Title: RENAL ARTERY DOPPLER
1RENAL ARTERY DOPPLER
2Objectives
- Upon completion of the presentation
- the viewer should be able to
- Identify a normal renal artery signal.
- Describe Tardus-Parvus, RAR and Acceleration
index. - List causes for hypertension
- Outline a normal Renal Doppler exam
3Table of Contents
- Indications for a Renal Doppler Exam
- Renal Artery Stenosis
- Hypertension
- Anatomy Variants
- Diagnostic Criteria
- Doppler waveform
- Exam Protocol
- Case Examples
4Clinical Indications for Doppler
- Evaluate a hypertensive patient for renal artery
stenosis (RAS). - Hypertensive patients not controlled with medical
treatment. - Patients with abdominal aortic dissection.
- Evaluation of renal transplant.
- Audible Bruit
- Patients with AAA
5Renal Artery StenosisCauses
- Atherosclerosis Plaque deposits cause
narrowing/blockage. - Affects men gt women
- Typically effects age gt40 years
- Involves proximal aspect renal artery
- Fibromuscular Fibrous tissue growth in arterial
walls. - Affects women gt men ( approx.. 4 1).
- Typically affects ages lt 50 years
- Involves mid to distal aspects of renal artery
- Acute Traumatic injury causing obstruction.
6Hypertension and RAS
- Relationship
- Renal Artery Stenosis causes hypertension.
- Hypertension is the symptom that indicates RAS
Doppler needed
7Hypertension and RAS
Adrenal Gland
Kidney
8Hypertension and RAS
- RAS
- Increased PR
- Decrease renal blood flow
- Production of rennin
9Hypertension and RAS
- Rennin converts angiotensinogen to angiotensin.
- Angiotensin is a potent vasonstrictor.
10Hypertension and RAS
- Angiotensin also acts on the adrenal cortex to
produce aldosterone. - Aldosterone causes the kidney to absorbed more
sodium and water.
11Hypertension and RAS
- This leads to increased in blood volume and also
the BP.
12Renal Artery Stenosis
- Anatomy Variants
- Diagnostic Criteria
- Doppler waveform
- Exam Protocol
- Case Examples
13Renal Anatomy
- Kidneys
- Vessels
- Accessory Vessels
- Doppler Waveform
14Normal Anatomy of the Kidneys
- Size 9-11cm
- Difference between Lt. Rt. Renal Length lt 2 cm
15Normal Anatomy of the Kidneys
16Normal Anatomy of the Kidneys
17Celiac Axis
Rt Renal Artery
Lt Renal Artery
Superior Mesenteric Artery
Aorta
18Segmental arteries
Interlobar arteries
Main Renal artery
Arcuate arteries
19Normal Right and Left Renal Artery
Coronal View
Transverse
20Normal Right Renal Artery
Transverse
21Normal Left Renal Artery
Transverse
22Renal Artery Stenosis
- Normal Variants Accessory Vessels
23Normal Variants of Renal Arteries
- Most common anatomy is single right and left
renal artery (approx. 55 population)
24Normal Variants of Renal Arteries
- Second most common an is accessory renal artery
branching off a main renal artery (14)
25Accessory Renal Arteries
- Branch off a main renal artery or aorta.
- Supply small portions of the renal parenchyma.
- Can be
- 1) single or multiple
- 2) unilateral or bilateral
26Accessory Renal Arteries
27Accessory Renal Arteries
- Can extend to upper, mid,or lower poles of
kidney. - Stenosis in an accessory can result in
hypertension. - Best evaluated in coronal plane with color
Doppler.
28Accessory Renal Arteries
Two Left Renal Arteries
29The Normal Renal Waveform
- Low resistant waveform.
- Rapid and steep upstroke during systole.
- Dicrotic notch.
- Low resistant runoff during diastole.
30The Normal Renal Waveform
31RAS Exam
- Diagnostic Criteria
- Protocol
- Example of normal Exam
32Diagnostic Criteria
- Color Doppler non-visualization
- Peak Systolic Velocity
- RAR
- Acceleration time
- Acceleration Index
- End Diastolic Ratios
- Tardus Parvus
33Diagnostic Criteria
34Peak Systolic Velocity
- Normal gt1.8 m/sec
- Low grade(1-59)gt1.8 m/sec
- No post-stenotic disturbance
- High grade(60-99)gt1.8 m/sec
- Post-stenotic turbulence
- Total occlusion - no flow
35Peak Systolic Velocity
36Remember all angles MUST be 60 degrees or less!
