injury (CLI) is defined as the presence of perivenular mononuclear inflammation, hepatocyte dropout, and extravasated erythrocytes. In pediatric liver allografts, CLI has been associated with advanced fibrosis and chronic rejection (CR). We sought to better characterize the clinicopathologic features of CLI in the setting of T cell-mediated rejection (TCMR) and its association with complement component 4d (C4d) deposition. A total of 206 posttransplant pediatric patients (491 allograft liver biopsies) were available from 2000 to 2018, of which 63 patients (102 biopsies) showed evidence of TCMR and were included in the study. Of the patients, 35 (55.6%) had CLI on their initial episode of TCMR; those patients with CLI were significantly associated with the type of immunosuppression treatment (P = 0.03), severity of TCMR (P < 0.001), higher gamma-glutamyltransferase (P = 0.01), and advanced fibrosis (P = 0.03). There was a trend to shorter time interval from transplantation to presentation of CLI compared with those without CLI (P = 0.06). No difference was observed in graft or overall survival in the patients with CLI. In 20 patients with CLI, additional biopsies were available; in 45% of these patients, CLI was a persistent/recurrent finding. C4d deposition was noted in 12% of all biopsies (6 patients) with CLI. No significant correlation was noted in C4d deposition and CLI, CR, or graft/overall survival. In conclusion, CLI, although not significantly associated with worse graft survival, was significantly associated with severe TCMR and degree of fibrosis, which highlights the importance of active clinical management and follow-up for these patients.

Clinicopathological features and outcomes of parenchymal rejection in liver transplant biopsies

AIMS

The aim of this study was to perform a comprehensive retrospective analysis of liver transplant biopsies with parenchymal rejection (PR) at our institution, including histological features, laboratory values and follow-up biopsies, and to compare PR with portal-based acute cellular rejection (ACR).

METHODS AND RESULTS

Biopsies from 173 patients were evaluated (retrospective database search 1990-2017), including 49 isolated PR, 35 PR with portal ACR (PR/ACR), 34 mild ACR and 52 moderate ACR cases. The rise and fall of serum liver enzymes was calculated as a measure of acute liver injury and response to immunotherapy, respectively. Isolated PR was associated with delayed-onset acute rejection (P < 0.001), as well as younger age (P = 0.004), and showed a similar rise in liver enzymes to mild ACR. PR/ACR and moderate ACR showed the highest elevations in transaminases (P < 0.05). Isolated PR on an initial biopsy was associated with recurrent episodes of PR (P = 0.01), chronic ductopaenic rejection (P = 0.002) and chronic vascular rejection (P = 0.017). Immunohistochemistry for C4d was performed, and strong C4d staining of venules was only detected in one severe isolated PR case (one of three, 33%) and one moderate ACR case (one of 20, 5%).

CONCLUSIONS

Isolated PR represents a form of late acute rejection with distinct clinical and histological features. There is value in reporting PR in liver transplant biopsies to identify patients at higher risk of developing recurrent PR and chronic rejection. Standardisation of terminology and histological criteria of PR can help in uniform reporting and ensure appropriate management.

Pathology of liver disease: advances in the last 50 years

Liver disease has been recognized in various forms for centuries. Incredible advances, however, have been made especially in the last 50 years, driven by improvements in histology, the development of immunostains, the development of high resolution imaging methods, improved biopsy and resection methods, and the emergence of the molecular era. With these tools, pathologists and their clinical and basic science colleagues moved from classifying liver disease using an observational, pattern-based approach to a refined classification of disease, one based on etiology for medical disease and tumor classification for neoplastic disease. Examples of liver specific diseases are used to illustrate these exciting advances. These impressive advances of the past provide the foundation for hope in the future, as liver pathology continues to play an important role in improving patient care through disease identification and classification and emerging roles in guiding therapy for cures.

A hypothesis on paradoxical privileged portal vein metastasis of hepatocellular carcinoma. Can organ evolution shed light on patterns of human pathology, and vice versa?

Unlike other carcinomas, hepatocellular carcinoma (HCC) metastasizes to distant organs relatively rarely. In contrast, it routinely metastasizes to liver vasculature/liver, affecting portal veins 3-10 times more often than hepatic veins. This portal metastatic predominance is traditionally rationalized within the model of a reverse portal flow, due to accompanying liver cirrhosis. However, this intuitive model is not coherent with facts: 1) reverse portal flow occurs in fewer than 10% of cirrhotic patients, while portal metastasis occurs in 30-100% of HCC cases, and 2) portal vein prevalence of HCC metastasis is also characteristic of HCC in non-cirrhotic livers. Therefore, we must assume that the route for HCC metastatic dissemination is the same as for other carcinomas: systemic dissemination via the draining vessel, i.e., via the hepatic vein. In this light, portal prevalence versus hepatic vein of HCC metastasis appears as a puzzling pattern, particularly in cases when portal HCC metastases have appeared as the sole manifestation of HCC. Considering that other GI carcinomas (colorectal, pancreatic, gastric and small bowel) invariably disseminate via portal vein, but very rarely form portal metastasis, portal prevalence of HCC metastasis appears as a paradox. However, nature does not contradict itself; it is rather our wrong assumptions that create paradoxes. The 'portal paradox' becomes a logical event within the hypothesis that the formation of the unique portal venous system preceded the appearance of liver in evolution of chordates. The analysis suggests that the appearance of the portal venous system, supplying hormones and growth factors of pancreatic family, which includes insulin, glucagon, somatostatin, and pancreatic polypeptide (HGFPF) to midgut diverticulum in the early evolution of chordates (in an Amphioxus-like ancestral animal), promoted differentiation of enterocytes into hepatocytes and their further evolution to the liver of vertebrates. These promotional-dependent interactions are conserved in the vertebrate lineage. I hypothesize that selective homing and proliferation of malignant hepatocytes (i.e., HCC cells) in the portal vein environment are due to a uniquely high concentration of HGFPF in portal blood. HGFPF are also necessary for liver function and renewal and are significantly extracted by hepatocytes from passing blood, creating a concentration gradient of HGFPF between the portal blood and hepatic vein outflow, making post-liver vasculature and remote organs less favorable spaces for HCC growth. It also suggested that the portal vein environment (i.e., HGFPF) promotes the differentiation of more aggressive HCC clones from already-seeded portal metastases, explaining the worse outcome of HCC with the portal metastatic pattern. The analysis also offers new hypothesis on the phylogenetic origin of the hepatic diverticulum of cephalochordates, with certain implications for the modeling of the chordate phylogeny.

