From the Guidelines
Yes, if a computed tomography angiography (CTA) does not locate a gastrointestinal (GI) bleed, proceeding with colonoscopy and GI consultation is recommended. This approach follows a logical diagnostic sequence when managing suspected GI bleeding, as outlined in the guidelines from the British Society of Gastroenterology 1 and further supported by the consensus recommendations from the American College of Gastroenterology (ACG) and the Society of Abdominal Radiology (SAR) 1. After a negative CTA, colonoscopy becomes essential as it allows direct visualization of the colon and terminal ileum, potentially identifying sources of bleeding that CTA might miss, such as angiodysplasias, small polyps, inflammatory lesions, or diverticular disease.
The timing of colonoscopy depends on the severity of bleeding - urgent for active bleeding and within 24 hours for stable patients. Preparation is crucial for adequate visualization, typically using rapid bowel preparation solutions. GI consultation should occur concurrently, as gastroenterologists can provide expertise in managing complex cases, determine appropriate endoscopic interventions, and guide further diagnostic steps if colonoscopy is also negative, such as video capsule endoscopy or balloon-assisted enteroscopy to evaluate the small bowel. This stepwise approach maximizes diagnostic yield and improves patient outcomes in cases of occult GI bleeding, aligning with recommendations for the management of acute lower gastrointestinal bleeding 1. The most recent consensus recommendations 1 emphasize the role of imaging in GI bleeding, underscoring the importance of a structured approach to diagnosis and treatment.
From the Research
Diagnostic Approach for Gastrointestinal (GI) Bleeding
If a Computed Tomography Angiography (CTA) scan does not locate a GI bleed, the decision to proceed with a colonoscopy and GI consult should be considered based on the following points:
- Limitations of CTA: Studies have shown that CTA has a low sensitivity for detecting GI bleeding sources, ranging from 20% 2. This suggests that a negative CTA result does not rule out the presence of a GI bleed.
- Comparison with Endoscopy: Endoscopy, including colonoscopy, has been shown to have a higher diagnostic yield than CTA in detecting GI bleeding sources 3, 2. Therefore, proceeding with a colonoscopy and GI consult may be necessary to determine the cause of the bleed.
- Diagnostic Utility of CTA: Although CTA has been found to be useful in certain cases, its diagnostic utility is limited compared to other modalities such as endoscopy 4, 5.
- Algorithm for Diagnostic Work-up: A diagnostic algorithm for GI bleeding should include a combination of clinical assessment, endoscopy, and imaging studies, including CTA and scintigraphy 6.
Proceeding with Colonoscopy and GI Consult
Given the limitations of CTA and the importance of determining the cause of a GI bleed, proceeding with a colonoscopy and GI consult is a reasonable next step. This approach allows for a more thorough evaluation of the patient and can help identify the source of the bleed, guiding further management and treatment.
Key Considerations
- CTA should not be relied upon as the sole diagnostic tool for GI bleeding 2.
- Endoscopy, including colonoscopy, is a crucial component of the diagnostic work-up for GI bleeding 3, 2.
- A combination of clinical assessment, endoscopy, and imaging studies is necessary for an accurate diagnosis and effective management of GI bleeding 6.