Assessment of Bowel Wall Enhancement for the Diagnosis of Intestinal Ischemia in Patients with Small Bowel Obstruction: Value of Adding Unenhanced CT to Contrast-enhanced CT

Abstract

Purpose To determine whether adding unenhanced computed tomography (CT) to contrast material-enhanced CT improves the diagnostic performance of decreased bowel wall enhancement as a sign of ischemia complicating mechanical small bowel obstruction (SBO). Materials and Methods This retrospective study was approved by the institutional review board, which waived the requirement for informed consent. Two gastrointestinal radiologists independently performed retrospective assessments of 164 unenhanced and contrast-enhanced CT studies from 158 consecutive patients (mean age, 71.2 years) with mechanical SBO. The reference standard was the intraoperative and/or histologic diagnosis (in 80 cases) or results from clinical follow-up in patients who did not undergo surgery (84 cases). Decreased bowel wall enhancement was evaluated with contrast-enhanced images then and both unenhanced and contrast-enhanced images 1 month later. Diagnostic performance of decreased bowel wall enhancement and confidence in the diagnosis were compared between the two readings by using McNemar and Wilcoxon signed rank tests. Interobserver agreement was assessed by using κ statistics and compared with bootstrapping. Results Ischemia was diagnosed in 41 of 164 (25%) episodes of SBO. For both observers, adding unenhanced images improved decreased bowel wall enhancement sensitivity (observer 1: 46.3% [19 of 41] vs 65.8% [27 of 41], P = .02; observer 2: 56.1% [23 of 41] vs 63.4% [26 of 41], P = .45), Youden index (from 0.41 to 0.58 for observer 1 and from 0.42 to 0.61 for observer 2), and confidence score (P < .001 for both). Specificity significantly increased for observer 2 (84.5% [104 of 123] vs 94.3% [116 of 123], P = .002), and interobserver agreement significantly increased, from moderate (κ = 0.48) to excellent (κ = 0.89; P < .0001). Conclusion Adding unenhanced CT to contrast-enhanced CT improved the sensitivity, diagnostic confidence, and interobserver agreement of the diagnosis of ischemia, a complication of mechanical SBO, on the basis of decreased bowel wall enhancement. (©) RSNA, 2016.

Assessment of Strangulation in Adhesive Small Bowel Obstruction on the Basis of Combined CT Findings: Implications for Clinical Care

“…14, so we could have misinterpreted the degree of enhancement if hemorrhage and congestion were already present before contrast agent administration. Indeed, Chuong et al (28) recently showed that adding an unenhanced phase to the contrastenhanced phase could improve diagnostic confidence and interobserver agreement for evaluation of this CT sign. Decreased bowel enhancement remains an independent CT sign associated with irreversible bowel ischemia (positive predictive value, 65%; 95% CI: 48%, 85%).…”

A Systematic Review of the Clinical Presentation, Diagnosis, and Treatment of Small Bowel Obstruction

“…Performing both unenhanced and contrast-enhanced CT improves test sensitivity, diagnostic confidence, and interobserver agreement in the diagnosis of ischemia. Decreased or absent mural enhancement after administration of IV contrast is a useful, highly specific, indicator of intestinal ischemia (95-100%), despite variable sensitivity of 40-60% [46,57,58]. A recent meta-analysis showed that decreased mural enhancement was more predictive of ischemia than any other single CT sign [59,60].…”

“…A recent meta-analysis showed that decreased mural enhancement was more predictive of ischemia than any other single CT sign [59,60]. This sign was 100% specific and 56% sensitive for bowel ischemia [57][58][59][60]. Other CT signs of ischemia include bowel wall thickening and mucosal thumbprinting from intramural edema, inflammation, or hemorrhage; pneumatosis intestinalis from intramural gas produced by bacteria; and streaky mesentery from adjacent inflammatory infiltration as listed in Table 2 [11•, 24].…”

Diagnostic laparoscopy for pneumatosis intestinalis in a very elderly patient: A case report

“…To date, CT is the preferred imaging technique, and decreased bowel enhancement on CT, which is defined as decreased or absent enhancement after administration of contrast material, is considered the most useful finding to detect the bowel wall ischemia. This finding has a specificity of 95–100% but a variable sensitivity of 33%–78% [11] . In addition, decreased enhancement of the bowel wall during the arterial phase is difficult to evaluate, considering the rate of interobserver agreement [12] .…”