Author: CONTI Laura Roma Italy

An inverted diverticulum is rare (0.7–1.7% of colonoscopies) but can easily be mistaken for a polyp. Performing a polypectomy or biopsy may cause colonic perforation, a complication well documented in the literature. Recognizing it is essential to avoid hazardous interventions.

During colonoscopy, an inverted diverticulum may show:

Sessile, polyp‑like elevation — similar to a polyp but without a stalk

Fine concentric folds around the lesion (Aurora rings), highly suggestive

Mucosa identical to the surrounding mucosa — no change in pit pattern

Umbilicated or central dimple appearance

Location in diverticular segments — especially the sigmoid colon (≈75%)

Dynamic signs that help distinguish an ICD from a true polyp:

Eversion with biopsy forceps — gentle pressure may cause the lesion to “pop back” into the diverticular lumen

Water or air insufflation — the lesion may collapse and reveal a typical diverticulum

Methylene blue staining — highlights the concentric folds