Introduction
  • Gastrointestinal (GI) bleeding in the pediatric population can be a significant clinical concern, often necessitating timely and effective intervention.
  • Arterial interventions involving the gastrointestinal tract, particularly embolization, are primarily performed for acute GI bleeding that is unresponsive to conservative management, especially when endoscopy fails or is inconclusive.
  • GI bleeding accounts for approximately 10-15% of referrals to pediatric gastroenterologists, with causes varying between the upper and lower GI tract. 

Indications
Embolization is indicated for GI bleeding that does not respond to conservative measures such as fluid resuscitation, correction of coagulopathy, and administration of blood products. Specific indications include:
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  • Persistent bleeding requiring frequent blood transfusions (>500 mL in adult-sized patients).
  • Hemodynamic instability despite aggressive resuscitation.
  • Failure or contraindication of endoscopic therapy.
  • Bleeding from vascular lesions such as angiodysplasia, Meckel’s diverticulum, or arteriovenous malformations (AVMs).
  • Iatrogenic causes of bleeding, such as post-biopsy hemobilia.

Contraindications
There are no absolute contraindications.

Relative contraindications include:
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  • Uncorrected coagulopathy.
  • Severe coagulopathy that cannot be corrected.
  • Allergy to iodinated contrast agents.
  • Presence of significant bowel gas or recent barium studies that might obscure angiographic visualization.
  • Clinically unstable patients who may be better suited for surgical intervention.

Equipment Used
The following equipment is commonly employed in GI bleed embolization:
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  • Arterial Sheaths: Typically, 4 to 5 French arterial sheaths are used.
  • Guide Wires: Options include Glidewire, Amplatz, and Cope.
  • Catheters: Various catheters such as Cobra, Sos Omni, Simmons, and Pigtail (ranging from 4 to 8 French) are used for selective catheterization.
  • Microcatheters: Renegade Hi-Flo, STC. For superselective embolization, 1.7 to 2.8 French microcatheters are employed.
  • Embolic Agents: Gelfoam, glue (Histoacryl or nBCA), polyvinyl alcohol (PVA) particles, microcoils (detachable coils), and occasionally, liquid agents like NBCA.

​Pre-procedural evaluation
Before proceeding with embolization, a thorough evaluation is essential:
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  • Imaging:
  1. CTA: Gastrointestinal bleeding is often intermittent, and contrast extravasation may only be visualized if the bleeding rate is between 0.5 mL/min and 1.0 mL/min. However, in cases of massive acute GI bleeding, CTA has demonstrated an accuracy of up to 90%.
  2. Tagged Red Blood Cell Scan with Technetium: This imaging modality is capable of detecting slower bleeding rates, as low as 0.1 mL/min.
 
  • Laboratory Tests: Blood type and match, coagulation profile, CBC, and BMP are critical to assess the patient's baseline status and risk of bleeding.
 
  • Hemodynamic Stability: The patient should be as stable as possible before the procedure, with adequate blood products available.
 
  • Medical management: Depends on likely cause. Consider proton pump inhibitors, vasopressin, NG tube placement and bowel rest.
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  • Discussion: Discuss the treatment plan with the gastroenterologist and surgeon, particularly if endoscopy has already been performed.
​Patient with history of lupus presenting with GI bleed. CT-angiography shows active extravasation of intravascular contrast into small bowel lumen involving distal jejunum/proximal ileum of the left mid-abdomen.

Procedure

Preparation and Patient Evaluation
  1. Preprocedural Imaging: Confirm the bleeding site using Tc-99m RBC scans or angiography.
  2. Sterile Setup: Ensure a sterile field, with all necessary equipment within reach.
  3. Anesthesia: General anesthesia is preferred, especially in younger children, to minimize movement and ensure cooperation.
  4. Vascular Access: Gain vascular access via the common femoral artery using ultrasound guidance. A 4 to 5 French arterial sheath is typically placed.


