Mushroom cap sign (endometriosis)

Mushroom cap sign is one of the important signs of deep rectosigmoid endometriosis seen on T2 weighted MRI sequence. It indicates the submucosal involvement in the rectosigmoid colon.

The hypertrophic muscularis propria appears as heterogeneous low signal intensity surrounded by the high signal intensity of mucosa and submucosa. This gives the characteristic appearance of a mushroom cap.