I have never had a digital exam where the doc could not fully pass a finger beyond the sphincters. So, unless your doc has big sausage fingers, you are constricted. Still, I think your doctor is correct that you should be able to pass stool that is not too thick. I would stay away from roughage, no fiber supplements, and make sure to keep your fluids up. I hope it is not an abscess. Good luck with the CT.