Predicting the Pain Outcome of Surgery for Endometriosis

Endometriosis is a chronic gynaecological condition that affects around 10% of women of reproductive age. This condition can cause debilitating pain, infertility, and poor quality of life. Endometriosis is a condition where tissue resembling the womb lining is present outside of the womb and is associated with an inflammatory pelvic environment. Symptoms of endometriosis can consist of pain during periods, chronic (non-cyclical) pelvic pain, pain during sex, pain when urinating, pain when defecating, and fatigue. Current treatments for endometriosis consist of hormonal, anti-inflammatory and / or analgesic medications and surgery, which is usually laparoscopic ("key-hole"). However, surgery does not always result in a reduction in pain for patients with endometriosis, therefore, it is important to try and understand which patients are most likely to benefit from surgery for their pain management.

Endometriosis is categorized into 4 stages (I - IV), ranging from small areas of tissue that do not extend deeply (stage I) to deep lesions associated with significant scarring of the pelvis and ovarian cysts (endometriomas). Interestingly, symptoms do not correlate with stage of disease. An NIHR funded clinical trial is currently investigating whether surgical treatment of superficial peritoneal endometriosis is of clinical benefit (ESPriT2) and is expected to report early in 2026 (recruitment and baseline data collection are complete). However, women with more severe forms of the disease are excluded from this trial. Surgery is commonly recommended for those with more extensive disease (stages III and IV), however, the risks of surgery are considerably greater for these patients including risk of bladder and bowel damage (sometimes requiring stoma formation) and a negative impact on future fertility. Therefore it is important to better understand who will benefit from this type of surgery. Rather than performing a full clinical trial, the investigators will use a set of experimental tests that allow pain to be understood in more detail meaning less people need to be included in the study and results will be available sooner.

In the present study, patients with pelvic endometriosis at stage III or IV with planned surgical treatment scheduled will be recruited to the project. Participants taking part will provide data at 5 different time points: Time point 1 will consist of several baseline questionnaires, an experimental sensory assessment, and a brain functional magnetic resonance imaging (fMRI) scan. Time point 2 will be the date of their endometriosis surgery, where a questionnaire will be taken, the surgery will be completed, and several biological samples (e.g. blood and small amounts of pelvic fluid and tissue) will be taken. Time points 3 (3 months post-surgery), 4 (6 months post-surgery), and 5 (12 months post-surgery) will consist of completing online questionnaires. All data collected within this project will be used to investigate pain outcome following endometriosis surgery. This research is funded by NIHR BRC.

• Brain connectivity at rest [Time frame: prior to surgery]
• Brain volume [Time frame: prior to surgery]
• Non-cyclical pelvic pain measured on an 11 point numerical rating scale (NRS) [Time frame: prior to surgery and at 12 months post-surgery]
• Pain widespreadness [Time frame: Prior to surgery]
• Neuropathic-like pain [Time frame: prior to surgery]
• Pain catastrophising [Time frame: Prior to surgery]
• Pain self-efficacy [Time frame: Prior to surgery]
• Expectation of surgical efficacy [Time frame: Prior to surgery]