Chronic liver allograft rejection: a National Institute of Diabetes and Digestive and Kidney Diseases interinstitutional study analyzing the reliability of current criteria and proposal of an expanded definition. National Institute of Diabetes and Digestive and Kidney Diseases Liver Transplantation Database

Approaches to Research Determination of Late Acute Cellular Rejection in Pediatric Liver Transplant Recipients

A central pathology or site reading of biopsy slides is used in liver transplant clinical trials to determine rejection. We evaluated interrater reliability of readings of "rejection or not" using digitized slides from the Medication Adherence in Children who had a Liver Transplant (MALT) study. Four masked experienced pathologists read the digitized slides and then reread them after a study-specific histologic endpoint development program. Agreement was expressed throughout as a Kappa or Fleiss Kappa statistic (ҡ). A ҡ > 0.6 was predefined as desirable. Readings were correlated with immunosuppressant adherence (the Medication Level Variability Index, [MLVI]), and maximal liver enzyme levels during the study period. Interrater agreement between site and central review in MALT, and between 4 pathologists later on, was low (ҡ = 0.44, Fleiss ҡ = 0.41, respectively). Following the endpoint development program, agreement improved and became acceptable (ҡ = 0.71). The final reading was better-aligned with maximal gamma-glutamyl transferase levels and MLVI as compared with the original central reading. We found substantial disagreement between experienced pathologists reading the same slides. A unique study-specific procedure improved interrater reliability to the point it was acceptable. Such a procedure may be indicated to increase reliability of histopathologic determinations in future research, and perhaps also clinically.

[Liver transplantation. Current aspects of pretransplantation diagnosis and rejection]

Liver transplantation is an established treatment option for patients with end-stage liver disease. The therapy management of these patients is interdisciplinary and requires pathologists to have both clinical and immunological knowledge. Continuous advances in treatment and increasing clinical experience are accompanied by the further development of pathological transplant diagnostics. This article presents and discusses the latest classification of T‑cell-mediated rejection (TCMR), antibody-mediated rejection (AMR), and aspects of pretransplant diagnostics.

Acute, Chronic, and Humoral Rejection: Pathologic Features Under Current Immunosuppressive Regimes

Under current immunosuppressive regimes, T-cell-mediated acute and chronic rejection remain common and important posttransplant complications. The definition of humoral (antibody-mediated) rejection has been greatly expanded in recent years. The histopathologic assessment of allograft biopsies continues to serve an important role in the diagnosis of rejection and to facilitate patient management. The diagnosis of both acute and chronic antibody-mediated rejection requires integration of the results of donor-specific antibody testing and C4d immunostaining, as well as exclusion of other potential etiologies of allograft dysfunction. Chronic antibody-mediated rejection should also be included in the differential diagnosis for unexplained allograft fibrosis.

A comparison of outcomes between OKT3 and antithymocyte globulin for treatment of steroid-resistant rejection in hepatitis C liver transplant recipients

BACKGROUND

The treatment of steroid-resistant rejection (SRR) is associated with severe recurrent hepatitis C virus (HCV) infection after liver transplantation (LTx). After OKT3 was recently withdrawn from the market, thymoglobulin (TG) became the principal treatment for SRR.

METHODS

A retrospective analysis of 32 HCV patients who were treated for SRR with OKT3 (n=15) or TG (n=17) using yearly protocol liver biopsies. Mean follow-up was 4.3 years (OKT3) and 3.2 years (TG). We compared both groups for patient survival, graft loss, and severity of HCV recurrence, manifested as the mean stage of fibrosis (MSF).

RESULTS

Patient survival at 1, 2, and 5 years after LTx was 80%, 73%, and 67% in the OKT3 group and 82%, 77%, and 64% in the TG group, respectively. At 2 years after LTx, the graft losses were 3 versus 4 in the OKT3 and TG groups, respectively. At years 1 and 2, the MSF in the OKT3 group was 1.9 and 2.3 versus 2.4 and 2.8 in the TG group, respectively. None of the differences between both groups was statistically significant.

CONCLUSION

There was no significant difference in patient survival, graft loss, or severity of recurrent HCV, measured as MSF, between both groups.

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 %.

Hepatocyte cytokeratin 7 expression in chronic allograft rejection

We examined hepatocyte cytokeratin 7 (CK7) expression in chronic allograft rejection (CR), a ductopenic condition in which this has not been systematically evaluated, in 20 patients with the clinicopathologic diagnosis of CR and age-, sex-, and native-disease-matched control subjects. We also studied baseline biopsy specimens from both groups. Three pathologists independently reviewed H&E- and CK7-stained sections, counting interlobular bile ducts (BDs) and portal tracts (PTs), noting the morphologic pattern of injury and scoring hepatocyte CK7 expression (0, none; 1+, rare; 2+, multifocal, predominantly periportal; 3+, extension into the lobule; 4+, diffuse). Mean BD/PT ratios and CK7 scores were calculated. The mean BD/PT ratio (0.58) and CK7 score (1.01) for the "CR, diagnostic" group were significantly different from all other group means (P < .05); no other comparisons were significant (P > .05). A CK7 score of 1 or more was observed in 9 (56%) of 16 CR specimens and in 3 (7%) of 41 remaining specimens. Hepatocyte CK7 expression is frequently noted in CR, and it would appear to reflect ductopenia. CK7 staining may be a useful diagnostic adjunct in evaluation of transplant liver biopsy specimens.