Severe Phlebitis Accompanying Vascular Rejection Type Acute T Cell-Mediated Rejection in Renal Transplantation

PURPOSE

Renal transplant patients with vascular rejection type acute T cell-mediated rejection (ATCMR) grade II have a poor prognosis. Vascular lesions in those cases are thought to randomly occur, thus we searched for a novel pathological marker related to vascular rejection in kidney transplantation.

METHODS

We determined pathological characteristics in 14 ATCMR grade II patients treated during an acute phase from 2004 to 2013. We then examined whether those findings appeared in transplant kidney biopsy specimens, except for cases of vascular rejection, in patients examined from 2010 to 2014.

RESULTS

In 9 of the 14 ATCMR grade II patients, phlebitis was accompanied by inflammatory cells that formed polypoid projections in the venous lumen and partial disappearance of vascular endothelium. Further investigation showed those inflammatory cells to be T cells and macrophages. Histological findings revealed coexisting phlebitis in 2 of 13 patients with ATCMR grade I, 3 of 24 with borderline changes, and none with normal findings. Phlebitis occurred at a significantly greater rate than the other findings in cases of vascular rejection (P < .05). However, there was no significant difference in regard to graft survival between patients with and without phlebitis (P = .1829).

CONCLUSION

Our results suggest severe phlebitis as a novel finding associated with the pathology of vascular rejection in patients with a renal allograft.

Autoimmune liver disease, autoimmunity and liver transplantation

Primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH) represent the three major autoimmune liver diseases (AILD). PBC, PSC, and AIH are all complex disorders in that they result from the effects of multiple genes in combination with as yet unidentified environmental factors. Recent genome-wide association studies have identified numerous risk loci for PBC and PSC that host genes involved in innate or acquired immune responses. These loci may provide a clue as to the immune-based pathogenesis of AILD. Moreover, many significant risk loci for PBC and PSC are also risk loci for other autoimmune disorders, such type I diabetes, multiple sclerosis and rheumatoid arthritis, suggesting a shared genetic basis and possibly similar molecular pathways for diverse autoimmune conditions. There is no curative treatment for all three disorders, and a significant number of patients eventually progress to end-stage liver disease requiring liver transplantation (LT). LT in this context has a favourable overall outcome with current patient and graft survival exceeding 80% at 5years. Indications are as for other chronic liver disease although recent data suggest that while lethargy improves after transplantation, the effect is modest and variable so lethargy alone is not an indication. In contrast, pruritus rapidly responds. Cholangiocarcinoma, except under rigorous selection criteria, excludes LT because of the high risk of recurrence. All three conditions may recur after transplantation and are associated with a greater risk of both acute cellular and chronic ductopenic rejection. It is possible that a crosstalk between alloimmune and autoimmune response perpetuate each other. An immunological response toward self- or allo-antigens is well recognised after LT in patients transplanted for non-autoimmune indications and sometimes termed "de novo autoimmune hepatitis". Whether this is part of the spectrum of rejection or an autoimmune process is not clear. In this manuscript, we review novel findings about disease processes and mechanisms that lead to autoimmunity in the liver and their possible involvement in the immune response vs. the graft after LT.

Diagnosis, pathogenesis, and treatment of autoimmune hepatitis after liver transplantation

Autoimmune hepatitis can recur or appear de novo after liver transplantation, and it can result in hepatic fibrosis, graft loss, and re-transplantation. The goals of this review are to describe the prevalence, manifestations, putative pathogenic mechanisms, outcomes, and management of these occurrences. Autoimmune hepatitis recurs in 8-12 % of transplanted patients at 1 year and 36-68 % at 5 years. Recurrence may be asymptomatic and detected only by surveillance liver test abnormalities or protocol liver tissue examination. Autoantibodies that characterized the original disease, hypergammaglobulinemia, increased serum immunoglobulin G level, and histological findings of interface hepatitis, lymphoplasmacytic infiltration, perivenular hepatocyte necrosis, pseudo-rosetting, and acidophil bodies typify recurrence. Premature corticosteroid withdrawal and pre-transplant severity of the original disease are possible risk factors. De novo autoimmune hepatitis occurs in 1-7 % of patients 0.1-9 years after transplantation, especially in children. The appearance of autoantibodies may herald its emergence, and antibodies to glutathione-S-transferase T1 have been predictive of the disease. Recurrent disease may reflect recruitment of residual memory T lymphocytes and host-specific genetic predispositions, whereas de novo disease may reflect an allo-antigenic immune response and molecular mimicries that override self-tolerance. Treatment should be appropriate for autoimmune hepatitis and not based on anti-rejection drugs. Corticosteroid therapy alone or combined with azathioprine is the essential treatment. The substitution of mycophenolate mofetil for azathioprine and switch of the calcineurin inhibitor or its replacement with rapamycin have also been used for refractory disease. Re-transplantation has been necessary in 8-23 %.

