Diarrhea is the passage of loose or watery stools three or more times a day with or without discomfort. It happens when the water in the intestine is not being absorbed back into the body for some reason. Sometimes diarrhea can be caused by an overflow of intestinal liquids around stool that is lodged in the intestine (impaction). Other causes can include infections; surgery; anxiety; side effects of chemotherapy, radiation therapy to the abdomen, or medicines; supplemental feedings containing large amounts of vitamins, minerals, sugar, and electrolytes; and tumor growth. Diarrhea caused by chemotherapy or radiation therapy may last for up to three weeks after treatment ends.