Clinical usefulness of rectal biopsy in Crohn's disease.

Initial rectal biopsies from 349 patients judged on clinical, radiologic, or pathologic grounds to have Crohn's disease were studied, and findings were compared with a variety of clinical varibles. Biopsies from only 54 patients (15% of total) contained histologic changes characteristic of Crohn's disease, and all but one of these were previously known to have colonic involvement. Yield of diagnostic findings was directly associated with the presence of sigmoidoscopic or radiologic abnormality in the distal colon or rectum. Minor, nondiagnostic abnormalities were more common. It is concluded that routine single rectal biopsy in unselected cases of Crohn's disease has limited diagnostic value under usual conditions of practice, and that histologic abnormalities are most likely to be found in patients with known colonic, and especially sigmoid and rectal involvement.