The study of the functions and diseases related to the digestive system which comprises the esophagus, stomach, small intestine, colon and rectum, pancreas, gallbladder, bile ducts, and liver is referred to as gastroenterology. It encompasses the physiology of the gastrointestinal organs such as the movement of material through the stomach and intestine, and the digestion of food and absorption of nutrients into the blood. The excretion of waste from the system, and the function of the liver as a digestive organ is also studied within this field. Gastroenterology deals with diseases such as colon polyps and cancer, gastroesophageal reflux, hepatitis, peptic ulcer disease, colitis, gallbladder and biliary tract disease, nutritional problems, irritable bowel syndrome, and pancreatitis. This book presents the complex subject of gastroenterology in the most comprehensible and easy-to-understand language. The topics covered herein deal with the core subjects of this field. This book will serve as a reference to a broad spectrum of readers.