A 67-year-old man has 1 week of increasingly severe abdominal pain, fever, vomiting, and decreased appetite. Two years ago, he was admitted for a similar problem. He has intermittent left lower quadrant abdominal pain for 5 years. Temperature is 103°F, pulse is 105/min, respirations are 22/min, blood pressure is 150/90 mmHg, and white blood cell count is 21,000/mm3. Abdominal X-ray is nonspecific. Next step?
A) Immediate laparotomy
B) CT scan of the abdomen
C) Intravenous fluids and antibiotics
D) Diagnostic paracentesis