Collagenous colitis: an association with fecal leukocytes.

Collagenous colitis is an idiopathic inflammatory disorder of the colon associated with watery diarrhea, minimal to normal endoscopic findings, and a pathognomonic subepithelial band of collagen. This band is associated with a mucosal, acute and chronic inflammatory infiltrate. During the evaluation of four cases of collagenous colitis, we noted a remarkable number of acute inflammatory cells in the stool. This association has not been well recognized and carries important diagnostic significance because the mucosal appearance of the colon is frequently normal and nondiagnostic biopsies can occur early in the course of the disease or if obtained from the rectum. These cases suggest that collagenous colitis should be added to the differential diagnosis of diarrhea where fecal leukocytes are present.