Significance of isolated hepatic veno-occlusive disease/sinusoidal obstruction syndrome after liver transplantation

After liver transplantation (LT), hepatic veno-occlusive disease (VOD), which is also known as sinusoidal obstruction syndrome (SOS), has been reported initially in relation to azathioprine use and subsequently in relation to acute rejection (AR). Isolated veno-occlusive disease (iVOD)/SOS raises some questions about its significance and especially its treatment. From the post-LT biopsy samples of 1364 patients (2000-2008), 31 patients with index biopsy samples showing VOD/SOS (2.3%) were identified. After a review of the index biopsy samples and previous biopsy samples, those patients not exposed to azathioprine therapy were subdivided into 2 groups according to the absence or presence of AR. Fifteen of the 31 patients had no previous evidence of AR, whereas 16 experienced episodes of AR (before or concurrently with VOD). The 2 groups were similar in terms of demographic and clinical data and the range of histological centrilobular changes. AR episodes were characterized by an endothelial predilection. iVOD/SOS occurred later than acute rejection-related veno-occlusive disease (AR-VOD)/SOS (mean times of 65 and 4.4 months, respectively, P = 0.0098). There was a tendency for iVOD/SOS to progress less frequently to chronic rejection in comparison with AR-VOD/SOS (3/15 versus 9/15, P = 0.06). The histological resolution of iVOD/SOS was significantly more frequent in patients who benefited from increased immunosuppression in comparison with those who did not (5/7 versus 2/8, P = 0.05). When the groups were considered together, the same result was obtained (14/18 versus 4/12, P = 0.024). In conclusion, despite a constant overall prevalence of VOD/SOS, the proportion of iVOD/SOS has increased. The histological resolution of iVOD/SOS after increase in immunosuppression suggests an immune-mediated origin. Better optimization of immunosuppression may be a curative treatment.

Current views on rejection pathology in liver transplantation

Histological assessments continue to play an important role in the diagnosis and management of liver allograft rejection. The changes occurring in acute and chronic rejection are well recognized and liver biopsy remains the 'gold standard' for diagnosing these two conditions. Recent interest has focused on the diagnosis of late cellular rejection, which may have different histological appearances to early acute rejection and instead has features that overlap with so-called 'de novo autoimmune hepatitis' and 'idiopathic post-transplant chronic hepatitis'. There is increasing evidence to suggest that 'central perivenulitis' may be an important manifestation of late rejection, although other causes of centrilobular necro-inflammation need to be considered in the differential diagnosis. There are also important areas of overlap between rejection and recurrent hepatitis C infection and the distinction between these two conditions continues to be a problem in the assessment of liver allograft biopsies. Studies using immunohistochemical staining for C4d as a marker for antibody-mediated damage have found evidence of C4d deposition in liver allograft rejection, but the functional significance of these observations is currently uncertain. This review will focus on these difficult and controversial areas in the pathology of rejection, documenting what is currently known and identifying areas where further clarification is required.

Tissue factor expression demonstrates severe sinusoidal endothelial cell damage during rejection after living-donor liver transplantation

BACKGROUND/PURPOSE

Since it is well known that endothelial cells may be important targets during rejection after living-donor liver transplantation, in this study we investigated liver sinusoidal endothelial cell (SEC) damage during rejection by focusing on thrombomodulin (TM) and hyaluronic acid (HA) as plasma markers of SEC damage. We also examined tissue factor (TF) expression in SECs, because damage to endothelial cells leads to immediate activation of the coagulation system, with the damage being triggered mainly by TF.

METHODS

Living-donor liver transplantation was performed at Mie University Hospital between March 2002 and December 2007; there were 8 patients with rejection (4 with acute cellular rejection and 4 with chronic rejection) and 32 patients without rejection. Liver biopsy tissue was immunostained with an anti-TF antibody, and assessed for SEC damage. In addition, total RNA was extracted from liver biopsy tissue and tested for TF mRNA expression by reverse-transcription polymerase chain reaction (RT-PCR).

RESULTS

The plasma TM level was significantly higher in the rejection group than in the non-rejection group. TF expression was observed in SECs, in infiltrating inflammatory cells, and in the vascular endothelium in the rejection group. TF mRNA expression was significantly higher in the rejection group than in the non-rejection group.

CONCLUSIONS

We demonstrated that TF expression revealed severe SEC damage in grafted liver during both acute cellular rejection and chronic rejection.

Seeking beyond rejection: an update on the differential diagnosis and a practical approach to liver allograft biopsy interpretation

Pathologic evaluation of liver allograft biopsies plays an integral role in the management of patients after liver transplantation. This review summarizes the clinical context and classical histology of different types of allograft rejection and also the common entities that enter the differential diagnosis of allograft rejection, and provides practical approaches to liver allograft biopsy interpretation. In addition, some of the new developments in the field of liver transplant pathology are updated. The purpose of this review is to provide guidance for pathologists interpreting liver allograft biopsies, particularly those interested in developing expertise in the field of liver transplant pathology.

Pediatric liver transplantation

In previous decades, pediatric liver transplantation has become a state-of-the-art operation with excellent success and limited mortality. Graft and patient survival have continued to improve as a result of improvements in medical, surgical and anesthetic management, organ availability, immunosuppression, and identification and treatment of postoperative complications. The utilization of split-liver grafts and living-related donors has provided more organs for pediatric patients. Newer immunosuppression regimens, including induction therapy, have had a significant impact on graft and patient survival. Future developments of pediatric liver transplantation will deal with long-term follow-up, with prevention of immunosuppression-related complications and promotion of as normal growth as possible. This review describes the state-of-the-art in pediatric liver transplantation.

