Suggest Remedy For Blood During Bowel Movement

My son 36 yrs old has had a shunt since 3 mths. Has no problems for 26 years. Currently larges amounts of bright red blood when having bowel movements. Going on for 4 yrs. Severely anemic in hospital. Received 6 litiers of blood. Red blood count now 8.5 was 4. Upper and lower GI and colonoscopy did not find anything. Wondering if his shunt which is goes down into stomach and upper small intestines could have caused puncture, irritation, abses or something? Does this happen? He is having small intestine dye xray procedure tomorrow. If nothing is found would an appointment with a neurologist be something to consider. Also his caves , ankles, and feet were very swollen and he has heart racing and lightheadedness but feel this was from severe anemia.