Gastroenterologists are medical specialists who deal with the disorders of gastrointestinal system. Their main role is to diagnose and treat the diseases of stomach, intestines, liver and pancreas. Common diseases treated by a gastroenterologist are gastritis, peptic ulcer, constipation, diarrhea, hemorrhoids, ascites, Barrett’s esophagus, colon ulcer, esophagitis, gastroesophageal reflux disease, irritable bowel syndrome and ulcerative colitis.