Prevalence, ultrasound characterization, and oncologic differential diagnosis of endometriosis in postmenopausal women undergoing routine gynecological examination

Objective To systematically assess the prevalence, ultrasonographic characteristics, and clinical correlates of findings suggestive of deep endometriosis (DE) in postmenopausal women undergoing routine gynecological evaluation. Methods This prospective, observational study (NCT07503938) included consecutive postmenopausal women attending a regional gynecology outpatient clinic for routine examination over 12 months. All participants underwent a transvaginal ultrasound performed by an expert operator according to the standardized International Deep Endometriosis Analysis (IDEA) group criteria. Ultrasonographic findings suggestive of DE and/or endometrioma-like cysts were recorded and characterized. Clinical data were collected using a structured questionnaire. Univariable and multivariable logistic regression analyses were performed to identify factors independently associated with posterior compartment hypoechoic nodules. Results Four hundred ninety-two postmenopausal women were included (mean age 60.2 ± 6.1 years; median time since menopause 8.0 years). Ultrasound findings suggestive of endometriosis were identified in 40 women (8.1%; 95% CI 5.9–10.9%), including posterior compartment hypoechoic nodules in 36 (7.3%). Intestinal nodules (n=21; 4.3%) often displayed a thin, hypoechoic morphology with regular margins, minimal or absent Doppler vascularization, and rare submucosal layer involvement. The prevalence of DE nodules decreased progressively with increasing time since menopause (13.9% within ≤5 years vs 4.3% >10 years; p for trend = 0.02). In multivariable analysis, being within five years of menopause was independently associated with posterior hypoechoic nodules (adjusted OR 3.31, 95% CI 1.38–7.94), as were a history of dysmenorrhea (adjusted OR 2.26, 95% CI 1.08–4.74) and chronic pelvic pain (adjusted OR 2.37, 95% CI 1.18–4.87) during reproductive life. No independent association was observed with previous infertility, current pelvic, sexual, or bowel symptoms, nor with systemic hormone replacement therapy. Six ovarian cysts suggestive of endometriomas were identified (1,2%, 95%CI, 0.45%-2.64%, frequently (83.3%) displaying atypical sonographic features (multilocularity, heterogeneous internal echoes, focal papillary excrescences, or localized wall thickening). Importantly, one rectal hypoechoic lesion with marked vascularization and transmural involvement was diagnosed as rectal adenocarcinoma, and one surgically treated atypical endometrioma-like cyst was a FIGO stage I serous borderline ovarian tumor. Conclusions Ultrasound findings suggestive of DE may be detected in postmenopausal women and are strongly associated with early postmenopausal timing and a history of reproductive-age pain, rather than with current symptoms or hormonal exposure. These lesions most likely represent quiescent fibrotic sequelae of previously unrecognized disease. Given the potential for malignant mimics in clinical findings and endometriosis-associated adnexal neoplasia, expert ultrasound assessment and appropriate triage of atypical or vascular lesions are essential in this population.