CT Abdomen for Active GI Bleeding: IV Contrast Only (No Oral Contrast)

Introduction to CT Angiography for GI Bleeding

• The American College of Radiology recommends CT angiography (CTA) of the abdomen and pelvis without oral contrast for patients with active GI bleeding, using a multiphasic protocol with IV contrast 1

Protocol for CT Angiography

• Multiphasic CTA (unenhanced + arterial + portal venous phase) achieves 92% sensitivity for detecting GI bleeding, compared to only 83% for protocols using only arterial or portal venous phase alone 1, 2
• The American College of Radiology recommends noncontrast images with 100% consensus for CTA performed on single-energy CT 2, 4

Importance of Imaging Phases

• Unenhanced phase: Identifies baseline high-attenuation material (sentinel clot) that could be mistaken for active bleeding on contrast-enhanced images 4
• Arterial phase: Detects active arterial extravasation with sensitivity down to 0.3 mL/min bleeding rate 2, 4
• Portal venous/delayed phase: Captures slower or intermittent bleeding that may not be visible on arterial phase alone 2, 4

Imaging Extent and Common Pitfalls

• Both abdomen and pelvis should be imaged because the bleeding site is typically unclear without prior endoscopy 1, 2
• Do not order standard "CT abdomen with IV contrast" - this is distinct from CTA and lacks the multiphasic arterial timing necessary to detect active bleeding 4, 6

Clinical Performance of CTA

• Meta-analysis of 22 studies (672 patients) demonstrates CTA sensitivity of 85% and specificity of 92% for active GI bleeding 2
• CTA leads to faster triage toward definitive treatment compared to endoscopy or nuclear medicine studies 1, 2