What is the recommended initial imaging modality for an upper gastrointestinal (GI) bleed, such as computed tomography (CT) angiography (angio) or CT with contrast?

Imaging for Upper GI Bleed: CT Angiography Without and With IV Contrast

For upper GI bleeding when endoscopy is not performed or has failed, CT angiography (CTA) of the abdomen and pelvis WITHOUT and WITH IV contrast is the imaging modality of choice—not standard CT with contrast alone. 1

Critical Distinction: CTA vs Standard CT with Contrast

The 2024 ACR Appropriateness Criteria explicitly state there is no significant literature supporting the use of standard CT abdomen/pelvis with IV contrast alone for upper GI bleeding. 1 The key differences are:

• CTA requires both non-contrast AND contrast phases to identify sentinel clot and distinguish active bleeding from pre-existing high-density material 1
• CTA uses optimized arterial timing and multiphasic acquisition specifically designed to detect contrast extravasation 2, 3
• CTA includes 3D reconstructions that provide superior vascular detail compared to standard contrast CT 2
• Standard CT with contrast alone is rated as "usually not appropriate" (rating 2-3) across all clinical scenarios 1

Clinical Scenarios and Recommendations

When Endoscopy Not Performed (Variant 1)

• CTA abdomen and pelvis without and with IV contrast is usually appropriate (the preferred imaging) 1
• This applies when patients present with large volume bleeding or clinical instability preventing initial endoscopy 1
• Visceral arteriography is an equivalent alternative if immediate intervention capability is needed 1

When Endoscopy Confirms Bleeding But Source Unclear (Variant 2)

• CTA abdomen and pelvis without and with IV contrast remains usually appropriate 1
• Visceral arteriography rated equally appropriate (rating 8-9) as it allows simultaneous diagnosis and therapeutic embolization 1

Post-Surgical or Traumatic Upper GI Bleeding

• CTA abdomen and pelvis without and with IV contrast is usually appropriate when endoscopy is contraindicated 1
• CTA is the examination of choice for aortoenteric fistula, which is superior to endoscopy for this diagnosis 1
• The non-contrast phase is particularly important to identify sentinel clot in trauma cases 1

Technical Performance Characteristics

CTA can detect bleeding rates as slow as 0.3 mL/min, compared to 0.5 mL/min for conventional angiography. 4, 2 The diagnostic accuracy includes:

• Sensitivity: 79-85% for active GI bleeding 1, 4
• Specificity: 92-95% 1, 4
• Positive predictive value: 86% 1
• Negative predictive value: 92% 1

Critical Protocol Requirements

The ACR guidelines emphasize specific technical requirements for CTA in GI bleeding:

• Multiphasic acquisition is mandatory: non-contrast phase followed by arterial and venous phases 1, 2
• No positive oral contrast should be given—it renders the examination non-diagnostic by obscuring intraluminal blood 1, 5
• Thin collimation (≤1 mm) enables high-quality multiplanar reformations 2
• Early imaging (within first 5 hours of presentation) significantly increases detection of extravasation 1, 2

Common Pitfalls to Avoid

Do not order standard "CT abdomen with IV contrast" when you mean CTA—these are distinct procedures with different protocols, and standard CT with contrast is inadequate for detecting active bleeding. 1 Key pitfalls include:

• Intermittent bleeding may result in false-negative studies even with proper CTA technique 2, 6
• Venous bleeding can be missed if only arterial phase is obtained 1
• Without the non-contrast phase, you cannot distinguish active extravasation from pre-existing high-density material 1, 2

When CTA May Not Be First-Line

One 2024 study found CTA had only 20% sensitivity when used as the initial diagnostic test before endoscopy, with 67% of patients with negative CTA having bleeding lesions identified on subsequent endoscopy. 7 However, this contradicts the established guidelines and reflects CTA use as a screening tool rather than in the appropriate clinical context of failed endoscopy or unstable patients where endoscopy cannot be performed. 1

Role of Dual-Energy CT

Dual-energy CT can generate virtual non-contrast images from contrast-enhanced data, potentially eliminating the need for a separate non-contrast acquisition and reducing radiation exposure. 1, 2 However, this remains institution-specific and is not yet standard practice. 1

Subsequent Management

If CTA identifies active bleeding, catheter angiography with intent to embolize should be performed, with technical success rates up to 95% and clinical success around 67%. 4 The CTA provides a roadmap that allows faster selective catheterization and more efficient embolization. 1, 3