Long-term follow-up of women with endometriosis symptoms and normal ultrasound examination : do visible endometriosis lesions develop over time?

Introduction: The natural course of endometriosis is not fully understood. The diagnostic delay in endometriosis is approximately 7-8 years. Prevalence of endometriosis increase with age, which might indicate a delay until visible endometriosis appear at ultrasound examination. Aim: Investigate if women with symptoms suggestive of endometriosis and no abnormal ultrasound findings at the first examination develop visible lesions at ultrasound examination during long-term follow-up up to eight years. Methods: This was a prospective cohort study performed at the Ultrasound Unit, Department of Obstetrics and Gynecology, Skane University Hospital, Malmo, Sweden. Women were examined with transvaginal ultrasound by an experienced ultrasound examiner at long-term follow-up. Endometriosis was assessed according to the International Deep Endometriosis Analysis group consensus protocol and reported according to the #Enzian classification. Results: In total, 100 women underwent follow-up examination. Endometriosis was found in 8 women (8%, 95% CI 3.5-15.2%); 4 women (4%) had endometrioma, 1 woman (1%) had deep endometriosis and 3 women (3%) had combination of endometrioma and deep endometriosis. Median time to follow up was 70 months (range 51-104 months). Laparoscopy because of suspected endometriosis was performed in 22 women (22%) during follow-up time, in 10 women (10%) peritoneal endometriosis was found and surgically treated. One woman (1%) was diagnosed with abdominal wall endometriosis. In women with previously diagnosed peritoneal endometriosis at laparoscopy, endometrioma was seen in one woman (1%) and deep endometriosis in one woman (1%) at follow-up ultrasound examination.Conclusions and impact: Endometriosis visible at ultrasound was found in 8% of symptomatic women at follow-up up to eight years.