Role of color doppler ultrasound in rvhtn
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Renal Color Doppler Ultrasound. After studying this presentation one will be able to perform and interpret ultrasound. This presntation in my opinion is best short analog to text.
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Role of color doppler ultrasound in rvhtn
- 1. Role of Color Doppler Ultrasound in Renovascular Hypertension Dr. Muhammad Bin Zulfiqar Alnoor Diagnostic Centre
- 2. Agenda • Introduction of renovascular hypertension • Normal Anatomy – Kidney – Renal Arteries • Parenchymal Echogenicity grades • Basic Technique of Renal Doppler • Normal Renal Artery Doppler • Doppler in Renovascular Hypertension
- 3. Definition • Secondary elevation of blood pressure produced by variety of conditions interfering with arterial circulation of kidney tissue causing renal tissue ischemia
- 4. Renovascular Hypertension • Most common secondary form of hypertension • Not easily recognizable clinically • Significant renal artery disease (> 60 % stenosis) has been found in 7 % of population Braunwald heart disease 7th ed.page 977
- 5. Misconception • Renal artery stenosis always cause hypertension • Revascularization always reverse or improve hypertension as hypertension my be comorbid with renal artery stenosis • Renovascular hypertension means atheromatous or fibromuscular disease
- 6. Normal anatomy of the kidney Paspulati RM et al. Ultrasound Clin 2006 ; 1 : 25 – 41. Renal parenchyma: cortex & medullary pyramids Renal sinus: arteries, veins, lymphatics, collecting system, & fat Renal hilum: Concave, in continuity with renal sinus
- 7. Anatomy of renal arteries RRA: Usually passes posterior to inferior vena cava LRA: Usually courses posterior to left renal vein Multiple renal arteries in 25% (inferior polar artery from aorta)
- 8. Arterial blood supply to the Kidney Myers KA & Clough A. Making sense of vascular ultrasound. Arnold, London, 2004. Segmental artery Apical, upper, middle, lower, posterior Interlobular artery Between renal pyramids Glomerular arteriole Main renal artery Arcuate artery Between cortex & medulla
- 9. Classification of renal parenchymal echogenicity 4 types based of US appearance Hypoechoic compared to liver Isoechoic compared to liver Hyperechoic compared to liver Isoechoic to renal sinus Normal Normal Pathological Pathological Grade 0 Grade I Grade II Grade III
- 10. Kidney parenchyma compared to liver parenchyma Hypoechoic Isoechoic Hyperechoic Fiorini F et al. J Ultrasound 2007 ; 10 : 161 – 167.
- 11. Abdominal aorta • Normal abdominal aorta 1.5 – 2.5 cm • Ectatic aorta 2.5 – 3 cm • Aortic aneurysm > 3 cm • Annual growth of aneurysms 0.33 cm/year between 4 & 5.5 cm * Bhatt S et al. Ultrasound Clin 2008 ; 3 : 83 – 91.
- 12. Technical points • Fasting for at least 6 hours before the exam • Duration of the examination: 30 – 45 min • Rare failure: Non-cooperative patient – Gas • Intestinal preparation: not necessary • Operator-dependent technique • Slow learning curve • Most complex & difficult Doppler examination
- 13. Sites for pulsed Doppler of renal arteries Aorta Ostium of main renal artery Trunk of main renal artery Hilum of kidney Upper pole of kidney Middle pole of kidney Lower pole of kidney
- 14. Norma right renal artery Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. Transverse gray scale image Right main renal artery Transverse color Doppler image Right main renal artery
- 15. Norma left renal artery Gray scale image Color Doppler image Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. Proximal main left renal artery Proximal main left renal artery
- 16. ‘‘banana peel’’ or “Isikoff” view Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. Isikoff MB et al. Am J Roentgenol 1980 ; 134 : 1177 – 1179. Origins of right & left renal arteries Gray scale image Origins of right & left renal arteries Color Doppler image Longitudinal transhepatic view in Left lateral decubitus
- 17. Normal right renal artery Coronal images of IVC Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. RRA is the only vessel to course laterally under the IVC Often slightly indents the IVC
