Introduction
Assessment of renal arterial anatomy and interventions for improvement of arterial flow, revascularization and embolization. Localize renovascular cause of hypertension.

Indications
  • Hypertension of unknown cause, requiring antihypertensive medications and/or elevated creatinine.
  • Progressive atrophy of kidney.
  • Renal artery thrombosis.
  • Hematuria.
  • Renal trauma.
  • Vasculitis.

Contraindication
  • Advanced renal disease, limited renal function.
  • Creatinine >3-4 mg/dL.
  • Severe bleeding diathesis.
  • If possible, delay intervention in infants <10 kg in weight.

Pre-Procedure
Clinical Evaluation:
  • Peri and post-procedural management of anti-hypertensive medications should be coordinated with nephrology.
  • Arrange for post-procedural admission if angioplasty is considered.

​Imaging:
  • Baseline Doppler ultrasound of the kidneys for all patients.​ ​
Picture
14 year old girl admitted with hypertensive urgency. Spectral Doppler traces from the main renal arteries demonstrate markedly elevated PSV in the proximal left MRA
Picture
Left arcuate artery Doppler demonstrates decreased resistive index and a parvus tardus waveform.

 
  • Cross sectional imaging, CTA preferred to determine:
    1. Number of renal arteries.
    2. Location, length, and degree of stenosis.
    3. Associated disease of the aorta, celiac axis and SMA.
Picture
CTA reformat of left renal artery.
  • Consider MRI for patients with renal impairment.
    • MAG3 may be useful in determining relative function of the kidneys.
    • MRI brain if there is history of neurofibromatosis or possibility of rapid decrease in BP post procedure​.

Labs
  • CBC
  • BUN, Creatinine, Electrolytes
  • Coags (PT, INR, PTT)
  • Type and Screen (cross match for angioplasty)

Technique
Protocol
  • Patient positioning and planned approach
  • Level of anesthesia desired (request paralysis)
  • Determine size of angioplasty balloons
  • Determine what catheter and sheath size is required for selected angioplasty balloons

Procedure
  • Consent for angiography, angioplasty, possible stent placement and embolization. Renin sampling if indicated.
  • Access: Femoral artery is the standard. Brachial may be indicated in older children with severe angulation of the renal arteries.
  • Anticoagulation: If angioplasty is planned, administer 75-100 u/kg prior to dilation.
  • Sheath: If diagnostic angiography only, 4F Pinnacle. If considering angioplasty, this may be determined by balloons to be used. Consider 5/6Flong sheaths(e.g. 6F Balkin, 30-45 cm, 5/6F Flexor Ansel, 45-55 cm).
  • Contrast dose limit: 6 ml/kg of Optiray 300, preferably closer to 3 ml/kg if evidence of decreased renal function. Consider biplane DSA in smaller children to conserve contrast dose.

Angiography
  • Abdominal aortogram: 
Picture
Aortogram demonstrates normal appearance of the aorta and right renal artery and confirms stenosis on the left.
  • Multi-sidehole, calibrated flush catheter (4 or 5 Fr Sos Omniflush pigtailcatheters) placed below the level of the SMA.
  • Contrast volume/rate: 1-1.5ml/kg injected over 2 seconds. For most older children 20 ml of Optiray 300 at 10 ml/sec should suffice. For adults and larger children this can be increased to 30 ml at 15 ml/sec.
  • DSA at 4 frames/sec for 4 seconds and 1/s after.
  • Paralysis with apnea during DSA.
  • Administer glucagon (10 ug/kg) to decrease artifacts from movement of bowel. Consider re-dosing as needed.
​​
Selective renal angiography
4 or 5F catheters (Cobra or reversed curve).
Picture
Selective left renal arteriogram shows stenosis of the mid renal artery, with a beaded appearance suggestive of fibromuscular dysplasia.
  • At least one frontal and two oblique projections coned to the kidney area.
  • Pre-procedure cross sectional imaging can be used to the calculate the best angle of obliquity to demonstrate ostium and area of stenosis.
  • At least one projection should demonstrate reflux of contrast into the aorta.
  • Assess parenchymal and venous phase on frontal projection.
  • Selective arteriography of all accessory renal arteries should be performed.

Angioplasty
Picture
Post angioplasty arteriogram demonstrates resolution of renal artery stenosis.
Picture
Angioplasty of the left renal artery.

 If bilateral disease, consider staging. Re-evaluate during the procedure following angioplasty of first kidney.
  • An angled guiding sheath (5/6F) is preferred and advanced to near the ostium of the artery to be treated.
  • Pressure measurement can be performed with the use of a microcatheter or pressure guidewire (Verrata guidewire, Philips Volcano system). A pressure gradient of 9 mm Hg or more is significant.
  • If available, IVUS can be used for further assessment of stenosis.
  • Advance a microguidewire (0.014” Stabilizer) and exchange the diagnostic catheter for the angioplasty balloons. The microguidewire should remain across the stenosis until angioplasty has been completed.
  • For most children, balloons are 2-6 mm in diameter.
  • Emerge (Boston Scientific) available in 1.2-4 mm diameter, 8-30 mm in length. OTW balloon requires 0.066” inner diameter guiding catheter.
  • Mustang (Boston Scientific) available in 3 mm or greater in diameter, minimum 20 mm in length, 0.035” guidewire system, 5F sheath, shorter shaft length, higher burst pressure.
  • Crosstella (Terumo),  2-6 mm, 5F sheath.
  • Oversize conventional balloons up to 1 mm greater than normal arterial diameter (do not measure area of post-stenotic dilation).
  • Cutting balloons (Flextome–Boston Scientific).Do not oversize cutting balloons.
  • ​Consider direct catheter injection nitroglycerine if evidence of spasm (1ug/kg aliquots).

