Endoscopic mucosal biopsies are useful in distinguishing granulomatous colitis due to Crohn's disease from tuberculosis

Background-Intestinal tuberculosis and Crohn's disease are chronic granulom atous disorders that are difficult to differentiate histologically. Aims-To characterise distinctive diagnostic features of tuberculosis and Cr ohn's disease in mucosal biopsy specimens obtained at colonoscopy. Methods-Selected histological parameters were evaluated retrospectively in a total of 61 biopsy sites from 20 patients with tuberculosis and 112 biops y sites from 20 patients with Crohn's disease. The patients were chosen on the basis of clinical history, colonoscopic findings, diagnostic histology, and response to treatment. Results-The histological parameters characteristic of tuberculosis were mul tiple (mean number of granulomas per section: 5.35), large (mean widest dia meter: 193 mu m), confluent granulomas often with caseating necrosis. Other features were ulcers lined by conglomerate epithelioid histiocytes and dis proportionate submucosal inflammation. The features characteristic of Crohn 's disease were infrequent (mean number of granulomas per section: 0.75), s mall (mean widest diameter: 95 mu m) granulomas, microgranulomas (defined a s poorly organised collections of epithelioid histiocytes), focally enhance d colitis, and a high prevalence of chronic inflammation, even in endoscopi cally normal appearing areas. Conclusions-The type and frequency of granulomas, presence or absence of ul cers lined by epithelioid histiocytes and microgranulomas, and the distribu tion of chronic inflammation have been identified as histological parameter s that can be used to differentiate tuberculosis and Crohn's disease in muc osal biopsy specimens obtained at colonoscopy.