Multidetector helical CT in the evaluation of acute small bowel obstruction: comparison of non-enhanced (no oral, rectal or IV contrast) and IV enhanced CT.

PURPOSE: To compare accuracy of non-enhanced CT (NECT) (no oral or IV contrast) and enhanced CT (ECT) (IV enhanced only) to diagnose small bowel obstruction and evaluate reviewer's experience impact.

MATERIALS AND METHODS: Ninety-nine adult patients underwent 105 NECT and ECT (6 patients had 2 examinations) on a four-detector CT. An abdominal radiologist, an abdominal imaging fellow, a second-year radiology resident retrospectively reviewed NECTs and ECTs separately and independently blinded to outcome. Discrepancy of diameter of proximal and distal small bowel+/-a transition was considered indication of mechanical bowel obstruction. Reference standard was surgery in 26 and chart review in 79.

RESULTS: Mechanical obstruction was present in 56% (59/105). The average sensitivity, specificity, negative and positive predictive and accuracy values for NECT were 88.1% (CI: 80-96%), 77% (CI: 65-89%), 83.0% (CI: 72-95%), 83% (CI: 74-92%), and 83% (CI: 76-90%) with no significant difference between three reviewers. The corresponding numbers for ECT were 87.6% (CI: 79-96%), 75% (CI: 63-88%), 82.6.0% (CI: 71-94%), 82.1% (CI: 73-92%), and 82% (CI: 75-90%) (p>0.5). Area under curve (AUC) of ROC curves of three reviewers did not show significant statistical difference (p>0.5).

CONCLUSIONS: NECT and ECT have comparable accuracy to diagnose mechanical small bowel obstruction and can be interpreted by reviewers with different levels of expertise.