Long Distance Between the Superior Mesenteric Artery Root and Bottom of the External Anal Sphincter Is a Risk Factor for Stoma Outlet Obstruction After Total Proctocolectomy and Ileal-Pouch Anal Anastomosis for Ulcerative Colitis.

Background: Stoma outlet obstruction (SOO) is much more common after total proctocolectomy (TPC) and ileal-pouch anal anastomosis (IPAA) for ulcerative colitis (UC) compared to after rectal surgery for cancer. Few prior reports have evaluated anatomical risk factors for SOO. In this study we aimed to clarify the risk factors for SOO after IPAA, focusing on the anatomical perspective.

Methods: This study included 68 UC patients who underwent IPAA with diverting ileostomy. These cases were analyzed based on clinicopathological factors and computed tomography (CT)-based anatomical factors.

Results: SOO was identified in 18 patients (26.5%). We compared this SOO group with the non-SOO group. The two groups significantly differed in sex distribution, and patients in the SOO group tended to have a longer postoperative hospital stay. Regarding surgery-related factors, patients who underwent two-stage surgery and experienced high-output syndrome tended to develop SOO. Analysis of anatomical risk factors revealed that SOO was more common in patients with a longer distance between the root of their superior mesenteric artery and the bottom of the external anal sphincter (rSMA-bEAS). This tendency remained significant even with adjustment for patient height. In multivariate analyses, adjusted rSMA-bEAS (>191.0 mm/m) and male sex were independent risk factors associated with SOO.

Conclusion: A long rSMA-bEAS distance suggests that the mesentery is likely to be under tension. In such cases, surgeons should endeavor to avoid tension in the mesentery as much as possible.