Postoperative Pneumoperitoneum: Clearing the Air

Introduction: Pneumoperitoneum seen on postoperative imaging presents a diagnostic dilemma. It can be a normal finding secondary to air that was introduced at surgery, which typically resolves in a matter of days. On the other hand, it could also represent a sign of a perforated viscus or an anastomotic leak, which might require reoperation. Distinguishing one from the other is critical to successful management. This study examines clinical and radiological findings in order to determine objective criteria to facilitate the distinction between benign and pathological postoperative pneumoperitoneum. Methods: A retrospective analysis of medical records from a large urban teaching hospital was performed. Imaging studies reporting “pneumoperitoneum”, “free air”, and “free intraperitoneal air”, from 2008-2011 were selected for review. The cases were divided into two groups: patients who ultimately were returned to the operating room and had findings requiring operative intervention and those who were managed expectantly. Demographic, physical findings and laboratory studies were recorded. Results: 52 patients were found to have postoperative pneumoperitoneum after abdominal surgery. Nine (17.3%) underwent re-exploration because of presumed intra-abdominal complication and the remainder of patients was managed by observation alone. At re-operation, all 9 patients were found to have pathologic conditions requiring intervention. Thirty-seven patients had an open surgery initially and 15 had a minimally invasive abdominal procedure. The patients in each group were similar with regard to age, gender, vital signs, pain score, physical findings, or open vs. laparoscopic procedure. However, patients requiring re-operation were found to have pneumoperitoneum 7.7 days after initial surgery compared to postoperative 4.3 days for those that could be managed expectantly (P = 0.003). Also, patients requiring re-operation had an average WBC of 17.4 compared to 9.7 for those managed conservatively. This suggests that postoperative pneumoperitoneum after postoperative day 5 with a WBC greater than 10.5 was 80 % sensitive for patients requiring re-operation. Conclusions: This study suggests that patients with postoperative free air still present a diagnostic and therapeutic challenge. However, free air several days following surgery with an elevated WBC may provide an indication that this finding should be of greater concern. Such patients have a greater likelihood of requiring reoperation for the treatment of a postoperative complication.