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Indications & Contraindications
Patient selection, AAST grading, hemodynamic criteria
Indications
- Blunt / penetrating renal injury — AAST grade III–V with arterial extravasation on CTA
- Pseudoaneurysm (PSA) — traumatic or iatrogenic renal artery PSA with risk of delayed rupture
- Arteriovenous fistula (AVF) — post-traumatic or post-biopsy renal AVF with hematuria or high-output state
- Persistent gross hematuria with hemodynamic compromise or falling hemoglobin
- Post-biopsy hemorrhage — subcapsular hematoma with active extravasation or expanding hematoma
- Post-surgical renal bleeding — after partial nephrectomy, PCNL, or nephrostomy placement
Contraindications
- Hemodynamic instability requiring nephrectomy — patient too unstable for angiographic approach; proceed to OR
- Main renal artery avulsion — grade V pedicle injury; surgical management indicated
- Relative: solitary kidney (weigh risk of renal function loss vs hemorrhage control)
- Relative: severe contrast allergy without premedication
- Relative: uncorrectable coagulopathy (may still proceed in life-threatening hemorrhage)
AAST Renal Injury Grading (2018 Revision)
| Grade | CT Findings | Embolization Role |
|---|---|---|
| I | Subcapsular hematoma / contusion without laceration | Observation; embolization rarely needed |
| II | Perirenal hematoma confined to Gerota’s fascia; laceration ≤1 cm | Observation; embolization if active extravasation |
| III | Laceration >1 cm without collecting system rupture; vascular injury or active bleed within Gerota’s | Embolization indicated for active hemorrhage |
| IV | Laceration into collecting system; segmental vessel injury; active bleed beyond Gerota’s | Primary role for embolization; coordinate with urology |
| V | Main renal artery/vein laceration or avulsion; shattered kidney | Embolization if hemodynamically stable; surgical if unstable or complete avulsion |
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Pre-Procedure Planning
CTA review, labs, team communication
Imaging Review
- CTA abdomen — arterial phase: identify site of active extravasation, pseudoaneurysm, or AVF; map renal arterial anatomy including accessory arteries
- CTA — delayed phase (5–10 min): critical for detecting collecting system injury and urinoma; collecting system injury is NOT fixed by embolization
- Classify injury using AAST renal injury grading scale (Grades I–V)
- Assess for concomitant injuries — blunt renal trauma often coexists with other abdominal injuries (~24% of intra-abdominal trauma involves kidneys)
- Identify number of renal arteries — accessory renal arteries present in 25–30% of patients
Labs & Coordination
- Creatinine (baseline) — critical if potential renal function loss; document pre-procedure value
- CBC (hemoglobin trend), PT/INR, platelets, type & screen
- Hematuria assessment — gross vs microscopic; trending urine output
- Communication: direct contact with urology and/or trauma surgery before proceeding
- Blood products available — PRBC on standby; massive transfusion protocol if hemodynamically unstable
CTA reviewed (arterial + delayed phases). Site of hemorrhage identified; AAST grade assigned; accessory renal arteries noted; collecting system injury assessed.
Baseline creatinine documented. Essential for post-procedure monitoring of renal function decline.
Urology / trauma surgery notified. Collaborative plan established; surgical backup available if embolization fails or hemodynamic instability worsens.
Blood products available. Type & screen completed; PRBCs on standby.
Consent obtained. Key risks discussed: renal infarction (expected with segmental embolization), hypertension (Page kidney), renal function decline, need for repeat procedure, nephrectomy as salvage.
Access site planned. CFA access confirmed; sheath size determined (typically 5–6F).
