LATA-IBD TRIAL a Controlled Feasibility Study for the Introduction of Transanal Minimally Invasive IPAA-Surgery. Evaluation of Operative Results and Bowel Function After Introducing Transanal IPAA-surgery to Replace Conventional Laparoscopic IPAA-surgery.

Study Design This is a prospective feasibility study comparing consecutive patients undergoing ta-IPAA with a historical cohort of patients treated with lap-IPAA at the same institution.

Endpoints The primary endpoints were conversion rate and anastomotic leakage rate. Conversion was defined as the need for laparotomy before pouch construction and/or specimen extraction, or the requirement to extend or alter the initial incision during pouch construction. Anastomotic leakage was defined and graded according to the International Study Group of Rectal Cancer (18).

Secondary endpoints included mortality, intraoperative bleeding, operative time, postoperative complications (graded according to the Clavien Dindo classification (19)), reoperations, readmissions, length of hospital stay and pouch function. Pouch function was assessed using the Öresland score (OS) (20) two years after surgery. The OS consists of 11 parameters measuring bowel function after IPAA and ranges from 0-15 (higher scores indicate worse function). Scores ≥8 are associated with impaired pouch function and reduced quality of life. Pouch failure was defined as the need for a diverting stoma or excision of the pouch.

Data collection Study data were collected prospectively using a paper case report form (CRFs) completed at predefined time points: preoperatively, intraoperatively, at hospital discharge and 3, 6, 12 and 24 months after ta-IPAA. For the historical control group, data were retrieved retrospectively from medical records. Intraoperative data were excluded from the lap-IPAA group, as these could not be reliably retrieved.

Training The surgical team consisted of three colorectal surgeons and experienced operating room nurses, all with prior expertise in laparoscopic Total Mesorectal Excision (TME) and IPAA-surgery. The team underwent formal training in taTME-surgery, including participation in dedicated courses, observational visits and on-site proctoring by an international center with significant experience in ta-IPAA.

Surgical Procedure The procedure began with takedown of the loop ileostomy. If mesenteric length was sufficient, the pouch was constructed immediately; otherwise, pouch construction was delayed until the abdominal phase, using either a midline or suprapubic incision. The abdomen was insufflated, and the mesentary was freed from adhesions and the duodenum. Mesenteric lengthening techniques were applied as required before constructing the ileal pouch.

Rectal dissection was performed in a modified TME plane, remaining closer to the rectum, particularly anteriorly, for the first two-thirds of the dissection. The transanal approach was used for the final third, employing standard equipment including the GelPOINT Path Transanal Access Platform®, Lone Star retractor®, and AirSeal® System. Dissection was performed with monopolar cautery, and the purse-string suture was placed with 3-0 V-Loc®. The rectum was extracted transanally or, if necessary, via an abdominal incision. The ileoanal anastomosis was constructed with a circular stapler, and a diverting stoma was created at the previous ileostomy site. (21)

Inclusion criteria

• 18 years and over.
• UC or FAP.
• Fit for laparoscopic IPAA-surgery
• Signed informed consent.

Exclusion criteria

• Not meeeting inclusion criteria above.