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 extrarenal (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 extraparenchymal 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: Not Good Enough! Specificity = 70% 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