Renal artery Doppler and renal transplant by Dr. Subash pathak

1. Renal Doppler Study
Dr Subash Pathak
2nd year Resident
Radiodiagnosis
NAMS

2. Outline of Presentation
• Anatomy of renal vessels
• Indications, procedures, and analysis of Doppler of renal vessels.
• Doppler indices.
• Applications in some important pathologies.
• Doppler in renal transplants.

3. Anatomy
• renal arteries arise from the aorta, slightly below the origin of the
SMA.
• Right slightly superior to left
• Right from anterolateral aspect of aorta and passes posterior to IVC
• Left renal artery from the posterolateral aspect of aorta

5. Renal artery division
• Renal arteries:
• typically divide into anterior and posterior divisions
• lie, respectively, anterior and posterior to the renal pelvis.
• Anterior division divides into four segmental arteries.
• Posterior division supplies only a single renal segment.
• Segmental arteries further branch within the renal sinus into interlobar
arteries penetrates the renal parenchyma.
• Then forms the arcuate arteries curving in the corticomedullary junction,
then gives cortical or interlobular branches.

7. Important Variants of renal vessels
• Precaval RRA – 1-5%
• Multiple renal arteries – 20-30% of population
• Early bifurcation – 10-15%
• Retroaortic LRV – 3%
• Circumaortic LRV – 9%
• Multiple renal veins – 25%

8. Sagittal grayscale and coronal color images in patient with two renal
arteries on either side.

9. Color Doppler depiction of supernumery renal arteries. The patient has a single
right renal artery and duplicate left renal arteries.

10. A retroaortic left renal vein. A transverse color Doppler image shows
the renal vein passing posterior to the aorta before emptying into the
IVC (A). A sagittal power Doppler image shows the left renal vein in
cross section just underneath the abdominal aorta (B).
A B

11. A circumaortic left renal vein. The transverse grayscale image shows the
left renal vein dividing before reaching the aorta with one branch
passing posterior and the other anterior between the SMA and aorta
(A). A sagittal color Doppler image shows the renal vein in cross section
on each side of the abdominal aorta (B).
A B

12. INTRODUCTION
• Renal Doppler
• Noninvasive test for many important renal diseases
• Important initial test for suspected renal artery stenosis
• Difficult to perform routinely
• High technical failure rate for the study of main renal arteries
• Problems in performing renal Doppler:
• Obese patients
• Patients with gaseous abdomen
• Patients who can not suspend respiration

13. Indications of renal Doppler
1. Renal artery stenosis (RAS)
2. Renal arterial occlusion and infarction
3. Renal vein thrombosis
4. Renal artery aneurysm
5. Renal arteriovenous fistula and malformations
6. Renal Transplants.
7. Uncontrolled HTN
8. Abdominal bruit

14. Principles of examination of renal vessels:
• Challenging: Small size, depth and variant anatomy
• Need of adequate knowledge of local anatomy, normal waveform
pattern, and image optimization.
• Several Imaging modalities available:
1. Catheter angiography: Gold standard
2. CTA/MRA: Can only provide anatomic information.
3. Doppler analysis

15. Doppler examination of renal vessels
• Inexpensive, non-invasive, no contrast media
• Both physiologic and anatomic information
• Hemodynamic significance of lesion and need of intervention
• Clarifies uncertain or indeterminate lesions as seen in CTA/MRA

16. Successful abdominal Doppler: Key elements
• Adequate patient preparation
• Modern ultrasound unit – adequate gray scale imaging with sensitive
color, power and pulsed Doppler modalities.
• Harmonic imaging – improves resolution and decrease artifacts.
• Operator experience.

17. Patient preparation
• Patient should be NPO from midnight.
• No smoking
• Take all morning medications with small sips of water.
• Renal imaging should be done in AM time to avoid excessive gases.

18. Technique
• Use 2.5-5 MHz curved array transducers for adequate depth.
• Optimize the gray-scale and color Doppler parameters so as to
improve renal artery visualization as well as the conspicuity of flow-
reducing lesions.
• Optimization performed in areas of Laminar flow eg Abdominal aorta
• Perform color flow imaging – identifies patent renal arteries and areas
of flow disturbances.
• Significance can only be analyzed in conjunction with spectral
analysis.

