Gallstone pancreatitis. Gallstone pancreatitis is caused by transient obstruction of the ampulla of Vater by a migrating gallstone. Intraglandular activation of pancreatic enzymes occurs (by an unclear mechanism), and their entry into the circulation causes most of the local and systemic events of pancreatitis. The diagnosis is based on history and physical examination, an elevation of serum amylase above 1000 IU/L, and ultrasound and CT scans. Endoscopic retrograde cholangiopancreatography can be used in less certain cases to confirm the presence of common bile duct stones. Because of the absence of an agent that can abort progression of the disease, therapy should consist of adequate resuscitation, nutritional support, and careful monitoring to detect early complications. In patients with mild pancreatitis, surgery usually can be performed within 48 or 72 hours of admission or as soon as symptoms and amylase levels return to normal. For patients with severe disease, endoscopic sphincterotomy is emerging as the therapeutic modality of choice. Elective treatment of the associated biliary disease should be performed during the same hospitalization after the acute phase of the disease has subsided. 