Magnetic resonance enema versus rectal water contrast transvaginal ultrasonography in the diagnosis of rectosigmoid endometriosis

OBJECTIVES: To compare the accuracy of magnetic resonance enema (MR-e) and rectal water transvaginal ultrasonography (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 endometriosis. The findings of MR-e and RWC-TVS were compared with surgical and histological results. RESULTS: Out of 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). The sensitivity, specificity, positive predictive value, negative predictive value, likelihood ratio positive and likelihood ratio negative of MR-e and RWC-TVS (%, 95% C.I.) in the diagnosis of recto-sigmoid endometriosis were 95.36% (90.68%-99.11%), 97.78% (93.63%-99.51%), 97.96% (94.14%-99.55%), 94.96% (89.89%-97.94%), 42.91 (14.01-131.46), 0.05 (0.02-0.10) and 92.72% (87.34%-96.30%), 97.04% (92.58%-99.17%), 97.22% (93.03%-99.22%), 92.25% (86.56%-96.06%), 31.29 (11.90-82.25), 0.08 (0.04-0.13), respectively. Both MR-e and RWC-TVS underestimated the size of the endometriotic nodules; in both imaging techniques the underestimation was greater for nodules with diameter ≥30 mm. There was no significant difference in the mean intensity of pain experienced by the patients during the two exams. 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 exam. Considering that MR-e is more expensive that RWC-TVS, it should be used only when the findings of RWC-TVS are unclear.