Significance of central perivenulitis in pediatric liver transplantation

Central perivenulitis (CP) encompasses dropout of zone 3 hepatocytes, red blood cell extravasation, and perivenular mononuclear inflammation. In the liver transplant setting, CP can occur in isolation or it can occur in association with portal-based disease such as acute cellular rejection (PB-ACR). Some CP is also thought to be a manifestation of chronic rejection, particularly when accompanied by zone 3 fibrosis. Prior studies of CP in pediatric liver allografts have been hampered by lack of protocol biopsies and low rates of histologic follow-up. We studied 62 consecutive liver allografts from 55 pediatric patients (age: < or =18 y) who underwent transplant from the years 1995 to 2007. Forty-nine allografts (79%) had > or =1 year of histologic follow-up, 32 (52%) > or =3 years, and 24 (39%) > or =5 years. We reviewed a total of 445 allograft biopsies (mean: 7.2 per allograft) obtained at 2 days to 11 years; 213 (48%) of these were protocol biopsies. Seven explanted livers that were removed during the course of retransplantation for graft failure in this group were also reviewed. All specimens were scored for the following features: (1) CP (mild, moderate, and severe), (2) portal ACR (mild, moderate, and severe), (3) zone 3 fibrosis (mild=perivenular or severe=bridging), and (4) ductopenia. CP was present in 120 (27%) of 445 biopsies, including 73 with CP+PB-ACR, 16 with CP within 1 month of PB-ACR, 27 with isolated CP, 3 with CP+de-novo autoimmune hepatitis, and 1 with CP+Epstein-Barr virus infection. Overall, CP was observed on at least 1 occasion in 41 (66%) allografts. It was not associated with any specific liver function test abnormality or pattern of liver function test abnormalities, it was not associated with vascular compromise as judged by Doppler ultrasound examinations, and it was not related to type of immunosuppression. CP overall was equally prevalent in the early (< or =3 mo) and late (>3 mo) post-transplant periods, but isolated CP increased in the late period. On follow-up, 6 (15%) of 41 allografts with CP developed ductopenic chronic rejection (4 requiring retransplantation) and 10 (25%) developed zone 3-based fibrosis without ductopenia (2 severe, 8 mild). In contrast, none of the 21 allografts without CP developed chronic rejection (P=0.09) and none had zone 3-based fibrosis on their last biopsy (P<0.001). All patients who developed ductopenia had 1 or more episodes of CP+PB-ACR. In contrast, isolated CP [seen in 17 (27%) allografts on at least 1 occasion] was associated with zone 3-based fibrosis in 50%, but did not lead to ductopenic chronic rejection. These results underscore the high frequency of CP in pediatric liver transplantation, occurring in 27% of all allograft biopsies and 66% of allografts overall. CP is most common in conjunction with portal ACR, where it carries a significant risk for the development of zone 3 fibrosis and a trend toward the development of ductopenic chronic rejection.

The prevalence and natural history of untreated isolated central perivenulitis in adult allograft livers

Central perivenulitis (CP) in the allograft liver can be associated with portal-based acute cellular rejection and autoimmune hepatitis or can occur in isolation (isolated CP). Although several studies have demonstrated the significance of CP, the prevalence and natural history of untreated isolated CP have not been well studied. We examined 100 adult allograft liver recipients who had long-term follow-up, had routine protocol biopsies, and received no treatment for isolated CP. Isolated CP was identified in 28 (28%) patients. It occurred late at a mean of 658 days. Interestingly, patients with late isolated CP (defined as >3 months posttransplant) usually manifested only mildly to modestly elevated liver function tests. However, late isolated CP was associated with prior and subsequent allograft complications. Nearly all (94%) cases of late isolated CP occurred in patients who had early episodes of CP and/or acute cellular rejection. Of 13 patients who developed adverse outcomes in their allografts (zone 3 fibrosis in 10, de novo autoimmune hepatitis in 3, and ductopenia in 3), all experienced episodes of prior CP, and 12 (92%) had late CP; 1 patient required retransplant for chronic rejection, but all were alive within the last year. In summary, "transplant-associated" isolated CP occurs in 28% of adult patients, early CP is predictive of late CP, and late CP (often present as isolated CP) is associated with long-term liver injury in some patients.

General aspects and pitfalls in liver transplant pathology

Pathology in a liver transplant setting addresses four different topics: establishment of a definite diagnosis of the liver disease before listing for transplantation, evaluation of the donor liver with regard to pre-existing diseases, in particular macrovesicular steatosis and fibrosis, assessment of the hepatectomy specimen, and post-transplant biopsy evaluation. Of these, post-transplant biopsy evaluation is the most challenging and clinically the most relevant issue. It requires fast diagnoses to facilitate specific treatment and it has to incorporate a broad spectrum of differential diagnoses. Precise knowledge about rejection, post-transplant therapy, pathology of immunosuppression, and recurrence of the initially underlying liver disease including the characteristic time peaks and atypical histological presentations (e.g., fibrosing cholestatic hepatitis) is needed to evaluate specific and combined histological pictures of liver damage. For adequate interpretation of post-transplant biopsies the hepatopathologist has to be informed about the essential clinico-anamnestic aspects such as time course, medication, imaging results, and serology.

Systemic siRNA delivery via hydrodynamic intravascular injection

The main barrier to the use of RNAi in mammalian systems is the difficulty in delivering siRNA or shRNA to the appropriate tissues. Although progress has been made in this area, many of the technologies developed require specialized expertise and reagents that are beyond the reach of most investigators. In contrast, the hydrodynamic injection technique is simple to perform and enables highly efficient delivery of naked, unmodified siRNA to a number of tissues, especially the liver. This review describes the development of the technique and explores the possible mechanisms that enable uptake of siRNA to biological effect. Examples of the use of hydrodynamic injection in animal models of disease and for the study of gene function are presented and discussed.

Mechanism of plasmid delivery by hydrodynamic tail vein injection. II. Morphological studies

BACKGROUND

The efficient delivery of plasmid DNA (pDNA) to hepatocytes by a hydrodynamic tail vein (HTV) procedure has greatly popularized the use of naked nucleic acids. The hydrodynamic process renders onto the tissue increased physical forces in terms of increased pressures and shear forces that could lead to transient or permanent membrane damage. It can also trigger a series of cellular events to seal or reorganize the stretched membrane. Our goal was to study the uptake mechanism by following the morphological changes in the liver and correlate these with the fate of the injected plasmid DNA.

METHODS

We utilized both light microscopic (LM) and electron microscopic (EM) techniques to determine the effect of the HTV procedure on hepatocytes and non-parenchymal cells at various times after injection. The LM studies used paraffin-embedded livers with hematoxylin and eosin (H&E) staining. The immune-EM studies used antibodies labeled with sub-nanometer gold particles followed by silver enhancement to identify the location of injected pDNA at the subcellular level. The level of overall damage to liver cells was estimated based on alanine aminotransferase (ALT) release and clearance.

RESULTS

Both the LM and EM results showed the appearance of large vesicles in hepatocytes as early as 5 min post-injection. The number of vesicles decreased by 20-60 min. Plasmid DNA molecules often appeared to be associated with or inside such vesicles. DNA could also be detected in the space of Disse, in the cytoplasm and in nuclei. Non-parenchymal cells also contained DNA, but HTV-induced vesicles could not be observed in them.

