The American Association for the Surgery of Trauma (AAST) established anatomic grading in 2015 to facilitate risk stratification and risk adjusted outcomes in emergency general surgery. This study validates the AAST anatomic grading system for acute cholecystitis (AC) at a tertiary, academic referral medical center.

This is a retrospective cohort study of 315 patients admitted for AC between 2013 and 2016. Cholecystitis severity was graded based on clinical, imaging, operative, and pathologic criteria in accordance with the published AAST anatomic grading scale. Grade I is acute cholecystitis, grade II is gangrenous or emphysematous cholecystitis, grade III is localized perforation, grade IV and V have regional and systemic peritonitis respectively. There was very good interrater (2 independent raters) reliability for anatomic grading, kappa=1.00, p<0.005.

Concordance between the AAST grade and outcomes including mortality, length of stay (LOS), ICU use, and adverse events was assessed using statistical methods. Incidence of complications, LOS, ICU use, and any adverse event increased with increasing anatomic grade. When compared to grade I disease, patients with grade II were more likely to undergo cholecystectomy (Odds Ratio 4.07 [1.93-8.56]), require ICU use (Odds Ratio 2.41 [1.31 -- 4.44]) and develop a complication (Odds Ratio 2.07 [1.22 -- 3.53]). Grade III patients were at higher risk of adverse events (Odds Ratio 3.83 [1.34-10.94]) and ICU use (Odds Ratio 8.07 [2.43-26.80]).

In conclusion, AAST severity grading scores were independently associated with clinical outcomes in patients with AC. Despite most patients having low grade disease, complications were common. Therefore, a refinement of the scoring system for cholecystitis may be necessary for more granular prediction of outcomes at milder levels of disease.