Digital Subtraction Angiography (DSA) in Gastrointestinal Bleeding
Indications for DSA in GI Bleeding
Digital Subtraction Angiography (DSA) is recommended for hemodynamically unstable patients with active GI bleeding when endoscopy fails to identify or control the bleeding source, or when endoscopy is contraindicated. 1
The primary indications for DSA in GI bleeding include:
- Hemodynamically unstable patients (shock index >1) with suspected active bleeding after initial resuscitation 1, 2
- Cases where endoscopy has confirmed bleeding but failed to identify the source 1
- Patients with continued bleeding despite endoscopic intervention 2, 3
- Postsurgical and traumatic causes of GI bleeding where endoscopy is contraindicated 1
- Following positive CT angiography (CTA) that has localized the bleeding site 1, 4
Diagnostic Pathway and Timing
The optimal diagnostic pathway for GI bleeding typically follows this algorithm:
- For hemodynamically stable patients: Endoscopy should be the first-line diagnostic procedure 4, 3
- For hemodynamically unstable patients (shock index >1): CTA should be performed immediately before any intervention 1, 2
- Following positive CTA: Proceed to catheter angiography with embolization within 60 minutes for unstable patients 2, 4
Upper GI Bleeding Considerations
- DSA is particularly valuable in the upper GI tract, where it can rapidly locate bleeding sites with high accuracy 5
- When endoscopy identifies but cannot treat a source of upper GI bleeding, DSA should be performed with intent to embolize 1
Lower GI Bleeding Considerations
- For lower GI bleeding, DSA is typically performed after CTA has localized the bleeding site 1
- Radionuclide imaging (tagged RBC scan) may be performed before angiography to increase diagnostic yield by screening out patients who are not actively bleeding 1
Technical Aspects and Performance
- DSA can detect bleeding at rates as low as 0.5-1.0 mL/min 1
- Technical success rates for embolization are above 95%, though up to 25% of patients may present later with recurrent bleeding 1
- The sensitivity of DSA ranges from 30-47% with 100% specificity for active GI bleeding 1, 3
- In small intestinal bleeding specifically, DSA has shown sensitivity of 91.7%, specificity of 100%, and accuracy of 92% 6
- Dual-source dual-energy CT angiography techniques have shown improved sensitivity (88.6%) and specificity (100%) compared to conventional techniques 7
Limitations and Pitfalls
- DSA is invasive and carries risks including groin hematoma, vessel injury, and contrast-induced nephropathy 1
- Bowel ischemia may occur in up to 10% of cases following embolization, though most patients remain asymptomatic 1
- Intermittent bleeding can be missed on angiogram, leading to false negatives 1
- In the lower GI tract, DSA's usefulness may be limited by the small field of view and misregistration artifacts caused by bowel motion 5
- Only arterial or capillary bleeding can be detected; venous bleeding is rarely detected on the venous phase of an arteriogram 1
Alternative Imaging Approaches
- CTA has largely replaced DSA as the first-line imaging study for suspected active GI bleeding due to its non-invasiveness, wide availability, and ability to detect bleeding rates as low as 0.3 mL/min 1
- For obscure GI bleeding with slower rates, video capsule endoscopy has shown higher diagnostic yield than angiography 3
- Optimized multidetector CT protocols have shown excellent results in diagnosing active obscure GI bleeding, potentially superior to DSA in some cases 8