The sudden, severe epigastric pain radiating to the back is a classic presentation of acute pancreatitis. This pain results from inflammation of the pancreas, which irritates surrounding tissues and nerves. Unlike gastric ulcers or cholecystitis, the pain often has a characteristic radiation to the back. The severity and onset distinguish it from myocardial infarction, which typically presents with chest pain. Early recognition is crucial as acute pancreatitis can rapidly progress to systemic inflammation and multi-organ failure, impacting surgical and medical management decisions.

Reference: Sabiston Textbook of Surgery, Townsend CM et al., 21st Edition.