The American Association for the Surgery of Trauma Severity Grade is valid and generalizable in adhesive small bowel obstruction

BACKGROUND The American Association for the Surgery of Trauma (AAST) anatomic severity grading system for adhesive small bowel obstruction (ASBO) was validated at a single institution. We aimed to externally validate the AAST ASBO grading system using the Eastern Association for the Surgery of Trauma multi-institutional small bowel obstruction prospective observational study. METHODS Adults (age ≥ 18) with (ASBO) were included. Baseline demographics, physiologic parameters (heart rate, blood pressure, respiratory rate), laboratory tests (lactate, hemoglobin, creatinine, leukocytosis), imaging findings, operative details, length of stay, and Clavien-Dindo complications were collected. The AAST ASBO grades were assigned by two independent reviewers based on imaging findings. Kappa statistic, univariate, and multivariable analyses were performed. RESULTS There were 635 patients with a mean (±SD) age of 61 ± 17.8 years, 51% female, and mean body mass index was 27.5 ± 8.1. The AAST ASBO grades were: grade I (n = 386, 60.5%), grade II (n = 135, 21.2%), grade III (n = 59, 9.2%), grade IV (n = 55, 8.6%). Initial management included: nonoperative (n = 385; 61%), laparotomy (n = 200, 31.3%), laparoscopy (n = 13, 2.0%), and laparoscopy converted to laparotomy (n = 37, 5.8%). An increased median [IQR] AAST ASBO grade was associated with need for conversion to an open procedure (2 [1-3] vs. 3 [2-4], p = 0.008), small bowel resection (2 [2-2] vs. 3 [2-4], p < 0.0001), postoperative temporary abdominal closure (2 [2-3] vs. 3 [3-4], p < 0.0001), and stoma creation (2 [2-3] vs. 3 [2-4], p < 0.0001). Increasing AAST grade was associated with increased anatomic severity noted on imaging findings, longer duration of stay, need for intensive care, increased rate of complication, and higher Clavien-Dindo complication grade. CONCLUSION The AAST ASBO severity grading system has predictive validity for important clinical outcomes and allows for standardization across institutions, providers, and future research focused on optimizing preoperative diagnosis and management algorithms. LEVEL OF EVIDENCE Prognostic, level III.