Efficacy of abdominal plain film and CT in bowel obstruction

The studies of 106 patients who underwent both plain film and CT studies in the course of assessment for suspected bowel obstruction were subjected to a blinded retrospective analysis. Plain film and CT scans were divided into six groups on the basis of bowel gas pattern (within normal limits = WNL, non-obstructive ileus = NOI, small bowel obstruction suspected = SBOs, small bowel obstruction definite = SBOd, large bowel obstruction suspected = LBOs, large bowel obstruction definite = LBOd), and a comparison was made with the surgically and/or clinically proved diagnosis. Overall sensitivity was 71.7% on plain film and 83.0% on CT. The positive predictive value of SBO was 80.3% on plain film, 95.1% on CT. The false negative ratio in small bowel obstruction was 8.2% on plain film, but only 1.6% on CT. Half of the cases (50.8%) that were read as SBOs on plain film were "definite" on CT. Causes of obstruction and abnormalities other than bowel lesion were more often detected by CT. The author stresses that a plain film study should initially be carried out in bowel obstruction and that, by adding CT as a subsequent examination, diagnosis becomes more definite.