Diagnostic Arteriography
  1. Fluoroscopic Setup:
    • Position the patient under fluoroscopy and ensure the imaging equipment is calibrated for optimal visualization.
    • Initial aortography may be performed to provide a broad overview of the visceral vascular anatomy but can be bypassed if there is a concern for contrast limit.
  2. Selective Angiography:
    1. Begin with selective catheterization of the suspected bleeding vessel based on clinical, endoscopic, and imaging data.
    2. For upper GI bleeding (hematemesis, melena), catheterize the celiac artery first, followed by the superior mesenteric artery (SMA).
    3. For lower GI bleeding (bright red blood PR), catheterize both the SMA and the inferior mesenteric artery (IMA).
    4. Use an angled catheter (e.g., Cobra, Sos Omni) for difficult vessel origins.
  3. Assessment of Bowel Peristalsis:
    1. Perform brief fluoroscopy of the abdomen to evaluate the extent of bowel peristalsis.
    2. If peristalsis is substantial, administer intravenous glucagon to inhibit motion and reduce artifacts during digital subtraction angiography (DSA).
  4. Visualization of Bleeding:
    1. Inject contrast media through the catheter to identify active extravasation (intraluminal contrast) or stasis of contrast.
    2. Identify and confirm the bleeding source by observing for contrast leakage into the GI lumen.
    3. Consider provocative angiography (use of anticoagulants, vasodilators) if bleeding is suspected but not immediately visible.
    4. Note: Tortuous small arteries or ileal branches may extend to the antimesenteric border in Meckel’s diverticulum.
    5. If vasospasm, consider nitroglycerine in 1-2 μg/kg aliquots.
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Embolization
  1. Catheter Positioning:
    1. Ensure the catheter tip is positioned safely within the bleeding vessel, close to the site of extravasation, but without causing vessel injury.
    2. Use super-selective catheterization techniques for precise targeting, especially in small or tortuous vessels, while assessing the collateral flow.
  2. Vasopressin infusion:
    1. Consider vasopressin infusion when the hemorrhage site is inaccessible with a microcatheter or if the bleeding involves a more diffuse area.
    2. Administer at a rate of 0.1–0.4 units/minute, with gradual tapering to avoid rebound bleeding.
  3. Embolic Agent Selection:
    1. Select embolic agents based on the type of bleeding, vessel size, and desired outcome.
    2. Temporary Agents: Gelfoam slurry (mixed with contrast and saline) is preferred for initial control, especially in cases where temporary hemostasis is acceptable.
    3. Permanent Agents: PVA particles (minimum size 300 μm), microcoils (detachable coils), or glue (Histoacryl or nBCA) may be used for more definitive control. PVA particles are particularly effective for occluding small vessels.
  4. Embolic Agent Preparation:
    1. Mix the embolic particles (e.g., PVA, Embospheres®) with contrast media (typically a 1:1 ratio) to allow real-time visualization during injection.
    2. Prepare coils or liquid agents (e.g., nBCA) according to manufacturer instructions, ensuring sterility and readiness.
  5. Embolic Material Delivery:
    1. Inject embolic particles using a controlled, pulsatile technique under fluoroscopic guidance, observing the flow and distribution within the vessel.
    2. Coil Embolization:
      1. Deploy coils into the vessel in a proximal-to-distal manner to achieve segmental occlusion, ensuring both proximal and distal sites are secured ("bridging technique").
      2. Consider "sandwich" embolization (occluding both sides of the bleeding point) to prevent rebleeding through collateral circulation.
    3. Liquid Embolic Agents:
      1. Carefully deliver liquid agents like nBCA using microcatheters to avoid non-target embolization. These are typically used for high-flow lesions.
  6. Monitoring During Embolization:
    1. Continuously monitor the patient's hemodynamic status and adjust the procedure as needed to avoid complications such as hypotension or ischemia.
    2. If necessary, use balloon occlusion to control high-flow vessels during embolic agent delivery.
  7. Completion of Embolization:
    1. Once satisfactory occlusion is confirmed, withdraw the catheter carefully while maintaining hemostasis at the access site.
    2. Perform a post-embolization angiogram to verify the cessation of bleeding and ensure no residual flow to the treated area.

Angiography
1. SMA – Focal extravasation from vasa recta branch of the SMA
2. ​Selective ileal branch arteriogram: Active extravasation seen, with likely small aneurysm.
Selective DSA image demonstrating the site of active extravasation.
3. ​Post-embolization SMA: No evidence of extravasation following embolization with PVA particles.

Post-Procedure Care
  • Hemostasis and Access Site Management:
    • Transfer to PACU for recovery.
    • Achieve hemostasis at the arterial access site, typically through manual compression or using a closure device. Deflate Safeguard at 2 hours and re-inflate if persistent oozing.
    • Monitor the access site for signs of bleeding or hematoma formation.
  • Post-Embolization Monitoring:
    • Observe the patient for signs of bowel ischemia, rebleeding, or other complications.
    • Monitor vital signs, hematocrit levels, and coagulation parameters closely.
    • Maintain the patient in a monitored setting, such as an ICU, especially if vasopressin infusion or significant embolization was performed.
  • Follow-Up Imaging:
    • Perform follow-up imaging (e.g., ultrasound, CT angiography) to assess the treated area for complications and ensure the long-term success of the embolization.

Complications
Potential complications of GI bleed embolization include:
  • Ischemia/Infarction: Overly aggressive embolization can lead to bowel ischemia, particularly in areas with limited collateral circulation. It is more common in lower GI embolization.
  • Infection: Although rare, infection at the vascular access site or within the embolized tissue may occur.
  • Rebleeding: There is a risk of rebleeding, especially if the underlying cause is not fully addressed.
  • Thrombosis

References
  1. Pediatric Interventional Radiology by Richard Towbin and Kevin M. Baskin MD
  2. Walker TG, Salazar GM, Waltman AC. Angiographic evaluation and management of acute gastrointestinal hemorrhage. World J Gastroenterol. 2012;18(11): 1191–201.
  3. Loffroy R, et al. Embolization of acute nonvariceal upper gastrointestinal hemorrhage resistant to endoscopic treatment: results and predictors of recurrent bleeding. Cardiovasc Intervent Radiol. 2010;33(6): 1088–100.
  4. Cherian MP, et al. Arterial interventions in gastrointestinal bleeding. Semin Intervent Radiol. 2009;26(3):184–96.
  5. Kwak HS, Han YM, Lee ST. The clinical outcomes of transcatheter microcoil embolization in patients with active lower gastrointestinal bleeding in the small bowel. Korean J Radiol. 2009;10(4):391–7.
  6. Sudheendra D, et al. Radiologic techniques and effectiveness of angiography to diagnose and treat acute upper gastrointestinal bleeding. Gastrointest Endosc Clin N Am. 2011;21(4):697–705.
  7. Kickuth R, et al. Acute lower gastrointestinal hemorrhage: minimally invasive management with microcatheter embolization. J Vasc Interv Radiol. 2008; 19(9):1289–96.e2.
  8. Okazaki M, et al. Emergent embolotherapy of small intestine hemorrhage. Gastrointest Radiol. 1992; 17(3):223–8.
  9. Guy GE, et al. Acute lower gastrointestinal hemorrhage: treatment by superselective embolization with polyvinyl alcohol particles. AJR Am J Roentgenol. 1992;159(3):521–6.
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