In vivo diagnosis of collagenous colitis new diagnostic possibilities

Introduction: The main symptom of collagenous colitis is chronic diarrhrea with unspecific complaints, but normal macroscopic appearance of the colonic mucosa, so endoscopic and radiological investigations have always played a minor role in the diagnostic process. The diagnosis relies on histopathologic examination, characterized by following microscopic features: thickened subepithelial collegen band of >10µm, a intraepithelial lymphocytosis with preserved crypt architecture. The newly developed confocal laser colonoscope allows in vivo endomicroscopy and enabls virtual histology. For the first time the evidence of a thickened subepithelial collagen layer can be seen during the endoscopy itself and enable a diagnosis of collagen colitis in vivio.

Case report: A 67 year old woman was admitted with chronic watery diarrhea. Laboratory data shown no abnormalities. A abdominal CT disclosed a pathological thickening of the intestinal wall of colon descendens and colon sigmoideum. A colonoscopy with a confocal laser endoscope was performed. Conventional colonoscopic observation revealed only a slightly edematous mucosa. The confocal images of the conspicous region of the colon revealed a thickening of the subepithelial collagen layer along with increased intraepithelia cell amount.

The histopathological examination confirmed a thickened subepithelial layer of collagen band with intraepithelial lymphocytis without destruction of the crypt architecture, in accordance with the histological profile of collagen colitis. A therapy with 50mg Prednisolon lead to the desired success.

Discussion: The pathogenesis of collagenous colitis remains unknown although several hypothesis have been raised (immun dysregulation, autoimmunity, unknown intraluminal agent, chronic NSAIR intake) So far, the diagnosis relies on histopathological examination. For the first time it was possible to predict the diagnosis of a collagneous colitis by in vivo histology with effidence of a thickend collagen band in the confocal laser endoscopy. We could proof in several patients the diagnosis of colagenous colitis in vivo with endomicroscopy.