IMAGING OF RENAL HYPERTENSION

1. IMAGING OF RENAL HYPERTENSION

3.  Renal artery divides into 4-5 interlobar
segmental arteries.
 Interlobar arteries arch over the base of
pyramids to form arcuate arteries.
 Arcuate arteries branched in to interlobular
arteries which further divides into afferent
arterioles which going to the glumerulous ,
blood leave the glumerulous through efferent
arterioles.

4. ANATOMY

5.  Hypertension is a common disease affecting
about 20% of adult population.
 5-20% due to secondary causes.
 Common causes;
 Kidneys disease.
 Adrenal disease.
 Coarcatation of aorta.
 Pregnancy.
 Contraceptive pills.
 Alcohol addiction.
 Thyroid dysfunction.

6.  Renovascular hypertension is the most type
of secondary hypertension , its prevalence
between 0.5-5% of general hypertensive
population.
 significant renal artery stenosis is 60% by
Doppler study and 50% by cath.Angiography.

7.  Common causes
 Atherosclerosis 90 %
 Fibromuscular dysplasia 10%
 Rare causes
 Vasculitis.
 Embolic disease.
 Dissection.
 Post trauma.
 Extrinsic compression.

8.  Classic polyarteritis nodosa (PAN or c-PAN)
is a systemic vasculitis characterized by
necrotizing inflammatory lesions that affect
medium-sized and small muscular arteries,
preferentially at vessel bifurcations.
 These lesions result in micro aneurysm
formation, aneurysmal rupture with
hemorrhage, thrombosis, and, consequently,
organ ischemia or infarction may occur.

9.  Direct catheter angiography is far more sensitive
to changes within small vessels, although a good
quality CTA can also demonstrate changes.
Findings include:
 multiple microaneurysms
 characteristic but not pathognomonic
 typically 2-3 mm in size but can be up to 1 cm
 in the kidneys, the microaneurysms typically involve
the interlobar and arcuate arteries
 hemorrhage may be present due to focal rupture
 occlusion may be present.

13.  0-hypo- echogenic than liver, maintained
cortico0medullaryy differentiation.
 1-iso echoic as the liver with maintained cortico-medullary
differentiation.
 2-more echogenic than liver with maintained cortico-
medullary differentiation.
 3-more echogenic than liver with poor cortico-medullary
differentiation.
 4-more echogenic than liver with loss C.M differentiation.

15. ESRD --ATROPHY

16.  Chronic kidney disease can be classified in a variety of ways.
One such classification, proposed in 2005, can be divided into
five stages based on the GFR (ml/min/1.73 m2)
 stage 1: >90: kidney damage with normal or elevated GFR
 stage 2: 60-89: kidney damage with mild reduction in GFR
 stage 3: 30-59: moderate reduction in GFR, this can be
further sub divided as
 stage 3a: 45-59
 stage 3b: 30-44
 stage 4: 15-29: severe reduction in GFR
 stage 5: <15 (or dialysis): end-stage kidney disease (ESKD)

17.  There are no specific imaging features for CKD,
and the diagnosis is based on clinical and
laboratory findings.
 Radiological exams, especially ultrasound, are
performed in most of the cases for etiological
investigation (e.g. renal artery stenosis, polycystic
kidney disease, hydronephrosis and treatment
follow-up).

18.  Ultrasound with Doppler examination of intrarenal vessels is usually
performed in patients with CKD, and it is common to have a normal
exam.
 Typical B-mode findings of a long-standing severe CKD (especially stage
5) are :
 reduced renal cortical thickness <6 mm
more reliable than length.
 reduced renal length.
 increased renal cortical echogenicity .
 poor visibility of the renal pyramids and the renal sinus.
 marginal irregularities.
 papillary calcifications.
 cysts .
 Abnormal Doppler findings in these patients are :
 reduced renal vascularity
 increased resistance index (RI) values (segmental and interlobular
arteries).

19.  RAS 50% under perfusion of the kidney
activation of rennin angiotensin system.
 Angiotensin angiotensin I.
 Angiotensin I angiotensin II.
 Angiotensin II is a potent vasopressor responsible for
the vasoconstrictive element of renovascular
hypertension.
 Angiotensin II increase adrenal gland production of
aldostrone with subsequent retention of sodium and
water.

