Deep infiltrating endometriosis (DIE) involving the bowel, particularly the rectosigmoid region, is associated with significant gastrointestinal symptoms and impaired quality of life. Rectal shaving is a conservative surgical technique aimed at removing endometriotic lesions while preserving bowel integrity; however, it may result in residual disease or excessive thinning of the bowel wall, potentially leading to recurrence or complications.

Intraoperative ultrasound (IOUS) allows real-time assessment of residual nodule thickness and bowel wall thickness after shaving. This prospective observational study aims to evaluate the relationship between intraoperative ultrasound measurements and postoperative clinical outcomes, including gastrointestinal symptoms and quality of life.

The study also seeks to identify ultrasound cut-off values that may guide intraoperative surgical decision-making and optimize the balance between radicality and safety.

Endometriosis affects approximately 7-10% of women of reproductive age and is frequently associated with delayed diagnosis. Deep infiltrating endometriosis involving the posterior compartment often causes gastrointestinal symptoms such as dyschezia, constipation, diarrhea, and rectal bleeding.

Surgical management of bowel DIE includes conservative approaches (rectal shaving) and radical procedures (disc excision or segmental resection). Current guidelines emphasize individualized treatment decisions.

Rectal shaving avoids bowel resection and is associated with lower morbidity but carries risks of residual disease and bowel wall thinning. Intraoperative ultrasound enables precise measurement of residual lesions and bowel wall thickness, potentially improving surgical outcomes.

This study evaluates whether:

• Greater residual nodule thickness is associated with persistent or recurrent symptoms;
• Reduced bowel wall thickness is associated with increased postoperative complications.

Inclusion Criteria:

• Female patients aged 20-60 years
• Rectal or sigmoid nodule with muscularis propria infiltration ≥1 mm and <20 mm (assessed by expert transvaginal ultrasound)
• Indication for surgery agreed upon with the patient
• Written informed consent

Exclusion Criteria:

• Previous major bowel surgery or primary indication for bowel resection
• Inflammatory bowel disease, malignancy, or severe pelvic pathology
• Inability to complete study questionnaires

The study population consists of women of reproductive age diagnosed with deep infiltrating endometriosis involving the rectum or sigmoid colon, with muscularis propria infiltration between 1 and 20 mm as assessed by expert preoperative transvaginal ultrasound. Eligible patients are those scheduled to undergo laparoscopic rectal shaving as part of standard clinical care at a tertiary referral center for endometriosis. All participants provide written informed consent prior to enrollment.