A short anogenital distance on MRI is a marker of endometriosis

International audience; STUDY QUESTIONCould the anogenital distance (AGD) as assessed by MRI (MRI-AGD) be a diagnostic tool for endometriosis?SUMMARY ANSWERA short MRI-AGD is a strong diagnostic marker of endometriosis.WHAT IS KNOWN ALREADYA short clinically assessed AGD (C-AGD) is associated with the presence of endometriosis.STUDY DESIGN, SIZE, DURATIONThis study is a re-analysis of previously published data from a case–control study.PARTICIPANTS/MATERIALS, SETTING, METHODSWomen undergoing pelvic surgery from January 2018 to June 2019 and who had a preoperative pelvic MRI were included.

C-AGD was measured at the beginning of the surgery by a different operator who was unaware of the endometriosis status.

MRI-AGD was measured retrospectively by a senior radiologist who was blinded to the final diagnosis.

Two measurements were made: from the posterior wall of the clitoris to the anterior edge of the anal canal (MRI-AGD-AC), and from the posterior wall of the vagina to the anterior edge of the anal canal (MRI-AGD-AF).

MAIN RESULTS AND THE ROLE OF CHANCEThe study compared MRI-AGD of 67 women with endometriosis to 31 without endometriosis (controls).

Average MRI-AGD-AF measurements were 13.3 mm (±3.9) and 21.2 mm (±5.4) in the endometriosis and non-endometriosis groups, respectively (P < 10−5).

Average MRI-AGD-AC measurements were 40.4 mm (±7.3) and 51.1 mm (±8.6) for the endometriosis and non-endometriosis groups, respectively (P < 10−5).

There was no difference of MRI-AGD in women with and without endometrioma (P = 0.21), or digestive involvement (P = 0.26).

Moreover, MRI-AGD values were independent of the revised score of the American Society of Reproductive Medicine and the Enzian score.

The diagnosis of endometriosis was negatively associated with both the MRI-AGD-AF (β = −7.79, 95% CI (−9.88; −5.71), P < 0.001) and MRI-AGD-AC (β = −9.51 mm, 95% CI (−12.7; 6.24), P < 0.001) in multivariable analysis.

Age (β = +0.31 mm, 95% CI (0.09; 0.53), P = 0.006) and BMI (β = +0.44 mm, 95% CI (0.17; 0.72), P = 0.001) were positively associated with the MRI-AGD-AC measurements in multivariable analysis.

MRI-AGD-AF had an AUC of 0.869 (95% CI (0.79; 0.95)) and outperformed C-AGD.

Using an optimal cut-off of 20 mm for MRI-AGD-AF, a sensitivity of 97.01% and a specificity of 70.97% were noted.LIMITATIONS, REASONS FOR CAUTIONThis was a retrospective analysis and no adolescents had been included.WIDER IMPLICATIONS OF THE FINDINGSThis study is consistent with previous works associating a short C-AGD with endometriosis and the absence of correlation with the disease phenotype.

MRI-AGD is more accurate than C-AGD in this setting and could be evaluated in the MRI examination of patients with suspected endometriosis.STUDY FUNDING/COMPETING INTEREST(S)N/A.TRIAL REGISTRATION NUMBERThe protocol was approved by the ‘Groupe Nantais d’Ethique dans le Domaine de la Santé’ and registered under reference 02651077.