PURPOSE:Colon gas analysis using abdominal radiography has been reported as a reliable method for assessing functional bowel disorders. The aim of this study was to clarify the relevance of colon gas distribution in postoperative disorders such as constipation and feelings of incomplete evacuation following rectal cancer operation.METHODS:Colon gas volume score was calculated using plain abdominal radiographs and evaluated in 50 patients who had received low anterior resections. Twenty‐one constipated patients who required laxatives and 29 patients who did not were compared in terms of colon gas distribution. In addition, 32 patients with postoperative feelings of incomplete evacuation and 18 patients without such feelings were assessed in similar fashion.RESULTS:Left colon gas scores in patients who required laxatives were significantly higher (2.82 ± 3.23 percent) than in nonusers (1.21 ± 0.96 percent;P< 0.01). Patients with feelings of incomplete evacuation displayed significantly higher left side colon gas scores (2.51 ± 2.66 percent) than those without such feelings (0.77 ± 0.81 percent;P< 0.0001).CONCLUSION:Patients with postoperative functional bowel disorders such as constipation or feelings of incomplete evacuation may experience relatively high volumes of gas in the left colon.