Acute and chronic hepatic allograft rejection: pathology and classification

Area of Science:

• Transplantation immunology
• Hepatology

Background:

• Hepatic allograft rejection presents in three forms: humoral, acute (cellular), and chronic (ductopenic).
• Humoral rejection is rare in liver transplants and not graded.
• Acute and chronic rejection significantly impact liver allograft survival and patient outcomes.

Purpose of the Study:

• To describe the characteristics and clinical significance of different hepatic allograft rejection types.
• To detail the diagnostic criteria and grading system for acute liver allograft rejection.
• To outline the histological features and typical timing of chronic liver allograft rejection.

Main Methods:

• Review of existing literature on hepatic allograft rejection.
• Description of diagnostic criteria, including Snover's triad for acute rejection.
• Presentation of a grading system for acute rejection and its associated outcomes.
• Histological characterization of chronic rejection.

Main Results:

• Acute rejection occurs in ~50% of liver allografts, primarily in early post-transplant weeks.
• Acute rejection is diagnosed by portal hepatitis, endothelialitis, and lymphocytic cholangitis.
• Grading of acute rejection (mild, moderate, severe) correlates with short-term and long-term unfavorable outcomes.
• Chronic rejection, characterized by duct loss and vasculopathy, typically manifests months to a year post-transplant.

Conclusions:

• Understanding the distinct forms, diagnostic criteria, and grading of hepatic allograft rejection is crucial for patient management.
• Acute rejection is often reversible with treatment, but its severity influences prognosis.
• Chronic rejection poses a significant long-term challenge due to progressive graft damage.