20. Anatomical
Unilateral
Unilateral in single
functioning kidney
Bilateral
Proximal
Distal
Severity
Mild < 50%
Moderate 50-75%
Severe > 75%
Total occlusion

21.  Refractory hypertension
 Severe hypertension, diastolic flow is >120
mmHg.
 Hypertension associated with renal impairment.
 Onset of hypertension before 30 year.
 Abrupt onset of hypertension.
 Generalized atherosclerosis.
 Abdominal bruit.

22.  IVU
 U.S
 CT SCAN
 MRI
 Renal scintigraphy
 Renal angiography.

23. IVU is no longer used for the diagnosis of renal
artery stenosis.
 IVU sign of renal artery stenosis are;
 A renal size difference more than 1.5 cm.
 Delayed renal blush and delayed elimination of
contrast in early X-ray films.
 Notching of the ureter due to compensatory
hypertrophy of the ureteric artery.

24. First step in investigation.
 Size disparity between two kidneys (1.5-2 cm).
 Exclude an obvious structural abnormality ,
coexistent condition that may relate to the
hypertension (renal scaring and rarely renal or
adrenal tumors).

25. Small kidney ,
smooth outline

26.  MRA is a very good noninvasive technique
capable of demonstrating the renal vascular
anatomy and direct visualization of renal artery
lesions without iodinated contrast material.
 The limitations of MRA are its expense and its
contraindication in patients with metallic clips,
pacemakers, intraocular metallic devices, or other
implants.
 The sensitivity of MRA > 90% for proximal
RAS, 82% for main RAS, and very low ( 0%) for
segmental stenosis.

27.  Non contrast MRA.
 Contrast MRA.
 Cine phase contrast imaging diffusion and
perfusion to measure renal ischemia.
 MRI BOLD to assess renal oxygenation.

28.  Three currently used techniques to analyze BOLD-MRI. (Left) Classical ROI-
based technique, with placement of circle-shaped regions of interest (ROIs) in the
renal cortex (yellow) and medulla (red); (Middle) Twelve-Layer Concentric
Objects (TLCO) technique, which divides the renal parenchyma in 12 layers of
equal thickness; (Right) Fractional hypoxia technique, which counts the percentage
of voxels with an R2* value >30 sec−1.

30. Dynamic gadolinium-enhanced magnetic resonance
angiogram (MRA) shows normal renal arteries.

31. MRA, MIP shows bilateral severe proximal RAS , associated with small
size left kidney .

32.  Exposure to gadolinium contrast agents in patients
with renal failure and those maintained on dialysis
has recently been linked with the development of
nephrogenic systemic fibrosis a debilitating and
sometime fatal disease affecting the skin , muscle
and internal organs.

33.  Evaluation of branch vessels.
 The presence of a metallic stent.
 Detection of accessory arteries.

34.  Advantages
 Disadvantages
 Normal results from CTA virtually rule out
RAS.

37. RAS due to atherosclerotic changes ;Secondary signs ; post stenotic
dilatation, renal atrophy, decrease cortical enhancement.

38. Coronal MIP CT angio, shows rt.renal artery stenosis due to FMD,
(string of pearls appearance) , Multiple alternating narrowing and
dilatation.

39.  Flush aortography.
 Selective renal angiogram.
Considered reference standard for demonstrating
RAS.
 Angiography has high spatial resolution for
evaluating the main renal arteries as well as the
branch renal arteries.

45. Flush Aortogram .
Radiograph shows a
complete occlusion of the
right renal artery and
marked stenosis of the left
renal artery.

46. Left renal artery stenosis
Aortogram shows a focal
left renal artery stenosis
With post stenotic dilatation
Right renal artery is normal
shows early dilivery of
Contrast to right kidney.
Courtesy of Jonathan
Kruskal, MD.
CONVENTIONAL AORTOGRAM

47. Common renal radio nuclides
1- DMSA; Dimercapto succinic acid.
2-MAG3; Mercaptuacetyltriglycine.
3-DTPA; Diethylen triamine penta acetic
acid.
4- OIH; Orthoiodohippurate I 131.
5- EDTA; Ethylenediamine tetra acetic acid.

