The large intestine is used to create the pouch, which acts like a bladder and stores urine. Where the small intestine joins to the large intestine, there is a valve. The valve stops urine from draining out of the pouch. The end of the small intestine is brought out to the abdominal wall to make an opening. This opening, called a stoma, is used to pass a catheter to drain the pouch. See picture D.