CT Findings
Colonic diverticula + pericolonic fat stranding + colonic wall thickening at site of inflammation. Sigmoid colon involved in >90% of cases. CT sensitivity ~97%, specificity ~100%. Hinchey classification guides management of complicated disease.
Hinchey Classification
| Stage | Description | Management |
|---|---|---|
| Hinchey Ia | Pericolic/mesenteric phlegmon or confined pericolic abscess (<4 cm) | IV antibiotics; most resolve conservatively |
| Hinchey Ib | Pericolic abscess >4 cm | IV antibiotics ± percutaneous drainage if accessible |
| Hinchey II | Pelvic, retroperitoneal, or distant abscess | Percutaneous drainage; elective surgery after resolution |
| Hinchey III | Purulent peritonitis (ruptured pericolonic abscess) | Surgical emergency |
| Hinchey IV | Feculent peritonitis (free colonic perforation) | Surgical emergency; highest mortality |
Complicated Features
| Complicated Feature | CT Findings | Management Implication |
|---|---|---|
| Contained perforation / phlegmon | Pericolonic gas bubbles + inflammatory mass; no free pneumoperitoneum | IV antibiotics; admission; most resolve without intervention |
| Free perforation | Pneumoperitoneum; diffuse peritoneal enhancement; ascites | Surgical emergency (Hinchey III/IV) |
| Abscess | Rim-enhancing fluid collection adjacent to or distant from colon; may contain gas | >3–4 cm = IR percutaneous drainage; elective sigmoid resection 6–8 weeks later |
| Fistula | Colovesical: air/fecal matter in bladder · Colovaginal: air in vagina | Surgical repair after bowel prep; colovesical most common |
| Obstruction | LBO/SBO from extrinsic compression by phlegmon or fibrosis | NG decompression; surgical consult if complete |
Surgical Emergency Threshold
Free air + diffuse peritoneal enhancement = Hinchey IV. Always report free intraperitoneal air with diverticulitis — even small amounts change management.
Reference
Radiopaedia — Hinchey classification of acute diverticulitis