Gastrointestinal and Hepatobiliary · Colorectal imaging · Original and commonly used CT-modified classification

Hinchey Classification of Acute Diverticulitis

Grades the anatomical severity of acute diverticulitis from localised inflammation or abscess formation to generalised purulent or faecal peritonitis.

Purpose

To describe the anatomical extent and complications of acute diverticulitis, support communication between radiologists and surgeons, and contribute to treatment planning.

Modified stage	Defining finding	Relationship to original Hinchey
0	Mild clinical diverticulitis; diverticula with or without colonic wall thickening	Not included in the original classification
Ia	Confined pericolic inflammation or phlegmon without a drainable abscess	Extension of original stage I
Ib	Confined pericolic or mesocolic abscess	Corresponds to original stage I: pericolic abscess
II	Pelvic, distant intra-abdominal or retroperitoneal abscess	Original stage II
III	Generalised purulent peritonitis without gross faecal contamination	Original stage III
IV	Generalised faecal peritonitis due to free colonic perforation	Original stage IV

How to use it

The original Hinchey classification was an operative classification for perforated diverticular disease and comprised stages I–IV.
The commonly used modification adds stage 0 and subdivides stage I into Ia inflammation or phlegmon and Ib pericolic or mesocolic abscess.
Stage II indicates a distant abscess rather than a confined pericolic collection.
Stages III and IV describe generalised peritonitis and are fundamentally operative or clinical diagnoses; CT may demonstrate free perforation and diffuse contamination but may not reliably distinguish pus from faecal contamination.
Management must also incorporate haemodynamic status, immune status, abscess size and accessibility, comorbidity and contemporary surgical guidance.

Common mistake

Do not label free or pericolic extraluminal gas alone as Hinchey III: stage III requires generalised purulent peritonitis. Also state whether the original or modified Hinchey system is being used.

Exam pearl

Remember the progression: stage I is local, stage II is a distant abscess, stage III is generalised pus and stage IV is generalised faecal contamination.

Viva questions

What is the purpose of the Hinchey classification?: It grades the anatomical severity of acute diverticulitis, progressing from a localised abscess to generalised purulent or faecal peritonitis.
Enumerate the original Hinchey stages.: Stage I is a pericolic abscess, stage II is a pelvic or other distant abscess, stage III is generalised purulent peritonitis and stage IV is generalised faecal peritonitis.
What is the difference between modified Hinchey Ia and Ib?: Stage Ia is confined pericolic inflammation or phlegmon without an abscess, whereas stage Ib is a confined pericolic or mesocolic abscess.
What constitutes modified Hinchey stage II?: Stage II is a pelvic, distant intra-abdominal or retroperitoneal abscess rather than a collection confined to the pericolic or mesocolic region.
How do Hinchey stages III and IV differ?: Stage III is generalised purulent peritonitis without gross faecal contamination, while stage IV is generalised faecal peritonitis from free colonic perforation.
Can CT reliably distinguish Hinchey III from Hinchey IV?: Not always. CT can demonstrate free perforation, free gas and diffuse fluid, but the distinction between purulent and faecal peritonitis is fundamentally clinical or operative.
Does pericolic extraluminal gas automatically indicate Hinchey III diverticulitis?: No. Localised pericolic gas can occur with a contained perforation; Hinchey III specifically requires generalised purulent peritonitis.
Why should a radiology report specify which Hinchey version is being used?: The original classification contains stages I–IV, whereas modified systems add stage 0 and subdivide stage I. Naming the version prevents ambiguity in multidisciplinary communication.