Diverting LI for severe UC were first reported in 1913, and various stoma-related complications have been reported to date [10]. In particular, SOO prolongs the hospital stay and can lead to serious complications such as perforation. Therefore, in cases of repeated SOO, early stoma closure or re-creation of the stoma must be considered after evaluating the status of the anastomotic site. SOO rarely occurs within 1 week after surgery and mostly occurs after oral intake becomes sufficient [11]. In this study, all SOOs performed within 30 days of surgery were included. In 2021, diverting EI was introduced for all patients to reduce mesenteric tension, and this study revealed that EI significantly prevented SOO relative to LI.

Enterostomal therapists found LI more difficult to manage than EI, with more severe skin complications in LI [12, 13]. Effective management requires a 1.5-cm ileostomy protrusion, which is challenging with LI in IPAA cases but easily achieved with EI. Nonetheless, earlier investigations have demonstrated that the primary benefit of LI over EI for stoma closure is a reduced length of surgery [1]. Therefore, to facilitate anastomosis during stoma closure, we applied anti-adhesive agents and performed fixation of the intestine in the preceding operation (Fig. 4).

IPAA without a diverting stoma is performed when the status of anastomosis is quite good, but a large-scale study reported that approximately 75% of patients have a diverting ileostomy and 1-stage procedures are not common [2]. The ECCO guidelines suggest that modified 2-stage IPAA may have fewer complications and a shorter length of stay than 3-stage or 2-stage IPAA in expert centers [14]. However, previous studies have shown that the IPAA leakage rate is not low (approximately 10%) using a modified 2-stage approach [15]. In the absence of a diverting stoma, the pouch function and fertility are greatly affected by the occurrence of anastomotic leakage [16]; thus, selection requires careful consideration. Moreover, > 90% of patients in this study underwent diverting ileostomies with IPAA.

Previously reported risk factors for SOO include laparoscopic surgery, loop ileostomy, male sex, low BMI, rectoabdominal wall thickness at the stoma site, HOS, distance from the pouch to the LI (< 30 cm), and a long distance from the rSMA to the bEAS [2, 3, 5, 9, 17, 18]. Our study also revealed that a long distance from the rSMA to the bEAS and HOS was independently associated with a high risk factor of SOO. However, laparoscopic surgery was not a significant risk factor, because only a few patients underwent open surgery. Regarding sex, a significant difference was identified in the univariate analysis, but not in the multivariate analysis. Multiple studies have indicated ways to prevent SOO, such as making vertical fascia incisions instead of cruciate incisions, creating adequate space in the abdominal wall tunnel, and positioning the proximal side of the elevated intestinal tract in the 3 o’clock direction to minimize twisting of the mesentery [4, 5, 11]. In our study, EI was found to be an independent preventive factor for SOO.

IPAA requires pulling the ileal pouch into the pelvis, and previous studies have shown that 1.8% of patients could not undergo IPAA due to technical difficulties such as severe obesity, a large volume of mesentery, or ischemia of the pouch with mesenteric distraction [19, 20]. Although mesenteric panniculitis and sclerosing mesenteritis are both associated with thickened mesentery, there is no established consensus on the impact of steroid use in relation to these conditions. In this study, the lower frequency of preoperative steroid use in the EI group was likely due to the emergence of new treatment options (beyond steroids) over time. In terms of SOO, we considered the effect of steroid use to be minimal. The anastomotic site experienced pulling tension due to extension of the pouch mesentery [21]. Therefore, surgeons have implemented several measures to improve this, such as sufficient mobilization of the small intestine, division of the mesenteric serosa, vascular dissection, and manual guidance of the pouch [6,7,8, 20]. After introducing EI, there were no cases in which IPAA could not be performed. Although LI is easier and preferable without tension of the ileal mesentery, tension frequently exists in IPAA cases, unlike in rectal cancer cases. It seems reasonable to consider EI as an option if there is tension in the ileal mesentery and anastomosis remains difficult despite various countermeasures or if the stoma height cannot be maintained, as this would increase the risk of SOO.

The present study was associated with several limitations. First, all data were obtained from Japanese patients; therefore, the applicability of the results to other nationalities remains unclear. Second, the study was conducted using data obtained from a single center and was a retrospective observational study with a small sample size. A larger, long-term, prospective study is required to validate our findings.

In conclusion, this study demonstrates that EI can reduce SOO after RPC and IPAA. In addition, reduction of mesenteric tension using EI might be a solution for cases in which anastomosis is difficult.