Butterfly Feasibility Trial; comparison of two surgical treatment approaches for early stage endometriosis.

The interventional arm of the trial will be standard excisional treatment of endometriosis plus a posterior peritonectomy to determine whether the addition of posterior peritonectomy improves overall pain and quality of life at one year. If the participant is allocated to posterior peritonectomy, this will be performed with the instruments of the surgeon’s choice, with the margins defined as extending from the level of the infundibular pelvic ligament down to the Pouch of Douglas including the ovarian fossae and the uterosacral ligament peritoneum bilaterally. Peritoneum will be divided into ovarian fossae, uterosacral peritoneum and Pouch of Douglas and sent for histology. The posterior peritonectomy is anticipated to take an additional 10minutes of surgical time. Following completion of the procedure an anti-adhesion fluid (Adept) will be instilled into the pelvis for all patients. If concurrent gynaecological procedures were required such as tubal dye studies, ovarian cystectomy or hysteroscopy these can be performed in both study arms. Surgeons are asked at the end of the operation whether they have complied with the randomised allocation, which is entered into the research database. Histology will be checked to confirm the areas and size of peritoneum removed.