Comparison of routine pelvic US and MR imaging in patients with pathologically confirmed endometriosis

Purpose: To estimate the benefit of pelvic magnetic resonance (MR) imaging after routine pelvic ultrasound (US) in patients with pathologically or surgically proven endometriosis. Methods: Patients with surgically or pathologically proven endometriosis who had routine pelvic US followed by pelvic MR within 6 months prior to surgery were included. Patients were excluded if they had previously confirmed endometriosis, pregnancy, or surgery > 6 months after MR. The detection rate of endometriosis by pelvic US and MR was compared to the surgical/pathological reference standard. Results: 83 female patients (mean age 40 ± 9) met inclusion criteria and had surgical/pathological confirmation of endometriosis. The mean time interval between pelvic US and MR was 33 ± 43 days, with 64 ± 69 days between MR examination and surgery. US detected endometriosis in 22% (18/83) of patients compared to 61% (51/83) for MR (p < 0.0001). 51% (33/65) of patients with a negative pelvic US exam had a positive MR. MR identified additional sites or sequela in the majority of patients with a positive US (14/18; 78%), including extraovarian locations [e.g., fallopian tubes 7/18 (39%), uterus 7/18 (39%), uterine ligaments 6/18 (33%), posterior cul de sac 5/18 (28%), pelvic side walls 5/18 (28%), abdominal wall 1/18 (6%)] and sequela [ovarian tethering 5/18 (28%), 6/18 (33%) bowel adhesive disease, posterior cul de sac obliteration 2/18 (11%), hydrosalpinx 2/18 (11%), and hydronephrosis 1/18 (6%)]. 3 T MR detected endometriosis in 33/46 (72%) patients compared to 18/37 (49%) for 1.5 T MR (p = 0.03). Conclusion: Pelvic MR imaging had a higher detection rate of surgically/pathologically proven endometriosis and provides more information about disease location and sequela compared to routine pelvic US.