Colorectal cancer is the second most common type of cancer in the United States after lung cancer and is responsible for about 50,000 deaths annually (Chapter 41: The Intestines: III. Neoplasms). Gastric cancer is less common in the United States but has a high prevalence in Japan and South America (Chapter 38: The Stomach). Cancer of the esophagus (Chapter 37: The Esophagus) also has a marked geographic variation, being much more common in China than in the United States—except for adenocarcinomas complicating Barrett's esophagus, which is presently increasing rapidly in incidence in the United States. These geographic variations provide insights into causes of cancer (see Chapter 18: Neoplasia: II. Mechanisms & Causes of Neoplasia).
Gastrointestinal infections (Chapter 40: The Intestines: II. Infections; Inflammatory Bowel Diseases) are very prevalent in developing countries where poor sanitary conditions favor fecal-oral transmission of infection (see Chapter 14: Infectious Diseases: II. Diagnosis of Infectious Diseases). Acute appendicitis (Chapter 40: The Intestines: II. Infections; Inflammatory Bowel Diseases) is the most common surgical emergency. Peptic ulcer disease (Chapter 38: The Stomach) and reflux esophagitis (Chapter 37: The Esophagus) are common all over the world. Inflammatory bowel disease (ulcerative colitis and Crohn's disease, Chapter 40: The Intestines: II. Infections; Inflammatory Bowel Diseases) is common in the United States and Europe, but uncommon in tropical Asia and Africa.