My Son Has Had Diarrhea For Almost 7 Months. It

My son has had diarrhea for almost 7 months. It started after he had surgery at RUH. he has taken Flagyl twice. The last Stool analysis showed no C difficele Yet his diarrhea had not stopped. He has lost wait because of it and seem to me dehydrated. I have tried everything I know with him (probiotics, yoghurt and honey, white bread, white rice, boiled potatoes and carrots, olives, Turkish coffee, boiled chicken and beef). I am not sure what more can I do. His family physician referred him to a gastroenterologist, but we were told that it might take 12 months for him to be seen. I am worried lest he has something serious and his condition would get worse during that long waiting period.
Dr. Mansour