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Indications & Contraindications
Hemorrhage, tumor, AVM, aneurysm, and other indications
Indications
- Renal hemorrhage — trauma (blunt/penetrating), post-biopsy bleeding, post-surgical hemorrhage
- Angiomyolipoma (AML) >4 cm — prophylactic embolization to prevent rupture; emergent for acute hemorrhage (rupture risk ~50% when ≥4 cm)
- Pseudoaneurysm — post-biopsy, post-partial nephrectomy, post-nephrostomy
- Pre-operative devascularization — large RCC before nephrectomy to reduce intraoperative blood loss
- Arteriovenous fistula / malformation — post-biopsy AVF, congenital AVM with hematuria or hypertension
- Renal artery aneurysm — ≥1.5–2 cm, symptomatic, women of childbearing age, polyarteritis nodosa
- Palliative — unresectable renal tumors (pain, hematuria control)
- End-stage renal disease — polycystic kidneys with intractable pain/hematuria for transplant prep; irreversible transplant rejection
Contraindications
- Uncorrectable coagulopathy (INR >1.5, platelets <50K) — relative in emergent hemorrhage
- Severe contrast allergy without adequate premedication
- Renal artery stenosis as cause of symptoms (better treated with angioplasty)
- Relative: solitary kidney — superselective embolization mandatory; maximize nephron preservation
- Relative: severely impaired renal function — risk/benefit discussion; hydration critical
- Relative: pregnancy — radiation exposure considerations
Embolic Agent Selection by Indication
| Indication | Preferred Embolic | Technique |
|---|---|---|
| Pseudoaneurysm / AVF | Coils (microcoils) | Superselective — coil across neck or feeding artery |
| AML (elective) | Coils + microspheres/PVA | Superselective to feeding artery |
| Trauma / acute hemorrhage | Coils ± Gelfoam | Coils to injured segmental artery; Gelfoam for temporary occlusion |
| Tumor devascularization (RCC) | PVA / microspheres + coils | Particles first (arteriolar level), then coil main feeders |
| AVM (complex) | Ethanol / NBCA glue ± coils | Sclerosant to ablate nidus; coils to reduce flow first |
| Total embolization (ESRD) | Ethanol/PVA + coils | Peripheral particles first, then coils in main renal artery |
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Pre-Procedure Planning
Imaging review, labs, hydration, consent points
Imaging & Labs
- CTA abdomen — identify bleeding source, renal arterial anatomy, number of renal arteries (accessory arteries in 25–30%), AML vascularity, aneurysm morphology
- Assess for replaced/aberrant renal arteries and collateral supply
- Labs: Creatinine / GFR (baseline renal function), CBC, PT/INR, platelets
- Type & screen — recommended for hemorrhage cases
Patient Preparation
- Hydration — especially critical if solitary kidney or transplant kidney; 1 L NS IV before start
- NPO 6h before (moderate sedation)
- IV access; Foley catheter for prolonged cases or total embolization
- Consent: discuss renal function impact (infarction risk), post-embolization syndrome (pain, fever, nausea), non-target embolization risk
CTA reviewed. Bleeding source identified, renal artery anatomy mapped, number of renal arteries confirmed, accessory arteries noted.
Labs reviewed. Creatinine/GFR (baseline documented), INR ≤1.5, platelets ≥50K. Correct coagulopathy if possible (emergent cases may proceed).
IV hydration initiated. 1 L NS before procedure, especially for solitary/transplant kidney.
Consent obtained. Key risks discussed: renal infarction/function loss, post-embolization syndrome, non-target embolization, access site complications.
Antibiotics administered (if indicated): Cefazolin 1g IV for tumor embolization or abscess risk cases.
Embolic agents confirmed. Coils, microspheres/PVA, Gelfoam, and/or ethanol available based on planned indication.
