The value of rectal biopsy in distinguishing self-limited colitis from early inflammatory bowel disease.

When a patient presents for the first time with acute diarrhoea, it can be difficult to distinguish acute self-limited colitis from idiopathic inflammatory bowel disease. This study was designed to determine whether detailed interpretation of rectal histology can enable this distinction to be made early in the course of the illness. Seventy-two rectal biopsies, taken at the time of presentation from patients with undiagnosed colitis, were reviewed independently by two observers without access to clinical information. Distorted crypt architecture, crypt atrophy, basal lymphoid aggregates and dense lymphocytic infiltrates each emerged as features with a 76 to 86 per cent probability of predicting idiopathic inflammatory bowel disease, but their discriminant value was limited by inter-observer disagreement (16-29 per cent). Isolated basal giant cells, epithelial surface erosions and epithelioid granulomas were found to be the most reliable histological features in the early diagnosis of idiopathic inflammatory bowel disease, and their interpretation was associated with the lowest inter-observer disagreement (6 per cent).