Chapter 37: Disorders of Gastrointestinal Function

Disorders of Gastrointestinal Function details the diverse pathologies affecting the gastrointestinal (GI) system, beginning with common manifestations such as anorexia, nausea, and vomiting, explaining their underlying physiology and the coordinating role of the medullary centers. It then explores disorders of the esophagus, including congenital defects like esophageal atresia and tracheoesophageal fistula, swallowing difficulties (dysphagia, achalasia), anatomical issues like hiatal hernia, and chronic acid exposure leading to Gastroesophageal Reflux Disease (GERD), which can progress to Barrett esophagus or esophageal cancer. Gastric disorders center on the breach of the protective gastric mucosal barrier, covering acute and chronic gastritis, as well as peptic ulcer disease (PUD), emphasizing the primary etiologic agents: Helicobacter pylori infection and NSAID usage. Further stomach issues include rare hypersecretory conditions (Zollinger–Ellison syndrome) and ulcers induced by acute physiological stress (Curling and Cushing ulcers). Pathology of the small and large intestines encompasses the functional disorder irritable bowel syndrome (IBS), characterized by altered bowel habits and pain, and the chronic, relapsing inflammatory conditions of inflammatory bowel disease (IBD)—specifically comparing the transmural Crohn disease with its skip lesions to the continuous mucosal inflammation of ulcerative colitis. Infectious agents causing enterocolitis (viral, bacterial, protozoan) are examined, alongside structural problems like diverticular disease and appendicitis. Finally, the chapter addresses motility disturbances (diarrhea and constipation), life-threatening intestinal obstruction and peritonitis, malabsorption conditions such as celiac disease (an immune response to gluten), and gastrointestinal neoplasms, noting the development pathway from adenomatous polyps to common colorectal cancer.