Acute Diverticulitis

A 67-year-old man presents to the Emergency department with an eight-hour history of constant left lower quadrant pain. He has no other gastrointestinal, no genitourinary symptoms. He is otherwise in good health, apart from hypertension, for which he takes perindopril. His blood pressure is 132/76 mmHg, pulse 70/min and temperature 37.8 °C. His abdomen is soft, apart from some tenderness in the left iliac fossa. His examination is otherwise unremarkable. His stool is negative for occult blood. Urinalysis reveals no leukocytes or RBCs, and Gram stain is negative. Laboratory tests reveal a leukocyte count of 16 x 10^9 cells/L and normal electrolytes and renal function. A CT scan is performed.

Which one of the following changes seen on the CT would be most indicative of the necessity of an emergency admission for this patient?
Choose the single best answer.

• Fat stranding

• Mucosal oedema

• Fistula formation

• Free fluid in the pelvis

• A pericolic abscess of 6 cm