A 56-year-old woman presents with severe epigastric abdominal pain and vomiting of 14 hours' duration, symptoms that developed shortly after dinner the previous evening. She has no history of alcohol use, takes no medications, and has no family history of pancreatitis. On physical examination, she has a heart rate of 110 beats per minute and moderate epigastric abdominal tenderness without peritoneal signs. The white-cell count is 16,500 per cubic millimeter, and the hematocrit is 49 percent. Amylase, lipase, alanine aminotransferase, and lactate dehydrogenase levels are elevated. Calcium, albumin, triglyceride, and electrolyte values are normal. How should this patient be further evaluated and treated?