CONCLUSIONS

Our studies suggest an alternative or additional pathway for naked DNA into hepatocytes besides direct entry via membrane pores. It may be difficult to prove which of these pathways lead to gene expression, but the membrane pore hypothesis alone appears insufficient to explain why expression happens preferentially in hepatocytes. Further study is needed to delineate the importance of each of these putative pathways and their interrelationship in enabling oligonucleotide (siRNA) activity and pDNA expression.

Liver biopsy interpretation for causes of late liver allograft dysfunction

Evaluation of needle biopsies and extensive clinicopathological correlation play an important role in the determination of liver allograft dysfunction occurring more than 1 year after transplantation. Interpretation of these biopsies can be quite difficult because of the high incidence of recurrent diseases that show histopathological, clinical, and serological features that overlap with each other and with rejection. Also, more than one insult can contribute to allograft injury. In an attempt to enable centers to compare and pool results, improve therapy, and better understand pathophysiological disease mechanisms, the Banff Working Group on Liver Allograft Pathology herein proposes a set of consensus criteria for the most common and problematic causes of late liver allograft dysfunction, including late-onset acute and chronic rejection, recurrent and new-onset viral and autoimmune hepatitis, biliary strictures, and recurrent primary biliary cirrhosis and primary sclerosing cholangitis. A discussion of differential diagnosis is also presented.

Centrilobular necrosis in autoimmune hepatitis: a histological feature associated with acute clinical presentation

AIMS

The characteristic histological feature of autoimmune hepatitis (AIH) is interface hepatitis with predominant portal lymphoplasmacytic necroinflammatory infiltration. Centrilobular necrosis (CN), reminiscent of toxic or circulatory liver injury, has been reported in AIH. The aim of this study was to assess the frequency of CN in patients with AIH and its correlation with laboratory and clinical data.

METHODS

Liver biopsies were obtained from 114 patients (90 women, 24 men, mean (SD) age 45.4 (19.4) years) with AIH and were evaluated under code by a single pathologist according to the modified Knodell score.

RESULTS

CN was found in 20 (17.5%) patients with virtually unaffected portal areas in four cases. Patients with AIH with CN had a higher total hepatic activity index (median (range) 11 (6 to 15) v 5 (2 to 10)) and presented less frequently with cirrhosis (10% v 38%). Patients with CN had a higher frequency of acute onset (87% v 32%), higher bilirubin (median (range) 12.0 (0.43 to 40.0) v 1.9 (0.36 to 46)) and higher ALT levels (median (range) 25.6 (2.7 to 63.9) v 7.2 (0.7 to 62.6)), than did patients with AIH without centrizonal injury.

CONCLUSION

CN with sparing of the portal areas represents a rare histological pattern in AIH. CN is associated with an acute clinical presentation and might reflect an early lesion preceding portal involvement. Recognition of this particular histological appearance enables early diagnosis of AIH and a timely initiation of immunosuppressive therapy.

Histologic characteristics of late cellular rejection, significance of centrilobular injury, and long-term outcome in pediatric liver transplant recipients

Cellular rejection is a common event in orthotopic liver transplantation, leading to significant morbidity and mortality. Late acute cellular rejection, which occurs at least 3 months post-transplant, affects 8-32% of pediatric liver transplant recipients. The histopathology and clinical outcome of patients affected by late cellular rejection are incompletely understood. The aims of this study were 1) to characterize late cellular rejection in the pediatric liver transplant population and describe the histopathology of late cellular rejection, with specific attention to centrilobular injury, including necrosis, inflammation, and endothelialitis and 2) to characterize the long-term outcome of pediatric liver transplant recipients with centrilobular injury, including necrosis, inflammation, and endothelialitis. All liver biopsies performed from August 1997 to August 2002 on pediatric patients at least 6 months post-transplant were reviewed, scored for rejection by Banff criteria and examined for centrilobular inflammatory changes. Histology was then correlated with clinical outcomes. Fifteen percent of biopsies had late cellular rejection by Banff criteria. Centrilobular inflammation, necrosis and central vein endothelialitis were common in these biopsies. In patients with similar centrilobular changes, but not meeting Banff criteria for rejection, 29% were treated for rejection and responded well clinically. The long-term outcome of patients with isolated centrilobular injury is similar to that of patients with centrilobular changes associated with portal based rejection. In conclusion, the presence of centrilobular inflammation, necrosis, or central vein endothelialitis should prompt consideration of late cellular rejection.

Centrilobular necrosis after orthotopic liver transplantation: association with acute cellular rejection and impact on outcome

Several studies have linked centrilobular necrosis (CN) to acute cellular rejection (ACR) following liver transplantation. However, it may be difficult to establish the diagnosis of ACR when the classic portal features are absent. The aim of the present study was to identify specific features that would help to recognize ACR in biopsies with CN. One hundred and forty liver biopsies with CN were identified from 97 patients who underwent liver transplantation. The following histopathologic features were assessed: CN, steatosis, lobular inflammation, cholestasis, endothelialitis, and fibrosis. CN was graded semiquantitatively. A number of clinical and biochemical parameters were also recorded. Biopsies with CN were assessed for the presence or absence of ACR and divided into two groups accordingly. The associations of the biochemical, pathologic, and clinical features with ACR were assessed using a multivariate logistic regression model. The outcomes of patients with and without rejection were compared using the Cox proportional hazards regression model. Seventy-four biopsies (52.9%) showed evidence of ACR, and 52 patients (53.6%) had evidence of ACR at the first biopsy with CN. The multivariate analysis showed the presence of cholestasis, lobular inflammation, the ALT level, and time since liver transplantation to be independent predictors of the presence of ACR in biopsies with CN. Patients with ACR on their first biopsy with CN were significantly more likely to experience graft loss compared with patients without ACR. In conclusion, the presence of cholestasis and lobular inflammation on biopsies with CN appeared helpful in predicting its association with ACR.