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Relevant Anatomy
Renal artery branches, segmental supply, end-artery physiology
Renal Arterial Supply
- Renal arteries arise from the aorta at L1–L2 level; right renal artery courses posterior to IVC
- Anterior division — supplies upper, middle, and lower anterior segments (4 segmental arteries)
- Posterior division — supplies posterior segment (single segmental artery)
- Segmental arteries are end-arteries — no collaterals between segments; any embolization causes infarction of the supplied territory
- Segmental → interlobar → arcuate → interlobular arteries
Variants & Key Points
- Accessory renal arteries present in 25–30% of population — must identify on CTA/aortogram; may supply bleeding territory
- Early branching of main renal artery (prehilar branching) in ~10% — may require multiple selective catheterizations
- AML vascularity: dysplastic, tortuous feeding arteries with microaneurysms; characteristic “onion skin” appearance of abnormal vessels
- Pseudoaneurysms: focal contrast pooling on angiogram; contained rupture of arterial wall — often at biopsy tract
Angiographic Landmarks
On flush aortogram, identify renal artery origins at L1–L2 (tennis racket or Omni-Flush catheter positioned with tip just above renal artery origins). Selective renal angiogram defines anterior/posterior division and segmental branches. In the nephrographic phase, assess for parenchymal defects (prior infarcts), mass effect (tumor), and early venous filling (AVM/AVF). Superselective catheterization into the feeding segmental or interlobar artery using microcatheter allows precise identification of the target lesion before embolization.
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Supplies & Setup
Access, catheters, embolic agents
Access & Catheters
- 5F vascular sheath (6–8F if balloon-assisted technique)
- 5F renal curve catheter — C2 Cobra (primary), SOS Omni, or RC-2
- Microcatheter (2.4–2.8F) + 0.018″ microwire for superselective access
- Flush catheter for aortogram (Tennis Racket or Omni-Flush)
- 0.035″ guidewire (angled Glidewire, Bentson)
- Standard access kit: micropuncture set, lidocaine 1%
Embolic Agents
- Coils: pushable and/or detachable (0.018″ microcoils for superselective; 0.035″ for main artery)
- Microspheres / PVA: 300–900 μm particles for tumor devascularization and AML
- Gelfoam: pledgets or slurry for temporary occlusion (benign hemorrhage, pre-nephrectomy)
- Ethanol 98–99%: for sclerosis of AVM nidus or total renal ablation (use with balloon occlusion)
- NBCA glue: for high-flow AVM when rapid occlusion needed
Medications
- Moderate sedation: midazolam 1–2 mg + fentanyl 50–100 mcg IV
- Nitroglycerin 100–200 mcg IA (for vasospasm)
- Heparinized saline flush
- Cefazolin 1g IV (if tumor/abscess risk)
- IV fluid: NS at 100–150 mL/h during and post-procedure
- Ketorolac 15–30 mg IV PRN (post-embolization pain)
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Procedure Steps
Femoral access, selective catheterization, embolization technique
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Vascular Access
Common femoral artery (CFA) access using micropuncture technique. Place 5F vascular sheath (upsize to 6–8F if balloon-assisted technique planned). Contralateral CFA preferred for renal artery selection; ipsilateral acceptable. If femoral access not feasible (severe aortoiliac disease, bilateral groin issues): radial artery access preferred over brachial — 6F radial sheath with 90–110 cm long sheath provides excellent renal artery reach with lower hemostatic complication rate.
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Flush Aortogram
Position flush catheter (Tennis Racket or Omni-Flush) with tip just above the renal artery origins. Perform abdominal aortogram to map renal artery origins, identify accessory renal arteries, and assess for aortic disease. Confirm number and origin of all renal arteries.
▶ Renal artery anatomy — pre-embolization mapping
Flush aortogram: identify all renal arteries including accessory vessels and their relationship to the target lesion before selective catheterization.
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Selective Renal Artery Catheterization
Exchange to 5F renal curve catheter (C2 Cobra most common). Engage the target renal artery origin. Perform selective renal angiogram to identify the bleeding source, AML feeding vessels, aneurysm, or AVF. Assess anterior/posterior divisions and segmental branches. Use DSA with road mapping.
