Factors associated with enteral nutrition tolerance after trauma laparotomy of the small bowel and mesenteric injuries by blunt trauma

**Background:** Blunt bowel and/or mesenteric injury (BBMI) accounts for approximately 5% of all abdominal injuries and is the third most common cause. In South Korea, blunt trauma accounts for over 70% of traumatic injuries. Early enteral nutrition (EEN) is recommended after abdominal surgery as part of enhanced recovery after surgery (ERAS) protocols, but its application in trauma patients—particularly those with BBMI—has not been well established. This study aimed to identify factors affecting early postoperative small bowel obstruction (EPSBO) and the timing of tolerance to solid food and defecation (SF+D) after surgery in BBMI patients.

**Methods:** The authors retrospectively reviewed patients who underwent laparotomy for BBMI at Chonnam National University Hospital Regional Trauma Center, Gwangju, Korea, between January 2013 and July 2021. Of 316 patients initially identified, 257 were included after excluding those who died within 72 hours post-surgery, were transferred, had hopeless discharge, or had severe traumatic brain injury (GCS 3-8). Patients with AIS scores for other abdominal organs higher than those for small bowel or mesentery were also excluded. Abdominal injury was classified using the Organ Injury Scale (OIS) 2020 and Abbreviated Injury Scale (AIS) 2015. EPSBO was defined as: within 30 days post-surgery, (1) failure of flatus passage and bowel function return with nausea, vomiting, or abdominal distention preventing regular diet; or (2) small bowel loops and fluid levels on plain abdominal radiograph or CT. Patients developing these symptoms within 72 hours were excluded to avoid including paralytic ileus. Statistical analysis used Pearson chi-squared test, Fisher's exact test, Wilcoxon rank-sum test, Pearson's product-moment correlation, and multiple logistic regression.

**Key Results:** Of 257 patients, 190 were in the non-EPSBO group and 67 in the EPSBO group. Male sex was significantly different between groups (72.6% vs. 85.1%; p=0.041). The EPSBO group received more crystalloid within 24 hours (3,000 vs. 2,400 cc; p=0.015) and more blood products (pRBC: p=0.015; FFP: p=0.022; PC: p=0.012). Small bowel OIS (p=0.009) and mesentery OIS (p=0.008) scores differed significantly between groups. Drain removal within 7 days was more common in the non-EPSBO group (42.1% vs. 23.9%; p=0.008). On multivariate logistic regression, mesentery OIS (AOR: 2.10; 95% CI: 1.07-4.12; p=0.031) and small bowel OIS (AOR: 0.52; 95% CI: 0.28-0.95; p=0.035) were identified as factors related to EPSBO. Higher mesentery OIS was associated with higher EPSBO incidence, while small bowel OIS was not. Correlation analysis showed that crystalloid volume, pRBC, FFP, PC transfusion, drain removal time, ISS, and extremity AIS correlated with the postoperative day of tolerance to SF+D.

**Clinical Implications:** This study demonstrates that mesenteric injury severity has a greater impact on EPSBO than small bowel injury severity in BBMI patients. The findings suggest that clinicians should consider mesentery OIS scores when planning early enteral nutrition, as patients with higher mesenteric injury grades may experience delayed bowel function recovery. The amount of crystalloid and blood products transfused within 24 hours, drain removal timing, ISS, and extremity AIS also correlate with when patients can tolerate solid food and defecation. These factors may help guide postoperative feeding decisions. However, as a single-center retrospective study, limitations include potential confounding from opioid use, ambulation status, and intra-abdominal infection. Large-scale multicenter studies are needed to confirm these findings and determine whether mesentery OIS should be formally incorporated into EEN decision-making for BBMI patients.