What causes uncontrollable diarrhea when a colonoscopy is clear?

Irritable Bowel Syn. Many things can cause uncontrollable diarrhea. A common cause is ibs. Ibs causes dysfunctional GI problems, ex diarrhea, constipation or both. Cause is unknown but may be stress, certain foods, etc. But there is nothing visibly wrong with your GI tract, so colonoscopy is clear. Another cause could be celiacs --gluten allergy that affects the small intestine, (not seen on a colonoscopy) or infecti.
Prep. The prep contains a laxative which stimulates diarrhea.