Detection of intestinal ischemia in patients with acute small-bowel obstruction due to adhesions or hernia: efficacy of CT.

Abstract

OBJECTIVE: The purpose of this study was to determine whether CT can be used to diagnose ischemia of the small intestine in patients with small-bowel obstruction due to adhesions or hernia. SUBJECTS AND METHODS: During a 12-month period, 60 patients underwent surgery for complete or high-grade small-bowel obstruction due to adhesions or hernia, and 29 (48%) had evidence of associated intestinal ischemia. All of these patients had been preoperatively diagnosed by CT as having high-grade small-bowel obstruction. At the same time, a prospective determination was made based on the CT as to whether there was any associated intestinal ischemia. All CT scans were performed within 24 hours of the operation. A CT diagnosis of ischemia was based on the presence of two or more of the following signs: bowel-wall thickening, high attenuation of the bowel wall on unenhanced CT scans, mesenteric edema or fluid, asymmetric bowel-wall enhancement on i.v. contrast-enhanced CT scans, pneumatosis, or portal venous gas. Results of the CT examination and surgical findings were then compared. Further evaluation was done with a retrospective multivariate discriminant analysis. RESULTS: Ischemia was prospectively diagnosed on the basis of CT findings in 41 (68%) of the 60 patients. There were no false-negative CT diagnoses (sensitivity, 100%); however, there were 12 CT diagnoses that were false-positive (specificity, 61%). The multivariate analysis corroborated the prospective results by showing high sensitivity (90%) and diminished specificity (50-64%). Bowel-wall thickening and high attenuation of the bowel wall were the most important signs of ischemia on unenhanced CT scans, whereas abnormal bowel-wall enhancement and mesenteric fluid correlated best on enhanced CT examinations. CONCLUSIONS: CT is a sensitive but not completely specific preoperative indicator of intestinal ischemia in patients with small-bowel obstruction due to hernias or adhesions.