19. • Spectral Doppler examination
• Perform using small sample volume (1.5-2 mm)
• Keep Angle of Insonation to <60 degrees
• Select PRF so that waveforms are large and easy to read provided that
causes no aliasing (too low PRF).

20. Protocol
• Complete evaluation of the kidneys (take note of echogenicity,
thickness of parenchyma, size, atrophy, scarring, hydronephrosis,
calculi or masses).
• Longitudinal survey of the abdominal aorta (from celiac artery to iliac
bifurcation) – evaluate for amount of atherosclerotic plaque, size and
location of AAAs.
• Obtain angle corrected PSV from abdominal aorta at the level of renal
ostia. (for RAR)

21. Evaluation of renal arteries
• Direct evaluation of both renal arteries and the segmental arteries at
hila.
• Use all the approaches available.
• First, via anterior approach, attempt to locate the renal artery origin
on transverse plane.
• RRA is easily identified and can be followed throughout its length.
• LRA is difficult via this approach (mid or distal part) – due to presence
of bowel gas.

22. • Then use posterolateral approach placing the patient in decubitus
position. (here kidneys serve as acoustic windows).
• Perform transverse and sagittal sweeps of abdominal aorta and
kidneys to identify accessory arteries.

23. What to evaluate in renal arteries
• Color flow imaging – origin to hilum with segmental branches.
• Areas of high velocity (likely stenosis) – Color shifts or aliasing.
• Interrogating these areas with spectral Doppler analysis.
• Routinely obtain PSV from Origin, proximal, mid-, and distal segments
of each renal artery.
• Finally, waveforms obtained from segmental arteries in upper, mid
and lower poles of each kidneys.

24. Anterior approach/Posterolateral approach
Color Doppler image displays
the entire right renal artery
(RRA) from the aorta (AO) to
the renal hilum. Note that the
anterior liver parenchyma
serves as an acoustic window.
RRV, right renal vein.
Color Doppler scan through the left kidney,
obtained in the right lateral decubitus position,
allows complete visualization of the left renal artery.

25. Multiple duplicate renal arteries
(arrows) are identified on this
longitudinal color Doppler image
obtained through the left kidney

26. Renal artery Doppler waveforms
• Normally renal artery shows Low resistance flow pattern with rapid
systolic upstroke.
• Continuous forward flow is present in diastole because of low
resistance in the renal vascular bed.
Present at all levels including the intrarenal branches.

27. Normal Waveforms: Normal renal artery waveforms demonstrate a
rapid systolic upstroke with persistent forward flow in diastole (low-resistance bed)
An early systolic compliance peak (ESP) or notch may be seen in some patients
A, Normal Doppler waveform obtained at the origin of the
right renal artery (RRA ORIG) demonstrates a low-
resistance flow pattern with a rapid systolic upstroke and
early systolic compliance peak.
B, Waveforms obtained from a segmental artery branch,
at the renal hilum, demonstrate normal waveform shape
andacceleration.

28. Scanning Technique
• Two approaches:
• Anterior approach
• Flank approach

29. Anterior approach:
• The proximal course of the right renal artery is often perpendicular to
the beam.
• This is an excellent angle for B mode imaging but is not suitable for
Doppler.
• Moving the probe slightly to the left of midline and angling it toward
the patient’s right side can sometimes improve the Doppler angle

30. In most individuals, the renal arteries arise from the abdominal aorta
immediately distal to the origin of the superior mesenteric artery
(SMA). The right renal artery passes underneath the inferior vena cava
(IVC) and posterior to the right renal vein

32. • Color Doppler helps to localize the artery and define the Doppler
angle.
• The mid to distal right renal artery is not often imaged adequately
from an anterior approach and when it is, the distance to the Doppler
gate is usually large.
• This decreases Doppler sensitivity and reduces the PRF at which
aliasing will occur, making it more difficult to accurately measure high
velocities.

