A 52-year-old woman with a history of cholelithiasis presents with acute onset epigastric pain and vomiting for 8 hours. On examination, she is afebrile, heart rate 95/min, blood pressure 118/74 mmHg, with mild epigastric tenderness. Serum amylase is 950 U/L and serum lipase is 1800 U/L. Abdominal ultrasound shows multiple gallstones, a dilated common bile duct (8 mm), and mild pancreatic edema. What is the most appropriate next step in management?