O052 Erect chest X-ray is inadequately diagnostic and falsely reassuring in assessment of abdominal visceral perforation: a retrospective cohort study

Abstract

Abstract Introduction Pneumoperitoneum refers to air in the abdominal cavity due to abdominal visceral perforation and can be visualised as air under the diaphragm on erect chest x-ray. This study aims to evaluate the accuracy of erect CXR in detecting the presence of abdominal visceral perforation. Methods A retrospective cohort study in a single centre was conducted between January 2014 and January 2020. The study population comprised of all patients with gastrointestinal perforation confirmed by assessment during emergency laparotomy. The outcome measure of this study was perforation detection rate, defined as detection of air under diaphragm in preoperative erect CXR confirmed by two independent qualified radiologists. Results A total of 219 patients were eligible for inclusion in this study. Among 219 patients with intraoperative evidence of abdominal visceral perforation, preoperative erect CXR showed air under diaphragm in 43 patients. The perforation detection rate was 20% (95% CI 15-26%). Subgroup analysis based on the level of perforation showed that the perforation detection rate was 32% (95% CI 21-43%) in patients with upper gastrointestinal perforation and 13% (95% CI 8-20%) in patients with lower gastrointestinal perforation. Conclusion Erect CXR can only detect the presence of abdominal visceral perforation in 20% of patients and does not provide any information about the level or cause of perforation. The time is to move away from the use of erect CXR in assessment of patients with acute abdominal pain. It is inadequately diagnostic and falsely reassuring. All patients with suspected perforation should have immediate CT scan.