The yield of colonic biopsy in the evaluation of chronic unexplained diarrhea

Background and aims In clinical practice, colonoscopy is widely used for the workup of chronic unexplained diarrhea. The aim of this study was to determine the yield of colonic biopsy in such an endeavor. Methods In a computerized database of 130 204 patients evaluated for chronic diarrhea, we tested the influence of biopsy site, number of tissue fragments, patient symptoms, and indication on the outcome of histopathologic evaluation. Results The population comprised 69% women and 31% men aged (mean±SD) 52.8±17.4 years. In 19% of patients, histopathological analysis revealed various types of mucosal lesion, the most common being microscopic colitis (8.6%), ulcerative colitis (2.2%), Crohn's disease (0.6%), active colitis (5.0%), diverticulitis (0.1%), and colonic ischemia (0.5%). In 29% of patients, the colonoscopy also revealed the presence of colon polyps. Endoscopists tended to take significantly more tissue samples from endoscopically visible lesions than for random biopsies of macroscopically normal-appearing mucosa. Conclusion Overall, these associations suggest that specific diagnoses lead to more biopsies, rather than more biopsies leading to more diagnoses. Colonoscopy is a successful tool in the workup of chronic diarrhea, yielding a definitive diagnosis in almost one-fifth of all patients. As an added benefit, it also contributes to cancer prevention through the incidental findings of colonic neoplasm.