Anti-thymocyte globulin for the treatment of acute cellular rejection following liver transplantation

INTRODUCTION

Acute cellular rejection (ACR) post-liver transplantation (LT) can usually be reversed with pulse dose steroids. Anti-thymocyte globulin (ATG) is used to treat steroid-resistant rejection (SRR).

PATIENTS AND METHODS

We report 15 male and five female LT recipients with a median age of 48.3 (range 14.3-71.7) years, who received ATG for biopsy-proven steroid-resistant rejection (n =13), severe rejection (6), and severe rejection/recurrent autoimmune hepatitis (n = 1) median 42 (range 6-2,456) days following LT.

RESULTS

Underlying liver diseases included HCV (n = 7), alcoholic cirrhosis (n = 3), NASH (n = 2), HBV (n = 2), autoimmune hepatitis (n =1), PSC (n = 1), miscellaneous (n = 4) including three re LTs. All patients responded to treatment (median AST declined from 172 to 34U/l, median total bilirubin from 9.1 to 1.3 mg/dl; p < 0.001). Three patients developed recurrent ACR, and none chronic rejection. All HCV patients developed recurrence with significant rises in HCV RNA levels. Infections included pneumonia, sepsis, intraabdominal infection, chronic diarrhea, wound infection, EBV, and CMV disease. After a median follow-up of 65.5 (range 4.3-101.7) months post-ATG and median 67.7 (range 9.3-306.3) months post-LT, 17 patients are alive, two died from sepsis/multi-organ failure and one from HCV recurrence.

CONCLUSION

ATG effectively reversed severe and SSR; HCV recurrence and infections remain significant complications.

Diagnosis in Pediatric Transplant Biopsies

Infant recipients have better survival after solid organ transplantation than older children and adults possibly due to immune tolerance. Over the past two decades, postsurgical complications have markedly decreased, and multidrug immunosuppressive regimens have become effective in preventing and treating rejection. Immunocompromised for life, these patients are susceptible to both the usual bacterial as well as opportunistic infections that often involve the lung. Post-transplant lymphoproliferative disease seems to be decreasing even further in frequency. This article focuses on the findings seen on biopsy, usually of the transplanted organ, and also of other sites affected by post-transplant complications.

Chronic rejection of the liver: the role of immunosuppression

Liver transplantation is now widely recognised as an effective treatment option for patients with advanced liver disease. Many units now achieve greater than 85% survival at 1 year, with the majority of patients having a high quality of life. The maintenance of a high quality of life requires careful clinical management to ensure that the continued maintenance of excellent liver graft function is not achieved at the expense of immunosuppressive drug complications or morbidity. Acute liver rejection will occur in between 30 to 45% of patients, although with modern immunosuppressive protocols, usually combining one of the calcineurin agents, either cyclosporin or tacrolimus, with both azathioprine and corticosteroids (prednisolone) ensures that relatively few grafts are lost from severe acute rejection. While the incidence and severity of acute rejection may be one factor in raising the risk of chronic rejection, it may not be the principal one in many patients. It is important to recognise that the frequency of rejection also varies with the primary underlying liver disease, with patients with hepatitis B or alcoholic liver disease having relatively low rejection rates, compared with patients with primary biliary cirrhosis (PBC) or primary sclerosing cholangitis (PSC), which range between 20 to 70%. Chronic rejection will account for some 5% of grafts lost in the first 3 to 5 years. Indeed, there is some evidence that the incidence of chronic rejection is actually declining over the past few years. While the reason for this apparent decline is uncertain, and it could relate to better immunosuppression management, or more likely to the growing recognition that chronic graft dysfunction may be due to recurrent liver disease, such as autoimmune hepatitis, PBC, PSC, or recurrent hepatitis C. The differentiation of recurrent primary liver disease from chronic rejection can prove to be very difficult in clinical practice. Thus, the clinician must carefully monitor liver and graft function, evaluate any biochemical changes, and try to reach a clear diagnosis before considering any modification of immunosuppressive schedules.

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.

Protocol liver allograft biopsies

Protocol liver allograft biopsies are liver biopsies carried out at specific time points according to predetermined guidelines, rather than in response to specific indications such as change in the patient's clinical status or biochemical tests. Use of protocol liver allograft biopsy has been declining over the last decade: an informal survey of 35 transplant units showed that whereas 65% of units undertake protocol biopsies for those grafted for Hepatitis C virus infection, only 25% do so for patients grafted for other indications. In this overview, we consider the arguments against and those in favor of liver biopsies in adult liver allograft recipients. Arguments against the use of protocol liver biopsies are that they biopsies put the patient are associated with a small risk of morbidity and mortality, are expensive, do not provide useful information and do not alter clinical practice. The estimated rate of major complications is 0.6% and the estimated mortality rate 0.02%. However, the argument in favor of protocol biopsies is that even when standard liver tests are normal, there is on-going inflammation in the graft which, if immunosuppression is not altered, will lead to progressive fibrosis, cirrhosis and even graft loss. Conversely, normal liver histology may allow for reduction in the immunosuppression and so lower the risk of the complications associated with immunosuppression. Currently available diagnostic techniques are not yet sufficiently sensitive or specific to provide an accurate reflection of the state of the graft and the presence or absence of graft damage. We conclude that, while there are no clear data showing that protocol liver allograft biopsies are cost effective and lead to improved patient and graft outcome, such biopsies still have a role in the management of the liver transplant recipient.

