On CT of the abdomen in a 70-year-old with LIF pain and fever, there is pericolonic fat stranding, thickening of the sigmoid colon wall (>4 mm), and a 3 cm fluid collection with a rim-enhancing wall adjacent to the sigmoid. Which complication of sigmoid diverticulitis does the rim-enhancing collection represent?
- A Free perforation with fecal peritonitis (Hinchey Stage IV)
- B Phlegmon (Hinchey Stage Ib)
- C Colovesical fistula
- D Peridiverticular abscess (Hinchey Stage II) ✓
Explanation
A rim-enhancing fluid collection adjacent to the sigmoid colon in the context of acute diverticulitis represents a pericolic/peridiverticular abscess, classified as Hinchey Stage II. Hinchey Classification: Stage I = pericolic phlegmon or microperforation; Stage Ib = pericolic abscess; Stage II = pelvic or distant abscess; Stage III = purulent peritonitis; Stage IV = fecal peritonitis. A 3 cm abscess can be treated by CT-guided drainage + antibiotics if accessible. Free perforation (Hinchey III/IV) shows pneumoperitoneum and/or fecal peritonitis requiring emergency surgery. A phlegmon is inflammatory fat stranding without a discrete liquid collection.
Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.
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