Postoperative pneumoperitoneum: Guilty or not guilty?

Purpose: The aim of this study was to determine the incidence and duration of postoperative pneumoperitoneum on plain radiographs and to identify the radiologic findings associated with anastomotic leakage. Methods: A retrospective analysis was conducted on plain radiographs of 384 patients who underwent intra-abdominal anastomoses between March 2005 and December 2008. Results: Of the 384 patients, 93 patients (24.2%) had postoperative pneumoperitoneums. Of the 93 patients, 86 patients (92.5%) had physiologic pneumoperitoneums and 7 patients (7.5%) had pneumoperitoneums associated with anastomotic leakage. The initial air height was significantly greater in the leakage group than the physiologic air group (12.16 ±7.65 mm vs. 7.71 ±5.08 mm, P = 0.04). The area under the receiver operating characteristic curve of the initial height of free air for anastomotic leakage was 0.69 (95% confidence interval, 0.59 to 0.78). The best cut-off point was 11.7 mm. The height of the pneumoperitoneum increased with time in the leakage group. Ileus was significantly more prevalent in the leakage group than the physiologic air group (P <0.01). Conclusion: Postoperative pneumoperitoneum is a common phenomenon after abdominal surgery. An initial air height >11.7 mm, increasing air height over time, and the presence of ileus on plain radiographs suggest a high likelihood of anastomotic leakage.