Atypical Sites of Deeply Infiltrative Endometriosis: Clinical Characteristics and Imaging Findings

Endometriosis is defined as the presence of endometrial tissue that is located outside the uterine cavity and associated with fibrosis and inflammatory reaction. It is a polymorphic and multifocal disease with no known cure or preventive mechanisms. Patients may be asymptomatic or may experience chronic pelvic pain, dysmenorrhea, dyspareunia, or infertility. The pelvic cavity is the most common location for endometriotic implants, which usually affect the retrocervical space, ovaries, vagina, rectosigmoid colon, bladder dome, and round ligaments. Atypical endometriosis is rare and difficult to diagnose. The most common atypical locations are the gastrointestinal tract, urinary tract, lung, umbilicus, inguinal area, breast, and pelvic nerves, as well as abdominal surgical scars. Gastrointestinal lesions are the most common extragenital manifestation, and the diaphragm is the most frequent extrapelvic site. The catamenial nature of the symptoms (occurring between 24 hours before and 72 hours after the onset of menstruation) may help suggest the diagnosis, but imaging by specialists is fundamental to evaluation. Depending on the area affected, radiography, ultrasonography, thin-section computed tomography, or magnetic resonance imaging can be used to assess suspected lesions. Because isolated extragenital endometriosis is rare, concomitant evaluation of the pelvic cavity is mandatory. Surgical excision is the only therapeutic option for definitive treatment, and comprehensive disease mapping is necessary to avoid residual disease. The authors review atypical locations for endometriosis and emphasize the most appropriate imaging protocols for investigation of various clinical manifestations. (c) RSNA, 2018