Acute hepatic allograft rejection: a comparison of patients with and without centrilobular alterations during first rejection episode

The histologic diagnosis of acute hepatic allograft rejection is usually based upon the identification of characteristic portal tract features. In addition to these, centrilobular alterations such as central vein endothelialitis, zone 3 inflammation, and hepatocyte necrosis may also be seen during episodes of acute rejection. The purpose of this study was to identify any differences in the subsequent clinical course of patients with and without centrilobular alterations during their first biopsy-proven episode of acute rejection. Acute rejection was diagnosed at least once in 35 liver recipients who had undergone allograft biopsy. Of these, 15 (43%) had centrilobular alterations in their first posttransplant biopsy. These 15 patients developed ductopenia (60% vs. 30%) and subsequent episodes of acute rejection (53% vs. 25%) more often than did the 20 patients who lacked centrilobular alterations in their first posttransplant biopsy. Time to first episode of acute rejection and rates of subsequent recurrent hepatitis and death were similar between the 2 groups. Patients with centrilobular alterations during a first episode of acute rejection are more likely to have subsequent episodes of acute rejection and to develop features of chronic rejection than are patients without these changes. These patients may benefit from more vigilant clinical follow-up and/or higher levels of immunosuppression.

Can early liver biopsies predict long-term outcome of the graft?

BACKGROUND

Chronic rejection (CR) in liver allografts show a rapid onset and progressive course, leading to graft failure within the first year after transplantation. Most cases are preceded by episodes of acute cellular rejection (AR), but histological features predictive for the transition toward CR are not well documented.

METHOD

We assessed the predictive value of centrilobular necrosis, central vein endothelialitis (CVE), central vein fibrosis, and lobular inflammation in the development of CR. One-week and one-month biopsy specimens of 12 patients with CR were compared with those of a control group consisting of 17 patients, who experienced AR without developing CR. The progress of the histological changes was further evaluated in follow-up biopsy specimens of the CR group taken at 2 months and beyond 3 months after transplantation.

RESULT

Centrilobular necrosis, CVE, central vein fibrosis, and lobular inflammation were common features in both groups at 1 week. At 1 month, the incidence declined in the control group. The CR group showed an increased incidence and persistence of these features in the follow-up specimens. The incidence and median grade of severity of CVE was significantly higher in the CR group (p=0.04, and P<0.001). The severity of portal and lobular inflammation was also more pronounced in the CR group (P+0.01 and 0.069). Conversely, in the control group the incidence of the lobular features decreased and the severity of CVE declined significantly (P=0.03).

CONCLUSION

The shift from a predominantly portal-based process toward lobular graft damage represents the early transition of AR to CR, for which a modification of immunosuppression might be necessary to prevent graft loss.

Real-time monitoring of acute liver-allograft rejection using the Banff schema

BACKGROUND

The Banff schema is the internationally accepted standard for grading acute liver-allograft rejection, but it has not been prospectively tested.

METHODS

Complete Banff grading was prospectively applied to 2,038 liver-allograft biopsies from 901 adult tacrolimus-treated primary hepatic allograft recipients between August 1995 and September 2001. Histopathologic data was melded with demographic, clinical, and laboratory data into a database on an ongoing basis using locally developed software.

RESULTS

Acute rejection developed in 575 of 901 (64%) patients and the worst grade was mild in 422 of 575 (73%). At least one episode of moderate or severe acute rejection developed in 153 of 901 (17%) patients and most episodes, irrespective of severity, occurred within the first year after transplantation. Patients with moderate or severe acute rejection showed higher alanine aminotransferase (P =0.007) and aspartate aminotransferase ( P=0.07) levels and were more likely to develop perivenular fibrosis on follow-up biopsies (P =0.001) and graft failure from acute or chronic rejection ( P=0.004) than those with mild rejection. Regardless of severity, 80% of patients with acute rejection did not develop significant fibrosis in follow-up biopsies, and graft failure from acute or chronic rejection occurred in only 11 of 901 (1%) allografts.

CONCLUSIONS

Most acute-rejection episodes are mild and do not lead to clinically significant architectural sequelae. When tested prospectively under real-life and -time conditions, the Banff schema can be used to identify those few patients who are potentially at risk for more significant problems. Creation, capture, and integration of non-free text, or "digital," pathology data can be used to prospectively conduct outcomes-based research in transplantation.

Centrilobular fibrosis in long-term follow-up of pediatric liver transplant recipients

BACKGROUND

Centrilobular fibrosis after liver transplant in adults is caused mainly by viral hepatitis, chronic rejection, and azathioprine toxicity. The aim of this study was to investigate possible etiologies and the long-term outcome of this lesion in children.

METHODS

We identified centrilobular fibrosis in 12 of 117 pediatric liver transplant recipients who were investigated for persistent elevations in aminotransferases. Etiologic factors, histologic features on serial biopsies, and clinical and biochemical changes over time were noted for 8 recipients in whom a readily identifiable cause was not apparent.

RESULTS

Centrilobular fibrosis developed a mean of 1.7 years (range: 30 days-3.6 years) posttransplantation in patients receiving cyclosporine, azathioprine, and prednisone. Centrilobular fibrosis was always associated with portal fibrosis and, in six recipients, with persistent, low-grade, cellular rejection. None demonstrated chronic cholestasis, ductopenia, or identifiable vasculopathy. Ischemic, viral, and autoimmune etiologies were excluded. Discontinuing azathioprine did not lead to biochemical or histological improvement. After changing to tacrolimus, aminotransferases normalized in three recipients and repeat biopsies in six were unchanged during a further 2 years of follow-up.

CONCLUSIONS

Centrilobular fibrosis may develop in a small number of pediatric liver transplant recipients, resulting in considerable difficulties in biopsy interpretation. It is not associated with viral hepatitis nor with classical features of chronic rejection. The prognostic significance of centrilobular fibrosis is uncertain, although no child has required retransplantation in up to 12 years of follow-up. A role for a low-grade, chronic form of cellular rejection heralded by persistent, variable, and otherwise unexplained elevations in aminotransferases is suggested.

