Free air on plain film: Do we need a computed tomography too?

Standard teaching is that patients with pneumoperitoneum on plain X-ray and clinical signs of abdominal pathology should undergo urgent surgery. It is unknown if abdominal computed tomography (CT) provides additional useful information in this scenario.

The aim of this study is to determine whether or not CT scanning after identification of pneumoperitoneum on plain X-ray changes clinical management or outcomes.

Retrospective study carried out over 4 years at a tertiary care academic medical center. All patients in our acute care surgery database with pneumoperitoneum on plain X-ray were included. Patients who underwent subsequent CT scanning (CT group) were compared with patients who did not (non-CT group).

The Wilcoxon rank-sum test, t-test and Fisher's exact test were used as appropriate to compare the groups.

There were 25 patients in the non-CT group and 18 patients in the CT group. There were no differences between the groups at presentation. All patients in the non-CT group underwent surgery, compared with 83% (n = 15) of patients in the CT group (P = 0.066). 16 patients in the non-CT and 11 patients in the CT group presented with peritonitis and all underwent surgery regardless of group. For patients undergoing surgery, there were no differences in outcomes between the groups. After X-ray, patients undergoing CT required 328.0 min to arrive in the operating room compared with 136.0 min in the non-CT group (P = 0.007).

In patients with pneumoperitoneum on X-ray and peritonitis on physical exam, CT delays surgery without providing any measurable benefit.