33. Transverse Bmode view of the abdominal aorta and right renal artery from an anterior approach.
The ultrasound probe is oriented at midline and the Doppler cursor placed in the proximal right
renal artery (A). The angle of incidence of the Doppler beam to the flow is unacceptable at
approximately 89 degrees. By moving the probe to the left of midline and angling toward the
patient’s right, an acceptable Doppler angle of 60 degrees is achieved (B).
A B

34. • The origin of the left renal artery is posterior compared to the right
renal artery.
• On grayscale alone, the left renal artery is usually difficult to see from
an anterior approach, but once color is activated the proximal portion
is often well visualized.
• The left renal vein is an excellent landmark for locating the renal
artery

35. • By positioning the transducer slightly to the right of midline and
angling toward the left, an adequate Doppler angle can usually be
achieved for the proximal portion of the artery.
• The mid to distal left renal artery is often not seen in this view except
in ideal patients.

36. Transverse color Doppler images of the abdominal aorta, left renal vein and artery. The
left renal vein is a good landmark for locating the artery. The renal vein is usually
recognized first as a red vessel just lateral to the aorta (A). Careful inspection will reveal
the renal artery as a blue vessel (color Doppler is NOT inverted), located just posterior
to the renal vein
A B

37. Flank Approach

38. • The flank approach is usually the most successful view
for imaging the entire length of both renal arteries.
• An excellent Doppler angle (60 degrees or less) can
nearly always be achieved with this view.
• There are several variations to the flank approach.
• It’s often necessary to slightly vary the window until an
optimal view is found for each individual patient.

39. Evaluation of Rt. Renal Artery
• Patient is rolled into a left decubitus position.
• The patient is asked to relax the abdominal muscles as much as
possible.
• The probe is placed in a sagittal view in the soft part of the abdomen
below the rib cage.
• The probe is manipulated slightly until the aorta and IVC are seen in
long axis.
• By slightly varying the probe angle, both renal arteries can be seen
arising from the aorta.
• This has been described as the “banana peel” view. The right renal
artery will course toward the probe and the left will course away.
• This is an excellent view for obtaining a Doppler signal from each renal
artery origin as well as the abdominal aorta

40. Flank approach showing the abdominal aorta and
origin of both renal arteries

41. The Doppler sample volume is placed within the proximal right renal artery. In this view,
an acceptable Doppler angle of 60 degrees or less is easily obtained (A). The Doppler
reading of the abdominal aorta is taken near the level of the renal arteries. This value is
applied to the RAR (B).
A B

42.  Next, the probe is oriented into a transverse
plane and positioned at the renal hilum to image
the mid and distal portion of the right renal artery
 The entire length of the renal artery from the
aorta to the renal hilum can be visualized.
 A transverse view of the kidney will be seen at the
top left of the image and the aorta will be seen in
transverse at the bottom right.
 The renal artery will be seen just posterior to the
vein.

43. Transverse color Doppler image using the flank
approach

44. Evaluation of left renal artery
• The patient is rolled into a right decubitus position.
• The probe is positioned in a sagittal plane over the left kidney.
• Again, color Doppler is activated and the color box sized so that it is long and
narrow.
• The probe is angled until both the abdominal aorta and left kidney are visible in
the image.
• Imaging of the renal artery can be performed through either a sagittal or
transverse orientation of the kidney

45. Color Doppler highlights the origins of both renal arteries and a Doppler reading
obtained from the left renal artery

46. Image (A) shows aliasing of the spectral waveform. The frequency shift
is too high for the PRF setting & velocity measured is incorrect. By
raising the PRF and lowering the baseline, the peak velocity is displayed
correctly and an accurate velocity is obtained (B).
A B

47. Evaluation of intrarenal
vasculature:
In lateral decubitus position, the
probe is placed along the axillary
line.
 The kidney is close to the surface
in this view and the segmental
renal arteries will course directly
toward the probe at small angles
 There should be no spleen or
liver visible between the probe
and the kidney to minimize the
distance to the intrarenal vessels
 Color Doppler is essential to map
the vascular anatomy.

