Collagenous colitis.

Collagenous colitis is a very rarely recognized disease characterized clinically by watery diarrhoea and histologically by a broad, band-like deposition of collagen under the surface epithelium of the colon and rectum. Two cases of collagenous colitis are reported in this paper. After treatment of one of the patients with metronidazole, the symptoms cleared up and biopsy specimens from the colon showed regression of the pathological picture. The pathogenesis of the diarrhoea is discussed. The aetiological agent seems to be infectious, but is still unknown.