Review Question - QID 216246

A 48-year-old man presents to the emergency room with a 2-hour history of severe abdominal pain, nausea, and vomiting. He states that he has not passed gas or had a bowel movement in 4 days and his pain has worsened and become constant over the past 2 hours. His only medical history includes an appendectomy that he underwent as a child, and he takes no daily medications. His temperature is 38.5°C (101.3°F), blood pressure is 92/60 mmHg, pulse is 138/min, and respirations are 25/min. His pulse oximetry is 99% on room air.There are no cardiopulmonary abnormalities on auscultation. His abdomen is distended and tender in all quadrants, with guarding and rebound present. He also has increased bowel sounds throughout. Laboratory results are as follows:

Hemoglobin: 11 g/dL
Leukocyte count: 16,500/mm^3 with normal differential
Platelets: 250,000/mm^3

Serum:
Creatinine: 1.0 mg/dL
Glucose: 95 mg/dL
Lipase: 45 U/L
Total bilirubin: 0.8 mg/dL
Alkaline phosphatase: 74 U/L
Aspartate aminotransferase (AST, GOT): 32 U/L
Alanine aminotransferase (ALT, GPT): 45 U/L
Lactate: 7.0 mmol/L

Which of the following is the most appropriate next step in management?