Hello dear user, Actually injury to the bladder is the most common complications during a intestinal surgery. There might be sphincteric problem for late onset of urination and injury because he have symptom of painful urination. Pseudomembranous colitis, a cause of antibiotic-associated diarrhea (AAD), is an inflammation of the colon. It is often, but not always, caused by the bacterium Clostridium difficile. Try weaning amoxicillin as early as possible. Take home made food rich in zinc and food like garlic to boost up immunity. Have a good health, Thanks.