Endometriosis is defined as the presence of ectopic glandular tissue and endometrial stroma outside the endometrial cavity. It affects up to 10% of premenopausal women. [1] The pelvic presentation forms are:

1. Superficial peritoneal implants → without serosa infiltration

2. Ovarian endometrioma (1 cm endometrioma).

3. Deep pelvic endometriosis → infiltrating solid nodules that invade> 5mm of the peritoneum.

Deep pelvic endometriosis is more common in the posterior compartment (uterosacral ligaments, vagina, ureters, intestine), and on the left side.

Approximately 12-37% of patients with deep pelvic endometriosis have intestinal involvement being more frequent in the recto-sigma territory. [2] In these cases, the right side predominates over the left side (appendix, ileocecal valve), and in up to 99% of patients, it is associated with other pelvic endometriotic implants. [3]

The most frequent locations within the gastrointestinal tract are, in descending order: rectum, rectum-sigmoid, sigma, appendix, cecum and ileocecal valve, small bowel and omentum. Fig. 1

Fig. 1: Fig. 1: Most frequent locations of endometriosis implants within the gastrointestinal tract.[2]

The pelvic MRI can show the following features:

• Nodular or masslike bowel wall thickening (hypertrophy of muscularis mucosae).
• “Mushroom cap” sign: the mural thickening produces attraction of the anterior surface of the recto-sigma, with an obtuse angle (> 90º and <180º), a low signal on T2W images caused by hypertrophy and fibrosis of the muscularis mucosae and high signal of mucosa and submucosal layers (displaced into the bowel lumen) [4] Fig. 2 Fig. 3
• Internal cystic areas and hemorrhagic component. Fig. 4
• Retraction and loss of fat plane between the bowel wall thickening and adjacent organs due to fibrotic adhesions. Fig. 5

The involvement of the extrapelvic bowel is rare and usually courses asymptomatic, although it is considered a potentially serious disease due to the risk of intestinal occlusion.

Intestinal involvement can be multifocal in up to 55% of patients, especially when rectal endometriosis is present.

Obtaining a pre-surgical map and remove the endometriosis foci is important to prevent complications and achieve long periods without symptoms.

Pelvic MRI allows to optimally evaluate recto-sigma endometriosis, but not the entire intestinal tract. MRI – Enterography helps us to see the whole picture.