Transducer Selection. Renal Artery Duplex Exam. Renal Scan. Renal Scan Echogenicity. How to Perform an Optimal Renal Artery Doppler Examination

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1 How to Perform an Optimal Renal Artery Doppler Examination Director of Ultrasound Education & Quality Assurance Baylor College of Medicine Division of Maternal-Fetal Medicine Maternal Fetal Center Imaging Manager Texas Children s Hospital, Pavilion for Women Houston Texas & Clinical Instructor Thomas Jefferson University Hospital - Radiology Department Philadelphia, Pennsylvania Transducer Selection Curved linear 3-6 MHz Sector 2-4 MHz Exam Renal B-scan should be performed before Doppler assesment Size Cortical Thinning Cortical Echogenicity Hydronephrosis Calcification Masses Renal Scan Renal Scan Echogenicity Glomerulonephritis Glomerulosclerosis Collagen vascular diseases Diabetic nephropathy Chronic pyelonephritis Sickle cell disease Interstitial nephritis AIDS nephropathy 1

2 Urothelial Thickening Renal Scan Central Collecting System Emphysematous Pyelonephritis Renal Scan Small kidney is irreparable Concentrate Doppler on normal sized kidney 2

3 Know Your Landmarks Which Windows to Use? Which Windows to Use? Which Windows to Use? 3

4 Which Positions to Use? Tips on How to Find the Renal Arteries Supine Supine Scanning Difficult Patients 4

5 Use Multiple Approaches Right Coronal supine / decubitus Use Multiple Approaches Right Coronal supine / decubitus Oblique Oblique SAG TRV Oblique SAG TRV 5

6 Oblique SAG TRV Oblique SAG Tilt Oblique SAG Tilt Oblique SAG Tilt Oblique SAG Tilt Supine 6

7 Supine Supine SMA A LRV IVC PC LRV SMA A SV LRA Supine Supine Supine Without Any Push 7

8 With Push Left Coronal supine / decubitus Left Coronal supine / decubitus Left Coronal Left Coronal supine / decubitus 8

9 Left Coronal Renal Aortic Ratio PSV in MRA jet PSV in or just above the level of renal arteries Renal Aortic Ratio Renal Aortic Ratio 9

10 Renal Artery Stenosis Renal aortic ratio greater than 3.5 suggests > 60% stenosis Note: presence of aortic atherosclerosis and AAA may falsely lower or elevate the RAR Renal Artery Disease Two most common primary diseases: Atherosclerosis FMD Hypertension & ischemic nephropathy Age > Male Origin of MRA Proximal 1/3 of MRA Progression common Occlusion common Diabetes, aorto-iliac disease, CAD Atherosclerosis Fibromuscular Dysplasia (FMD) Age % female Distal 2/3 of MRA & branches Progression rare Occlusion rare Cause unknown Renal Artery Stenosis - FMD Treatment Percutaneous transluminal angioplasty or stent placement Surgical repair/bypass Cure hypertension Salvage renal function 10

11 Renal artery PSV > 200 cm/s (constitutes > 60% stenosis) Renal artery EDV > 150 cm/s (constitutes > 80% stenosis) 11

12 Segmental Artery Normal Acceleration Index > 300 cm/s 2 Intrarenal Evaluation Upper & lower poles Record early systolic acceleration* Low Doppler angle Fast sweep speed* Low scale to enlarge spectra* 12

13 Rate of Systolic Acceleration Acceleration time Acceleration index Length of time from onset of systole to ESP Acceleration Time Acceleration Index Slope of line from onset of systole to ESP Stavros, Radiology: 1992 Stavros, Radiology: 1992 Onset of systole ESP SP Segmental Arteries * * Incorrect * Correct 13

14 Segmental Arteries Segmental Arteries AI is decreased to < 300 cm/s 2 Pre Post Angioplasty Arcuate Artery Arcuate Artery RI < 0.75 Arcuate Artery Causes of resistance Acute & chronic parenchymal disease Obstruction Renal vein thrombosis 14

15 Caution Rely on Multiple Parameters for the Diagnosis of RAS Renal Artery Doppler 1. Renal artery to aortic ratio (RAR) 2. Increased peak systolic velocity 3. Acceleration time or systolic rise time + B-mode assessment Follow renal artery from aorta to hilum sample every cm, any area of color aliasing Narrowing by color Doppler Disturbed flow downstream Spectral Doppler Low PRF before aliasing Lowest possible wall filter Small sample volume Obtain spectral Doppler from proximal, mid & distal main renal artery as well as segmental & arcuate arteries Diagnostic Criteria Renal aortic ratio > 3.5 suggests > 60% stenosis Thank You Renal artery PSV > 200 cm/s constitutes > 60% stenosis Renal artery EDV > 150 cm/s constitutes 80% stenosis Acceleration index < 300 cm/s 2 15