Download Diagnosis of Renal Artery Stenosis(RAS)

May 2001
Diagnosis of
Renal Artery Stenosis (RAS)
Kurt Fink, Harvard Medical School, Year III
Gillian Lieberman, MD
Kurt Fink, HMSIII
Gillian Lieberman, MD
Epidemiology
Hypertension
-Affects 60 million Americans
Essential HTN
Secondary HTN
>95% of cases
1-5% of cases
Renovascular HTN
Other Causes:
*accounts for majority of
cases of secondary HTN
Hyperaldosteronism
Cushing's Syndrome
Pheochromocytoma
Aortic Coarctation
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Physiology of RAS
Hypertension
RAS
 RBF
 Renin
 AII
Efferent Arteriolar
Vasoconstriction
Key:
RBF=Renal Blood Flow
Maintains GFR!!
If this compensatory
mechanism fails, patient will
experience renal failure!!
AII=Angiotensin II
GFR=Glomerular Filtration Rate
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Clinical Presentation of RAS
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Onset of HTN in patient >60 or <20 y.o.
Acute rise in B.P. above stable baseline
Acute elevation in plasma creatinine
Abdominal bruit
Atherosclerotic disease (PVD, CAD)
Unilateral small kidney (<9cm)
Patients presenting with any of the above findings warrant
further evaluation for RAS…
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Major Forms of RAS
1) Atherosclerotic
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Accounts for 90% of cases of RAS
Often associated with diffuse atherosclerotic disease
Usually involves ostium and proximal 1/3 of renal artery
Progressive: unilateral  bilateral
2) Fibromuscular Dysplasia
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Classically seen in young women
Etiology unknown
Can affect intima, media or adventitia of vessel
Involves distal 2/3 of renal artery and segmental branches
Aneurysmal appearance on angiography
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Anatomy
Medulla (pyramids)
Main Renal Artery
Minor Calices
Cortex
Segmental Arteries
Interlobar Arteries
Netter FH. Atlas of Human Anatomy. New Jersey, Novartis, 1997, p. 315.
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Kurt Fink, HMSIII
Gillian Lieberman, MD
“Patient E.O.”
• 90 y.o. woman with a h/o CAD, CHF, HTN and
hypercholesterolemia
• Over a period of 6 months, her previously wellcontrolled HTN has progressed and is currently
refractory to treatment with maximum dosages of
4 antihypertensive medications
• Additionally, during this time, her Creatinine has
increased to 1.5 from a baseline of 1.0-1.2
• No Abdominal bruit was detected on examination
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Work-up of suspected RAS
Menu of tests
Invasive
Conventional Angiography
Non-Invasive
MR Angiography
Renal Scintigraphy
Doppler Ultrasound
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Kurt Fink, HMSIII
Gillian Lieberman, MD
MR Angiogram (MRA)
General
 3-D anatomic reconstruction using MRI
 Sensitivity=100%; Specificity=96%
Advantages
 Excellent anatomic visualization (especially w/ gadolinium)
 Non-invasive, no contrast, no ionizing radiation
Disadvantages
 Costly
 Limited availability
 Claustrophobia
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Kurt Fink, HMSIII
Gillian Lieberman, MD
MRA of Patient E.O.
Stenosis of
Left Renal Artery
Stenosis of
Right Renal Artery
PACS, BIDMC.
PACS, BIDMC.
MRA clearly demonstrates bilateral stenosis of proximal Renal Arteries
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Kurt Fink, HMSIII
Gillian Lieberman, MD
MRA of Another Patient
Celiac Trunk
Superior Mesenteric Artery
Right Renal Artery
Enlargement of
Infrarenal Aorta
(~4.2cm)
Left Renal Artery
with focal stenotic lesion
PACS, BIDMC.
Click for 3-D Animation and Labels!
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Renal Scintigraphy
General
 Assesses differential renal blood flow using Tc99m-MAG3, a
compound that is NOT filtered, but IS secreted.
 PPV=85%; NPV=90% (in high risk patients)
Advantages
 Most Funtional Study
 Preferred method in suspected Fibromuscular Dysplasia
 Non-invasive, no contrast
Disadvantages
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Poor at detecting Bilateral RAS
Not as useful in elderly, as their HTN tends not to be renin-dependent
Poor NPV
Some exposure to radioactivity
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Renal Scintigraphy
• This is a pre ACE Inhibitor
renal scan of a patient with
RAS. Notice that uptake and
excretion of Tc99-MAG3 is
symmetrical in the two
kidneys. Thus, this patient is
well-compensated and is able
to maintain GFR.
Courtesy of Mallinckrodt Institute of Radiology, Washington University, http://gamma.wustl.edu/rs001te187.html.
Hypertension
RAS
 RBF
 Renin
 AII
Efferent Arteriolar
Vasoconstriction
Maintains GFR!!
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Renal Scintigraphy
•After administration of an
ACE Inhibitor, notice that
the right kidney (on your
right-hand side! As these are
posterior views) has normal
uptake and excretion, while
the left kidney demonstrates
significant retention of Tc99MAG3, with impaired
excretion. This implies a
drop in GFR in the left
kidney, and is a positive test
for RAS.
Courtesy of Mallinckrodt Institute of Radiology, Washington University, http://gamma.wustl.edu/rs001te187.html.
Hypertension
RAS
 RBF
 Renin
 AII
Effects of ACE Inhibitor...
Efferent Arteriolar
Vasoconstriction
Drop in GFR!!
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Renal Scintigraphy in action...
Post ACE Inhibitor
Courtesy of Dr. Donohoe, BIDMC.
