Ultrasonographic characterization of parametrial endometriosis: a prospective study.

OBJECTIVE:To study the ultrasonographic diagnostic accuracy and characteristics of parametrial endometriosis comprehensively. DESIGN:This prospective study enrolled patients with suspected deep endometriosis (DE) scheduled for laparoscopic surgical treatment. Preoperative ultrasonographic examinations were performed following the International Deep Endometriosis Analysis criteria. This study aimed to evaluate the presence of parametrial endometriosis and its ultrasonographic characteristics, using surgical diagnosis as the reference standard. Additionally, indirect signs of DE and concomitant DE nodules associated with parametrial involvement were identified, assessing their predictive significance in the anterior, lateral, and posterior parametrial areas. SETTING:Referral institution for endometriosis. PATIENTS:Patients with suspected DE scheduled for surgical treatment. INTERVENTIONS:Standardized preoperative ultrasonographic examination. MAIN OUTCOME MEASURES:The diagnostic accuracy of transvaginal ultrasound in identifying parametrial endometriosis, including sensitivity and specificity, and the ultrasonographic characteristics of parametrial nodules, prevalence in distinct parametrial areas, and associations with indirect DE signs and concomitant DE nodules. RESULTS:Surgical confirmation of parametrial nodules was observed in 105 of 545 patients (left, 18.5; right, 17.0%). Transvaginal ultrasound demonstrated a sensitivity of 77.1% (95% confidence interval, 68.0%-84.8%) and specificity of 99.1% (95% confidence interval, 67.7%-99.8%). Parametrial nodules typically exhibited characteristics such as a mild hypoechoic appearance (83.6%), starry morphology (74.7%), irregular margins (70.2%), and low vascularization. The posterior parametrial region was the most common location (52.2%), followed by the lateral (41.0%) and anterior (6.8%) parametrial regions. Concomitant DE nodules in the rectum (63.5%) and infiltrating the rectovaginal septum (56.5%) were significantly more prevalent in patients with parametrial involvement. Indirect DE signs, such as the ovaries fixed to the uterine wall (71.8%) and the absence of a posterior sliding sign (51.8%), were also more common in women with parametrial nodules. Hydronephrosis, although relatively uncommon in patients with parametrial involvement (8.2%), was largely detected in lateral parametrial nodules (70.0%). CONCLUSIONS:This study represents a systematic ultrasonographic characterization of parametrial endometriosis. Specifically, it comprehensively assesses the diagnostic accuracy of transvaginal ultrasound in identifying parametrial involvement within a sizable cohort of patients with preoperative suspicion of DE. CLINICAL TRIAL REGISTRATION NUMBER:NCT06017531.