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

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

Methods: Twenty-two women underwent surgery with histopathology due to symptoms highly suggestive of endometriosis. The 22 preoperative MRIs were analysed retrospectively, blinded to histopathology, and a classification of the preoperative aspect of USLs linked to PPVs was designed.

Results: According to their aspects, 6 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 haemorrhagic 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 6 uteri with lateral deviation, only one false-positive result concerning the stretched USL was induced.

Conclusions: In women with endometriosis symptoms, our MRI classification identified 2 USL categories, corresponding to 2 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 non-invasive staging of the disease, making it much clearer for clinicians and patients. Hence, we are able to propose a suitable diagnostic and therapeutic procedure for each radiological type.