Staging of pelvic endometriosis using magnetic resonance imaging compared with the laparoscopic classification of the American Fertility Society: a prospective study.

PURPOSE: To introduce a staging of pelvic endometriosis based on Magnetic Resonance Imaging (MRI) features, compared with the American Fertility Society (AFS) laparoscopic classification. MATERIALS AND METHODS: Thirty-five consecutive females with clinically suspected endometriosis underwent MRI examination using TSE T1, T2W, and SE FAT-SAT T1W sequences, to demonstrate the presence of endometriomas and pelvic implants. Laparoscopy was performed within two weeks (mean 8 days) of the examination. A radiologist experienced in pelvic pathology evaluated the presence of endometriomas and implants and calculated a score to classify endometriosis in four classes, comparable with those of AFS laparoscopic staging. The MRI score was based on size, edges, wall thickness, septations, signal intensity on T2-weighted images of endometriomas and presence of pelvic implants. The concordance between MRI and laparoscopic classification was evaluated using k-statistics. RESULTS: Laparoscopy confirmed 47/48 endometriomas, ranging in size from 10 to 62 mm, detected by MRI, with only one false positive due to an hemorrhagic corpus luteum. Nevertheless, 2 intra-ovarian endometriomas were detected by laparoscopy only thanks MRI guidance. Implants were discovered in 17/30 patients with MRI, laparoscopically in 18/30. MRI detected 46 endometrial implants out of 57 detected by laparoscopy (80.7%): 17/46 implants were directly confirmed by laparoscopy, 29/46 were indirectly confirmed by the presence of adhesions. As regards staging, there was agreement between the MRI and AFS classification in 33/35 patients with only two case of discordance (K= 0,892). CONCLUSIONS: Although MRI has limitations such as suboptimal depiction of small implants and adhesions, this technique is very useful for guiding laparoscopy. Moreover, the high level of agreement (96.6%) between the MRI staging proposed in this paper and laparoscopic classification demonstrates a further advantage of the use of MRI in the preoperative staging of endometriosis.