Grading and staging systems for inflammation and fibrosis in chronic liver diseases

Liver biopsy is an important part of the evaluation of patients with a variety of liver diseases. Besides establishing the diagnosis, the biopsy is often used to assess the severity of the disease in terms of both grade and stage. The stage in most chronic liver diseases relates to the degree of scarring with the end stage being cirrhosis with its clinical complications. The grade relates to the severity of the underlying disease process, with features that vary with the pathogenetic mechanisms. Chronic viral hepatitis has been the object of the most extensive efforts at grading and staging, stimulated by the advent of new forms of therapy. Systems have also been developed for fatty liver disease, allograft rejection and chronic cholestatic diseases, but these have not been as widely used. Simple grading and staging systems for chronic hepatitis, including the IASL, Batts-Ludwig, and Metavir systems, are most appropriate for management of individual patients, while more complex systems such as the Histology Activity Index (HAI) are appropriate for evaluation of large cohorts of patients when statistical analysis is required.

Incidence of arterial injuries detected by arteriography following percutaneous right-lobe ultrasound-guided core liver biopsies in human subjects

PURPOSE

To determine the incidence and significance of arterial injuries detected by angiography subsequent to ultrasound-guided random core liver biopsies in normal healthy adults.

MATERIALS AND METHODS

Retrospective analysis of 55 potential living related liver donors who underwent an ultrasound-guided random liver biopsy and a visceral angiogram was performed (January, 1999 to May, 2002). All liver biopsy samples (obtained by 2-3 18-gauge needle passes) were re-evaluated prospectively by a transplant pathologist for adequacy (defined: >or=5 complete portal triads). Subjects who underwent angiograms before the biopsy or >7 days after the biopsy were excluded from the arterial injury evaluation. Angiograms were reviewed by two angiographers. Arterial injuries were identified and classified by consensus into contusions, active bleeding, arterial-venous fistulae, and pseudoaneurysms.

RESULTS

Mean needle pass was 2.1. No major complications were encountered. All samples were deemed pathologically adequate. Forty-eight potential donors were included for the arterial injury evaluation. Three arterial injuries (two arterioportal fistulae, 4.2%) were found in 48 angiograms (6.3%). None of the three injuries required intervention.

CONCLUSION

The incidence of arterioportal fistulae following core liver biopsies has not changed over the past three decades despite improvement in biopsy needle technology, reduction of needle caliber, and the use of image guidance.

Distinguishing between recurrent primary sclerosing cholangitis and chronic rejection

1. Recurrent primary sclerosing cholangitis (PSC) is extremely difficult, if not impossible, to distinguish from other causes of biliary strictures or sclerosing cholangitis in allografts using needle biopsy evaluation alone. Technical problems with biliary reconstruction, long cold ischemic times, non-heart beating donors, ABO blood group incompatibility, antibody-mediated rejection, and small-for-size syndrome in reduced-size or living donor livers can also cause similar manifestations in a peripheral core biopsy. 2. Some difficulties in distinguishing between sclerosing cholangitis and chronic rejection (CR) arise because: a) at risk populations are similar; b) both can cause "cholestatic" elevation of liver injury tests; and c) both can lead to intrahepatic cholestasis and small bile duct loss. 3. Etiopathogenesis and pathology of CR and sclerosing cholangitis have some overlapping features, but show distinct differences that result in significantly different and discriminating pathologic manifestations. 4. Clues in the clinical history, evaluation of serial biopsies, and histopathology can be used to distinguish with confidence between sclerosing cholangitis and CR. 5. Potential discriminating features include liver size and gross appearance, and histopathology findings in the arterial tree, hilar lymph nodes, large and small bile ducts, interface zone, lobular, and perivenular regions.

Safety and Efficacy of Fluoroscopic versus Ultrasound Guidance for Core Liver Biopsies in Potential Living Related Liver Transplant Donors: Preliminary Results

PURPOSE

To describe and evaluate the safety and efficacy of fluoroscopically guided percutaneous liver biopsies in comparison with ultrasound (US)-guided percutaneous liver biopsies in potential living related liver donors.

MATERIALS AND METHODS

Retrospective analysis of 133 consecutive preoperative workups of potential living related liver donors was performed. The subjects were treated from January 1999 through May 2002. Subjects were divided into those who underwent US-guided subcostal 18-gauge core liver biopsies (group I) and those who underwent fluoroscopically guided intercostal 18-gauge core liver biopsies (group II). Group II biopsies were performed in a manner similar to percutaneous transhepatic cholangiography. All samples obtained during the study period were reevaluated prospectively by a transplant pathologist blinded to guidance modality for sample adequacy (defined as >or=5 complete portal triads). Subjects were followed for 4 hours before discharge and afterward in the transplant clinic until donation. Subjects who did not donate organs were followed for at least 1 month.

RESULTS

One hundred thirty-three potential donors were evaluated (55 for group I, 78 for group II). Mean follow-up was 1.7 months, and 77% of subjects donated. The mean numbers of needle passes were 2.1 and 2.3 for groups I and II, respectively. No major complications were encountered, and all subjects were discharged in 4 hours. Incidences of minor complications were 3.6% (vasovagal reactions) and zero for groups I and II, respectively. Sample adequacy rates were 100% and 99% for groups I and II, respectively. One case (1.8%) in group I, although pathologically adequate, had additional renal tissue.

