Value of thin-section oblique axial T2-weighted magnetic resonance images to assess uterosacral ligament endometriosis

BACKGROUND: Thin-section oblique axial magnetic resonance imaging (MRI) is useful in staging endometrial and cervical carcinomas but there are no data on its contribution to assessing deep endometriosis. We evaluated the contribution of this MRI technique to diagnosis of uterosacral ligament (USL) endometriosis. METHODS: In this retrospective study, two radiologists, who were blinded to the surgical and histological results, compared the results from conventional sagittal and axial MRI with those from conventional plus thin-section (3 mm) oblique axial MRI in 100 symptomatic patients. Descriptive statistical analyses including sensitivity, specificity, positive and negative predictive values, accuracy and positive and negative likelihood ratios were performed. Kappa for inter-observer agreement was calculated. RESULTS: Conventional MR images for the diagnosis of left/right USL endometriosis revealed accuracies of 69/76 and 59/75%, sensitivities of 66/71 and 52/71% and specificities of 76/86 and 76/82% for senior and junior readers, respectively. The combination of conventional and thin-section oblique axial MR images revealed accuracies of 82/87 and 74/81%, sensitivities of 89/93 and 73/81% and specificities of 61/72 and 76/79%, for senior and junior readers, respectively. When conventional MRI combined with oblique axial T2-weighted MRI was compared with conventional MRI use only, significant differences in diagnostic accuracies were observed for right (P = 0.04) and left (P = 0.01) USL endometriosis. CONCLUSIONS: Thin-section oblique axial T2-weighted imaging can improve the success of conventional MRI for assessment of USL endometriosis. Further prospective studies are required before this new MR protocol is performed routinely for suspected pelvic endometriosis.