48. • The intrarenal Doppler waveforms must be
obtained at angles less than 30 degrees or the
early systolic peak may not be visualized
• The probe is rotated more posteriorly to improve
the Doppler angle for the upper pole intrarenal
arteries.
• For the mid kidney, the probe is centered in a
coronal plane.
• The best Doppler angle for the lower pole
intrarenal arteries is usually obtained by rotating
the probe slightly anterior to the mid coronal line

49. • Doppler frequency of 3.5 MHz or higher is preferred.
• High Doppler frequencies provide larger waveforms because the
frequency shift is greater compared to lower frequencies
• The patient is asked to suspend respiration and a Doppler reading is
taken from within one of the arteries best aligned to the cursor

50. Color and spectral Doppler image of the intrarenal vasculature Color Doppler
identifies the vessels and helps to locate a segmental or interlobar artery at an
optimal angle of 30 degrees or less .

51. • Some arterial waveforms demonstrate an early systolic peak (ESP)
followed by a notch and smooth peak systolic velocity flow curve.
Early systolic peak can often be encountered in renal arteries
• Measurements of acceleration should be performed with respect to
ESP, not PSV.

56.  A range of normal
waveforms.
 The early systolic peak
(ESP) is detected on each
waveform.
 In some cases, the ESP is
the highest peak, but in
others, the highest peak
occurs later in systole.
 The Acceleration Time
(AT) is always measured
to the first systolic peak,
which is the ESP in normal
waveforms.

57. Correct and incorrect measurement of AT: The systolic acceleration time (AT) is
measured from start of the systolic upstroke to the first peak or ESP

58. • The intrarenal waveform obtained from a segmental or interlobar
artery has an acceleration time (AT) of less than 0.07 seconds.
• Acceleration index (AI)= Slope of the systolic upstroke: >3m/s2
• The normal peak systolic velocity of the main renal artery is less
than 150 cm/sec.
• The velocity decreases in the distal intrarenal arteries.

59.  Systolic acceleration times greater than 0.07
second are consistent with a main renal artery
stenosis exceeding 60%.
 The RI is measured and compared between
kidneys.
 A difference in RI between the ipsilateral and
contralateral kidney increases suspicion for renal
artery stenosis on the side with the lowest RI.
 This difference is significant when it exceeds 5%.
 Other parameters that have been recommended
include acceleration (ACC) and acceleration index
(AI).

60. Renal Artery Stenosis
Causes
• Atherosclerotic disease:
• Older patients
• Typically males
• Mostly proximal segment of the artery
• Fibromuscular dysplasia:
• Younger patients.
• Typically females.
• Commonly in the mid to distal aspect of the renal arteries.
• Produces a beaded appearance on angiography that has been described as a “string
of pearls”
• Others: Arteritis (Takayasu and PAN), arterial dissection, AAA, compression
by the retroperiton etc.

61. Doppler Ultrasound in RAS
• Principal criterion: Doppler detected flow velocity elevation in the
stenotic portion of the vessel.
• Flow velocity proportional to severity of luminal narrowing.
• Post-stenotic flow disturbances/turbulence
• Intrarenal arterial waveforms showing damping effect.
• Findings of damp waveform:
• Absence of ESP
• Prolonged systolic acceleration time
• Reduced acceleration index

62. Diagnostic Criteria
• PSV at stenotic site: >/= 180-200 cm/sec
• RAR >/= 3.5
• RAR = PSV@ stenotic portion/PSV aorta @ renal artery level.
• Compensates for the hemodynamic variability in patients.
• Damping of intrarenal arterial signals
• AI: < 300 cm/sec2
• AT: > 0.07 sec

64. A, Renal artery stenosis. Pulsed Doppler interrogation of the right renal artery, at the site of color aliasing,
reveals elevated peak systolic velocities (PSVs; 382.3 cm/sec.) B, Pulsed Doppler sampling of the aorta, at the
level of the renal arteries, reveals a PSV of 88.6 cm/ sec. The renal-aortic ratio is 4.3, consistent with significant
renal artery stenosis. C, Renal hilar sampling reveals characteristic damping (tardus-parvus) of the segmental
artery waveform. Note the absence of the early systolic peak, rounded contour, and prolonged systolic
acceleration time.

