1. Ultrasound evaluation of the RENAL ARTERIES and the kidney
Technique and Interpretation
Holdorf RVT

3. The renal arteries arise within 1
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
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. Suggests > 60% diameter reduction
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. Highest Renal artery PSV = 260
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
Aorta with a PSV of 3.7 m/s or 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
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
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