Characteristics, outcomes, and prognostic factors in patients with penetrating and blunt traumatic diaphragmatic injury: a nationwide retrospective cohort study in Japan.

Background: Traumatic diaphragmatic injury (TDI) is well-known worldwide as rare and life-threatening. However, because no nationwide cohort study of penetrating and blunt TDI has been conducted in Japan and other countries where penetrating trauma is relatively uncommon, the clinical characteristics of all TDI are unknown. We aimed to describe the characteristics of TDI patients, compare penetrating TDI with blunt TDI, and identify mortality risk factors in Japan.

Methods: We retrospectively identified TDI patients between 2004 and 2019 using data from the Japan Trauma Data Bank. We extracted data on patient demographics, type of trauma, cause of trauma, physiological parameters, region of concomitant injury, associated injury, and management. We compared penetrating and blunt TDI for each variable. The primary outcome was mortality. Multivariable logistic regression was performed to identify mortality risk factors.

Results: Of the 338,744 patients, 1,147 (0.3%) had TDI, of which 771 were eligible for analysis (excluding 308 in cardiac arrest on arrival). Penetrating TDI represented 29.8% and blunt TDI 70.2%, and comparing penetrating and blunt TDI, the most common cause was self-inflicted (48.7%) vs. accident (85.6%), males were 68.7% vs. 66.0% of the patients (P = 0.50), and the mortality rate was 8.3% vs. 26.4% (P < 0.001). Multivariable analysis found that age (odds ratio [OR] 1.03, 95% confidence interval [CI] 1.01-1.04), Injury Severity Score (OR 1.03, 95%CI 1.006-1.06), Revised Trauma Score (OR 0.55, 95%CI 0.45-0.67), severe concomitant abdominal injury (OR 2.45, 95%CI 1.32-4.56), severe concomitant upper extremity injury (OR 3.38, 95%CI 1.24-9.17) were independent predictors of mortality, and computed tomography (CT) (OR 0.32, 95%CI 0.15-0.69) and diaphragm repair (OR 0.44, 95%CI 0.25-0.78) were protective factors.

Conclusions: In Japan, we found that penetrating TDI was mainly caused by self-injury and the male-female ratio was the same as for blunt TDI, although blunt TDI was much more frequent. TDI was considered highly lethal, with over 25% of patients in cardiac arrest on arrival. Our unique independent predictors were CT, severe concomitant abdominal injury, and severe concomitant upper extremity injury. These findings may help in the management of TDI in countries with less common penetrating trauma.