Portacaval shunt causes apoptosis and liver atrophy in rats despite increases in endogenous levels of major hepatic growth factors

BACKGROUND/AIMS

The response to the liver damage caused by portacaval shunt (PCS) is characterized by low-grade hyperplasia and atrophy. To clarify mechanisms of this dissociation, we correlated the expression of 'hepatotrophic factors' and the antihepatotrophic and proapoptotic peptide, transforming growth factor (TGF)-beta, with the pathologic changes caused by PCS in rats.

METHODS

PCS was created by side-to-side anastomosis between the portal vein and inferior vena cava, with ligation of the hilar portal vein. Hepatic growth mediators were measured to 2 months.

RESULTS

The decrease in the liver/body weight ratio during the first 7 days which stabilized by day 15, corresponded to parenchymal cell apoptosis and increases in hepatic TGF-beta concentration that peaked at 1.4 x baseline at 15 days before returning to control levels by day 30. Variable increases in the concentrations of growth promoters (hepatocyte growth factor, TGF-alpha and augmenter of liver regeneration) also occurred during the period of hepatocellular apoptosis.

CONCLUSIONS

The development of hepatic atrophy was associated with changes in TGF-beta concentration, and occurred despite increased expression of multiple putative growth promoters. The findings suggest that apoptosis set in motion by TGF-beta constrains the amount of hepatocyte proliferation independently from control of liver volume.

Histologic and biochemical changes during the evolution of chronic rejection of liver allografts

Criteria for histologic diagnosis of chronic rejection (CR) are based on changes seen late in the disease process that are likely to be irreversible and unresponsive to treatment. Changes occurring during the evolution of CR are less clearly defined. The serial biopsy specimens, failed allografts, and biochemical profiles of 28 patients who underwent retransplantation for CR were examined with the aim of identifying histologic and biochemical features that were present during the early stages of CR. For each case, a point of acute deterioration in liver function tests (LFTs) was identified ("start time" [ST]) that subsequently progressed to graft failure. Biopsy specimens before, at the time of ("start biopsy" [SB]), and after the ST were assessed histologically, and findings were correlated with the biochemical changes. CR resulted from acute rejection (AR) that did not resolve. Centrilobular necroinflammation (CLNI) associated with an elevated aspartate transaminase (AST) level and portal tract features of AR were present at the start. Portal AR features resolved, CLNI persisted, AST level remained elevated, and bilirubin and alkaline phosphatase levels progressively increased throughout the evolution of CR. Portal tracts also showed a loss of small arterial and bile duct branches, with arterial loss occurring early and bile duct loss as a later progressive lesion. Foam cell arteriopathy was rarely seen in needle biopsy specimens. In conclusion, findings from this study may help identify patients at risk of progressing to graft loss from CR at a stage when the disease process is potentially reversible and amenable to treatment.

Centrilobular histopathologic changes in liver transplant biopsies

We evaluated centrilobular histologic changes seen on post-orthotopic liver transplantation (OLT) biopsies to refine the pathologic diagnosis by systematic study of morphologic and clinical data with possible identification of prognostic criteria. A total of 110 biopsies with zone 3 pathology from 59 patients were reviewed and correlated with clinical findings. Within the first 6 months post-OLT (group I), 39 of 47 patients had combinations of centrilobular hepatocytic dropout, ballooning, and cholestasis on single or multiple biopsies attributed to perioperative ischemic/perfusion injury; 12 of 39 patients with all 3 features present had increased incidence of biliary complications and sepsis and decreased 1-year patient and graft survival; 17 of 39 patients with 2 of the 3 features had increased biliary complications but not decreased 1-year survival; and the remaining 8 of 47 patients had central venulitis associated with acute cellular rejection. After 6 months post-OLT (group II), 14 patients, including 2 from group I, had biopsies with centrilobular pathology; 8 of 14 had central venulitis related to rejection (acute, 4; chronic, 4), and fibrosis was seen in 8 (rejection, 6; cardiac problems, 2). In conclusion, combinations of centrilobular hepatocytic ballooning, dropout, and cholestasis are seen in association with reversible or irreversible ischemic/perfusion damage in the early post-OLT period. The presence of all 3 features is associated with a poor outcome. Central venulitis as a feature of acute/chronic rejection is seen at any time post-OLT and is not a predictor of poor graft/patient survival.

Centrilobular necrosis in children after combined liver and small bowel transplantation

BACKGROUND

Centrilobular necrosis is not an uncommon finding after isolated liver transplantation. In this study, we sought to describe hepatic centrilobular necrosis in children after combined liver and small bowel transplantation (LSBT), and to assess the predictive factors, possible causes, and prognosis.

METHODS

Six children aged 4 to 11 years, in whom liver biopsy showed centrilobular necrosis at least once, 3 weeks to 2 years after LSBT, were compared with nine children without this pathology. All six children experienced an acute complication in the few weeks preceding the finding of centrilobular necrosis. In addition, one child had an early arterial thrombosis and one, severe colitis 3 years after LSBT.

RESULTS

Centrilobular necrosis was associated with centrilobular swelling, dropout, endotheliitis, and inflammation. Fibrosis developed early and worsened on follow-up biopsy in three children. Portal symptoms of acute rejection were not constant, and there was no ductopenia. Biologic abnormalities were responsive to increased immunosuppression, including mycophenolate in four cases. However, follow-up biopsies showed persistent lesions in five patients, mildly inflammatory in four. Baseline immunosuppression had to be maintained at high levels. No viral infections, vascular compromise (except in one), and autoimmunity were found. We compared the two groups of children for initial diagnosis, age at transplantation, time receiving parenteral nutrition, ischemic time, presence of an associated transplanted colon, number of reoperations and infections, intestinal rejection, and immunosuppression, and found no differences.

CONCLUSIONS

This severe manifestation of chronic liver rejection occurred despite the heavy immunosuppression needed for LSBT. The previous acute clinical event could have triggered rejection by modifying the effective immunosuppression at the tissue level. Despite high baseline immunosuppression, histologic lesions persisted and significant fibrosis developed in half the children. We speculate that the lack of induction of tolerance in this particular setting of LSBT could be responsible for constant immune stimulation, thus chronic rejection. The optimal protocol of immunosuppression has yet to be defined to avoid this complication.

