A 35-year-old man presents to the emergency department complaining of 18 hours of severe, steady epigastric abdominal pain after heavy meal. The pain is radiating to his back and does not relieved by vomiting. On physical examination, mild abdominal guarding and epigastric tenderness can be elicited on palpation, with hypoactive bowel sounds. Laboratories show a total white blood cell count of 17,200/mm3 with 88% polymorphonuclear cells,and 10% lymphocytes, an alanine aminotransferase (ALT) of 98IU/L, aspartate aminotransferase(AST)of 81IU/L,total bilirubin of 32μmol/L with a direct fraction 17μmol/L, and serum amylase of 1721IU/L. Which of the following is the most likely diagnosis