AP-NOSES: A Prospective Multicentre Registry of Natural Orifice Specimen Extraction in Minimally Invasive Colorectal Surgery

Natural orifice specimen extraction (NOSE) is an established minimally invasive colorectal surgical technique that enables removal of the surgical specimen through transanal or transvaginal routes while avoiding an abdominal specimen extraction incision. Existing retrospective studies and meta-analyses suggest that NOSE may reduce postoperative pain, wound morbidity, and length of hospital stay without compromising oncologic outcomes. However, prospective multicenter data evaluating long-term abdominal wall outcomes and patient-reported outcomes remain limited.

Incisional hernia is a common long-term complication following colorectal surgery and is closely associated with the abdominal extraction site. By avoiding an abdominal extraction incision, NOSE may reduce extraction-site morbidity and long-term incisional hernia risk. AP-NOSES was designed to prospectively evaluate these outcomes in a multicenter setting using predefined eligibility criteria and a concurrent comparator cohort.

AP-NOSES is a prospective observational multicenter registry coordinated by Singapore General Hospital. Consecutive adult patients undergoing elective minimally invasive colorectal resection with planned intact specimen extraction are eligible for enrollment. Participating centers include tertiary colorectal units within the Asia-Pacific region.

The primary comparative analysis is conducted within a predefined NOSE-eligible cohort. Exposure groups are defined according to planned specimen extraction strategy:

• Planned NOSE extraction (transanal or transvaginal), and
• Planned transabdominal extraction among patients meeting protocol NOSE eligibility criteria.

Planned and achieved extraction routes, reasons for non-performance of NOSE, operative details, postoperative complications, and oncologic outcomes are prospectively recorded.

The primary outcome is time to incisional hernia within 24 months following index colorectal surgery.

Secondary outcomes include postoperative complications, extraction-site morbidity, surgical site infection, readmission, reoperation, pathologic outcomes, patient-reported quality-of-life and functional outcomes, bowel function, urinary and sexual function in selected patients, and oncologic outcomes including recurrence and disease-free survival.

Patient-reported outcomes are assessed using validated instruments including EQ-5D-5L, Body Image Scale (BIS), Low Anterior Resection Syndrome (LARS) score, International Prostate Symptom Score (IPSS), International Index of Erectile Function-5 (IIEF-5), and Female Sexual Function Index-6 (FSFI-6), where applicable.

This study is observational and does not mandate changes to standard surgical or postoperative management. Data are entered into a secure centralized REDCap database using coded study identifiers.

Inclusion criteria

• Age 21 years or older
• Elective minimally invasive colorectal resection (laparoscopic or robotic intent)
• Planned intact specimen extraction
• Eligible for natural orifice specimen extraction (NOSE) or transabdominal specimen extraction according to study protocol
• Ability to provide informed consent

Exclusion criteria

• Emergency colorectal surgery
• Planned transanal total mesorectal excision (TaTME)
• Planned ultralow anterior resection with planned anastomosis 3 cm or less from the anal verge
• Planned abdominoperineal resection (APR)
• Planned permanent end stoma without restoration of intestinal continuity
• Planned multivisceral resection
• Generalized peritonitis or uncontrolled intra-abdominal sepsis
• Pregnancy
• Pre-existing ventral or incisional hernia at the planned extraction site
• Planned specimen extraction through a prior laparotomy incision containing mesh
• Fixed distal obstruction, severe pelvic stenosis, or other anatomical constraint precluding intact specimen extraction