Magnetic resonance enema vs rectal water‐contrast transvaginal sonography in diagnosis of rectosigmoid endometriosis

Objective To compare the accuracy of magnetic resonance enema (MR‐e) and rectal water‐contrast transvaginal sonography (RWC‐TVS) in the diagnosis of rectosigmoid endometriosis. Methods This prospective study included 286 patients of reproductive age with clinical suspicion of rectosigmoid endometriosis. Patients underwent MR‐e and RWC‐TVS before laparoscopic excision of endometriotic lesions. The findings of MR‐e and RWC‐TVS were compared with surgical and histological results. Results Of the 286 patients included in the study, 151 (52.8%) had rectosigmoid endometriosis. MR‐e and RWC‐TVS had similar accuracy in the diagnosis of rectosigmoid endometriosis (P = 0.063). In the diagnosis of rectosigmoid endometriosis with MR‐e, the sensitivity was 95.4% (95% CI, 90.7–99.1%), specificity was 97.8% (95% CI, 93.6–99.5%), positive predictive value (PPV) was 98.0% (95% CI, 94.1–99.6%), negative predictive value (NPV) was 95.0% (95% CI, 89.9–97.9%), positive likelihood ratio (LR+) was 42.91 (95% CI, 14.01–131.46) and negative likelihood ratio (LR−) was 0.05 (95% CI, 0.02–0.10). For diagnosis with RWC‐TVS, sensitivity was 92.7% (95% CI, 87.3–96.3%), specificity was 97.0% (95% CI, 92.6–99.2%), PPV was 97.2% (95% CI, 93.0–99.2%), NPV was 92.3% (95% CI, 86.6–96.1%), LR+ was 31.29 (95% CI, 11.90–82.25) and LR− was 0.08 (95% CI, 0.04–0.13). MR‐e and RWC‐TVS underestimated the size of the endometriotic nodules; for both imaging techniques the underestimation was greater for nodules with a diameter ≥ 30 mm. There was no significant difference in the mean intensity of pain experienced by the patients during the two examinations. Conclusions RWC‐TVS should be the first‐line investigation in patients with clinical suspicion of rectosigmoid endometriosis and physicians should be trained in performing this examination. Considering that MR‐e is more expensive than RWC‐TVS, it should be used only when the findings of RWC‐TVS are unclear. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.