Chemical colitis due to endoscope cleaning solutions: a mimic of pseudomembranous colitis.

A unique form of colitis was observed during endoscopy of the lower gastrointestinal tract in 21 patients. The patients were prepared using either tap-water enemas or standard lavage solutions. Patients were found to have discrete or confluent white plaques adherent to the colonic mucosa, mild to severe erythema of the surrounding mucosa, and variable amounts of foamy liquid upon withdrawal of the endoscope. Stool assays for Clostridium difficile toxin and bacterial cultures were negative. Mucosal biopsies revealed vacuolar changes in the lamina propria, with slight to moderate vascular congestion and foci of intramucosal hemorrhage. Five patients developed rectal bleeding, tenesmus, and increased frequency of stools, lasting up to 12 days. We believe these cases were due to contamination of the endoscope's air-water channel with solutions used during endoscope cleaning. Recognition of this entity is important, as it is preventable and may mimic pseudomembranous colitis.