CONCLUSION

Fluoroscopically guided liver biopsy shows encouraging initial safety results and is as effective as US-guided liver biopsy in normal subjects.

Safety of percutaneous liver biopsy in infants less than three months old

OBJECTIVES

To evaluate the safety, outcomes, and complications of percutaneous liver biopsies (PLB) in infants aged 0 to 3 months.

METHODS

We retrospectively reviewed the hospital records of all infants less than 3 months old who underwent PLB at Children's Memorial Hospital between July 1, 1997 and June 30, 2004 for complications surrounding the procedure and risk factors that might lead to complications.

RESULTS

Sixty-six PLBs were performed in 63 infants. Most patients tolerated the procedure without complications. Twelve complications were recorded, for an overall complication rate of 18%. Of these, five were directly related to the procedure, and seven were sedation related. Three patients experienced a drop in hemoglobin greater than 2 gm/dL, one patient developed a bile leak, and one developed a skin hematoma. Seven patients had respiratory difficulty related to sedation, which manifested as increased work of breathing or decreased respiratory rate with depression in pulse oximetry.

CONCLUSION

We conclude that PLB in young infants is associated with a somewhat higher risk of complications than in older children, particularly complications related to sedation.

Outcome and Risk Factors of De Novo Autoimmune Hepatitis in Living-Donor Liver Transplantation

BACKGROUND

Graft dysfunction mimicking autoimmune hepatitis (AIH) develops only rarely after liver transplantation for nonautoimmune liver disease. The long-term prognosis and risk factors of de novo AIH after living-donor liver transplantation (LDLT) are unknown.

METHODS

We review our LDLT series to investigate the incidence and outcome of this form of graft dysfunction, focusing on follow-up histology.

RESULTS

Of 633 patients who underwent LDLT at Kyoto University from 1990 to 2002, 13 (2.1%) developed graft dysfunction with interface hepatitis resembling AIH (2 males, 11 females). The median age at LDLT of these 13 patients was 10 years (8 months to 26 years). All received tacrolimus-based immunosuppression. The dysfunction presented at a median interval of 3.1 (0.7-9.5) years after LDLT. Nine had definite AIH, and four had probable AIH at the onset of hepatitis. Patients were followed after a median of 3.5 (0.1-8) years from the onset of de novo AIH. Of 11 patients who underwent follow-up histologic evaluation, 3 underwent retransplantation, and 8 continued to have similar findings on subsequent biopsies, with fluctuations in the amount of necroinflammatory activity and an increase in fibrosis despite treatment. In a multivariate analysis, acute rejection episodes and recipient age between 11 and 15 years at LDLT independently had predictive value for the development of de novo AIH. Human leukocyte antigen-A, B, and DR mismatches and sex mismatch did not influence the occurrence of de novo AIH.

CONCLUSION

This series highlights the more severe histologic outcome of de novo AIH with longer follow-up despite immunosuppressive treatment. De novo AIH may arise from alloimmunologic injury, marked by clinically obvious episodes of acute rejection.

Bile duct strictures after adult liver transplantation: a role for biliary reconstructive surgery?

There is no accurate method to determine the functional significance of bile duct strictures after liver transplantation, and although biliary reconstructive surgery (Roux-en-Y hepaticojejunostomy, HJ) is the second-line treatment in patients with persistent allograft dysfunction following failed endoscopic therapy, there is no evidence to support this approach. Liver transplant recipients with allograft dysfunction and demonstrable bile duct strictures who had undergone hepaticojejunostomy were identified from a prospective database. Preoperative and follow-up clinical, biochemical, and radiological data were collected. Perioperative liver biopsies were evaluated prospectively by two histopathologists blinded to clinical information. The biopsies were scored according to presence and severity of biliary features, fibrosis, and coexisting diseases. The effects of preoperative factors on postoperative allograft function were analyzed using SPSS statistical software. After hepatico-jejunostomy, graft function returned to normal in 8/44 patients (18%), improved in 16/44 (36%), but remained abnormal in 20/44 (45%), including 4 patients who subsequently underwent retransplantation. Hepaticojejunostomy was more likely to yield a favorable outcome (improved or normal graft function) when performed within 2 years of transplantation. Prolonged duration of biliary obstruction was associated with development of advanced graft fibrosis at the time of surgery, but neither factor significantly influenced postoperative graft function. In conclusion, biliary reconstruction successfully restores graft function in the majority of patients who present with anastomotic strictures within the first 2 years after liver transplantation. In patients presenting with bile duct strictures late after transplantation, surgery should be reserved for selected patients without histological evidence of graft fibrosis (moderate-severe) or significant nonbiliary pathology.

Total fibrous obliteration of main portal vein and portal foam cell venopathy in chronic hepatic allograft rejection

CONTEXT

Chronic hepatic allograft rejection is characterized by arteriopathy and bile duct loss. Pathology of the portal vein or its branches is not considered to play a major role in chronic rejection.

OBJECTIVE

A recent case of chronic rejection with total fibrous obliteration of the portal vein at the hilum and graft loss prompted us to retrospectively analyze cases of failed allografts for portal vein changes.

DESIGN

Six cases of failed hepatic allograft recorded in our files from 1994 to 1998 were selected for the study. For comparison, 4 cases of hepatitis C cirrhosis were included. Clinical features, including arteriograms or Doppler studies, were reviewed whenever available. Sections taken from the hilum and random parenchyma stained with routine hematoxylin-eosin, elastic van Gieson, and Masson trichrome were examined by 3 experienced liver pathologists in a randomized, blinded fashion.

