Numerous case reports suggest that diversion of the fecal stream results in nonspecific colitis, with abnormalities ranging from minimal friability to gross ulceration. Published reports consist largely of patients with symptomatic colitis, and there are scant data suggesting at what frequency diversion colitis actually occurs. In an attempt to identify the frequency of diversion colitis and any associated etiologic factors, 20 patients scheduled for colostomy closure at Grady Memorial Hospital between 8/1/88 and 6/15/89 underwent colonoscopy, including the excluded segment, to evaluate for diversion colitis. Colostomies were performed for the management of diverticulitis, trauma, cancer, protection of an anastomosis, and diversion of fecal fistula. Patients with ulcerative colitis or Crohn's disease were excluded. The colon was classified grossly as normal or colitis (including easy friability, edema, inflammation, and ulceration as colitis). Fourteen of the 20 patients (70%) had findings of diversion colitis (DC), while six had a normal exam (NL). Nine biopsies were performed in the DC group and all revealed microscopic abnormalities. One of the normal patients was also biopsied, revealing mild, nonspecific changes. There was no difference in mean age (DC 49.3, NL 48.2), interval from formation of colostomy (DC 9.21 +/- 7.27 months, NL 2.83 +/- 1.94 months), type of colostomy, or reason for colostomy in the two groups. None of the DC patients had symptoms of colitis (mucous or bloody discharge, tenesmus, or pain), and one of the DC patients manifested symptoms of colitis after colostomy closure. We conclude that diversion colitis is a common subclinical problem in patients with a diverting colostomy.(ABSTRACT TRUNCATED AT 250 WORDS)