Histologic study of colonic mucosa in patients with chronic diarrhea and normal colonoscopic findings

BACKGROUND: There are controversies about the importance of biopsies of normal colon mucosa in the investigation of patients with chronic diarrhea. STUDY: Colonic and terminal ileum biopsies of 167 patients were reviewed. In 5 patients, used as controls, colonoscopy was done due to family history of colon cancer. RESULTS: The 5 patients without symptoms had no histologic abnormalities. The histologic findings in 162 patients with chronic diarrhea were as follows: 110 patients (67.9%) with normal histology, microscopic colitis not otherwise specified, and isolated small granulomas; 17 (10.5%) patients had findings of borderline diagnostic significance, including possible collagenous colitis, some features of lymphocytic colitis and melanosis coli; and 35 (21.6%) patients, with diagnostic significant histologic findings as collagenous colitis, lymphocytic colitis, minimal change microscopic colitis, eosinophilic colitis, pericrypt eosinophilic enterocolitis, intestinal spirochetosis, schistosomiasis, and Crohn's disease. Of the 52 patients with either borderline or significant diagnostic abnormalities, in 8 (15.4%) the diagnosis was done only with a proximal study (ascending, transverse, or descending colons). CONCLUSIONS: Histologic lesions of possible diagnostic value could exist in 32.1% of chronic diarrhea patients with normal colonoscopy, which can justify, in certain cases, mucosa biopsies, which might contribute for a more precise etiologic diagnosis; also, the distribution of these histologic changes has pointed out the importance of having all colon segments biopsied.