65. A, Elevated velocities (peak systolic velocity = 282 cm/sec) are identified in the left
renal artery consistent with significant stenosis, confirmed with magnetic resonance
angiography. B, Hilar waveforms obtained from the left kidney are normal in
appearance.
This is a false-negative finding obtained by indirect arterial
sampling.

66. Post operative/stent placement findings for the
evaluation of success of treatment
Elevated velocities (peak systolic
velocity [PSV] = 315.5 cm/sec at LRA
origin
Typical tardus waveforms (delayed
upstroke and rounded contour)
intrarenal artery
Following renal artery
stent placement PSV at
stenotic site – 52 cm/s
and normal intrarenal
waveform

67. Renal Arterial Occlusion & Infarction
 Acute complete obstruction:
◦ Gray scale image: Normal/ swollen echo poor kidney
◦ Absent flow to the kidney in duplex and color doppler
sonography.
 Segmental of focal infarction:
◦ Wedge-shaped mass indistinguishable from acute
pyelonephritis
◦ Absent flow in the affected branch artery
 Chronic occlusion:
◦ Small, scarred kidney.

68. A-V fistula & malformations:
• Causes:
• ~75% acquired: mostly iatrogenic; secondary to tumor erosion, traumatic
• ~25% congenital
• Imaging:
• Gray-scale may reveal no abnormality

69. Duplex imaging
• The region of the fistula has a high velocity blood flow
which causes turbulence resulting in perivascular focal
tissue vibration. This is demonstrated as a mosaic color
pattern.
• Due to the anomalous connection with the vein, spectral
analysis shows an abnormal low resistance arterial
waveform with higher diastolic flow velocities.
• The venous flow pattern will also demonstrate an
abnormal arterialized waveform due to increased flow in
the vein.

72. Renal artery aneurysm:
• Normal renal artery size – 4.5-5 mm at ostium.
• Aneurysms rarely exceed >2 cm.
• Cause:
• Congenital
• Inflammatory
• Traumatic
• Atherosclerotic
• Related to fibromuscular disease
• If large (>2.5cm), non calcified or associated with pregnancy,
possibility of rupture increases.

73. • Imaging:
• Gray-scale
sonography: A cystic
mass
• Duplex & color
doppler: Arterial
flow within the cystic
mass
Renal artery aneurysm. A, Color Doppler image of the
right renal artery reveals a focal saccular dilatation of the
distal renal artery at the renal hilum that fills in with color
(arrow). B, Conventional angiography of the same patient
reveals contrast enhancement of the aneurysm

74. Doppler in Renal Transplant

75. Gray-Scale assessment
• Easy assessment being superficial location in
right or left lower quadrant.
• Oriented with long axis parallel to surgical
incision, hilum facing inferiorly and
posteriorly.
• Measurement of width and depth in sagittal
and transverse planes through hilum.
• Needed for future comparison, increased
volume d/t hypertrophy by up to 15% within
2 weeks and up to 40% by 6 months (final
size).

76. Doppler Assessment
• Color Doppler: global assessment of intra-parenchymal perfusion and
localizing main renal artery and vein.
• Spectral traces to be obtained from the interlobar arteries from upper, mid
and lower pole regions.
• Normal waveform: low impedance with a brisk upstroke and continuous
diastolic flow.
• RI: Normal: 0.6-0.8; Equivocal: 0.8-0.9 and > 0.9 abnormal
• PSV in main renal artery < 200 cm/sec (provided there is normal flow in
recipient common iliac vein.
• Continuous, monophasic flow in the intra- and extraparenchymal renal vein
along with normal velocity gradient across the venous anastomosis.

78. Abnormal renal transplants
Possible etiologies is approached based on:
1. Parenchymal pathology: ATN, Acute and chronic rejection, infection
2. Prerenal problems: All pathologies affecting blood flow to and from
the kidney.
3. Postrenal complications: intrinsic or extrinsic lesion causing
calyceal or ureteric obstruction.