RESULTS

Significant hepatic artery occlusion with foam cell change and bile duct loss was seen in all cases of chronic rejection (3/3), but not in the other cases. Foam cell change in the portal vein at the hilum (3/3) and occasionally into the distal branches (2/3) with variable occlusion of the lumen was seen only in cases of chronic hepatic allograft rejection. Mild luminal narrowing was observed in all the cases of cirrhosis (4/4) as a result of phlebosclerosis, most likely representing a change secondary to portal hypertension. Total obliteration of the portal vein at the hilum was seen in the index case (case 1) only.

CONCLUSION

Portal venopathy can be a significant finding in chronic hepatic allograft rejection and may contribute to graft dysfunction or failure. Two-vessel disease must be considered in cases of chronic hepatic allograft rejection, and pathologists should thoroughly examine the hilum in explanted hepatic allografts.

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.

Recent advances in the immunology of chronic rejection

Chronic allograft rejection is a slowly progressive, insidious process in which the host immune system continues to mount an immunological attack on a transplanted organ, ultimately resulting in the failure of the graft. To varying degrees, all solid organ grafts are at risk for chronic rejection and undergo a stereotypic process of injury and inflammation, eventually leading to parenchymal fibrosis. The clinical consequences of chronic rejection are particularly apparent in thoracic transplantation, where both patient and graft survival decline steadily over time and the opportunities for re-transplantation or long-term extracorporeal support are limited. A variety of antigen-dependent and antigen-independent factors are known to modulate the propensity for an organ to undergo chronic rejection. Recent clinical and laboratory research has suggested that distinct immunologic mechanisms may underlie the process of chronic rejection. Ultimately, strategies to induce long-term tolerance to alloantigens will be necessary to prevent chronic rejection and to abrogate the deleterious sequelae of chronic immunosuppression.

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.

Accuracy of bile duct changes for the diagnosis of chronic liver allograft rejection: reliability of the 1999 Banff schema

Chronic rejection (CR) after liver transplantation is thought to be a dynamic and potentially reversible process. The Banff working group has developed recommendations for its histopathologic staging. The 1999 Banff classification of CR (i.e., bile duct dystrophy >50% and/or bile duct loss >20%) was applied to: 1) biopsies from patients retransplanted for CR (N = 19) and pathologies other than CR (N = 21) to evaluate its specificity and sensitivity, especially of the early stage lesions of CR; and 2) biopsies from nonretransplanted patients (N = 21) to evaluate the evolution of CR lesions. Atypical forms of CR were also described. Including an early stage into the definition of CR has resulted in a much higher sensitivity for its diagnosis, as compared with the former classification (i.e., bile duct loss >50%) (89% vs. 33%; P =.0001), while keeping an acceptable specificity (74% vs. 100%; P =.03). In 55% of the nonretransplanted patients, CR lesions were reversible. No histologic feature reliably predicted CR outcome. Transient lobular hepatitis, unrelated to viral infection, and veno-occlusive disease were seen significantly more often in the CR group (P =.04 and P =.03, respectively). We conclude that the application of the 1999 Banff classification is superior to the previous classification for the diagnosis of CR. However, limited information can be drawn regarding the outcome of CR based on histology alone. Transient lobular hepatitis, unrelated to viral infection and veno-occlusive disease, may be an unusual expression of CR.

Large-needle biopsy versus thin-needle biopsy in diagnostic pathology of liver diseases

BACKGROUND/AIMS

A study was carried out to determine whether thin-needle biopsy (TNB) yields enough material to study diffuse liver diseases.

METHODS

Using TNB (20G and 21G) and a conventional Menghini-type large-needle biopsy (LNB; 17G), the amounts of tissue obtained and the histopathological diagnoses were compared. The biopsies were obtained by surgeons with a several-stroke method (17GS) and by physicians with a single-strike method (17GP, 20GP, 21GP). A total of 343 biopsy specimens from 258 patients were included in the study.

RESULTS

A comparison of the mean values for the length of the core biopsy, as well as the mean numbers of portal tracts and terminal hepatic veins among the four groups showed significant differences (p<0.001): the mean number of portal tracts obtained with 17GS was 13.8+/-6.5, with 17GP it was 9.7+/-5.9, with 20GP it was 6.7+/-4.4, and with 21GP it was 4.0+/-3.1. A comparison of the histopathological diagnoses showed no major differences between 17GP and 20GP; the diversity and frequencies of the diagnoses were similar.

CONCLUSION

We suggest that the use of TNB, particularly 20G-size needles, could be extended to the investigation of diffuse liver diseases in which LNB carries a high risk of complications or is contraindicated, and when the diagnosis is the primary reason for the biopsy rather than grading or staging of a known diffuse disease.

Orthotopic liver transplantation for autoimmune hepatitis and cryptogenic chronic hepatitis in children

BACKGROUND

Autoimmune hepatitis (AIH) and cryptogenic chronic hepatitis (CCH) are important causes of liver failure in children, frequently necessitating orthotopic liver transplantation (OLT). The aim of this study is to review disease progression and potential differences between subgroups of children with AIH and CCH.

METHODS

The medical records of 65 children diagnosed with AIH or CCH between 1980 and 1998 were evaluated.

