BACKGROUND While the incidence of incisional hernia (IH) following elective laparotomy has been well described, incidence following emergent laparotomy for combat trauma has been much less studied. This retrospective cohort investigates the latter to better describe the burden IH represents for the injured warfighter. METHODS Data were obtained from the Expeditionary Medical Encounter Database for service members who survived a combat-related injury between January 2002 and December 2016 and underwent abdominal surgery in the first 30 days after injury. Incisional hernia diagnosis at least 30 days after injury was determined from inpatient and outpatient records in the Military Health System's Medical Data Repository. Means and SDs were reported for age and continuous Injury Severity Score, and frequency and percentages were reported for sex, branch of service, paygrade, mechanism of injury, Injury Severity Score, and maximum abdominal Abbreviated Injury Scale. Service members with and without a hernia diagnosis were compared using t test for continuous variables and χ2 or Fisher exact test (depending on cell size) for categorical variables. Multivariate logistic regression models were used to examine relationships between IH diagnosis and the covariates previously mentioned. Data analysis was completed using SAS software version 9.4 (SAS Institute Inc., Cary, NC). RESULTS Of the 570 laparotomy patients, 109 (19.1%) developed IH. Of these, 58 (53%) were diagnosed within the first year after injury. An additional 21 (19%) were diagnosed within the following year, and 30 (28%) were diagnosed more than 2 years after injury. Presence of gastrointestinal injury, Abbreviated Injury Scale score of 4 and 5, and 5-year increments of age were positively associated with hernia formation. CONCLUSION The incidence of postlaparotomy IH in combat trauma is 19.1%, a considerable source of disability for injured warfighters. Further investigation into hernia-preventive closure strategies is warranted. LEVEL OF EVIDENCE Therapeutic study, level IV.

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