Ultrasound of the Renal Arteries Greg Curry Vascular Ultrasound Workshop Aug 2017
The Examination Technique Pathophysiology Role of US then and now Background Live Scanning Ultrasound
Population: 20% Hypertensive Increase risk: Heart attack/stroke <1-5% Renovascular cause Renal Artery stenosis (RAS) RAS Renal failure Need: Screening Test!
Pathophysiology
Pathophysiology RAS Hypertension Decrease blood volume Enzyme renin is secreted Activates angiotensin mechanism Salt / H20 retention Increase in blood volume Vasoconstriction Accessory RA Intrarenal Vessels
Pathophysiology Atherosclerosis Fibro-Muscular Dysplasia (FMD) Mid sized vessels Non-atherosclerotic Non-inflammatory Abnormal intimal growth Inflammatory http://humanbiologylab.pbworks.com/w/page/105655224/renal%20artery%20stenosis
EVERYONE GETS A STENT Background
Key Points We now know that Unselected stenting does not improve outcomes Degree of renal artery stenosis is not the most important determinant of outcome (Ritchie et al 2014) Why do we bother looking for RAS? Better medical management May still be influenced by the presence and severity of RA disease Intervention? Flash pulmonary edema Preserving of Kidney Function
Background Nuc. Med DPTA, Mag 3? >90% sens. spec. MRA >95% sens. spec. Knopp, 1999 CT Angio 90-98% sens. spec. Prokop,1999 Angiography 95-100 % est. gold standard Ultrasound?
Background RESISTANT HT Clinical Index of Suspicion Resistant HT Low/Moderate High Continued high blood pressure At least 3 antihypertensive agents Negative Colour Doppler Ultrasound?? Positive Functional Testing Captopril Renal Scan Renal Vein Renin Angiography (+/-PTA Stenting) Stop MRA /CTA
The Dilemma Intrinsic Limitations Bowel gas Patient size, respiration Vessel Location, Tortuosity, Ca++ Good Technique can improve our chances (later)
The Examination DIRECT INDIRECT Local protocols
US technique Direct-Yes Kohler 1986, Moneta 1988, Direct- No Kletter 1990, Desberg 1990, Berland 1990 DIRECT INDIRECT Indirect-Yes Handa 1988 Stavros 1992 Indirect- No Kliewer 1993 etc Direct- Olin Annals of Int Medicine 1995 122:833-854 93% sensitivity, 98% spec
US technique RI >0.8 Rademacher INDIRECT Resistive Indices Acceleration times Waveform shape RI = PSV-EDV/ PSV 5950 patients 138 angioplasty/ stenting Post Sx. Creatine clearance / Blood pressure 34/35 RI >0.8 V. poor outcome 74/80 RI< 0.8 Good outcome
1. Direct RA assessment V good when visualisation Visualisation improving 2. Intrarenal Very easy Still has a role as Marker Functional stenosis If intervention planned Predicts Success
The Examination
DIRECT Approx 75% visualisation in literature higher Technical Limitations B-mode (?atherosclerosis/ca2++) Colour (?Focal aliasing) Local Protocol
DIRECT 64 yo male Hypertensive PSV AA= 58 cm/s PSV RRA= 295 cm/s RAR > 3:1
60 yo male Hypertensive Hx of RAS Bil RA stents DIRECT
60 yo male Hypertensive Hx of RAS Bil RA stents DIRECT
INDIRECT Waveform Shape Tardus Parvus Resistive Indices Superior, mid, inferior
INDIRECT Early Systolic Peak AT > 0.07sec AI < 3.0 Variation RI > 0.05 AI = ΔV \ ΔT RI = PSV-EDV/ PSV ΔV ΔT
INDIRECT Normal Abnormal Early Systolic Peak Tardus Parvus
Early Systolic Peak INDIRECT
INDIRECT Normal/ Abnormal? 33yo woman Severe hypertension
INDIRECT FMD 33yo woman Severe hypertension
INDIRECT Normal/ Abnormal? 21yo female Severe hypertension Hx of Takayasu Arteritis
INDIRECT Occluded RA - Collaterals 21yo female Severe hypertension Hx of Takayasu Arteritis
21yo female Severe hypertension Hx of Takayasu Arteritis INDIRECT
INDIRECT Normal/ Abnormal? 55yo Male Acute severe hypertension
55yo Male BMI++ Acute severe hypertension INDIRECT
The Examination 1. Renal Ultrasound 2. Intrarenal evaluation 3. Main Renal A. 4. Accessory Renal A 5. Aorta: PSV level of SMA 6. Worksheet
The Examination
0 = Non visualisation, No Spectral 1 = V. poor colour, Angle Uncertainty 5 Grades 0,1 = Sub- optimal examination 2 = Segmental colour, Angle certainty 3 = Full colour visualisation, Angle certainty 4 = As per 3 + Colour enabling assessment of aliasing
The Examination Important 5mins B-mode 5 mins Intrarenal 20 mins Direct
The Examination Renal Size > 9.0 cm > 2.5cm difference Cortical volume Co-existent pathology
The Examination Lobules Cortical Rim Medullary Pyramid Calyces (not seen) Capsule Cortex Sinus fat Pelvic-calyceal
The Examination
The Examination SET UP IMPORTANT ENLARGE IMAGE FAST SWEEP SPEED REDUCE SCALE NO FILTER
The Examination 10 windows- Rt 5, Lt 5 Gentle Compression B-mode! Dynamic Range Transducer Frequency Fasted! Other parameters: Filters Persistence Power etc
The Examination 20% of kidneys? Prevalence of isolated ARA stenosis Windows > 50 % visualisation
R4 view Coronal view
The 10 MAGIC WINDOWS ASA March 2002 Ask the Experts section Renal Arteries by Peter Coombs greg.curry@monashhealth.org
The Examination
US has important role in screening Less common test Integrate: Intrarenal/ Extrarenal Intrarenal debate Emphasis on Direct Structured technique: Windows = Success