• Again, notice that there is
marked asymmetry in function
between the two kidneys, with
normal uptake and excretion by
the right kidney, but significant
retention of radiolabeled MAG3
by the left kidney, with little or
no excretion. Once again, this is
a positive scan for RAS of the
left renal artery.
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Doppler Ultrasound
General
 Evaluates post-stenotic, intra-renal vessels for alterations in normal
renal waveforms
 PPV=99%; NPV=97% (in high risk patients)
Advantages
 Funtional & Anatomic
 Inexpensive
 Non-invasive, no contrast, no ionizing radiation
Disadvantages
 Time-consuming (often >1-2 hours)
 Highly operator-dependant
 Limited by obesity and bowel gas
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Doppler Ultrasound of
Renal Arteries
Right Renal Artery
Abdominal Aorta
Radiologic Clinics of North America 1996; 5: 1017-1036.
Left Renal Artery
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Doppler Ultrasound Waveforms
Normal waveforms
Radiologic Clinics of North America 1996; 5: 1017-1036.
Rapid upstroke & early systolic peak (arrow)
RAS waveforms
Radiologic Clinics of North America 1996; 5: 1017-1036.
“Tardus & Parvus” waveform, i.e.
slowed uptroke and low amplitude peak
Quantitative characterization of waveforms has not proven to be more sensitive
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than “pattern recognition” in doppler ultrasound detection of RAS.
Kurt Fink, HMSIII
Gillian Lieberman, MD
Conventional Angiography
General
 Gold Standard
 “Digital Subtraction” angiography has allowed for use of
decreased volume of contrast
Advantages
 Anatomic
 Allows for immediate intervention (PTCA/stent)
Disadvantages
 Invasive
 Iodinated contrast can be nephrotoxic in patients with renal failure!
 Exposure to ionizing radiation
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Kurt Fink, HMSIII
Gillian Lieberman, MD
…Back to our Patient “E.O.”:
• Given her clinical scenario of worsening
HTN and renal function, along with the
finding of bilateral RAS on MRA, the
decision was made to proceed to
Angiography for further imaging and
possible intervention.
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Kurt Fink, HMSIII
Gillian Lieberman, MD
EO: Digital Subtraction Angiography
Collateral vessels
• A catheter is advanced through E.O.’s
Left Femoral Artery into the upper
Abdominal Aorta
• Contrast is injected, allowing for
visualization of anatomy of Aorta,
Renal Arteries, etc.
• Digital Subtraction involves
“subtracting” an initial scout image (no
contrast) from the aortogram, providing
enhanced vascular detail
Bilateral Stenosis of Renal Arteries
PACS, BIDMC.
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Kurt Fink, HMSIII
Gillian Lieberman, MD
EO: Angioplasty
• This fluoroscopic image shows
the positioning of a guidewire in
a segmental renal artery
• Contrast in collecting system
• Black dots represent proximal
and distal ends of angioplasty
balloon on catheter that has
been advanced over guidewire
into left renal artery
PACS, BIDMC.
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Kurt Fink, HMSIII
Gillian Lieberman, MD
EO: Angioplasty
• Injection of contrast allows for
visualization of angioplasty
balloon in relation to stenotic
lesion
• 3 and 5 mm angioplasty balloons
are then serially inflated
• A Corinthian stent, mounted on a 5
mm balloon, was then positioned
and inflated
PACS, BIDMC.
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Kurt Fink, HMSIII
Gillian Lieberman, MD
EO: Stent Placement
Stent
PACS, BIDMC.
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Kurt Fink, HMSIII
Gillian Lieberman, MD
EO: S/P Stent Placement
• Upon injection of contrast,
correction of stenosis is confirmed
visually
• In addition, pre- and post-procedure
pressure measurements are
compared:
 Aortic Pressure
= 159/49
 Post Stenosis L. Renal Artery Pressure:
 Prior to PTCA/Stent = 43/31
 After PTCA/Stent = 172/55
• Similar stenting was carried out in
the R. Renal Artery
PACS, BIDMC.
• Post-op, E.O. experienced return of
both BP and Creatinine to her
previous baseline
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Patient 2: Characteristic Angiographic
appearance of Fibromuscular Dysplasia
• Beaded, aneurysmal
appearance of distal
Right Renal Artery in a
young woman with
refractory HTN and
Fibromuscular Dysplasia
N Engl J Med 2001; 344: 431-442.
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Algorithm & Summary
• This figure represents one
author’s algorithm for the
evaluation of suspected
RAS. However, as you
have gathered from
Patient E.O., there is
considerable variability
involved in how suspected
cases of RAS are workedup by various physicians,
reflecting the controversy
of the field.
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N Engl J Med 2001; 344: 431-442.
Kurt Fink, HMSIII
Gillian Lieberman, MD
References
•
Dustan HP. Renal Arterial Disease and Hypertension. Medical
Clinics of North America 1997; 5: 1199-1212.
• Harbert JC, Eckelman WC, Neumann RD. Nuclear Medicine:
Diagnosis and Therapy. New York, Thieme Medical Publishers, Inc.,
1996, p. 713-724.
• Kaplan NM, Rose BD. Screening for Renovascular Hypertension.
UpToDate.com 2001.
• Mitty HA et al. Renovascular Hypertension. Radiologic Clinics of
North America 1996; 5: 1017-1036.
• Netter FH. Atlas of Human Anatomy. New Jersey, Novartis, 1997, p.
315.
• Safian RD, Textor SC. Renal Artery Stenosis. N Engl J Med 2001;
344: 431-442.
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Kurt Fink, HMSIII
Gillian Lieberman, MD
Acknowledgements
• Thanks to our Webmasters Larry Barbaras and
Cara Lyn D’amour!
• Special thanks to Dr. Reddy, Dr. Donohoe and Dr.
Matthew Spencer for their valuable input and
images!
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