RESULTS

The median age at presentation was 9 years, 8 months (range 4 months-19 years), and the median follow-up period was 8 years (range 3 months-18 years, 10 months). Forty-one patients (63%) were female. Twenty-eight patients were Hispanic, 28 were Caucasian, 8 were African-American, and 1 was Asian. Forty-three patients (66%) were diagnosed with type 1 AIH, 8 (12%) with type 2 AIH, and 14 (22%) with CCH. Forty patients (62%) underwent OLT (51% of those with type 1 AIH, 75% of those with type 2 AIH, and 86% of those with CCH). Thirteen (33%) of the transplanted patients experienced disease recurrence. African-American patients experienced a significantly higher rate of disease recurrence post-OLT than did Hispanic patients. Seven patients (11%) died, two without OLT, and five posttransplantation.

CONCLUSIONS

AIH and CCH frequently necessitate OLT in children. CCH is a more aggressive disease than Type 1 AIH among children with these disorders. Ethnicity influences the rate of disease recurrence after liver transplantation.

Does tacrolimus offer virtual freedom from chronic rejection after primary liver transplantation? Risk and prognostic factors in 1,048 liver transplantations with a mean follow-up of 6 years

Tacrolimus has proven to be a potent immunosuppressive agent in liver transplantation (LT). Its introduction has led to significantly less frequent and severe acute rejection. Little is known about the rate of chronic rejection (CR) in primary LT using tacrolimus therapy. The aim of the present study is to examine the long-term incidence of CR, risk factors, prognostic factors, and outcome after CR. The present study evaluated the development of CR in 1,048 consecutive adult primary liver allograft recipients initiated and mostly maintained on tacrolimus-based immunosuppressive therapy. They were evaluated with a mean follow-up of 77.3 +/- 14.7 months (range, 50.7 to 100.1 months). To assess the impact of primary diagnosis on the rate and outcome of CR, the population was divided into 3 groups. Group I included patients with hepatitis C virus (HCV)- or hepatitis B virus (HBV)-induced cirrhosis (n = 312); group II included patients diagnosed with primary biliary cirrhosis (PBC), primary sclerosing cholangitis (PSC), or autoimmune hepatitis (AIH; n = 217); and group III included patients with all other diagnoses (n = 519). Overall, 32 of 1,048 patients (3.1%) developed CR. This represented 13 (4.1%), 12 (5.5%), and 7 patients (1.3%) in groups I, II, and III, respectively. The relative risk for developing CR was 3.2 times greater for group I and 4.3 times greater for group II compared with group III. This difference was statistically significant (P =.004). The incidence of acute rejection and total number of acute rejection episodes were significantly greater in patients who developed CR compared with those who did not (P <.0001). Similarly, the mean donor age for CR was significantly older than for patients without CR (43.0 v 36.2 years; P =.02). Thirteen of the 32 patients (40.6%) who developed CR retained their original grafts for a mean period of 54 +/- 25 months after diagnosis. Seven patients (21.9%) underwent re-LT, and 12 patients (38.3%) died. Serum bilirubin levels and the presence of arteriopathy, arterial loss, and duct loss on liver biopsy at the time of diagnosis of CR were significantly greater among the 3 groups of patients. In addition, patient and graft survival for group I were significantly worse compared with groups II and III. We conclude that CR occurred rarely among patients maintained long term on tacrolimus-based immunosuppressive therapy. When steroid use is controlled, the incidence of acute rejection, mean donor age, HBV- and/or HCV-induced cirrhosis, or a diagnosis of PBC, PSC, or AIH were found to be predictors of CR. Greater values for serum bilirubin level, duct loss, arteriopathy, arteriolar loss, and presence of HCV or HBV were found to be poor prognostic factors for the 3 groups; greater total serum bilirubin value (P =.05) was the only factor found to be significant between patients who had graft loss versus those who recovered.

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.

Development of ductopaenic liver allograft rejection includes a "hepatitic" phase prior to duct loss

BACKGROUND/AIM

Recent reports suggest the possible role of a parenchymal inflammatory reaction in the developing phase of chronic rejection. The aim of this study was to identify both clinical and histological abnormalities related to the development of chronic rejection, especially the topography of the inflammatory reaction occurring in the post-transplant period.

METHODS

We studied retrospectively, 103 liver allograft biopsies from 10 patients. These 10 patients represented all the patients who developed chronic rejection (confirmed by duct loss and foamy arteriopathy in these grafts removed at retransplantation) and who had non-viral-related disease originally; in the study period 1990-1998 at the Royal Free Hospital (during which 451 liver transplants were performed). As a control population, we reviewed 28 patients who had been transplanted for non-viral end-stage liver disease at our institution in the same study period and who were retransplanted for complications other than chronic rejection.

RESULTS

In nine patients documented histologically lobular hepatitis preceded chronic rejection. In one patient, although non-specific lobular changes were present in the early post-transplant period, lobular hepatitis was identified repeatedly after chronic rejection had been diagnosed. Cytomegalovirus was identified immunohistochemically in one patient. In the remaining nine patients extensive clinical and histological investigations failed to demonstrate the presence of any known viral agent. Features of hepatitis were found in only 3 of the 28 patients of the control group.

CONCLUSIONS

A "hepatitic" phase anticipates chronic ductopaenic rejection. Further studies are necessary in order to clarify the pathogenesis of this reaction.

