Objectives: Chronic diarrhea of unknown origin is often associated with bile acid malabsorption, the pathogenetic role of which is uncertain. The aim of this study was to identify morphological abnormalities in the ileal and colonic mucosa in patients with this disorder.
Methods: We performed a prospective and blinded histopathological study (between June 1991 and November 1992) of endoscopic biopsies of the distal ileum and colon of 23 patients suffering from chronic diarrhea of unknown origin. In 14, the SeHCAT (75-selena-homo-cholic acid taurine) test was abnormal owing to bile acid malabsorption; in the other nine, the diarrhea control group, the test results were normal. A detailed evaluation of surface epithelium, immune response and inflammatory changes was made.
Results: in two patients and two controls, mild villous atrophy was observed; there was also slight inflammation of the ileal and colonic mucosa occurring with the same frequency in both groups. A slight replacement of goblet cells was more evident in the diarrhea control group.
Conclusions: Chronic diarrhea of unknown origin associated with bile acid malabsorption does not involve specific morphological changes of ileal or colonic mucosa, and its pathogenesis must be looked for in dysfunction of the ileum and/or colon.