- 18. Limits in visualization of main renal arteries • Obesity • Overlying bowel gas • Dyspnea • Shadowing from arterial calcifications • Cardiac arrhythmias • Poor angle of Doppler insonation • Accessory renal arteries (small size) Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. Expert sonographers detect 80 – 90% of main RA CEUS improves success rate to 95%
- 19. Normal segmental & interlobar renal arteries Normal segmental renal arteries (long arrows) Color Doppler image of the kidney Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. Normal inter-lobar renal arteries (short arrows)
- 20. Pourcelot’s resistive index RI S – ED / S Normal 50 – 70 % Abnormal > 80 %
- 21. Accleration time (AT) or Rise time (RT) • Length of time in sec from onset of systole to peak systole • Normal value: < 0.07 second
- 22. Spectral Doppler of renal arteries Normal values • PSV < 180 cm/sec • Renal Aortic Ratio (RAR) < 3 • Resistive index (RI) < 0.70 • ∆ RI (right – left) < 0.05 • Acceleration Time (AT) < 0.07 sec
- 23. Normal pulse Doppler waveform Renal segmental artery Sharp systolic upstroke Low resistance waveform Continuous forward diastolic flow
- 24. Indications of renal Doppler ultrasound • Renal artery stenosis • Renal artery thrombosis & emboli • Renal vein thrombosis • Aneurysm & pseudo-aneurysm • Arterio-venous communications • Nutcracker syndrome • Renal mass • Miscellaneous indications
- 25. Renal artery stenosis 1 – 5% of hypertensive population • Atherosclerosis • Fibromuscular dysplasia (FMD) • Dissection • Embolization • Aortic coarctation • Renal Artery Aneurysm • Arteritis • Congenital • Neurofibromatosis • Irradiation > 95 % of cases
- 26. Renal artery stenosis Atherosclerosis > 90% FMD < 10% Age After age of 50 Young Gender More common in males More common in females Location Proximal 1 cm of main RA Branching points Middle of renal artery Others (carotids) Post-stenotic dilatation Rare Frequent
- 27. Clinical risk factors for Renovascular HTN • Abrupt onset of severe HTN: diastolic >120 mm Hg • Accelerated or malignant HTN: grade III or IV retinopathy • HTN refractory to appropriate three-drug regimen • Onset of hypertension before age 30 or after age 60 • HTN with rapidly progressive renal failure • Renal failure that develops in response to ACE inhibitor • HTN associated with upper abdominal bruit • Episodes of recurrent severe HTN & pulmonary edema Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475.
- 28. Renal artery stenosis Direct signs Focal color aliasing Color bruit Turbulence PSV > 180 cm/sec Renal Aortic Ratio > 3.5 Indirect signs AT > 0.07 sec Δ RI (right – left) > 5 % Parvus tardus pattern Significant stenosis (50 – 85% diameter reduction) Sensitivity: 79 – 91% Specificity: 73 – 97% Severe stenosis (> 85 % diameter reduction) Sensitivity: 95% Specificity: 97%
- 29. Renal artery stenosis / Direct criteria Non-significant stenosis (< 50% diameter stenosis) Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Plaque in anterior wall of LRA PSV: 148 cm/sec Color Doppler US Power Doppler US Better visualization of plaque
- 30. PSV: 293 cm/sec – RI : 0.91 Controversial indication of PTA2 Aliasing in left renal artery Retro-aortic course of LRV 1 Schäberle W. Ultrasonography in vascular diagnosis. Springer-Verlag, Berlin, 2nd edition, 2011. 2 Jaeger KA et al. Ultraschall in Med 2007 ; 28 : 28 – 31. Renal artery stenosis / Direct criteria
- 31. Renal artery stenosis / Renal Aortic Ratio Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. Small right kidney (8.4 cm) PSV (aorta): 102 cm/s PSV (RRA): 465 cm/s High grade stenosis of RRA RAR: 4.5
- 32. Indirect criteria • Loss of early systolic peak • Distal to stenosis velocity of renal artery decreases • Tardus Parvus pattern • Acceleration time > 0.07 sec • RI values also decrease down to 0.45 to 0.5 • Difference between RI values of both kidneys > 5-10 %
- 33. Renal artery stenosis / Indirect criteria Schäberle W. Ultrasonography in vascular diagnosis. Springer-Verlag, Berlin, 2nd edition, 2011. PSV: 85.7 cm/s EDV: 47.2 cm/s RI: 0.64 Left renal hilumRight renal hilum PSV: 125 cm/sec EDV: 58.1 cm/s RI: 0.75 Δ RI (right – left) > 0.05 → RA stenosis in side of lower RI
- 34. Renal artery stenosis / Indirect criteria Right kidney Left kidney Δ RI (right – left) > 0.05 → RA stenosis in side of lower RI
- 35. Renal artery stenosis / Tardus-Parvus wave Severe stenosis (> 85 % diameter reduction) Tardus: Longer rise time Parvus: Low PSV Freeman SJ. Ultrasound 2004 ; 12 : 69 – 74.