Chronic liver allograft rejection in a population treated primarily with tacrolimus as baseline immunosuppression: long-term follow-up and evaluation of features for histopathological staging

BACKGROUND

Predisposing factors, long-term occurrence, and histopathological changes associated with recovery or progression to allograft failure from chronic rejection (CR) were studied in adult patients treated primarily with tacrolimus.

METHODS

CR cases were identified using stringent criteria applied to a retrospective review of computerized clinicopathological data and slides.

RESULTS

After 1973 days median follow-up, 35 (3.3%) of 1049 primary liver allograft recipients first developed CR between 16 and 2532 (median 242) days. The most significant risk factors for CR were the number (P<0.001) and histological severity (P<0.005) of acute rejection episodes and donor age >40 years (P<0.03). Other demographic and matching parameters were not associated with CR in this cohort. Ten patients died with, but not of, CR. Eight required retransplantation because of CR at a median of 268 days. Ten resolved either histologically or by normalization of liver injury tests over a median of 548 days. CR persisted for 340 to 2116 days in the remaining seven patients. More extensive bile duct loss (P<0.01), smallarterial loss (P<0.03), foam cell clusters (P<0.01) and higher total bilirubin (P<0.02) and aspartate aminotransferase (P<0.03) were associated with allograft failure from CR.

CONCLUSIONS

Early chronic liver allograft rejection is potentially reversible and a combination of histological, clinical, and laboratory data can be used to stage CR. Unique immunological and regenerative properties of liver allografts, which lead to a low incidence and reversibility of early CR, can provide insights into transplantation biology.

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.

Living related liver transplantation: histopathologic analysis of graft dysfunction in 304 patients

Between June 1990 and August 1997, 304 mainly pediatric patients underwent a total of 311 orthotopic living related liver transplantations (LRLTs) under tacrolimus immunosuppression at Kyoto University Hospital. Congenital biliary atresia was the most common underlying disease. The donor was a parent, and the left lateral segments were used as grafts in most cases. The average number of loci of HLA-A, -B, and -DR mismatches between the donor and the recipient were 2.1. Forty-three transplants were ABO-incompatible. Liver histology at the time of abnormal liver function after transplantation was analyzed. Preservation injury was rare and mild. Acute cellular rejection (ACR) occurred in 36% of transplants during the first 6 months. Average rejection activity index (the Banff schema) was 4.2 and severe rejection was rarely seen. The number of mismatching HLA loci and immunosuppression regimens affected the incidence of ACR. Chronic rejection (CR) occurred in 2% of transplants. Concerning humoral rejection, no hyperacute rejection was seen. However, hepatic artery thrombosis (delayed hyperacute rejection) was seen in an ABO-incompatible transplant. Acute hepatitis, including those related to cytomegalovirus and Epstein-Barr virus, occurred in 17% of transplants. Chronic hepatitis, including hepatitis B and C, developed in 3%. Acute or chronic cholangitis occurred in 16%, and a significantly higher incidence of cholangitis was found in ABO-incompatible transplants. Posttransplantation lymphoproliferative disease developed in 2%. In LRLT, milder preservation injury and less frequent ACR and CR were suggested, probably because of the short cold-ischemia time and the advantages of HLA histocompatibility, respectively.

Analysis of the reversibility of chronic liver allograft rejection implications for a staging schema

In contrast to all other vascularized organ allografts, chronic rejection (CR) of the liver is potentially reversible. We therefore studied demographic, perioperative, biochemical, and histologic features associated with reversibility or progression to graft failure. Using very stringent clinical and histological criteria, we identified a subgroup of 23 of 916 patients receiving primary liver allografts with CR from the Liver Transplantation Database. Of these, 13 experienced graft failure as a result of CR, and 10 patients recovered to normal histology or liver injury test results. Male-to-female sex mismatch (p = 0.07), younger recipient age (p = 0.09), younger donor age (p = 0.06), white-to-white race match (p = 0.09), primary diagnosis of biliary atresia (p = 0.02), and cold ischemia time of more than 12 hours (p = 0.02) were associated with graft failure. Patients who eventually recovered from CR were more likely to have acute rejection within the first 2 weeks (70% vs 23%; p = 0.04), had a higher number of acute rejection episodes (p = 0.08), and were more likely to have been treated with OKT3 (90% vs 46%, p = 0.07). Although overlap existed in the histopathologic findings between the patients whose grafts failed and those who recovered, those patients who developed bile duct loss in more than 50% of the portal tracts (p < 0.01), severe (bridging) perivenular fibrosis (p = 0.05), and the presence of foam cell clusters (p = 0.06) were more likely to require retransplantation. In contrast to other solid organ allografts, CR of the liver is not an irreversible process. These findings can be used to understand the evolution of CR and to design a biologically correct and clinically relevant staging system.

