Gastroenterologists provide diagnosis and treatment of disorders of the digestive system (the esophagus, stomach, small and large intestine, liver, pancreas and gallbladder), including trouble with swallowing, heartburn, chest pain not due to heart disease, ulcers, and problems with digestion/elimination. By using fiber-optic and video endoscopes, these physicians explore internal organs and perform diagnostic and therapeutic procedures such as screening for colon cancer and the removal of polyps by colonoscopy.