Short-term outcome of diverting loop ileostomy reversals performed by residents: a retrospective cohort prognostic factor study

**Background:** Diverting loop ileostomy (DLI) reversal is a common procedure often assigned to surgical trainees as an early operative experience. While generally considered low-risk, the procedure carries potential complications including small bowel obstruction, anastomotic leakage, wound infection, and incisional hernia. Prior evidence on whether surgeon experience affects outcomes has been mixed. This study aimed to compare outcomes of DLI reversals performed by surgical trainees versus attending surgeons and identify risk factors for postoperative morbidity.

**Methods:** This retrospective cohort study was conducted at the Department of General and Visceral Surgery, University Hospital Frankfurt, Germany. All DLI reversals performed between January 2009 and December 2019 were included; combined and emergency surgeries were excluded. Data were extracted from electronic health records and a dedicated cancer center database. The primary outcome was overall morbidity graded by the Clavien-Dindo classification (CDC). Secondary outcomes were surgical site infections (SSIs) and intestinal motility dysfunction. Surgeons were categorized as surgical trainees (any year of training) or attending surgeons. Logistic regression was used for multivariable analysis, including variables with p<0.05 from univariable analysis.

**Key Results:** Of 331 ileostomy reversals performed, 300 met inclusion criteria (118 by trainees, 182 by attendings). Mean age was 60 years (SD 14); 61.7% were male; 68.3% had malignant primary disease. Surgical trainees had significantly longer mean operative times (85 vs. 59 minutes, p<0.001). No significant differences were found between groups for CDC grade ≥3 complications (p=0.211), SSIs (7.6% vs. 5.5%, p=0.459), re-laparotomy (3.4% vs. 7.1%, p=0.207), or mortality (0% vs. 1.1%, p=0.521). Overall, 69.3% of patients had minor complications (CDC I-II), and 7.1% had major complications (CDC ≥3). Two patients (0.7%) died from myocardial infarction and ventricular fibrillation, both in the attending group. Multivariable analysis identified first bowel movement >3 days postoperatively as a significant risk factor for CDC ≥3 complications (OR 4.348; 95% CI 1.670–11.321; p=0.003). Independent risk factors for SSIs were elevated BMI (OR 1.162; 95% CI 1.043–1.294; p=0.007) and delayed first bowel movement (OR 3.973; 95% CI 1.300–12.138; p=0.015). For intestinal motility dysfunction, primary malignant disease was a risk factor (OR 1.980; 95% CI 1.120–3.500; p=0.019), while side-to-side stapled anastomosis was protective (OR 0.337; 95% CI 0.155–0.733; p=0.006). Attending surgeons performed stapled anastomosis significantly more often (14.3% vs. 5.1%, p=0.012).

**Clinical Implications:** DLI reversal can be safely performed by surgical trainees under supervision, with no increase in major complications despite longer operative times. The findings support continued resident involvement in this procedure for surgical education. Clinically, delayed bowel movement and elevated BMI are important modifiable risk factors for SSIs that warrant attention in perioperative management. The protective effect of stapled anastomosis on intestinal motility dysfunction suggests that technique selection may influence recovery, though this must be balanced against the educational value of hand-sewn anastomosis training. Limitations include the single-center retrospective design, potential selection bias in case assignment, and lack of granular data on the extent of resident participation.