Utility of CT Angiography (CTA) in Diagnosis and Treatment of Acute Lower GI Bleeding (LGIB)

Abstract

Introduction: To investigate the diagnostic performance of CTA in identifying the cause of acute lower GI bleeding and to determine the clinical features associated with positive test result of CTA. Acute Lower GI bleed warrants quick detection and localization of the bleed. Various studies have shown that CTA can detect active hemorrage at rate of 0.3 ml/min (compared to bleeding scan detection rate of 0.2 ml/min) Methods: Retrospective chart review study of all patients who had CTA performed for suspected acute LGIB in last 5 years in a community hospital in Brooklyn Results: 84 patients with mean age of 69 years were included. 41% were male and 59% were females. 49% were on antiplatelet therapy.29% had history of diverticulosis. Mean Hb value was 8.34 g/dL. Presenting complaints were lower GI bleeding in 86%, upper GI bleeding in 9.5%, abdominal pain with anemia in 4.5%. On abd CTA, 86% had no active bleeding and 14% had active bleeding. 9/12 had LGI and 3/12 had upper GI bleeding. EGD showed antral/duodenal ulcers in patients where CT had localized disease to upper GI tract. 5/9 with localized bleeding to lower GI tract had colonoscopy done. Colonoscopy showed diverticulosis in 3, mass in 1 and colitis in 1. CTA was negative in 44%, non-specific colitis 13%, diverticulosis in 15%. 20% patients had bleeding scan done. 11/17 had positive bleeding scan. In patients with positive bleeding scan,10/11 had initial negative CTA, 6/11 had EGD done which did not show active bleeding. 7 had colonoscopy done which did not show active bleeding. EGD was done in 41/84 patients. No active bleeding was identified in all patient who had EGD done. Conclusion: In patients with acute LGIB, CTA lacks sensitivity and was positive only in14% of the patients. Bleeding scan was more sensitive however, lacked specificity in localizing the bleeding. Patients who had positive CT scan for active bleeding, only one had active bleeding on Colonoscopy. All the patients who had CT evidence of diverticulosis, were found to have diverticulosis on colonoscopy.Diverticular bleeding is most common cause of LGIB. CTA should only be reserved for patients with continued bleeding despite usual standard of care and in patients in whom vascular intervention is needed. Majority of patients can be spared from radiation and IV contrast exposure from CTA. However, further large prospective studies are needed to define the role of CT in acute GI bleeding when other investigations are unable to provide a diagnosis.