Collagenous colitis: a recently recognised reversible clinicopathological entity.

A case of collagenous colitis is reported in an 86 year old man who presented with watery diarrhea. This case differs from previous reports in that five of the six reported cases involved women, mostly in their mid-forties, and that previously the collagenous band has been demonstrated in the mucosa of the left side of the colon only. This case is the first report to demonstrate the collagenous band in the right side of the colon as well as the left, and is the thickest band reported to date. In keeping with the two reported cases with follow-up, the subepithelial collagenous band was shown to have disappeared three months after the initial biopsy with a corresponding clinical improvement after symptomatic treatment only. The diagnosis needs to be considered in all patients presenting with watery diarrhea, and can only be confirmed after rectal or colonic biopsy.