From the Guidelines
Computed tomography angiography (CTA) can detect gastrointestinal (GI) bleeding at rates as slow as 0.3 mL/min. This capability is highlighted in the 2024 update of the ACR Appropriateness Criteria for nonvariceal upper gastrointestinal bleeding, which notes that CTA has been shown to detect bleeding rates comparable to or even slower than those detectable by conventional angiography and Tc-99m–labeled red blood cell scintigraphy 1. The detection of GI bleeding by CTA depends on several factors, including the timing of the scan, the use of contrast, and the specific protocol employed. Key considerations for optimizing CTA for GI bleeding detection include:
- The use of noncontrast images to detect intraluminal high-attenuation material that may mimic intraluminal blood on contrast-enhanced images 1
- The potential replacement of noncontrast images with virtual noncontrast reconstructions when using dual-energy CT 1
- The implementation of multiphase acquisition protocols, which can include arterial, portal venous, and delayed phases to capture contrast extravasation at different time points 1
- The avoidance of oral contrast, as it can render the examination nondiagnostic or dilute intraluminal hemorrhage 1 The sensitivity and specificity of CTA for detecting active GI bleeding have been reported as 85% and 92%, respectively, in a meta-analysis of 22 studies 1. Furthermore, studies have shown that CTA can lead to faster triage of patients toward definitive treatment by angiography compared to other diagnostic methods like Tc-99m–labeled RBC scintigraphy or endoscopy 1. Overall, CTA is a valuable tool for detecting GI bleeding, particularly when used appropriately and in conjunction with other diagnostic approaches as needed.
From the Research
Detection of Gastrointestinal Bleeding using Computed Tomography Angiography (CTA)
- The rate of gastrointestinal (GI) bleeding that can be detected by computed tomography angiography (CTA) is not explicitly stated in the provided studies, but the sensitivity and specificity of CTA for diagnosing GI bleeding are reported in some studies.
- A study published in 2023 2 found that the sensitivity of CTA for detecting acute GI bleeding was 68.6% and the specificity was 89.1%.
- Another study published in 2021 3 found that CTA can detect bleeding rates less than 0.1 mL/min, and that larger extravasation volumes correlate with higher bleeding rates and may identify patients who require hemostatic therapy.
Factors Affecting CTA Detection of GI Bleeding
- The presence of anticoagulation has a significant impact on the decision not to perform interventional treatments on patients with acute GI bleeding when CTA is positive 2.
- A pre-existing eGFR of less than 20 was associated with significantly increased odds of developing contrast-induced acute kidney injury (CI-AKI) after CTA 2.
- The use of dual-energy computed tomography angiography may also play a role in improving the detection of GI bleeding 4.
Clinical Applications of CTA in GI Bleeding
- CTA may be underutilized in the care of patients with GI bleeding, despite its validation against other diagnostic modalities 5.
- CTA can provide diagnostic information to guide management and may be a promising initial test for acute GI bleeding 6.
- CTA can help identify patients who require hemostatic therapy, have intraprocedural bleeding, and require blood transfusions 3.