MRI classification of uterosacral ligament involvement in endometriosis: the Hôtel-Dieu (HTD) classification.

OBJECTIVE: This study aimed to establish the first-ever MRI classification of uterosacral ligament (USL) involvement in deep endometriosis (DIE), based on reliable preoperative MRI features correlated with positive predictive values (PPVs) determined through histopathological analysis.

METHODS: 22 women underwent surgery with histopathology due to symptoms highly suggestive of endometriosis. The 22 preoperative MRIs were analyzed retrospectively, blinded to histopathology, and a classification of preoperative aspect of USLs linked to PPVs was designed.

RESULTS: According to their aspect, six radiological types of USL were identified. The "L-category" corresponded to linear types, with regular or irregular margins, including types 1, 2, 3A and 3B. The "N-category" corresponded to hemorrhagic or nodular types, including types 4, 5A, 5B and 6. For the L-category, PPVs ranged from 75% to 88%, depending on the USL radiological type. For the N-category, PPVs were 100% for each type. In women with endometriosis symptoms, MRI underestimated USL involvement, especially for type 1. Among the six uterus with lateral deviation, only one false positive result concerning the stretched USL was induced.

CONCLUSIONS: In women with endometriosis symptoms, our MRI classification identified two USL categories, corresponding to two kinds of PPV; in these symptomatic patients, a normal MRI does not rule out a DIE diagnosis.

ADVANCES IN KNOWLEDGE: Our MRI classification of USL involvement in endometriosis may be used as a noninvasive staging of the disease, much clearer for clinicians and patients. Hence, we are able to propose a suitable diagnostic and therapeutic procedure for each radiological type.