The histopathological approach to inflammatory bowel disease: a practice guide

Area of Science:

• Gastroenterology and Pathology
• Histopathology of Inflammatory Bowel Diseases

Background:

• Inflammatory bowel diseases (IBD) involve genetic and environmental factors, presenting lifelong challenges.
• Histological evaluation of ulcerative colitis and Crohn's disease is complex due to overlapping features.

Purpose of the Study:

• To provide a comprehensive guide for the histological assessment of IBD resection specimens and biopsies.
• To clarify diagnostic criteria, disease activity markers, and surveillance for complications.

Main Methods:

• Histopathological analysis of mucosal architectural abnormalities, lamina propria cellularity, and cell types.
• Assessment of disease activity through neutrophil infiltration and epithelial damage.
• Consideration of time-dependent, age-dependent, and differential diagnostic features, including cytomegalovirus (CMV) infection.

Main Results:

• Histopathological features for IBD diagnosis can overlap, necessitating terms like indeterminate colitis or inflammatory bowel disease unclassified.
• Disease activity, disease duration, and age of onset significantly influence histological presentation.
• Cytomegalovirus (CMV) reactivation is a critical differential diagnosis in severe colitis.
• Long-standing IBD increases adenocarcinoma risk, with dysplasia as a marker, though its assessment has poor inter-observer agreement.

Conclusions:

• Accurate histological diagnosis of IBD requires careful evaluation of multiple features and consideration of clinical context.
• Monitoring for CMV and dysplasia is crucial for managing long-term IBD patients.
• Expert pathological review is essential for diagnosing dysplasia and managing cancer risk in IBD.