▶ Renal pseudoaneurysm — selective angiogram
Selective renal angiogram: pseudoaneurysm opacification — note saccular morphology with narrow neck and surrounding normal parenchymal blush.
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Superselective Catheterization
Advance microcatheter coaxially through the 5F catheter into the target segmental/interlobar artery feeding the lesion. Perform superselective angiogram to confirm position and identify the specific feeding vessel(s). Goal: get as distal as possible to maximize nephron preservation.
▶ Superselective catheterization of PSA-feeding artery
Superselective microcatheter placement in the artery feeding the pseudoaneurysm — confirms target access before embolization.
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Embolization
Pseudoaneurysm/AVF: deploy microcoils across the pseudoaneurysm neck or into the feeding artery (pack until flow ceases). AML: superselective to feeding artery; deploy coils + microspheres/PVA (300–500 μm). Trauma: coils to injured segmental artery ± Gelfoam for temporary hemostasis. Tumor devascularization: PVA/microspheres first (arteriolar level embolization until stasis), then coils in larger feeders. Total embolization (ESRD): particles peripherally first, then coils in main renal artery — proceed until stasis or sluggish to-and-fro flow on completion angiogram.
▶ Post-embolization — coil pack confirming exclusion
Completion angiogram after coil embolization: pseudoaneurysm excluded with preserved perfusion to surrounding normal parenchyma.
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Completion Angiogram
Selective renal angiogram from the 5F catheter to confirm: cessation of bleeding/extravasation, occlusion of target vessel, no residual flow to lesion, and no non-target embolization. If incomplete embolization, deploy additional embolic material. Check for coil positioning and stability.
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Sheath Removal & Hemostasis
Remove catheter and sheath. Obtain hemostasis at CFA access site (manual compression or closure device). Monitor pedal pulses. Transfer to recovery with post-procedure monitoring plan.
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Troubleshooting
Intraprocedural problems and solutions
Vasospasm
Renal Artery Spasm During Catheterization
Common with wire/catheter manipulation in renal artery branches. Administer nitroglycerin 100–200 mcg IA through the catheter. Wait 1–2 minutes for resolution. Avoid forceful catheter advancement during spasm. If persistent, allow catheter to sit without manipulation for several minutes.
Accessory Renal Artery
Bleeding Territory Supplied by Accessory Renal Artery
If bleeding persists after embolization of the main renal artery branches, suspect an accessory renal artery supplying the hemorrhage territory. Return to aortogram to identify additional renal arteries. Accessory arteries (present in 25–30%) may arise from the aorta at any level from T12 to the iliac bifurcation. Selectively catheterize and embolize the accessory artery feeding the lesion.
Superselective Failure
Cannot Advance Microcatheter to Target
Ensure stable 5F guide catheter position in the main renal artery. Use a hydrophilic microwire (0.014–0.018″) to navigate tortuous or spastic segmental branches. Consider catheter exchange to a reverse-curve catheter (SOS) for better purchase. In difficult anatomy (large tumor mass effect, aortic aneurysm), try alternative catheter shapes (Simmons, RC-2). If vessel too small for microcatheter, consider particle embolization from a more proximal position.
Non-target Embolization
Embolic Material Reflux into Non-target Vessels
Stop embolization immediately. Inject slowly and under continuous fluoroscopy. Ensure catheter is positioned distal enough to prevent reflux. For high-flow lesions (AVM), consider balloon occlusion of the parent artery during embolization to prevent reflux. Use appropriately sized coils (oversize by 20–30% relative to vessel diameter). If coil migrates, retrieve with snare device.
Persistent Hemorrhage
Continued Bleeding After Embolization
Repeat angiogram from the main renal artery to reassess. Evaluate for: incomplete embolization of target, collateral supply from lumbar or capsular arteries, accessory renal artery, or new bleeding site. Deploy additional embolic material as needed. In refractory cases, consider more proximal embolization (accepting greater parenchymal loss) or surgical consultation.
