Prognostic value of free air under diaphragm on chest radiographs in correlation with peritoneal soiling intraoperatively

Purpose Gastrointestinal perforation is a significant injury that originates mainly from gastrointestinal ulcers. It is associated with a high rate of morbidity and mortality. The height of the column of the air under the diaphragm can be used to estimate the amount of peritoneal soiling due to viscus perforation. This study aimed to determine the correlation between this estimate and the incidence of morbidity and mortality. Methods To achieve this aim, a prospective cohort study was conducted on 83 patients at Kasr al ainy hospital who, between March 2021 and March 2022, presented to the emergency department with free air under the diaphragm at chest X-ray and required surgical intervention for a perforated viscus. For each case, the amount of peritoneal soiling and the amount of air under the diaphragm as determined by a chest X-ray were recorded. Results The mean air under the diaphragm in a plain erect chest X-ray was 1.78 ± 1.92 cm, and the mean amount of peritoneal soiling was 1201.83 ± 948.99 CC. There are positive correlations between the amount of air under the diaphragm as shown on an X-ray and the size of the perforation ( p = 0.034), the amount of peritoneal soiling ( p = 0.003), and the mortality ( p = 0.013). Conclusion There was a statistically significant correlation between air under the diaphragm according to X-ray and the amount of peritoneal soiling in patients with a perforated viscus. This measure can be used as a sensitive tool to predict morbidity and mortality as more free air in the chest X-ray is associated with significant mortality. These results may enhance the decision making using sensitive and available tool of diagnosis.