Design: Prospective, multicenter, randomized, controlled, double-blind study. 9 reference endometriosis centers in France.

Setting: Patients under anesthesia, treated by HIFU or in Sham intervention group.

Patients or Participants: 60 patients randomized in two arms, presenting with rectal endometriosis visible on preoperative imaging, and suffering from acute pelvic pain with a score higher than 3 despite potential hormonal treatment.

Interventions: endorectal HIFU probe operating treatment or in sham setting, in the operating room, under anesthesia.

Measurements and Main Results: The efficacy of HIFU treatment will be assessed by comparing changes in the level of acute pelvic pain assessed by visual analog scale (VAS), at 3 months, compared with the pre-treatment pain level in the HIFU group versus the sham intervention group. Quality of life and other symptoms related to endometriosis will be assessed as secondary criteria, using questionnaires at 1 and 3 months: gynecological and digestive symptoms (VAS), health status (MOSSF-36), fecal incontinence (WEXNER), constipation (KESS) and overall sexual health (FSFI). Change of lesion volume based on MRI will also be analysed. Today, the sixty patients have been included and the 3 months follow-up is completed for all the patients. Unblinding is planned in June 2024 and the results will be available for the coming AAGL congress (it will be the first presentation in a congress). The results of the safety study had already been presented in last AAGL congress in Nashville during a surgical tutorial session.

Conclusion: We feature here a unique design of clinical trial, with a French multicenter randomized double-blind clinical study to assess the efficacy of HIFU treatment compared with a sham intervention group.