...not sure tho - I'm TOTALLY not an IBD expert. Here's what MedicineNet had to say anyway...
Collagenous colitis is a newly-recognized disease of the colon. On sigmoidoscopy or colonoscopy the bowel lining appears to be normal but microscopic examination of biopsies shows inflammation and the presence of a band-like substance called collagen which is a component of scar tissue. We have no evidence that it is caused by an infectious agent nor does it appear to be related to any known causes of diarrhea. It was first described in 1976, and it is being diagnosed more frequently. The primary symptom of collagenous colitis is a watery diarrhea, but there also may be abdominal pain, mucus in the stool, and, rarely, weight loss. The usual tests for diagnosing the cause of diarrhea are normal, and the diagnosis is made with the microscopic exam of colonic biopsies. The disease may last for years and there is no specific therapy. A proportion of patients will respond to drugs used in inflammatory bowel disease (see the Ulcerative Colitis and Crohn's Disease sites in the Diseases and Treatments section) such as Azulfidine, Asacol, Dipentum, or various cortisone or prednisone preparations. Many other agents have been used with varying success. In a few cases the problem resolves spontaneously. Patients not responding to the medications usually are given the standard therapies for diarrhea such as Pepto-Bismol, Imodium, Kaopectate, etc.