A Gastroenterologist is an Internal Medicine, or for children - a Pediatric, medical doctor with additional qualifications enabling specialization in the evaluation and management of disorders of the digestive system including organs such as the stomach, intestines, pancreas, gallbladder and liver. Gastroenterologists may perform many specialized tests including endoscopy (upper GI endoscopy and colonoscopy) to visualize internal organs, potentially biopsy unusual lesions, and diagnose and treat diseases. This specialist treats conditions such as peptic ulcers, diarrhea, cancer, hepatitis and other causes of jaundice, ulcerative colitis and Crohn’s disease, and more.