John, a 47-year-old male, presents with a 6-hour history of severe epigastric pain radiating to the back, worsened after a heavy meal, and associated with nausea and vomiting. He has hypertension (on amlodipine) and hyperlipidemia (on atorvastatin). Examination reveals epigastric tenderness, hypoactive bowel sounds, and a fever of 38.2°C. Laboratory findings show elevated serum amylase (480 U/L) and lipase (950 U/L). Which of the following is the most common cause of this disorder?
