My sister is 3 years old and has a history of poor appetite, ear infections, and poor immunity. 3 weeks ago she began having bloody, foul smelling diarrhea containing mucus. The doctor did a stool test and determined nothing other than that she had some sort of lower abdominal issue, so we removed gluten and lactose from her diet. The chronic diarrhea continues, and she is losing weight rapidly. What could it be and how do we proceed?