- 36. Fibromuscular dysplasia Moniliform aspect of RRA Typical FMD in middle third of RRA Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. PSV 250 cm/sec No parallelism of RRA walls
- 37. Etiologies of renal artery dissection Stenotic or occlusive lesion • Atherosclerosis • Fibromuscular dysplasia • Extension of aortic dissection • Marfan syndrome & Ehlers-Danlos syndrome • Trauma & iatrogenic causes • Idiopathic Sidhu R et al. Semin Ultrasound CT MRI 2009 ; 30 : 271 – 288.
- 38. Coarctation of abdominal aorta Severe hypertension in a 6-year-old boy Moukaddam H et al. Ultrasound Clin 2007 ; 2 : 455 – 475. Bilateral & symmetric tardus parvus waveform Sagital view of aorta Severe narrowing at level of CA & SMA
- 39. Guidelines for diagnosis of RAS • Recommended as screening test Duplex US followed by CT angiography (except RF) & MR angiography • Not recommended as screening test Captopril renal scintigraphy Plasma renin activity Captopril test Selective renal vein renin measurements Hirsch AT et al. J Am Coll Cardiol 2006 ; 47 : 1239 – 1312.
- 40. Micro-aneurysms Contraindication of renal biopsy (bleeding) • Location Distal branches of cortex Segmental arteries rarely • Size 1 mm, 2-3 mm rarely • Cause PAN (micoaneurysms in 100%) • Clinic Fever – Abdominal pain – Hematuria – RF • Diagnosis Arteriography – Not visible by Doppler Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412.
- 41. Renal Doppler in nephropathies • Acute tubular necrosis • Tubulo-interstitial nephropathy • Micro-angiopathy • Nephro-angiosclerosis • Diabetic nephropathy Glomerulo-nephritis (↑ RI in end stage disease) Elevated RI Normal RI
- 42. Diabetic nephropathy Hélénon O et al. EMC-Radiologie 2005 ; 2 : 367 – 412. Increased resistive index: 0.89 Renal insufficiency
- 43. Advantages of Renal Doppler in Renovascular Hypertension • Cost effective • Easily available • No contrast • Excellent depiction of renal vasculature with high accuracy • Physiological information • Best for follow up after revascularization procedure
- 44. Take Home Message • Evaluation of direct doppler criteria in renovascular hypertension is possible in thin, lean, cooperative and fully prepared patients. • But even in unfavorable circumstances indirect signs are sufficient to document renovascular hypertension with high accuracy.
Editor's Notes
- The normal adult kidney is bean shaped with a smooth convex contour anteriorly, posteriorly, andlaterally. Medially, the surface is concave and known as the renal hilum. The renal hilum is continuous with a central cavity called the renal sinus. The collecting system (renal pelvis) lies posterior to the renal vessels in the renal hilum.
- ● The right renal artery is longer than the left, and passes posterior to the IVC. ● The left renal artery has a more horizontal course to the kidney.
- One of the most complex and difficult sonographic examination.
- Even expert sonographers detect only 80–90 per cent of renal arteries. Ultrasound contrast agents improve the technical success rate to 95 per cent.
- Because of the high prevalence of hypertension in the general population and the low incidence of RVH among these patients (0.5%–5%), however, screening all hypertensive patients is neither practical nor cost effective. Screening for RAS is thus recommended only for enriched patient populations considered to be at high risk for RAS. The clinical criteria most predictive of RAS are listed in Box 1. In such patient populations the prevalence of RVH increases to approximately 20% to 30%.
- PSV is recommended, may be combined with RAR (and ΔRI) to improve specificity.
- In vascular medicine, a reduction in diameter of 50% is commonly regarded as hemodynamically significant and should not be equated with clinical relevance.
- End organ damage may have already occurred in patients who have a small kidney with a thin, echogenic renal cortex or an RI greater than 0.8 in the intraparenchymal renal arteries, and that improvement of blood pressure or renal function is less likely following intervention in such patients.
- Tardus: slowed systolic acceleration Parvus: low-amplitude systolic peak
- Captopril test: measurement of plasma renin activity after captopril administration