Renal Artery Stenting
  • Discouraged in children due to expected growth of renal arteries and long life expectancy.
  • Most common indication is renal artery trauma / rupture.
  • Keep appropriately size stent in room when performing angioplasty.
  • Stent should be oversized to 20% greater than the normal renal artery diameter.
  • Balloon mounted stents (Atrium Advanta V12 (min diameter 5 mm) [Getinge], Express SD [Boston Scientific], Formula [Cook])

​Renal Vein Renin Sampling
  • Femoral or internal jugular vein access. 4F sheath.
  • 4F Kumpe, Cobra catheter. May require use of a microcatheter in smaller patients (larger inner diameter e.g. Renegade Hi-Flow or STC).
  • Sampling of main renal veins and segmental renal veins. Samples also taken from infra-renal (+/-supra-renal IVC).
  • 2-3 samples are collected from each location listed below using simple curved or reversed curved catheters (e.g 5 Fr Cobra). For selective renal vein branches, a large microcatheter (e.g. Renegade HF) may be needed. Discard the first1-2 ml of aspirated from catheter (dead space).
  • Interpretation (overall the test is sensitive, but not specific, and may not be accurate with bilateral disease):
    • Renin Ipsilateral/contralateral Ratio> 1.5 (=Renin hypersecretion).
    • Renin contralateral/ infrarenal IVC. Ratio < 1.3 (=Renin suppression).
  • Specimen handling details contained in tech manual.

Sheath Removal
  • If heparin administered within 1 hour, check ACT. Remove sheath if ACT <180.
  • Manual compression for 15 minutes.
  • Check ultrasound of puncture site following compression to document hemostasis, hematoma, patency of artery.
  • Place Safeguard (inflated to suggested volume (40 ml, 7 ml)). Deflate at 2hours and re-inflate if persistent oozing.
​

Complications
Thrombosis
  • Occlusion more commonly due to dissection, see above.
  • Alteplase 0.1 mg/kg site directed bolus dose.
  • Nitroglycerine 1-2 ug/kg.
​
Dissection
  • If flow limiting, ensure guidewire stays across the stenosis, inflate angioplasty balloon, therapeutic anticoagulation. If flow restored, patient remains on therapeutic anticoagulation overnight (ICU monitoring usually required).
  • If flow cannot be restored, contact vascular surgeon. 

Perforation/Rupture
  • Immediately re-inflate angioplasty balloon.
  • Consult vascular surgeon, consider stenting. 

​Contrast Induced Nephropathy
  • Assess urine output.
  • Renal function tests at 24, 48 and 72 hours.
  • Coordinate with nephrology.​ ​

Post-Procedure
  • Transfer to PACU for recovery.
  • Deflate Safeguard at 2 hours and re-inflate if persistent oozing.
  • Older children with diagnostic angiogram alone can be discharged in 2-4 hours.
  • Younger children and patients undergoing angioplasty admitted overnight to nephrology or ICP. ICU admission may be required for cutting balloons /complications. Monitor BP overnight, ultrasound prior to discharge the next day.
  • Consider prophylactic heparin infusion (10u/kg/hr)/ LMWH heparin post-angioplasty(0.5 mg/kg bid, max 40 mg).
  • Discharge on Clopidogrel bisulfate (75-mg loading dose, then37.5 mg daily). or aspirin (81 mg daily) for 1 month.

Follow-up
  • Follow-up with nephrology in 1 month.
  • Repeat ultrasound at 4 weeks and 6 months’ post-procedure.

References
  1. Donaldson, JS. Renal Arteriography and Interventions. M. Temple and F.E.Marshalleck (eds.), Pediatric Interventional Radiology: Handbook of Vascularand Non-Vascular Interventions, DOI 10.1007/978-1-4419-5856-3_5
  2. McLaren CA, Roebuck DJ. Interventional radiology for renovascular hypertension in children. Tech Vasc Interv Radiol. 2003;6:150–7
  3. Kari JA, Roebuck DJ, McLaren CA, Davis M, Dillon MJ, Hamilton G, Shroff R,Marks SD, Tullus K. Angioplasty for renovascular hypertension in 78 children. Arch Dis Child. 2015 May;100(5):474-8. doi: 10.1136/archdischild-2013-305886. Epub 2014 Dec 19. PMID: 25527520
  4. Meyers KE, Cahill AM, Sethna C. Interventions for pediatric renovascular hypertension. Curr Hypertens Rep.2014 Apr;16(4):422. doi:10.1007/s11906-014-0422-3. PMID: 24522941
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