Postoperative intra-abdominal free gas after open colorectal resection

PURPOSE: An erect chest radiograph for subdiaphragmatic free gas can bt a u seful adjunct in detecting a defect in gastrointestinal continuity. The use fulness of this test after laparotomy has not been defined, because the per iod of persistence of free gas is unknown. We set out to determine the leng th of time for natural absorption of postlaparotomy pneumoperitoneum in a p rospective cohort study. METHOD: Plain erect chest radiographs were perform ed on the second and fourth postoperative day and daily thereafter until th e disappearance of subdiaphragmatic free gas after laparotomy. RESULTS: Sev enty-five consecutive patients were studied after informed consent. The mea n age was 62.1 (standard error of the mean, 1.7) years. On the fifth postop erative day, sixth postoperative day, and seventh postoperative day, 71.6, 80, and 89 percent of patients, respectively, had no visible subdiaphragmat ic gas. Five patients had gas persisting beyond the tenth postoperative day . Two of these patients did not have an anastomosis. The use of drainage tu bes did not affect significantly the mean time to disappearance of subdiaph ragmatic free gas (4.5 vs. 4.9 days; P = 0.45; t-test). The duration of sur gery, body mass index, and time to resume bowel function had no significant effect on gas disappearance. Two patients had a clinical leak on the fifth postoperative day. This was manifested as an increase in the collection of subdiaphragmatic gas during the course of a da). CONCLUSION: By the sixth postoperative day 80 percent of patients had no subdiaphragmatic free gas o n an erect chest radiograph regardless of the presence of a drainage tube. The erect chest radiograph may therefore be a simple and readily available adjunct in the evaluation of postoperative abdominal pain, especially after the sixth postoperative day when a similar prior examination is done routi nely on the fourth postoperative day for comparison.