Evolving concepts in the diagnosis, pathogenesis, and treatment of chronic hepatic allograft rejection

Chronic hepatic allograft rejection is characterized by the histological findings of ductopenia and a decreased number of hepatic arteries in portal tracts in the presence of foam cell (obliterative) arteriopathy. Recent studies have extended the histological spectrum of chronic rejection to include the presence of biliary epithelial atrophy or pyknosis involving the majority of small ducts present in the liver biopsy specimen. Overall, the incidence of chronic rejection in adults appears to be decreasing and is currently approximately 4%. However, the incidence of chronic rejection in pediatric liver transplant recipients has been more stable and ranges from 8% to 12% in most studies. Clinical risk factors associated with chronic rejection include: underlying liver disease, HLA donor-recipient matching, positive lymphocytotoxic cross-match, cytomegalovirus infection, recipient age, donor-recipient ethnic origin, male donor into female recipient, number of acute rejection episodes, histological severity of acute rejection episodes, low cyclosporine trough levels, and retransplantation for chronic rejection. Chronic rejection, once diagnosed, frequently leads to graft failure; however, a number of reports indicated 20% to 30% of the patients with this diagnosis may respond to additional immunosuppressive therapy or even resolve spontaneously receiving baseline immunosuppression. Newer immunosuppressive agents, such as tacrolimus and mycophenolate, may successfully reverse chronic rejection, particularly when it is diagnosed in its early histological stages.

Pathology of the liver

Among the topics of recent investigation in liver pathology were an examination of normal portal tract structures in needle liver biopsies, computer reconstructions of the intrahepatic biliary tree, identification of oval cells (presumed progeny of hepatic stem cells) in a variety of biliary and nonbiliary diseases and tumors, the features and pathogenesis of nonalcoholic steatohepatitis, and further characterization of proliferating bile ductules. A morphometric study of portal structures in normal needle liver biopsies found that approximately one third in a given specimen may not show a portal vein and that a bile duct may not be seen in 7%. Apoptosis is a critical mechanism for the death of hepatocytes in viral hepatitis and also in endothelial injury in the cold perfusion-warm reperfusion sequence in liver transplantation. The results of two studies examining the relationship of steatosis to chronic hepatitis C virus infection in native and transplanted livers suggest that fatty change is a specific virus-mediated lesion. In the field of hepatic neoplasia, liver cell dysplasia (large cell change), long thought to be a premalignant lesion, was hypothesized to represent abnormal hepatocyte polyploidization.

The normal adult human liver biopsy: a quantitative reference standard

In assessing adult human liver histology, questions remain concerning the normal number of portal tracts and bile ducts in a liver biopsy. We therefore reviewed liver biopsies obtained with use of a percutaneous Menghini cutting needle (14G, internal diameter 1.6 mm), from 16 patients undergoing liver biopsy for screening procedures (age 49 +/- 14 years, +/-SD) and found to be normal by histological examination. The average aggregate length of the liver tissue was 1.8 +/- 0.8 cm (area of 16.4 +/- 10.7 mm2), representing 7 +/- 3 tissue fragments. Portal triads containing at least one profile each of a portal vein, hepatic artery, and interlobular bile duct numbered 11 +/- 6 per biopsy (range 3-23). Portal dyads, which did not contain one of these profiles, usually the portal vein, numbered 8 +/- 5 (range 1-18). On a per-specimen basis, 38% of portal tracts did not contain a portal vein, 7% did not contain a bile duct, and 9% did not contain a hepatic artery. Because of multiplicity of profiles within portal tracts, however, the average number of profiles per portal tract was 6 +/- 5 (range 2-35). Notably, on average there were 2.3 +/- 2.2 interlobular bile ducts per portal tract, compared to 2.6 +/- 2.3 hepatic arteries and 0.7 +/- 0.7 portal veins. The average minimum external diameter of interlobular bile ducts was 13 +/- 4 microm, of hepatic arteries 12 +/- 5 microm, and of portal veins 35 +/- 25 microm. Bile ducts greater than 30 microm in diameter were rare, only one each in two biopsies were observed. In contrast, probable canals of Hering were occasionally evident at the periphery of portal tracts (6 +/- 6 per biopsy) and within the lobular parenchyma as strings of cuboidal cells (5 +/- 5 per biopsy). We conclude that, although multiplicity of profiles is normal, portal dyads are almost as common as portal triads in normal peripheral liver tissue. On average, there are two interlobular bile ducts, two hepatic arteries, and one portal vein per portal tract, with 6 full portal triads per linear cm of tissue obtained by external Menghini biopsy technique with use of a 14G needle, equivalent to 0.8 +/- 0.5 portal triads per mm2. By serving as a reference standard for adult human liver histology, these findings may assist in the histopathological assessment of liver biopsies, particularly those performed for disease conditions featuring loss of intrahepatic bile ducts.

Immune cholangitis: liver allograft rejection and graft-versus-host disease

A pronounced similarity exists between liver allograft rejection and graft-versus-host disease (GVHD) in the damage and eventual destruction of small intrahepatic bile ducts. Although an immunologic reaction has an important role, precisely identifying the target antigens or reason for persistence of the immune response has been difficult. An important difference between GVHD and liver rejection is the development of obliterative arteriopathy only in rejection. The three main histopathologic features of acute rejection are a predominantly mononuclear but mixed portal inflammation, subendothelial inflammation of portal or terminal hepatic veins (or both), and bile duct inflammation and damage. In acute rejection, a controversial issue is determining when therapeutic intervention is needed. The recommended approach is to base treatment on a combination of histopathologic changes and liver injury or dysfunction. Chronic rejection, which usually does not occur before 2 months after transplantation, is characterized by two main histopathologic features: (1) damage and loss of small bile ducts and (2) obliterative arteriopathy. Acute GVHD begins within the first month after transplantation and most commonly involves the skin, gastrointestinal tract, and liver, whereas chronic GVHD usually develops more than 80 to 100 days after liver transplantation and affects 30 to 50% of long-term survivors. Recognition of the early, cellular stages of chronic GVHD is important in preventing irreversible damage.