Computed tomography compared with small bowel enema in clinically equivocal intestinal obstruction

To compare the findings in computed tomography (CT) and small bowel enema (SBE) in clinically equivocal small bowel obstruction in order to identify the reasons for the limitation of CT evaluation.

Over a period of 5 years, 49 patients who had both CT and SBE within a period of 1 week were analysed. The findings at SBE were categorized into partial low-grade, partial high-grade and complete obstruction and compared with the CT findings. A critical analysis of the CT false-negative cases was made. The predictive values for the determination of the presence of obstruction in CT were also obtained.

Forty-three out of the 49 patients had proven intestinal obstruction. CT correctly identified 34 cases including 19 of 20 with partial high-grade obstruction, two with complete obstruction and 13 out of 21 cases of partial low-grade obstruction. Among those cases with low-grade obstruction cases with complex or long segment narrowing or with masses were correctly identified while six patients with short stenotic segment due to various causes were not. CT also had two false-positive findings of obstruction in patients with mesenteric infarction. SBE had neither false positive nor false negative. The sensitivity, specificity, positive predictive value and negative predictive values for CT were 83%, 67%, 94% and 36%, respectively. Abrupt transition from dilated to collapsed loops in CT were caused by various intraluminal lesions apart from adhesions. CT was superior to SBE in showing extraluminal masses, revealing abscesses, tuberculous lesions and malignancy anterior adhesions as well as features of strangulation.

Apart from degree of obstruction and the presence of masses, the length of the stenotic part also affected CT detection. Abrupt change from dilated to collapsed segment could be due to various transmural and intraluminal lesions although adhesions was the commonest lesion. While SBE is more accurate in identifying the presence and location of obstruction, CT is superior for detection of the cause of small bowel obstruction and also for the presence of strangulation. In places where CT is more widely used for intestinal obstruction, SBE evaluation could be prudently considered in CT negative cases of clinically equivocal intestinal obstruction.