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Relevant Anatomy
Renal arterial supply, segmental branches, variants
Renal Arterial Anatomy
- Renal arteries arise from the abdominal aorta at L1–L2 level, below the SMA origin
- Each renal artery divides into anterior and posterior divisions
- Anterior division supplies: upper, middle, and lower anterior segments
- Posterior division supplies: posterior segment (Brodel’s avascular line at junction)
- Segmental arteries further branch into interlobar → arcuate → interlobular arteries
- Eight anatomical variants of renal arterial branching patterns have been described (Sampaio & Passos cadaveric study)
Critical Vascular Concepts
- Segmental branches are END-ARTERIES — no collateral supply; occlusion causes segmental infarction
- Accessory renal arteries present in 25–30% of patients — arise directly from the aorta; must be identified on CTA and interrogated at angiography
- Right renal artery passes posterior to IVC
- Left renal vein crosses anterior to aorta (nutcracker position)
- Kidneys are retroperitoneal, protected by Gerota’s fascia and perinephric fat
- Ureteropelvic junction and renal pedicle are the main attachment points — deceleration injuries can injure these structures
Collecting System Relationship
The renal collecting system (calyces, renal pelvis, UPJ) is closely related to the segmental arterial branches. Lacerations extending into the collecting system (AAST Grade IV) cause urinary extravasation visible on delayed-phase CTA. Collecting system injuries require urologic management (ureteral stent, nephrostomy) and are NOT addressed by arterial embolization. Always review delayed-phase imaging to identify urinomas, which may require separate percutaneous drainage.
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Technique
Endovascular approach, catheter selection, embolic agents
Access & Catheters
- Common femoral artery (CFA) access — micropuncture set
- 5F or 6F vascular sheath
- 5F renal curve catheter (e.g., C2, SOS Omni, Cobra) for main renal artery selection
- Microcatheter (2.4–2.8F) for superselective catheterization of segmental/interlobar branches
- 0.035” guidewire (Bentson, Glidewire) for initial selection
- 0.018” or 0.014” microwire for distal navigation
Embolic Agents
- Coils (microcoils) — first-line for focal PSA, AVF, or discrete segmental artery injury; permanent occlusion
- Gelfoam (gelatin sponge) — preferred for diffuse parenchymal bleeding; temporary (~2–4 weeks); allows potential reperfusion
- Particles — alternative for distal parenchymal bleeding; use with caution (risk of nontarget embolization)
- Stent grafts — for large vessel injury (main renal artery or large branch preservation)
Medications
- Heparinized saline flush
- Conscious sedation (midazolam + fentanyl) or MAC per anesthesia
- Nitroglycerin 100–200 mcg IA — for catheter-induced vasospasm
- Antibiotics per institutional trauma protocol
- IV contrast (iso-osmolar preferred if renal function borderline)
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Arterial Access
Common femoral artery access via micropuncture technique. Place 5F or 6F vascular sheath. In polytrauma patients, some institutions place an arterial sheath during the initial trauma survey to expedite IR access.
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Aortogram (if needed)
Flush aortogram at renal level if CTA not available or anatomy unclear. Identify renal artery origins, number of renal arteries (including accessory arteries), and level of injury.
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Selective Renal Artery Catheterization
Advance 5F renal curve catheter (C2, SOS Omni, or Cobra) into the main renal artery. Perform selective renal arteriogram to identify: active extravasation, pseudoaneurysm, AV fistula, or vessel irregularity/truncation. Correlate with CTA findings.
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Superselective Microcatheter Advancement
Coaxially advance microcatheter (2.4–2.8F) into the injured segmental or interlobar artery as distally as possible. Goal: catheterize the most distal vessel feeding the injury to preserve maximum nephrons. The availability of microcatheters with inner diameters from 0.018” to 0.010” enables superselective access throughout the renal arterial tree.
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Embolization
Focal PSA / AVF: deploy microcoils across the neck of the pseudoaneurysm or within the feeding artery of the fistula. — Parenchymal bleeding: inject Gelfoam pledgets ("torpedoes") or slurry into the feeding segmental branch. Gelfoam provides temporary occlusion (~2–4 weeks), often sufficient for vessel wall healing. — Multiple bleeding sites: systematically address each focus with superselective catheterization.
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Completion Angiogram
Perform post-embolization selective renal arteriogram to confirm: cessation of extravasation, occlusion of PSA/AVF, and preserved flow to non-injured segments. Check for additional bleeding sources not seen on initial run.