Peak Systolic Velocity
37Renal-Aortic Ratio
-
- RAR PSV renal artery
- PSV aorta
38Renal-Aortic Ratio
-
-
- PSV alone may be inaccurate due to
difficulty with Doppler angle insonation - RAR angle independent
- Obtain aortic signal 2cm distal to SMA
- Use highest main renal artery signal
39Renal-Aortic Ratio
- Normal lt 3.5
- Low grade (1-59) lt 3.5
- High grade (60-99) gt 3.5
- Total occlusion renal length lt 9cm
40End Diastolic Ratio
- Assess both parenchymal vascular resistance and
disease. - Sufficient perfusion gt 0.23
- Severe parenchymal vascular disease lt 0.23
41Acceleration Index
?V
AT
?T
AI ?V/ ?T
42Acceleration Index
- Acceleration time time for peak systolic
velocity - Acceleration index acceleration slope divided
change in time - lt 3.78 kHz/sec/MHz indicates greater than 50
stenosis.
43Acceleration Index
- To calculate
- Place the first cursor at the beginning of
systole. - Place the second cursor at the peak of systole.
44Acceleration Index
45Acceleration Time
- Acceleration time gt 0.1 sec indicates greater
than 50 stenosis. - Measure with sweep speed of 100 mm/sec.
- Normal waveforms have steep systolic upstrokes,
whereas waveforms distal to a stenosis have a
more gradual upstroke and dampened systolic peak.
46Abnormal Doppler Findings
- Peak systolic velocity ( PSV) in renal artery
( proximal, mid, or distal ) gt 180
cm/sec. - Renal Artery / Aorta Ratio ( RAR), gt 3.5.
- Tardus-Parvus.
47What is Tardus-Parvus?
- Tardus delayed early systolic acceleration or
upstroke - Parvus diminished amplitude and rounding
systolic peak.
48What is Tardus-Parvus?
Delayed upstroke
49What is Tardus-Parvus?
Rounded
50Tardus-Parvus
- Seen in distal segmental arteries, indicating
high grade stenosis proximally. - Measured using either
- Acceleration time (normal is less than 70ms)
- Acceleration Index ( normal is greater than 3/m/s
square) -
- When present, 100 indicative of RAS, but not
ALWAYS present in RAS patients
51Tardus-Parvus
Normal
52Tardus-Parvus
Abnormal
53Tardus-Parvus
Normal renal artery notice the steep upstroke
normal acceleration index in this waveform.
54Tardus-Parvus
Notice the rounded waveform and the blunted
upstroke with tardus-parvus.
55Renal Artery Protocol
- Exam Protocol
- Normal RAS Exam
56Renal Artery Doppler Scanning
- Test usually takes 60-90 minutes.With experience
the time can be reduced. - Patient should be fasting (at least 8 hours).
- Patient should be well hydrated, encourage water
intake. - 4 to 2 MHz transducer
57Protocol
- Grey Scale
- Measure and document kidney size, and any
abnormalities. (Normal size 9-13 cm.) - Rule out mass, stones, hydronephrosis, etc.
- Start with the abdominal aorta midline and
obtain and measure Doppler signal. Remember to
look for plaque (arteriosclerosis).
58Protocol / Kidneys
- Abnormalities
- Hydronephrosis
- Stones
- Renal Failure
- Polycystic Disease
59Protocol / Kidneys
60Protocol / Kidneys
61Protocol / Kidneys
62Protocol / Kidneys
63Protocol / Aorta
- Doppler Midline
- Beware of Plaque
64Protocol / Aorta
65Protocol / Aorta
66Protocol / Aorta
67Protocol
- Doppler and Measure
- Rt. and Lt. renal arteries, Prox , mid, and
distal aspects of each and any accessory
arteries. - ALL Doppler angles are 60 degrees or LESS.
- Segmental arteries (upper, mid, and lower poles)
of each kidney. - Acceleration index of segmental arteries. Look
for tardus-parvus.
68 A Normal Renal Artery Examination
69Proximal Right Renal Artery
70Mid Right Renal Artery
71Mid Right Renal Artery
72Mid Right Renal Artery
73Distal Right Renal Artery
74Segmental Renal Artery
75Segmental with Acceleration Index
76Angle lt 60
T 60
77Angle lt 60
T 78
78Overview of Renal Artery Study
- Routine US exam of the Kidneys
- evaluate size and echotexture, r/o pathology
- Doppler Aorta
- Measure PSV, for RAR calculation
- Doppler renal arteries
- Measure PSV, for RAR calculation
79Overview of Renal Artery Study
- Doppler segmental arteries
- obtain acceleration index
- look for Tardus-Parvus
- Calculate RAR
- RARPSV Renal artery/ PSV Aorta
80Renal Artery Stenosis Treatment
- Medically with ACE inhibitors
- Balloon angioplasty
- Arterial stent
- Surgically.