Abdominal pain after eating

My husband has been dealing with stomach pain after he eats for a few months now. He's a hemodialysis patient, so he's no stranger to pain and discomfort. The problem is, recently when he eats, he gets stomach pain in the upper left side of his abdomen just below his ribs. He's had a hida scan done and it showed nothing unusual with his gall bladder. He's had a CT scan done and nothing unusual with his pancreas. They've checked for ulcers and he has none. They've done blood work and nothing has jumped out as abnormal. He's losing weight fast because he can't eat normally. He's 5'10" and weighs about 160 lbs. He's nothing but skin and bone right now, he looks anorexic. We have not been able to get any kind of satisfactory answer from the doctors. We are out of ideas as to what it could be. Any ideas what else can be checked?