48.  Perfusion MAG3, DTPA
 Morphology DMSA
 Obstruction MAG3,DTPA,OIH
 GFR quantification EDTA, DTPA
 Relative function All

49. DMSA and glucoheptonate are accumulated in the
renal cortex, so they are helpful in evaluation of;
 Renal scarring
 Infarction.
 Renal ectopia and anomalies.
 Renal mass.
 Differential renal mass (proportion of total renal
mass contributed by each kidney.
 Tracer Tc-99m DMSA
 Acquisition 2-4 hrs post injection.

50. LPO RPO

51. The images are opposite
Right kidney is sharper in this position

56.  Acute or chronic pyelonephritis.
 Hydronephrosis.
 Cyst.
 Tumor.
 Trauma (contusion, laceration, rupture,
hematoma).
 Infarct.
 Abscess.

58. DMSA – left kidney agenesis

59.  Tracers: MAG3, DTPA
 Labeling with technetium 99 m gives a slower
radiation dose.
 Better imaging and mearement statistics.

62. NORMAL RENOGRAM

63.  Diuretic (Lasix ) Renal Scan

64. Lasix renogram
1- perfusion
2- excretion
3- analysis/curves

65. -Both kidneys should show
Simultaneous uptake in one
frame in appearance of great
vessels.
-The images are fuzzy, not so
clear.
-perfusion time is 1-10
seconds.
Followed images 10-20 sec
Then 20-30 sec and so on

66. These images
accumulated over time
Represent activity over
minutes.
In which frame the
kidney is more bright?
In subsequent frames ,
the brightness
diminished, is it
symmetrical?

67. Lasix is given after 15
minutes of radionuclide
injection.
In partial obstruction, it may
detected only by maximizing
urine output.
Images of the kidneys fades
rapidly.

68. On the line graphs, the
radioactivity are plotted on the
Y axis
While the time is plotted on X
axis.
Early component of the curve
represent perfusion and the late
represent drainage
With the curves, tables for
differential function and
clearance.

69. Normally the curve show rapid uptake (flow curve) and rapid
drainage (function curve)

70. Normal T1/2 is <12 min, if the
kidney doesn't reach T1/2 by 20
min. The kidney is considered to
be obstructed.
T1/2 12-20 min. Considered
indeterminate.
This Lasix renogram shows that
the T1/2 of left kidney is 19.2
min. In the indeterminate range.

71. Pre-Lasix

72. Post-Lasix

73. No- PUJO

74. T1/2 < 10 min. normal
10-20 min.indeterminate
> 20 min.obstruction

75.  Captopril Renal Scan
ACEI Renography

76.  Captopril renography is functional assessment of
renal perfusion.
 In patients with unilateral RAS , ACE inhibitor
scintigraphy induce significant changes in the
time activity curve of the affected kidney in
comparison with base line scintigraphy.

77.  Captopril renography: Radionuclide renal imaging can
be done using Tc99m DTPA, Tc99m MAG3 or OIH
( orthoiodohippuran).
 It is a safe and noninvasive way to evaluate renal blood
flow and excretory function.
 When Captopril is administered (especially in unilateral
RAS), the GFR of stenotic kidney falls by about 30%
and the normal kidney exhibits an increase in the GFR.
Sensitivity of this test is about 85-90% and specificity of
93-98%.
 Significant azotemia and bilateral RAS adversely affect
this accuracy, making it unsuitable for these situations.

78.  Off ACEI and AT II receptors for 3-7 days.
 Off diuretics for 5-7 days.
 No solid food for 4 hrs.
 Patient well hydrated.
10 ml/kg water 30-60 min pre and during test.
 ACEI, (Captopril) 25-50 mg oral (crushed), 1
hr pre-scan.

79.  Tracer; Tc-99m MAG3 or DTPA
 Protocol 1 day or 2 day test
 `1 day test baseline scan 1-2 mCi
followed by post –Capto scan 8-10 mCi.
 Acquisition; flow and dynamic for 20-30
min.

80.  Grade 1 mild delayed in Tmax 6-11 min using
99mTc –DTPA with a falling excretion phase.
 Grade 2 more prolonged delayed in Tmax
greater than 11min but still with an excretion
phase.
 Grade 3 with marked reduction in function of
the affected kidney.

