What is the purpose of renal artery embolization?

Purpose of Renal Artery Embolization

Renal artery embolization (RAE) is a minimally invasive endovascular procedure used primarily to control hemorrhage from renal trauma, manage renal tumors (both malignant and benign), and treat vascular abnormalities such as pseudoaneurysms, arteriovenous fistulas, and angiomyolipomas. 1, 2

Primary Indications

1. Renal Trauma and Hemorrhage Control

RAE is the first-line intervention for hemodynamically stable or stabilized patients with active renal bleeding, arterial contrast extravasation, or pseudoaneurysms on CT imaging. 1

• Indicated specifically for: arterial contrast extravasation, pseudoaneurysms, arteriovenous fistulas, and non-self-limiting gross hematuria in stable patients 1
• Success rates: 63-100% for blunt renal trauma, with 82-88% success for penetrating injuries (renal stab wounds with vascular injuries) 1
• Critical advantage: RAE has lower complication rates compared with surgery and better preserves renal function, with similar transfusion needs and re-bleeding rates 1

2. Renal Tumor Management

RAE serves three distinct roles in tumor management: 2, 3

• Pre-nephrectomy embolization: Reduces intraoperative hemorrhagic complications during surgical resection of large or vein-invading renal cell carcinomas 2, 4
• Palliative treatment: Controls symptoms (particularly hemorrhage) in unresectable renal malignancies 1, 2
• Primary treatment for angiomyolipomas: First-line therapy for bleeding angiomyolipomas and preventative treatment for those at risk of bleeding 3, 5

3. Vascular Abnormalities

RAE effectively treats renal artery aneurysms, pseudoaneurysms, and symptomatic arteriovenous malformations with lower complication rates than surgical alternatives. 2, 3

4. Alternative to Nephrectomy

RAE represents a less invasive alternative to surgical nephrectomy in specific medical conditions: 3

• Failed kidney allografts with graft intolerance syndrome (84% success rate, 0.1% mortality versus 4% with nephrectomy) 1
• Severe uncontrolled hypertension in end-stage renal disease 3
• Autosomal dominant polycystic kidney disease 3

Technical Approach and Key Principles

Embolization must be performed as selectively (super-selectively) as possible to limit parenchymal infarction. 1

• Embolic agents used: Metal coils with or without gelfoam are most common; ethanol is the material of choice for complete embolization 1, 4
• Agent selection depends on: Type of vascular injury (direct bleeding, pseudoaneurysm, arteriovenous fistula) 1, 2

Critical Clinical Decision Points

When RAE is Preferred Over Surgery

In solitary kidney patients with moderate (AAST III) or severe (AAST IV-V) renal trauma and arterial contrast extravasation, angiography with super-selective embolization should be the first choice. 1

In pediatric patients, RAE should be first-line even with active bleeding and labile hemodynamics, provided immediate access to angiographic suite, surgery, blood products, and intensive care is available. 1

When RAE is Contraindicated

RAE is not indicated and surgery is required in: 1

• Main renal vein injury without self-limiting bleeding 1, 6
• Hemodynamically unstable non-responders (WSES IV patients) 1
• Renal venous pedicle avulsion 1

Special Considerations for Main Renal Artery Injury

In hemodynamically stable patients with main renal artery injury, dissection, or occlusion, RAE and/or percutaneous revascularization with stent or stent-graft is indicated only in specialized centers and with limited warm ischemia time (<240 minutes). 1

• Critical caveat: Warm ischemia time >60 minutes leads to significant exponential kidney function loss 1
• Surgical revascularization has poor outcomes: <25% long-term kidney function preservation rate 1

Outcomes and Complications

RAE demonstrates superior outcomes compared to nephrectomy: 1

• Better renal function preservation 1
• Shorter ICU length of stay 1
• Rare renal dysfunction or renovascular hypertension directly linked to the procedure 1

Reported morbidity rate is 25%, including: 1

• Accidental embolization of healthy arterial branches
• Puncture-site bleeding
• Arterial dissection and thrombosis
• Contrast-induced nephropathy
• Post-embolization syndrome (back pain and fever)
• Coil migration
• Renal abscess

If initial embolization fails, repeat RAE should be considered, as success rates for repeat procedures are similar to initial attempts. 1

Important Pitfalls to Avoid

Blind embolization is not indicated in hemodynamically stable patients with both kidneys when angiography is negative for active bleeding, regardless of arterial contrast extravasation on CT scan. 1 This is because approximately 32% of blunt renal injuries with arterial contrast extravasation on CT have negative angiography and can be managed successfully without embolization 1

Factors associated with higher RAE failure rates include: 1

• Age and volume of blood products given in first 24 hours
• Center experience level
• Penetrating trauma