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.