A 42-year-old woman from Mumbai presents with acute severe diffuse abdominal pain, fever (39.2°C), and tachycardia (115/min). She reports a history of diverticular disease. On examination, she has rebound tenderness and guarding. A contrast-enhanced CT abdomen is performed. Which of the following CT findings would be most specific for colonic perforation secondary to diverticulitis?

Explanation

## CT Imaging of Perforated Diverticulitis ### Diagnostic Features of Perforation **Key Point:** Extraluminal air (pneumoperitoneum or localized air collection) adjacent to an inflamed diverticulum is the most specific CT finding for diverticular perforation. When coupled with pericolonic fat stranding and abscess formation, it confirms perforation with peritonitis. ### CT Findings in Diverticulitis Severity Spectrum | Grade | CT Findings | Perforation? | Management | |-------|-------------|--------------|-------------| | Uncomplicated | Colonic wall thickening, pericolonic fat stranding | No | Conservative (antibiotics, NPO) | | Complicated (microperforation) | Localized air, small abscess <4 cm | Microperforated | Percutaneous drainage ± antibiotics | | Perforation | Extraluminal air, large abscess, peritonitis | Yes | Surgery or percutaneous drainage | | Generalized peritonitis | Free air, diffuse ascites, peritoneal enhancement | Yes | Emergency surgery | ### Pathophysiology of Perforation in Diverticulitis Inflammation of a diverticulum erodes through the diverticular wall, allowing colonic contents and bacteria to escape into the pericolonic space. If the perforation is contained, a localized abscess forms; if uncontained, generalized peritonitis and free pneumoperitoneum develop. **High-Yield:** The presence of extraluminal air is the radiological hallmark of perforation. Pericolonic fat stranding and abscess indicate the inflammatory response and bacterial seeding. ### Clinical Correlation **Clinical Pearl:** This patient's acute severe diffuse pain, fever, and peritoneal signs indicate perforation with peritonitis. CT with IV contrast is the gold standard for diagnosing diverticulitis and determining the presence and extent of perforation, guiding management (percutaneous drainage vs. emergency colectomy). **Mnemonic:** **FAP** = **F**at stranding, **A**bscess, **P**erforation (extraluminal air) — the triad of complicated diverticulitis. ### Why Not the Other Options - **Target sign and mesenteric edema:** Indicates uncomplicated diverticulitis or inflammatory bowel disease, not perforation. - **Dilated colon with transition point:** Suggests acute colonic obstruction (e.g., colorectal cancer, volvulus), not diverticular perforation. - **Ascites with peritoneal enhancement:** A nonspecific finding seen in peritonitis from any cause; does not specifically indicate diverticular perforation.