Free abdominal gas on computed tomography in the emergency department: aetiologies and association between amount of free gas and mortality

Abstract

Introduction Free abdominal gas is an important finding with major clinical implications. However, data on the aetiologies and prognosis of patients with free gas are scarce. Our primary aim was to describe the sources of free abdominal gas on emergency department (ED) computed tomography (CT). The secondary aim was to evaluate the association between the amount of free gas and all-cause mortality. Methods All patients who underwent CT in the ED between February 2012 and February 2019 with free abdominal gas were included in the study. A scoring system was used to assess the amount of free gas: small – gas bubbles; medium – any gas pocket ≤2cm in diameter; large – any gas pocket >2cm. Data were collected from laboratory and clinical assessment regarding the source of free gas and all-cause mortality. Results A total of 372 patients had free abdominal gas. Colonic diverticulitis was the most common aetiology among those with a small or medium amount of free gas (81/250 [32.4%] and 12/71 [16.9%] respectively). For patients with a large amount of gas, peptic disease was the most common aetiology (11/51 [21.6%]). Three-quarters of the patients (280/372, 75.2%) had the source of free gas identified during ED admission. Ninety-day mortality rates were 7.2%, 9.9% and 21.6% for patients with small, medium and large amounts of gas respectively (p=0.007). Conclusions Colonic diverticulitis was the most common source of free abdominal gas and peptic disease was the most common cause of a large amount of free gas. Mortality rates correlated with the amount of gas and were significantly higher in patients with a large amount.