2

1. ULTRASOUND EVALUATION
OF THE RENAL ARTERIES AND
THE KIDNEY
Technique and Interpretation
Holdorf RVT

3. • The renal arteries arise within 1.5 cm of the origin of the superior mesenteric artery.
• They arise from the lateral sides of the aorta and enter each kidney.
• The right renal artery courses behind the IVC to enter the right kidney.
• Approximately 22% of patients have two renal arteries. A small percentage have
three or more.

4. Patient History:
• Many patients who are given a prescription to have a renal artery Doppler
examination will present with hypertension, controlled or not.
• Many patients who have hypertension have renovascular hypertension,
usually caused from renal artery stenosis.
• Renal artery stenosis can be secondary to
• Atherosclerosis
• Fibromuscular dysplasia
• A condition that causes stenosis or aneurysm of the medium-sized
arteries (Usually of the kidneys)
• Occlusion

5. • Mechanism of hypertension:
• Renin regulates the body's mean arterial blood pressure.
• Renin's primary function is to eventually cause an increase in blood pressure, leading to
restoration of perfusion pressure in the kidneys. Renin is secreted from kidney cells,
which sense changes in renal perfusion pressure, via stretch receptors in the vascular
walls.
Hypertension:
Abnormally high blood pressure and especially arterial blood pressure.
Normal Blood Pressure:
120/80
The top number refers to Cardiac output
The bottom number refers to peripheral resistance
Blood pressure measures the ARTERIAL blood pressure.

6. NORMAL RENAL ARTERIES

7. NORMAL RENAL ARTERIES
TWO ON THE RIGHT

8. RENAL STENOSIS

9. RENAL STENOSIS

10. RENAL ARTERY ULTRASOUND
TECHNIQUE
• Technique:
Obtain Celiac artery and SMA velocity data
Obtain Aorta PSV (Peak Systolic velocity)

11. NORMAL FLOW RESISTANCES
• Aorta high
• Renal artery low
• Celiac artery low
• SMA High (Pre-prandial)
LOW (Post Prandial)

12. MESENTERIC ISCHEMIA
• Mesenteric ischemia is a medical condition in which injury of the small intestine
occurs due to not enough blood supply.
• It can come on suddenly, known as acute mesenteric ischemia, or gradually, known
as chronic mesenteric ischemia. Acute disease often presents with sudden severe
pain.

13. CELIAC ARTERY VELOCITY

14. SMA VELOCITY

15. SMA VELOCITY

17. AORTA PSV-PEAK SYSTOLIC
VELOCITY

18. • In transverse:
• Locate renal arteries
• Left renal vein (LRV) is a landmark for identifying the left renal artery

19. LEFT RENAL ARTERY IN TRANSVERSE
VIEW

20. RIGHT RENAL ARTERY IN
TRANSVERSE VIEW

21. • Obtain kidney size (length)
• Observe morphology bilaterally

22. KIDNEY MEASUREMENT FOR LEFT
AND RIGHT

23. NORMAL LEFT KIDNEY

24. OBTAIN PEAK SYSTOLIC VELOCITY AND
END DIASTOLIC VELOCITY BILATERALLY
OF:
• Renal artery
• Proximal, mid and distal bilaterally
• Upper and lower pole of the kidneys in the segmental arteries

25. SEGMENTAL ARTERIES

26. RENAL ARTERY PEAK SYSTOLIC VELOCITY
ALSO SHOWING RENAL ARTERY END
DIASTOLIC FLOW

27. SEGMENTAL ARTERIES PSV: BRISK SYSTOLIC UPSTROKE (ARROWHEAD)
AND NORMAL SYSTOLIC NOTCH (ARROW) AND NORMAL RI
OF .64

28. DUPLEX RENAL ARTERIES: OBSERVE
FOR MULTIPLE RENAL ARTERIES

29. INTERPRETATION
• Renal arteries and kidney arteries are normally LOW RESISTANT in quality as are:
• Celiac arteries
• Hepatic arteries
• Splenic arteries
• The aorta is usually higher resistant in quality, as are a fasting SMA and IMA

30. LOW RESISTANT RENAL ARTERY
WAVEFORM

31. HIGH RESISTANT AORTIC
WAVE FORM

32. RAR: RENAL TO AORTIC RATIO
Highest Renal Artery PSV
Aorta PSV*
* Taken by the SMA

33. RAR INTERPRETATION
• Normal = < 3.5
• Abnormal = > 3.5 *
• Suggests > 60% diameter reduction

34. CANNOT USE RAR IF THE
FOLLOWING IS PRESENT
If AAA is detected
If aortic PSV > 90 cm/s
If aortic PSV < 40 cm/s

35. RAR Example:
Highest Renal artery PSV = 260
Aortic PSV = 55
260/55 = 4.7
• Normal = < 3.5
• Abnormal = > 3.5
Range is
Abnormal Renal artery

36. AORTA WITH A PSV OF 3.7 M/S
OR 368.7 CM/S
REASON: STENOSIS OF THE MIDDLE AORTIC SEGMENT

37. ABNORMAL RENAL ARTERY WITH
PSV = 326.6 CM/S

39. DOPPLER ULTRASOUND
INVESTIGATION OF THE KIDNEY
• Kidney arteries are normally low resistant in quality.
• Observe the kidney for morphologic abnormalities (cysts, cortex thinning, other
defects).
• Normal pole to pole length varies from 10 – 12cm, depending on patient size.

40. RENAL VASCULATURE

41. RENAL SEGMENTAL ARTERY
FIRST BRANCH OFF THE MAIN RENAL ARTERY

42. Resistive Index (RI)
PSV – EDV
PSV
Normal = < .8
Abnormal = > .8
• RI = (peak systolic velocity - end diastolic velocity ) /
peak systolic velocity
• the normal value is ≈ 0.60
• with 0.70 being around the upper limits of normal

43. Abnormal calculations indicate an increase in distal resistance (e.g. nephron-sclerotic
disease).
Example Data:
• PSV of 45cm/sec: EDV of 5 cm/sec.
End Diastolic Velocity EDV 5
Peak Systolic Velocity PSV 45
PSV – EDV 45 – 5 40
PSV 45 45
• The RI = 0.88 Normal value is <0.8

44. • An acceleration time (AT) of >100msec is considered abnormal.
• Proximal high grade stenosis/occlusion of the renal artery may result in dampened,
weak, Doppler signals distally, but still of low resistant quality.
• Another term for this is TARDUS-PARVUS.
• The stenosis is located proximal to the waveform
• The waveform is distal to the stenosis.

45. RENAL ARTERY TARDUS PARVUS