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Complications
Post-embolization syndrome, infarction, non-target embolization
Common / Expected
- Post-embolization syndrome (>90% with total embolization) — flank pain, fever, nausea/vomiting, elevated WBC; onset 1–3 days post-procedure; self-limited over several days; treat with analgesics, antipyretics, antiemetics
- Renal infarction — expected consequence of segmental artery embolization (end-arteries); superselective technique limits infarction to <10% of parenchyma in best cases
- Access site complications — groin hematoma (<2%), pseudoaneurysm; manual compression or closure device
Serious Complications
- Non-target embolization — reflux of embolic material into aorta causing spine, lower extremity, or bowel infarction; prevented by proper catheter positioning and slow injection
- Renal function loss — clinically significant with subselective embolization (up to 15–50% parenchymal infarction); rarely requires dialysis unless solitary kidney
- Abscess formation — infected infarct; low incidence; prophylactic antibiotics for tumor embolization
- Coil migration — occurs in <2% of cases; retrievable with endovascular snare
- Incomplete embolization — recurrent bleeding; usually apparent on completion angiogram; additional embolization required
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Pearls & Pitfalls
Clinical decision-making, technique optimization
✦
Superselective = nephron-sparing. Always catheterize as distally as possible. Superselective embolization results in <10% non-target parenchymal infarction vs up to 50% with subselective techniques.
✦
AML >4 cm: embolize prophylactically. Rupture risk is approximately 50% for angiomyolipomas ≥4 cm in diameter. Prophylactic embolization prevents life-threatening hemorrhage.
✦
Renal segmental arteries are end-arteries. No collateral circulation between segments. Any embolization will cause infarction of the supplied territory — make every particle and coil count by confirming position before deployment.
✦
Post-biopsy pseudoaneurysm: coil embolization is highly effective. Microcoil packing of the pseudoaneurysm sac and feeding artery has near-100% technical success for iatrogenic pseudoaneurysms.
✦
Always check for accessory renal arteries. Present in 25–30% of the population. An unembolized accessory artery supplying the bleeding territory is the most common cause of persistent hemorrhage after technically adequate embolization.
⚠
Reflux during total embolization. In ESRD kidneys with reduced arterial flow, embolic material may reflux into the aorta. Use temporary balloon occlusion catheter in the proximal main renal artery during embolization to prevent non-target embolization.
⚠
Ethanol requires caution. If using absolute alcohol for AVM sclerosis or total renal ablation, use general anesthesia for large volumes (>10 mL) due to intense pain and risk of cardiopulmonary collapse if ethanol escapes into systemic circulation. Always use balloon occlusion.
⚠
Gelfoam is temporary. Gelfoam provides occlusion lasting 2–3 weeks. Appropriate for pre-nephrectomy devascularization or acute hemorrhage, but not for definitive treatment of AML or AVM. Consider permanent agents for long-term control.
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References & Resources
Primary sources and related procedures
Key Technical Points
- Superselective embolization results in <10% non-target parenchymal infarction
- Technical success rate for emergent renal artery embolization: ~93%
- Incomplete embolization and coil migration occur in <2% of cases
- Recanalization of embolized arteries is rare with current embolic agents
Primary References
- Ginat DT, Saad WEA, Turba UC. Transcatheter renal artery embolization: clinical applications and techniques. Tech Vasc Interventional Rad. 2009;12:224–239.
- Sauk S, Zuckerman DA. Renal artery embolization. Semin Intervent Radiol. 2011;28(4):396–406.
- Schwartz MJ, Smith EB, Trost DW, Vaughan ED Jr. Renal artery embolization: clinical indications and experience from over 100 cases. BJU Int. 2007;99(4):881–886.
- Jain S, et al. Renal angiomyolipoma embolization: a systematic review. Cardiovasc Intervent Radiol. 2018;41(10):1485–1498.
- Somani BK, Nabi G, Thorpe P, et al. Image-guided biopsy-diagnosed renal cell carcinoma: critical appraisal of technique and long-term follow-up. Eur Urol. 2007;51(5):1218–1228.