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Check Accessory Renal Arteries
If pre-procedure CTA showed accessory renal arteries, or if hemorrhage persists despite embolization, catheterize and image all accessory renal arteries. These arise directly from the aorta and can be a source of occult continued bleeding.
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Access Site Management
Remove sheath and achieve hemostasis. Manual compression or closure device per institutional protocol. Document access site status. Transfer patient to ICU or trauma bay for continued monitoring.
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Landmarks & Correlation
Aortographic landmarks, CTA-angiographic correlation
Aortographic Landmarks
- Renal artery origin: typically at L1–L2, just below the SMA
- Right renal artery: slightly more inferior origin, longer course, passes behind IVC
- Left renal artery: slightly more superior, shorter course to hilum
- Accessory renal arteries: look for additional small vessels arising from the aorta at or below the main renal artery level, especially to the lower poles
- Segmental branch pattern: anterior/posterior division visible on selective injection
CTA–Angiographic Correlation
- Match CTA site of extravasation to angiographic bleeding source — use renal poles and segmental anatomy as reference
- PSA on CTA appears as focal contrast collection persisting on delayed images — correlate with angiographic "blush"
- AVF on CTA: early venous opacification — on angiogram appears as rapid flow with early draining renal vein filling
- Devascularized parenchyma on CTA (nonenhancing segments) indicates existing segmental injury — these areas will not bleed
- Delayed CTA phase: collecting system extravasation appears as contrast outside the expected course of calyces/pelvis/ureter
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Troubleshooting
Intraoperative problems and solutions
Multiple Bleeding Sites
More Than One Focus of Active Extravasation on Angiography
Systematically catheterize and embolize each bleeding source individually. Start with the most brisk extravasation. Use road-mapping from the selective renal arteriogram to guide microcatheter placement. In one study, more than two bleeding sites was a risk factor for failure of initial embolization. Consider using Gelfoam for diffuse bleeding and coils for focal sources. Re-image after each embolization to reassess.
Accessory Renal Arteries
Persistent Hemorrhage Despite Embolization of Main Renal Artery Branches
Accessory renal arteries (present in 25–30%) are a common source of occult continued bleeding. Perform aortogram at the renal level to identify accessory vessels. Selectively catheterize and angiogram each accessory artery. These most commonly supply the lower pole and arise from the infrarenal aorta.
Vasospasm
Segmental Artery Vasospasm Mimicking Vessel Injury
Catheter-induced vasospasm can cause vessel narrowing that mimics traumatic injury or dissection. Administer nitroglycerin 100–200 mcg intra-arterially through the catheter and wait 2–3 minutes. Repeat angiogram to distinguish spasm (resolves) from true injury (persists). Avoid unnecessary embolization of spastic but uninjured vessels.
Persistent Hematuria Post-Embolization
Ongoing Gross Hematuria After Successful Angiographic Hemostasis
If angiographic hemorrhage is controlled but hematuria persists, consider: (1) collecting system injury — lacerations extending into calyces/renal pelvis will cause hematuria that is NOT fixed by embolization; review delayed-phase CTA for urinoma; urology consultation for ureteral stent or nephrostomy. (2) Bladder clot retention — may require catheter irrigation. (3) Bleeding from a different source (contralateral kidney, bladder).
Failed Initial Embolization
Recurrent Hemorrhage After Embolization (≤16.5% Failure Rate)
Risk factors for failure: multiple percutaneous access sites, >2 bleeding foci, use of Gelfoam alone. Repeat angiography and re-embolize with more durable agents (coils instead of Gelfoam alone). If repeat embolization fails, escalate to surgical consultation for nephrectomy or surgical hemostasis.
