Shining light in a dark landscape: MRI evaluation of unusual localization of endometriosis

Abstract

Endometriosis is a systemic disease that affects about 10% to 20% of women during their reproductive age, characterized by the presence of endometrial glands and stroma outside the uterine cavity (1). Endometriosis lesions are characterized by intralesional recurrent bleeding during menses, because of the hormonal responsiveness of ectopic endometrial tissue, with resulting fibrosis. Typical symptoms are cyclic or chronic pelvic pain, dysmenorrhea, dyspareunia, and pain during defecation or urinating. Unusual endometriosis localizations may be associated with more specific symptoms depending on the site of the localization. According to Siegelmen et al. (2) there are three forms of pelvic endometriosis: (a) superficial peritoneal lesions; (b) ovarian endometrioma; (c) deep (or solid infiltrating) endometriosis (DIE), which is histologically identified as a lesion that extends more than 5 mm into the subperitoneal space and/or affects the wall of organs in the pelvis and ligaments. In superficial endometriosis, superficial plaques are disseminated across the peritoneum, adnexa and ligaments of the uterus; these noninvasive implants are well recognized at laparoscopy and not often detectable with magnetic resonance imaging (MRI). Laparoscopy is the standard of reference for the diagnosis of endometriosis but nodules covered by adhesions and subperitoneal disease are difficult to study. Pouch of Douglas, uterosacral ligaments, torus uterinus, and bowel are the most frequent sites of deep pelvic endometriosis localization. Atypical pelvic localizations of endometriosis can occur at level of the cervix, vagina, round ligaments, ureter, and nerves. Rare extrapelvic endometriosis implants can also be localized in the upper abdomen, subphrenic fold, or subcutaneous fat tissue of the abdominal wall. The focus of this review is to describe atypical pelvic and abdominal localizations of endometriosis that should be known by radiologists in order to correctly identify and characterize these lesions on MRI. Moreover, we describe the MRI appearance of the implants at specific sites and review the literature with special attention to imaging reports and description. 272From the Institute of Radiology, Diagnostic Area (B.G.  benedetta.gui@policlinicogemelli.it, A.L.V., V.N., M.M., V.Z., P.P.G., F.C., L.B.) and the Institute of Obstetrics and Gynecology, Female Health Area (M.G.), Catholic University of the Sacred Heart, Agostino Gemelli Hospital, Rome, Italy; "F. Miulli" Regional General Hospital (M.G.), Acquaviva delle Fonti, Bari, Italy. ABSTRACTEndometriosis is a disease distinguished by the presence of endometrial tissue outside the uterine cavity with intralesional recurrent bleeding and resulting fibrosis. The most common locations for endometriosis are the ovaries, pelvic peritoneum, uterosacral ligaments, and torus uterinus. Typical symptoms are secondary dysmenorrhea and cyclic or chronic pelvic pain. Unusual sites of endometriosis may be associated with specific symptoms depending on the localization. Atypical pelv...

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