I have right sided abdominal pain that is not IBS. What else can it be?

I have had right sided abdominal pain for over 5 months which is severe at times and other times tolerable. Sometimes the pain is a stabbing pain and sometimes an intense gripping pain. I dont have any change in my bowel habit or diarrheoa. Dr Says it isn't IBS. Ultrasound scan showed no gallstones (its lower than this anyway). Colorectal surgeon has requested a barium enema which he is sure will not sure anything. He thinks there is a problem with my cae - how can this be resolved?