Atypical sites of endometriosis: pictoral review
Type:Educational Electronic Presentation
Authors: Patrícia Silva Freitas, Ana Sofia Alves, Nuno Gião, João Lopes Dias
Keywords:atypical endometriosis; gastrointestinal endometriosis; appendiceal endometriosis; endometriosis of the rectus muscle; scar endometriosis; pleural endometriosis; bladder endometriosis; MRI; US
Educational objective

To review clinical and imaging features of extra-pelvic endometriosis, as well as main differential diagnoses.

Topic Review

Endometriosis is a multifocal and polymorphic disease, which can affect almost any organ or structure. It is a common gynecological disorder that is defined by the presence of endometrial tissue outside the uterine cavity, associated with inflammatory reaction and fibrosis. It is the most common cause of chronic pelvic pain and patients may experience dysmenorrhea, dyspareunia, or even infertility. Some may be asymptomatic.

Atypical endometriosis is rare and difficult to diagnose. The most common atypical location is the gastrointestinal tract (32.3%), urinary tract (5.9%), and other sites such as lung, pleura, breast, pelvic nerves, and abdominal surgical scars. Extra-pelvic endometriosis occurs in 8.9% of cases. To assess suspected lesions, it can be used ultrasonography (US), computed tomography (CT), or magnetic resonance imaging (MRI), depending on its... more

Figure 1.: Endometriosis of the rectum in a 50-year-old patient with bloody diarrhea and abdominal pain. T2-WI image shows an endometriotic lesion expressed by a parietal thickening of the rectal wall in a “fan-shaped” configuration (A, B). The differential diagnosis included a neoplastic lesion. Photomicrograph showing rectal mucosa and endometrial glands, H&E x100 (C).
Figure 2.: Endometriosis of the sigmoid colon in a 39-year-old patient with dysmenorrhea and chronic pelvic pain. T2-WI FS (A) and T1-WI FS (B) demonstrate endometriotic lesion expressed by a parietal thickening of the colon also in a “fan-shaped” configuration. The implant demonstrates an isointense signal compared to muscle on T2-WI (A) and T1-WI (B, arrow) sequences.


Atypical sites of endometriosis great variability in location and clinical manifestations. The catamenial nature of the symptoms may guide the diagnosis and clinical investigation.

The diagnosis and treatment of extra-pelvic endometriosis remain immature due to the low prevalence and limited research available in the literature.

Radiologists should be familiar with the epidemiology, symptomatology, and imaging characteristics of the atypical sites of endometriosis, to achieve an accurate diagnosis, adequate follow-up, and guide the eventual need for intervention. The approach of this disease should evolve a multidisciplinary collaboration.