79. Parenchymal pathology
ATN and Acute rejection
ATN: Donor organ ischemia either prior to vascular anastomosis or
secondary to perioperative hypotension.
Acute rejection:
• Up to 40% of patients in early post op period
• usually asymptomatic, some patients show flulike symptoms, malaise,
fever and graft tenderness.

80. Imaging features: No specific features, serial spectral analysis
and clinical/biochemical correlation can guide management.
Gray-Scale
• Increased length and cross-
sectional area (serial assessment)
• Increased cortical thickness
• Increased or decreased cortical
echogenicity
• Reduction of CMD
• Loss of renal sinus echoes
• Prominence of the pyramids
Color Doppler
• Normal or show diffuse decrease
of blood flow
• RI may be normal or elevated
• Severe cases, complete lack of
diastolic flow or even reversal.

81. Acute rejection. A, Sagittal sonogram shows increased cortical echogenicity. B, Spectral
Doppler ultrasound done initially shows no flow in diastole and thus a resistive index (RI) of
1.0. C, Follow-up spectral Doppler ultrasound 1 week later shows reversal of flow in diastole,
which coincided with the clinical deterioration of the patient.

82. Chronic Rejection
• Reduction in allograft function starting at least 3 months post-transplant.
• m/c cause of late graft loss
• m/c cause is recurrent previous episodes of acute rejection.
• USG:
• Progressive thinning of renal cortex
• Prominent renal sinus fat
• Reduced overall size of implant
• Diffuse dystrophic calcification
• End-stage, entire renal cortex is calcified, with sharp echogenic interface
and clean distal shadowing.

83. Chronic renal failure in six patients. A
and B, Cortical thinning. A, Sagittal scan
shows moderate cortical thinning with
abundant renal sinus fat. B, With
progression, the kidney (arrows)
becomes smaller and the cortex thinner.
C to F, Dystrophic
calcifications. Sagittal sonograms show C,
a few punctuate peripheral cortical
calcifications (arrows); D, multiple
peripheral and
central cortical calcifications (arrows);
and E, linear calcifications that extend
from the peripheral to deep cortex
(arrows). F, The end-stage
kidney becomes calcified, appearing as
an echogenic interface (arrow)
associated with dirty shadowing
(arrowheads). The kidney is frequently
not identified on sonography at this
stage.

84. Prerenal Vascular Complications
• Arterial Thrombosis
• Renal artery thrombosis in < 1% of patients; within 1st month
• Causes:
• Hyperacute or acute rejection
• Young paediatric donor kidney
• Atherosclerotic emboli
• Acquired RAS
• Hypotension
• Vascular kinking
• Cyclosporine/hypercoagulable states/intraoperative trauma/poor intimal
anastomosis

85. Doppler Findings
• Color and spectral Doppler: complete absence of arterial and venous
flow distal to occlusion, in both renal artery and intraparenchymal
vessels.
• Multiple renal artery: Segmental infarction in presence of preserved
renal function.
• D/D: Hyperacute rejection and Renal vein thrombosis showing absent
flow in kidney parenchyma.
• Main renal artery is patent and may show reversal of diastolic flow.

87. Renal Artery Stenosis
• Most common vascular complication post transplant; up to 10% of
patients within 1st year.
• Stenosis can occur in one of the three regions:
• Donor portion > end-side anastomosis
• Recipient portion: intraoperative clamp injury or intrinsic
atherosclerotic disease.
• Anastomotic site: end-end anastomosis

88. • Color Doppler used to detect precise location of stenosis and to detect
areas of aliasing.
• PSV >200 cm/sec in the presence of distant turbulent flow: Stenotic region.
• Intra-parenchymal arterial stenosis in case of chronic rejection d/t focal
scarring: Spectral Doppler shows prolonged AT in interlobar and segmental
arteries with normal main renal artery waveform.
• False positives:
• Abrupt turn in the main renal artery
• Severely tortuous artery
• Inadvertent compressen by sonographer

