I'm tagging in to follow this post. I had a CT scan for something else a few weeks ago, and the scan also found diffuse thickening of the colon wall with the suspicion of colitis. All lab tests, like C Diff, came back negative, and I actually just had my colonoscopy today. My doctor said that the inflammation wasn't visually-apparent today (even though it was at Mayo last January though those biopsies returned negative). Now I'm just waiting for the pathology to return.