US of Renovascular Hypertension

Jonathan R. Dillman, MD, MSc Associate Professor Director, Thoracoabdominal Imaging Disclosures

• Nothing Relevant • Unrelated grant funding • Siemens US • Toshiba US Objectives

1. Renovascular hypertension – background, causes & complications 2. Renal Doppler US approaches – direct vs. indirect 3. Does it work? (i.e., the literature) 4. Role of US? Pediatric Hypertension

• Most often primary (essential) >6 years-old • Multiple secondary, treatable causes • Renovascular (renin-mediated) = 5-10% • Suprarenal aortic narrowing • Renal artery stenosis

Tullus K, et al. Lancet 2008 Gomes RS, et al. Pediatr Nephrol 2011 Renovascular Hypertension

Castelli P, et al. AJR 2013 Renovascular Hypertension

• Clinically suspected when hypertension severe or refractory to multiple drugs • Untreated  Complications: • Hypertensive encephalopathy/stroke • Left ventricular hypertrophy/diastolic dysfunction • “-opathies” – kidney, retina • Detection allows: • Endovascular or surgical cure • Fewer complications • Less intense medical therapy

Causes of Aortic & Renal Artery Narrowing

• Developmental non-inflammatory arteriopathy: • Idiopathic/fibromuscular dysplasia • Complex medial/peri-medial dysplasia with intimal fibroplasia • NF1 • Williams syndrome • Tuberous sclerosis • Congenital aortic coarctation/interruption (thoracic or abdominal) • Inflammatory arteritis (including radiation-induced) • Catheter-related thromboembolic disease • Extrinsic compression Imaging of Renovascular Hypertension – Why (or why not) US? • Advantages: –Lack of ionizing radiation exposure –Low cost –Widespread availability • Disadvantages: –Operator dependent – requires operator experience/skill –Small/accessory/intra-renal arteries challenging to assess –Suboptimal diagnostic performance? Renal Doppler US Technique

• Renal Doppler US exam • Standard gray-scale imaging • Color Doppler • Main renal artery • Spectral Doppler • Main renal artery • Intra-renal spectral Doppler • How many samples from each kidney? • Upper, mid and lower?

Gray-Scale US

• What to look for… • Morphologically abnormal kidneys • Focal scarring • Dysplasia/hypoplasia • Retroperitoneal masses • Adrenal • Pheochromocytoma • Neuroblastoma • Adrenocortical neoplasm • Renal (Wilms, RCC, others)

Doppler US

• What to look for… • Abnormal spectral Doppler waveforms • Parvus et tardus • Parvus = weak/small • Tardus = delayed/late • Delayed acceleration • Low resistive index • Abnormal Doppler velocities • Peak systolic velocity (PSV) • Renal – Aorta Ratio (RAR) • Renal – Intrarenal Ratio (RIR) Doppler US – Abnormal Waveforms

• Assess distal to stenosis • Acceleration time • Time from onset of systole to PSV • Abnormal >0.07 sec • Resistive index • Compares peak systolic and end diastolic velocities • = (PSV-EDV)/PSV • Abnormal <0.5 Granata A, et al. J Ultrasound 2009 Abnormal Waveforms – How Good is Visual Assessment?

“Loss of ESP enabled identification of RAS with 95% sensitivity, 97% specificity, a 92% positive predictive value, a 98% negative predictive value, and 96% overall accuracy”

*ESP = early systolic compliance peak/ reflective-wave complex

Stavros A, et al. Radiology 1992 It’s Not Just Tardus… RI Matters Doppler US – Abnormal Velocities

• Interrogate length of main renal artery • Peak systolic velocity (PSV) • Abnormal >150-200 cm/s • Main renal artery PSV normalized to aortic PSV • Renal-Aorta Ratio (RAR) • Abnormal >3-3.5 • Main renal artery PSV normalized to intra-renal PSV • Renal-Intrarenal Ratio (RIR) • Abnormal >5 (50% stenosis in adults) • Sensitivity = 88%; specificity = 88% Li JC, et al. J Ultrasound Med 2006 Doppler US – Direct vs. Indirect Assessment • Direct: interrogate main renal artery with color/spectral Doppler • Challenging! • Intra-renal stenosis, >1 renal artery? • Indirect: interrogate intra-renal arteries with spectral Doppler • Abnormal wave waveform and/or low RI = proximal narrowing? • Aorta, main renal artery, or intra-renal • KEY POINT: if ABNORMAL, sample more proximal (main renal arteries & suprarenal aorta)

Doppler US

12 year-old boy with incidentally detected HTN in ED Doppler US

Teenage girl with newly diagnosed hypertension Don’t Forget…

• Causes of renal arterial narrowing in children are generally different from adults • Atherosclerotic disease RARE in children • Pediatric narrowings OFTEN syndromic • Thus: • Adults = usually central • Children = central, peripheral, or both • Multifocal, bilateral? Syndromic – Does it Matter?

• Including syndromes: • Stanley, et al. 2006 (n=97) • Aorta/main renal artery > segmental extra- renal (n=18) > segmental intra-renal (n=2) • Excluding syndromes: • Vo, et al. 2006 (n=21) • 15 intra-renal segmental lesions • 6 main & 3 accessory lesions

Stanley JC, et al. J Vasc Surg 2006 Vo NJ, et al. Pediatr Radiol 2006 So, Does it Work in Kids?

• Chhadia, et al. (2013): • 62 children (124 kidneys) • Renal Doppler ultrasound and catheter angiography in ALL • PSV >180 cm/sec, accel time >70 msec, parvus et tardus • Sensitivity = 65% (detected 11/17 lesions, 4 misses segmental) • Specificity = 94% • Reasonable specificity, BUT sensitivity not good enough!

Chhadia S, et al. Pediatr Radiol 2013 Does it Work in Kids?

• Trautmann, et al. (2016): • 99 children with renal artery stenosis • 36 unilateral major extra- parenchymal stenosis • 47 bilateral stenosis • 16 intrarenal small vessel disease • US sensitivity = 63% • US specificity = 95%

Trautmann S, et al. Pediatr Nephrol 2016 Does it Work in Kids?

• Castelli, et al. (2014): • 48 patients with confirmatory testing (CTA, MRA, angiography) • Overall diagnostic performance: • Sensitivity = 90% • Specificity = 68% • Patients with catheter angiography & renal artery stenosis (n=23): • Sensitivity = 75% Conclusion:• Specificity = 70% Not Good Enough! • Best performance if: • Older, aortic or main renal artery narrowing

Castelli PK, et al. Pediatr Radiol 2014 The Problem (Challenge)

RK = 8.8 cm LK = 8.6 cm

10 yo boy with refractory hypertension, normal CTA The Problem (Challenge)

Upper, RI = 0.6 Mid, RI = 0.63 Lower, RI = 0.47

Left kidney Doppler US The Problem (Challenge)

RI = 0.47 RI = 0.49

Additional left lower pole images The Problem (Challenge)

Outside Hospital CTA The Problem (Challenge)

Catheter Angiogram The Problem – Another Example

11 yo boy with refractory hypertension Role of Renal Doppler US?

• Appropriate initial test in children (adds value) • May direct further work-up • e.g., CTA/MRA of aorta • May provide alternative diagnosis • Retroperitoneal mass • Unsuspected renal parenchymal abnormality Final Take-Aways

• Generally, CANNOT STOP with US • Positive US – almost certainly need more aortic or renal artery imaging • CTA/MRA for aortic narrowings • Catheter angiography for renal artery lesions (bilateral, multifocal, intrarenal disease?) • Negative US – almost certainly need more imaging if suspicion moderate/high