Arcuate and interlobular phlebitis in renal allografts

Intimal arteritis in the renal allograft has a well-documented adverse effect on graft outcome. In contrast, venulitis is currently considered an innocuous finding, based largely on observations of thin-walled intermediary venules. Arcuate and interlobular veins have not been studied specifically. These veins have well-developed muscular walls, and inflammation at this level (phlebitis) could significantly alter renal hemodynamics. We studied the clinicopathologic correlates of arcuate and interlobular phlebitis in 31 renal allograft biopsy specimens. Phlebitis was seen in conjunction with borderline changes suggestive of acute cellular rejection (13 cases), or acute rejection Banff grade 1A (7 cases), Banff grade 1B (6 cases), Banff grade 2A (4 cases), and Banff grade 2B (1 case). Clinical follow-up (average 323 +/- 460 days) showed no adverse effects of phlebitis as judged by temporal changes in serum creatinine and the grade of chronic allograft nephropathy in follow-up biopsies. Thus it appears that arcuate and interlobular phlebitis in allograft biopsy specimens does not add prognostic information beyond that provided by conventional Banff criteria. However, this lesion frequently coexists with changes suggestive or diagnostic of acute cellular rejection, and intimal arteritis may be seen concurrently in up to 16% of cases.

Are parenchymal changes in early post-transplant biopsies related to preservation-reperfusion injury or rejection?

BACKGROUND

The progression of parenchymal changes in liver allograft biopsies due to preservation-reperfusion injury (PRI) and their differentiation from rejection related changes is poorly understood. The aim of this study was to determine which changes in a 1-week posttransplant biopsy could be attributed to PRI and which to acute rejection.

METHODS

One week protocol liver transplant biopsies from patients with mild PRI (day 1 AST<400 IU/L) were compared with those from patients with severe PRI (day 1 AST>2000 IU/L). Parenchymal changes (cholestasis, ballooning, steatosis, necrosis) and rejection-related inflammatory features (portal tract inflammation, bile duct inflammation, portal vein endothelial inflammation, hepatic vein endothelial inflammation, and centrilobular inflammation) were blindly assessed semiquantitatively.

RESULTS

Fat, cholestasis, and hepatocyte ballooning were significantly worse in the severe PRI group, and these features showed no correlation with histological features related to acute rejection. Centrilobular hepatocyte necrosis correlated with hepatic venular endothelial inflammation and centrilobular inflammation but not with rejection related features in portal tracts or with PRI. These findings suggest that centrilobular necrosis is a manifestation of a rejection-related parenchymal injury and may involve different pathogenetic mechanisms to rejection-related features in portal tracts.

CONCLUSIONS

This study indicates that in early posttransplant biopsies, fat, cholestasis, and ballooning can largely be attributed to PRI. By contrast, centrilobular hepatocyte loss should be suspected as a rejection related phenomenon, even if typical portal tract changes are not prominent, and augmentation of immunosuppression should be considered.

Fibrous obliterative lesions of veins contribute to progressive fibrosis in chronic liver allograft rejection

Fibrosis in liver allografts undergoing chronic rejection (CR) is variable and poorly understood. The temporal and spatial relationships of venous, arterial, and biliary lesions were studied to clarify their potential contributions to graft fibrosis. The severity, prevalence, and morphology of intimal lesions of vessels were analyzed and compared with the fibrosis stage. Three groups were found; group 1 (n = 5) with no hepatic vein (HV) lesions, group 2 (n = 5) with HV lesions only, and group 3 with lesions of both HV and portal veins (PV). The earliest lesion to develop, in 71% of grafts, was concentric intimal thickening of small HV. This was significantly more severe and frequent in grafts from group 3. With increasing frequency and severity of small HV sclerosis, fibrosis developed in medium/large veins. The morphology of larger vessel lesions suggested organized thrombus. Centrilobular fibrosis was significantly more severe in group 3 and developed unpredictably and sometimes rapidly. Conversely, portal fibrosis scores were significantly higher in grafts with ductular proliferation and did not correlate with venous lesions. This suggests that in CR, veno-occlusive-like lesions develop commonly in terminal hepatic venules, probably caused by immune-mediated damage. In only a proportion, with increased frequency and severity of the lesions, stasis and thrombosis in portal and larger veins occur and could result in loss of hepatic and portal venous outflow, which leads to ischemia and fibrosis. The stage of fibrosis did not correlate with foam-cell arteriopathy. A second pathway of portal fibrosis occurs in patients with longstanding biliary proliferation.

Clinicopathological analysis of liver allograft biopsies with late centrilobular necrosis: a comparative study in 54 patients

BACKGROUND

Centrilobular necrosis (CLN) in liver allografts can be a difficult lesion to interpret histologically. Although long recognized in association with developing chronic rejection, recent studies have described the lesion in association with a number of other disease processes. To clarify the histologic features that could allow a specific diagnosis to be made and to determine the outcome in different diagnostic groups, we assessed biopsies from 54 patients with CLN.

METHODS

Biopsies were classified as CLN with acute cellular rejection (ACR), CLN with hepatitis, CLN with developing chronic rejection (CR), and CLN of other etiology. Histologic features were assessed and then compared between groups, and clinical outcomes were noted.

RESULTS

Discriminating features for the different groups were as follows: CLN and ACR showed bile duct injury, endothelialitis, and acinar congestion. CLN and CR showed severe bile duct injury, bile duct loss, or centrilobular swelling. CLN and hepatitis was often a diagnosis of exclusion, although interface hepatitis was more common in this group. Cases of autoimmune hepatitis usually demonstrated plasma cell predominance in the portal and acinar inflammatory infiltrate. Significantly, there was considerable overlap in the histologic features between the groups, accounting for the diagnostic difficulty. Patients in whom the CLN was associated with CR or vascular complications generally required retransplantation or died, but in the groups with ACR and hepatitis, the outcome was more favorable.

CONCLUSIONS

With regard to most liver allograft biopsies showing late CLN, it is possible to make a specific diagnosis despite overlapping histologic features; this allows specific therapy to be instituted. Ultimately this is likely to contribute to improved graft survival.