Sonographic features of endometriosis infiltrating the lateral parametrium

Objective: Lateral parametrium endometriosis (LPE) can be associated with infiltration of ureters and hypogastric plexus, causing severe painful symptoms and functional impairment, and requiring complex and extensive surgery. The aim of this study was to evaluate the presentation of LPE lesions at transvaginal ultrasound, identifying sonographic features for disease recognition and mapping. Methods: This was a retrospective case-series of women with sonographic suspect of LPE confirmed at surgical exploration. We carried out a descriptive analysis of the ultrasound patterns of presentation and compared the features of the lesions according to their location cranially or caudally to the uterine artery. Results: Our population included 23 women, with a total of 26 parametrial lesions: all of them were hypoechoic, with absence of vascularization. Lesions lying above the uterine artery presented more frequently as ill-defined nodules (78.6 %, p < 0.01) and were associated with ipsilateral reduced or absent ovarian mobility (92.9 %, p < 0.01); the ones located below the uterine artery appeared more frequently as fan-shaped lesions with retraction of the surrounding tissues (83.3 %). Ureteral involvement was observed at surgery in 43.5 % of cases. In all patients, deep infiltrating endometriosis of the posterior compartment was observed: the utero-sacral ligaments were the most common location affected concurrently. Conclusions: LPE may present at transvaginal sonography as hypoechoic, not vascularized lesions, most frequently with a nodular or with a fan-shaped appearance, respectively cranially or caudally to the uterine artery. Reduced ovarian sliding and ureteral involvement are commonly associated.