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Complications
Expected outcomes and adverse events
Expected / Common
- Renal infarction (expected) — segmental branches are end-arteries; any embolization will cause infarction of the territory supplied; superselective technique minimizes parenchymal loss
- Post-embolization pain — flank pain from segmental infarction; usually self-limited; manage with analgesics
- Post-embolization syndrome — low-grade fever, pain, leukocytosis; supportive care
- Renal function decline — depends on volume of parenchyma sacrificed; monitor creatinine daily; more significant in patients with pre-existing CKD or solitary kidney
Serious Complications
- Hypertension (Page kidney) — subcapsular or perinephric hematoma compresses renal parenchyma, activating renin-angiotensin system; can present weeks to months after injury; monitor BP at follow-up
- Renal abscess — infarcted tissue susceptible to infection; fever and worsening flank pain; may require percutaneous drainage
- Persistent or recurrent hematuria — incomplete embolization or collecting system injury; may need repeat intervention or ureteral stent
- Nontarget embolization — coil migration or particle reflux to uninjured segments; ectopic coil placement reported
- Renal artery dissection — catheter-induced intimal injury during selective catheterization
- Nephrectomy — salvage surgery for uncontrolled hemorrhage or nontarget main renal artery embolization
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Pearls & Pitfalls
High-yield clinical tips and common mistakes
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End-arteries = any embolization causes infarction. Segmental renal arteries have no collateral supply. Every coil or Gelfoam pledget sacrifices parenchyma. Superselective catheterization as distally as possible is the key to nephron-sparing embolization.
✦
Always check for accessory renal arteries. Present in 25–30% of patients. If you do not look for them, you will miss a bleeding source. Perform an aortogram at renal level if any suspicion.
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Delayed-phase CTA shows collecting system injuries. Urinoma and calyceal disruption are visible only on delayed imaging (5–10 min post-contrast). These injuries require urologic management (stent, nephrostomy) — embolization addresses vascular injury only.
✦
Page kidney can cause hypertension months later. Subcapsular or perinephric hematoma compresses the renal parenchyma, activating the renin-angiotensin system.
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Main renal artery embolization = nephrectomy equivalent. This is a last resort. Complete devascularization of the kidney should only be performed when superselective embolization has failed and hemorrhage is life-threatening.
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Gelfoam allows potential reperfusion. For parenchymal bleeding without a discrete PSA, Gelfoam provides temporary occlusion (~2–4 weeks) while the vessel wall heals. This is frequently sufficient and may preserve more long-term perfusion than permanent agents.
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Do not confuse vasospasm for vessel injury. Catheter-induced spasm narrows segmental arteries and can mimic traumatic dissection. Always use IA nitroglycerin to differentiate before embolizing.
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Persistent hematuria after successful embolization does not always mean re-bleeding. Collecting system injury is the most common non-vascular cause. Do not reflexively re-embolize — review delayed imaging and consult urology.
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Solitary kidney or baseline CKD changes the risk calculus. Maximally superselective technique is even more critical. Discuss with nephrology pre-procedure. Consider CO2 angiography to reduce contrast load if renal function is marginal.
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References & Resources
Primary sources and related procedures
Embolic Agent Selection Summary
- Coils: focal PSA, AVF, discrete segmental artery injury — permanent occlusion
- Gelfoam: diffuse parenchymal hemorrhage — temporary occlusion allowing reperfusion
- Particles: distal parenchymal bleeding — use cautiously (nontarget risk)
- Stent graft: main renal artery or large branch preservation when vessel patency needed
Primary References
- Lopez-Gonzalez DB, Zurkiya O. Interventional radiology in renal trauma. Semin Intervent Radiol. 2021;38(1):113–122. DOI: 10.1055/s-0041-1726006
- Voelzke BB, Leddy L. The epidemiology of renal trauma. Nat Rev Urol. 2014.
- Sampaio FJ, Passos MA. Renal artery: anatomic study for surgical and radiological practice. Surg Radiol Anat. 1992;14(2):113–117.
- Kozar RA, Crandall M, Shanmuganathan K, et al. Organ injury scaling 2018 update: revision of the AAST organ injury scale. J Trauma Acute Care Surg. 2018;85(6):1119–1122.
- Page IH. The production of persistent arterial hypertension by cellophane perinephritis. JAMA. 1939;113(23):2046–2048.