Characterizing the Underlying Diagnoses for Exploratory Laparotomies to Improve Risk-adjustment Models of Postoperative Mortality

BACKGROUND: Surgeons perform emergent exploratory laparotomies (ex-laps) for a myriad of surgical diagnoses. We characterized common diagnoses for which emergent ex-laps were performed and leveraged these groups to improve risk-adjustment models for postoperative mortality. METHODS: Using American Association for the Surgery of Trauma criteria, we identified hospitalizations where the primary procedure was an emergent ex-lap in the 2012 to 2014 (derivation cohort) and 2015 (validation cohort) Nationwide Inpatient Sample. After tabulating all International Classification of Diseases-9th Rev.-Clinical Modification diagnosis codes within these hospitalizations, we divided them into clinically relevant groups. Using two stepwise regression paradigms-forward selection and backward elimination-we identified diagnostic groups significantly associated with postoperative mortality in multivariable logistic regressions. We evaluated the addition of these groups as individual covariates in risk-adjustment models for postoperative mortality using the area under the receiver operator characteristic curve. All regressions additionally adjusted for clinical factors and hospital clustering. RESULTS: We identified 4127 patients in the derivation cohort (median age, 50 years; 46.0% female; 62.1% white), with an overall mortality rate of 13.4%. Among all patients, we tabulated a total of 164 diagnosis codes, of which 27 (16.5%) may have led to an emergent ex-lap. These 27 codes clinically represented seven diagnostic categories, which captured a majority of the patients (70.4%). Backward elimination and forward selection led to four common diagnosis categories associated with mortality: bleeding, obstruction, shock, and ischemia. Adjusting for these four diagnostic groups in a multivariable logistic regression assessing postoperative mortality increased the area under the receiver operator characteristic curve from 74.5% to 88.2% in the derivation cohort and from 73.8% to 88.2% in the validation cohort. CONCLUSION: Seven diagnostic groups account for the majority of the emergent ex-laps. Adjusting for four groups may improve the accuracy of risk-adjustment models for mortality and validating such analytic standardization may optimize best research practices for EGS procedures. LEVEL OF EVIDENCE: Prognostic and epidemiologic, Level III.