81. ACEI Renography
Grading renogram
curves

82.  Not all cases of renal artery stenosis will cause renovascular
hypertension.
 Some patients will show no response to angioplasty or
stenting.
 ACE inhibition renography can be used to determine which
patients with renal artery stenosis could benefit from
intervention.
 High probability criteria for renovascular hypertension:
 10% decrease in differential (split) function (i.e. 50/50 to
60/40)
 (RCA) retained cortical activity at 20 minutes differing from
the controlateral kidney by more than 20%
 delay in time to peak activity in the affected kidney of more
than 2 minutes when compared to the baseline study or
unaffected kidney.

83. RIGHT RENAL ARTERY STENOSIS

85. Base line Tc-99m DTPA scintigrams Captopril scintigrams
Stenotic right accessory renal artery

86.  Bilateral RAS.
 Impaired renal function.
 Urinary obstruction.
 Chronic intake of ACE inhibitors.

87. Base line Tc-99m DTPA scintigrams Captopril scintigrams
Renal insufficiency

88. Renal artery anomalies
Multiple renal arteries (lower pole)
Early branching
Retro-aortic LRV
Kidney anomalies.

89. Patient preparation-fasting 8-12 hrs.
Explain breath hold.
Bilateral kidneys and renal arteries.
Complete evaluation of renal artery
Findings confirmed from two views

90. Longitudinal image of aorta.
Obtain spectral Doppler at SMA level.
Direct evaluation of both renal arteries.
Spectral Doppler of both arteries.
Indirect evaluation
Hilar analysis.
Renal parenchymal waveforms.
kidney length measurements.

91. Exam components
B-mode image- anatomical informations
Pulse Doppler- hemodynamic informations.
Optimize image by;
Color, power angio, harmonic imaging.

92. Images taken from multiple views

93. Doppler exam components
Insonate entire course of renal artery to obtain the maximum
PSV.
Doppler interrogation in sagittal view only.
-Small sample volume
-Center stream or center to flow jet
-Doppler angle <60
-Use angle correction , align cursor parallel to vessel wall.
-Calculate PSV from designated locations and any areas of
abnormalities.

95.  1- ANTERIOR APPROACH
The renal arteries are clearly imaged in B Mode
from an anterior, subcostal approach
 Supernumerary (duplicate) arteries can be seen
looking posterior to the IVC in B Mode and
Colour in a sagittal plane.
2- OBLIQUE APPROACH
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.

96.  3- CORONALAPPROACH
Roll the patient into a decubitus position to void
bowel gas and improve visibility of the renal
artery, especially the mid to distal portion.

 4- PRONE APPROACH The patient is lying
prone or decubitus and the probe is moved from
the spine laterally using the muscles as an
acoustic window to find the kidney initially and
then the renal hilum using Colour Doppler.

97. 1- PSV of aorta with and without angle.
2- Renal Artery Assessment- initially with colour
Doppler.
3- Renal Artery Spectral Analysis for origin, proximal,
mid and distal parts of the artery.
4-Interlobar/Segmental Artery Spectral Analysis-
Acceleration Time (AT) and Resistive index (RI).
(AT < 70msec and RI >0.8 for chronic renal disease)

98. Resistive Index
The Resistive Index (RI)is
between second systolic
peak and the lowest
diastole.
Acceleration Time
The Acceleration Time
(AT) is from beginning of
systole to the fist systolic
peak.
This should be less than
70ms

99. Rapid systolic rise
High velocity diastole
Small spike at the end of systolic rise
Normal peak systole <150 cm/s
RI of renal artery in the hilum is more than distal arteries.

100. Parenchymal waveforms
Medulla and cortex
Upper and lower poles

101.  Normal intrarenal waveform
 sharp upstroke with rapid acceleration to peak
systole.

102. 1-Aorta B Mode -Longitudinal and Transverse to
assess for an abdominal aortic aneurysm.
2- Kidney lengths-cortex assessment for reduced
size, <9 cm or 2 cm asymmetry.
3-Perfusion Kidney- colour Doppler used to assess
the perfusion to the edge of the renal cortex.
 Resistive Index- Spectral Doppler of kidney
parenchyma at the interlobar (segmental) arteries
and interlobular (arcuate)arteries and DSR.
 Acceleration Time.

