Acute Lower Intestinal Bleeding: Feasibility and Diagnostic Performance of CT Angiography

Purpose: To assess the diagnostic performance of computed tomographic (CT) angiography as the initial diagnostic examination for patients presenting to the emergency room with acute lower intestinal bleeding. Materials and Methods: The study was reviewed and approved by the ethics committee, and written informed consent was obtained from each patient or their closest relative when the clinical condition precluded consent by the patient. This prospective study comprised 47 patients (27 men, 20 women; mean age, 68 years) with acute lower gastrointestinal tract bleeding who were referred to undergo emergency colonoscopy for evaluation. CT angiography was performed in all patients shortly after arrival to the emergency room. Findings identified at CT angiography included active extravasation (ongoing hemorrhage) or hyperattenuating intraluminal contents on noncontrast material-enhanced images (recent hemorrhage). Presence and location of bleeding and likely cause of hemorrhage were determined and compared with the standard of reference (angiography, colonoscopy, or surgical findings). Data collected were analyzed with a statistical software package. Sensitivity, specificity, and positive and negative predictive values of CT angiography in depicting ongoing or recent hemorrhage were calculated and compared with those of standard of reference. Results: CT angiography demonstrated active bleeding in 14 patients and intraluminal hyperattenuating material in six patients. The sensitivity, specificity, positive predictive value, and negative predictive value of CT angiography in depicting active or recent bleeding were 100% (19 of 19), 96% (27 of 28), 95% (19 of 20), and 100% (27 of 27), respectively. Findings of CT angiography and the standard of reference were concordant for determining definite or potential cause of bleeding in 44 of 47 patients (93% accuracy). Conclusion: CT angiography performed in the emergency setting in patients with acute lower intestinal bleeding is feasible and correctly depicts the presence and location of active or recent hemorrhage, as well as the potential cause, in the majority of patients. (C) RSNA, 2011