89. Renal artery stenosis: recipient portion. A, Color Doppler
ultrasound shows focal area of aliasing (arrow)
proximal to the renal artery anastomosis. B, Spectral Doppler
of the region of aliasing seen in image A shows angle-
corrected peak velocities of 400 cm/sec. C, Angiography
shows a focal area of stenosis (arrow) arising from the
external iliac artery. D, Angiogram performed after
angioplasty shows resolution of the stenotic region (arrow
Renal artery stenosis: donor portion. A, Color Doppler
ultrasound of donor renal artery anastomosis shows
focal area of aliasing (arrow). B, Power Doppler shows area of
narrowing in this region (arrow). C, Spectral Doppler shows
elevated anglecorrected
velocities at the site of the arrow, greater than 400 cm/sec.

90. Renal Vein Thrombosis
• More common than arterial thrombosis; 4%
• C/F: Acute pain, swelling of the allograft, abrupt cessation of renal
function between 3rd- 4th post op day.
• Risk factors:
• Technical difficulties at surgery
• Hypovolemia
• Propagation of femoral or iliac thrombosis
• Compression by fluid collection

91. Findings
Intraluminal thrombus is
rarely detected.
1. Spectral/color Doppler:
Absence of flow in the
main renal vein
2. Reversal of diastolic flow
in main renal artery
Renal vein thrombosis. A, Sagittal sonogram shows
increased cortical echogenicity with a coarse echotexture.
B to D, Spectral Doppler ultrasound images of cortical
arteries (B), renal sinus arterial branches (C), and main
renal artery (D) show reversal of flow in diastole. No
venous flow was detected in the transplant.

92. Arteriovenous malformations
• Incidence 1-18%
• Large AVMs presents with bleeding, high output cardiac failure, decreased
renal perfusion
• Findings
• Color Doppler:
• Focal areas of aliasing with a myriad of intense colors
• Prominent feeding artery or draining veins
• Spectral Doppler:
• Low resistance, high velocity flow with difficulty in differentiating between
artery and vein within it.
• If dominant draining vein present, show pulsatile or arterialized waveform.

93. Arteriovenous malformations (AVM). A, Gray-scale ultrasound; AVM not detectable. B,
Corresponding color Doppler image shows large AVM. C, Sagittal sonogram shows lower-
pole AVM. D, Spectral Doppler of AVM in image C shows high-velocity, low-resistance
waveform. E, Sagittal sonogram shows AVM with feeding vessel (arrow). F, Sagittal scan
shows lower-pole AVM with surrounding tissue vibration.

94. Pseudoaneurysms
• Occur at the site of vascular anastomosis or vascular trauma to the
arteries during biopsy
• Intra- or extra-renal location
• Findings
• Gray-Scale: mimics simple/complex cyst
• Color Doppler: Flow in the patent pseudoaneurysm, swirling pattern
• Spectral Doppler: central to- and –fro waveform, or a disorganized
arterial tracing.

95. Sagittal sonogram
shows upper-pole
anechoic structure.
On color Doppler ultrasound, swirling
flow is identified
in the anechoic structure identified on
image A (arrow). This is adjacent to a
large central AVM.
Spectral Doppler ultrasound
shows disorganized flow in the
pseudoaneurysm (yellow arrow)
and low-resistance high-velocity
flow in the central AVM (white
arrow).

96. Conclusions
• Renal Vascular diseases, specially RAS, are potentially curable and can
prevent from developing chronic renal diseases.
• Renal Doppler ultrasound provides a reliable, easily available means of
assessing renal arteries with good diagnostic outcomes in skilled hands.
• Can avoid unnecessary invasive procedures to diagnose vessel related
diseases.
• Other imaging modalities are only used in indeterminate conditions, or
when interventions are required.
• Results depend on many factors including patient selection and
preparation, good skill and working knowledge of the radiologist.

97. References
• DIAGNOSTIC ULTRASOUND, Carol M. Rumack.
• Introduction to Vascular Ultrasonography by Pellerito Polak
• Ultrasoundpaedia: Ultrasound of the renal arteries
• Duplex ultrasound of the renal arteries by ROBERT G. ATNIP MD
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