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Acute diverticulitis
Inflammation around a colonic diverticulum, usually in the sigmoid; CT sets the severity, and severity — not the number of episodes — decides whether antibiotics, drainage or surgery are needed.
Why it matters in the exam
The classic case is an older patient with left lower quadrant pain, fever and leucocytosis — "left-sided appendicitis". Questions check that the right test is CT with intravenous contrast and not colonoscopy in the acute phase, and that you can translate the CT findings into a Hinchey stage: phlegmon, adjacent abscess, distant abscess, purulent peritonitis and faecal peritonitis. Each stage has a different treatment, and the exam likes to ask about the step from one stage to the next.
One area that has changed in recent years is antibiotics: in uncomplicated diverticulitis in an immunocompetent patient current guidelines recommend selective rather than routine use, and most patients are treated at home. Another change concerns elective resection: the old rule "operate after two episodes" has been replaced by an individual decision based on symptoms, complications and quality of life. Candidates are also asked about colonoscopy after recovery to exclude cancer, about a colovesical fistula, and about the difference between diverticulitis and diverticular bleeding.
Key points
- CT with intravenous contrast is the test for diagnosis and staging.
- Uncomplicated in a healthy patient: home treatment, antibiotics only selectively.
- Abscess of 4 cm or more — percutaneous drainage.
- Hinchey III–IV — surgery; faecal peritonitis in an unstable patient — Hartmann's procedure.
- Colonoscopy about 6–8 weeks after a complicated episode; elective resection by individual judgement.
Summary table
| Stage (modified Hinchey) | CT finding | Treatment |
|---|---|---|
| 0–Ia, uncomplicated | Wall thickening and pericolic phlegmon, no abscess or free air | Home treatment; antibiotics selectively, not routinely, in an immunocompetent patient |
| Ib — adjacent abscess | Pericolic abscess | Abscess smaller than about 4 cm — antibiotics; 4 cm or more — percutaneous drainage and antibiotics |
| II — distant abscess | Pelvic or retroperitoneal abscess | Percutaneous drainage and antibiotics; surgery if no improvement |
| III — purulent peritonitis | Free air and diffuse fluid, no faeces | Surgery: sigmoid resection (Hartmann's, or primary anastomosis with a diverting ileostomy); laparoscopic lavage only in selected patients |
| IV — faecal peritonitis | Faeces in the peritoneal cavity | Urgent surgery: resection, usually Hartmann's procedure in an unstable patient |
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Sources
- WSES guidelines for the management of acute left-sided colonic diverticulitis in the emergency setting, 2020 — Classification, antibiotics, percutaneous drainage and surgery
- AGA Clinical Practice Update on Medical Management of Colonic Diverticulitis, 2021 — Selective antibiotic use and colonoscopy after an episode
- Sabiston Textbook of Surgery, 21st edition (2022) — Colon and Rectum
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-02. The text may contain errors; when in doubt, check the source.