Mesenteric excision and Kono-S anastomosis trial (MEErKAT): A study protocol for a multicentre, 2 × 2 factorial, randomised controlled, open-label superiority trial.

Aim: Controversy exists over whether surgical technique can reduce recurrence following Crohn's resection. This study compares the rate of endoscopic recurrence after different approaches to mesenteric excision (extended/close) and anastomosis (Kono-S/standard of care) in adult patients undergoing ileocolic resection for primary or recurrent Crohn's disease.

Method: MEErKAT is a UK multicentre, 2 × 2 factorial, randomised, controlled, open-label superiority trial where participants (target sample size = 308) are blinded and centrally randomised (1:1:1:1) to one of four groups: (1) Kono-S + extended mesenteric resection. (2) Kono-S + close mesenteric resection. (3) Standard anastomosis + extended mesenteric resection. (4) Standard anastomosis + close mesenteric resection. The primary outcome is time to endoscopic recurrence of disease (up to 3 years follow-up). Secondary outcomes include rates of severe and symptomatic recurrence, complications, and quality of life scores. The locality of recurrence will be investigated using endoscopic assessment of the mucosa relative to mucosal tattoos placed at the time of operation. The degree and anastomotic locality of different immune cells will be compared before and after each intervention to better understand the mechanistic processes driving disease recurrence.

Conclusion: This study will robustly evaluate the efficacy of the Kono-S anastomosis technique and extended mesenteric excision in reducing endoscopic recurrence rates. The additive effect of these techniques and local tissue immune response will be investigated. This will provide important evidence to guide the optimal surgical technique and improve our understanding of the processes leading to recurrent disease.