103. kidney length >7-8 cm favour reconstruction.
Medical renal disease
DSR >3 normal.
RI< 0. 7 within normal.
In CKD ;RI > 0.8
If DSR is markedly abnormal , reconstruction show clinical failure.
Length =average of three

104. Indirect signs (distal criteria)
Loss of early systolic peak.
AT >70 msec.
Difference between the kidneys RI more than 5%.
Blunted and delayed systolic upstroke (tardus-parvus)

105. Clinical utility of resistive indices
Identify patient for revascularization
DSR <0.18 clinical failure
EDV <5 cm/s
RI > 0.7

106. Renal aorta ratio calculation RAR
Maximum renal artery PSV
---------------------------------- =RAR, normally < 3.5
Maximum aorta PSV
Limitations: AAA, aortic PSV< 40 cm/s

107. 1-Normal; RAR <3.5
Renal artery PSV<180 cm/s
2-<60% diameter stenosis
RAR <3.5.
PSV >180 <200 cm/s
No post stenotic turbulence
3-60-99% diameter reduction
RAR >3.5
PSV>200 cm/s
Post stenotic turbulence.
4- Occlusion:
No detected flow
Monophasic low velocity parenchymal signal.
;

112. Renal artery stenosis. Narrowing, elevated velocity
>200 cm/sec
Transplant Doppler

113. Renal vein thrombosis (complete) ;no main renal vein flow, decreased intrarenal
arterial flow. Very high resistance; reversed diastolic flow.
Transplant Doppler

114. 53 y post-transplant bx
AV FISTULA
Soft tissue bruit
very low resistance
Transplant Doppler

115. Transplant Doppler post-biopsy complications pseudo
aneurysm.
Transplant Doppler

116. Clinically : worse renal function ,
US : unilateral enlarged kidney
,loss of Corticomedullary
differentiation & reversal of end
diastolic flow.
Risk factors for renal vein
thrombosis : trauma ,sepsis
,dehydration ,diabetic mother.

117. • When the history is highly suggestive and no risk for
radiocontrast-mediated renal injury is present, an intraarterial
DSA or conventional angiogram is the appropriate initial test.
• In patients at risk, a carbon dioxide angiogram can determine
the presence of a stenosis, and the risk of radiocontrast
angiogram is imposed only on those individuals are most
likely to benefit.
• In moderate suspicion of renovascular disease exists
• a spiral CT scan, MRA, or duplex ultrasonography (depending
on availability and local experience) is performed.
• A negative test result indicates that an RAS is highly unlikely,
while a positive test result can be followed by renal
arteriography.

118.  A study done by Gilfeather et al for evaluation
of conventional angiography versus contrast
MRA
 In 54 patients with 107 kidneys.
 The study showed that in 70 kidneys 65% the
average degree of stenosis reported by readers of
both modalities differed in 10% or less.
 In 22 cases 21%, MRA overestimated the degree
of stenosis by more than 10% relative to
angiography.
 in 15 cases 14% MRA underestimated the
stenosis by more than 10%.

119. • The obvious advantages of conventional angiography are its
ability to accurately determine the extent of the lesion and
suggesting its clinical importance (by demonstrating post-
stenotic dilation) and the ability to concurrently perform
endovascular therapy.
• However, specialists should weigh these advantages against
the higher cost and greater morbidity of conventional
angiography.
 All these tests should be done if the pt is a reasonable
candidate for revascularization procedure.

120.  It is crucial to remember that
 not all HTN in the presence of anatomic RAS is
renovascular HTN.
 Many normotensive patients and those with
essential HTN can also have some degree of RAS
and do not need revascularization.

121. Include
*Medical therapy.
*Percutaneous transluminal angioplasty (PTA)
with or without vascular stent placement.
*Surgical revascularization.
*Intravascular ultrasonography-guided
atherectomy.

122. percutaneous transluminal angioplasty alone or
with stent implantation.
Selection of patient for revascularization;
 Refractory hypertension.
 Progressive azotemia.
 recurrent pulmonary edema.
 Bilateral renal artery stenosis.
 Stenosis of renal artery supplying single
functioning kidney.

127. A lot of thanks for your attention