Renal Artery Stenosis
What is renal artery
stenosis?
Renovascular hypertension is persistently high
arterial blood pressure (hypertension) caused
by narrowing of one or both arteries that supply
blood to the kidneys. The narrowing of one or
both arteries to the kidneys is called renal artery
stenosis. However, not all people with renal artery
stenosis develop high blood pressure. Some people
with renal artery stenosis may have no symptoms
at all, or they may have a problem with the filtering
ability of their kidneys. Fortunately, there are
tests available that can help to decide if a person
has renal artery stenosis and whether it is causing
any problems.
Back to top
What
causes renal artery stenosis?
Most of the time (90%) renal artery stenosis is
caused by atherosclerosis, the same condition
that causes hardening of the arteries to the heart,
brain, legs, and other areas of the body. Atherosclerosis
is the build-up of cholesterol and lipids on the
lining of arteries. People who have diabetes,
coronary artery disease and atherosclerosis in
other areas of the body are at higher risk of
having renal artery stenosis. When renal artery
stenosis from atherosclerosis is present, it can
get more severe over time.
The other condition that causes renal artery
stenosis is fibromuscular dysplasia. This is a
group of conditions in which the kidney arteries
develop thickening due to a build-up of muscle
tissue in the walls of the arteries. Unfortunately,
this thickened muscular tissue squeezes down on
the artery and interferes with blood flow. The
cause of fibromuscular dysplasia is unknown, but
may be related to smoking, hormones, or a family
history of the condition.
Back to top
Can
renal artery stenosis interfere with how the kidneys
work?
All organs in the body need a certain amount of
oxygen to function properly. When the arteries
to the kidneys become narrowed, this can result
in the kidneys not receiving enough oxygen. This
is known as ischemic nephropathy. When the kidneys
develop ischemic nephropathy, the ability of the
kidneys to cleanse the bloodstream and eliminate
waste products from the body may be affected.
Renal artery stenosis may be the cause of a sudden
drop in the filtering ability of the kidney (known
as acute renal failure) or unexplained gradual
deterioration of kidney function (known as progressive
azotemia). Up to one quarter of all people over
50 who have progressive azotemia have renal artery
stenosis.
Back to top
How
can I tell whether I have renal artery stenosis?
Determining this begins with a medical history
and physical examination by your physician. Factors
which suggest renal artery stenosis as a possible
cause of high blood pressure include a rapid onset
of high blood pressure, high blood pressure developing
in a person before the age of 50, and high blood
pressure present for less than one year. Listening
over the kidneys with a stethoscope, a physician
may hear a “whooshing” sound of blood
flow known as a bruit.
Back to top
Specialized
tests for renal artery stenosis
If your physician suspects that renal artery stenosis
may be a cause of high blood pressure, impaired
kidney function, or both, a number of tests are
available. These tests can include urine tests,
blood tests, or pictures of the kidneys. Urine
tests check whether the kidneys are losing their
ability to filter waste products such as protein.
Blood tests include those which measure overall
kidney function (such as creatinine) to those
which check the kidney to see if too much blood
pressure hormone is being produced by the body
(renin activity). Pictures of the kidneys can
be made using nuclear cameras (such as captopril
renography), sound waves (Duplex ultrasound),
CAT scans (known as CTA) or magnetic resonance
scans (known as MRA). CTA and MRA can produce
detailed pictures of the kidneys and show whether
renal artery stenosis is present.
Back to top
Who
needs treatment of renal artery stenosis?
Not all patients who have renal artery stenosis
need treatment beyond standard medical therapy
for their high blood pressure. The medical literature
also contains a variety of opinions as to which
people need treatment for renal artery stenosis
and which people do not. Most people agree that
when both renal arteries are narrowed, then treatment
should be considered.
When only one kidney artery is narrowed, and
that kidney has signs it is receiving less blood
than the other kidney (measured from a nuclear
scan), then treatment should be considered. When
renal artery stenosis is present to one kidney
but that kidney appears to be receiving enough
blood anyway, then treatment may be unnecessary
(except to eliminate risk factors such as smoking,
high cholesterol, and high blood pressure).
Back to top
Surgical
options for renal artery stenosis
Surgical management of renal artery stenosis consists
of creating a bypass around the narrowed area
of the kidney artery. This bypass can be made
directly to the major artery in the abdomen, the
aorta. This is known as an aortorenal bypass.
Another surgical option is to bypass the kidney
artery to the artery of a neighboring organ, such
as the spleen for the left kidney (a splenorenal
bypass) or the liver for the right kidney (a hepatorenal
bypass). In some patients, the surgeon is able
to clean out the plaque that is blocking the renal
artery. This is known as an endarterectomy.
These surgical treatments are highly effective
in restoring blood flow to the kidney. However,
they require surgical incisions, general anesthetic,
prolonged recovery periods, and are not without
major risks.
Back to top
Percutaneous
options for treating renal artery stenosis
“Percutaneous” means “through
the skin”. Specialized devices are passed
through a tiny nick in the skin without the need
for a surgical incision. Percutaneous options
for treating renal artery stenosis include balloon
angioplasty, where a balloon is positioned across
the area of narrowing in the renal artery. The
balloon is then inflated to a pre-set size to
“stretch” the artery open to increase
blood flow though the artery.
Balloon angioplasty is extremely effective in
people with fibromuscular dysplasia and in some
cases of atherosclerosis. In some people, the
plaque that is causing the narrowing of the renal
artery “hangs over” the opening of
the artery even after angioplasty. In this situation,
doctors will often place a small mesh tube known
as a stent to hold open the artery after angioplasty.
Over time, the stent becomes part of the wall
of the artery. Usually, the decision of whether
or not a stent is needed is made at the time of
the angioplasty procedure.
Back to top
How
well does percutaneous therapy work for renal
artery stenosis?
Patients with fibromuscular dysplasia are usually
cured after renal artery angioplasty, meaning
that they no longer need to take medications to
control their blood pressure. Patients with renal
artery stenosis caused by atherosclerosis are
less likely to be “cured” following
percutaneous treatment of renal artery stenosis
(angioplasty/stent placement) but most will achieve
a benefit. This benefit may be in the form of
needing fewer drugs to control their blood pressure,
needing smaller doses, or both. Patients who develop
complications of having both renal arteries narrowed
(such as fluid build-up in the lungs, known as
pulmonary edema) will improve by having fewer
and/or less severe episodes of this nature.
Back to top
How
do I know which treatment is right for me?
The best treatment for renal artery stenosis depends
on a number of factors, including your overall
health and the onset and severity of your high
blood pressure. You should discuss all your treatment
options with your physician. Some questions to
ask your doctor include:
- Is my high blood pressure caused by renal
artery stenosis (renovascular hypertension)?
- What are some of the signs and symptoms I
should watch out for?
- If I have renal artery stenosis, what caused
this condition?
- If treatment (other than medications) is required,
am I a candidate for percutaneous therapy, such
as balloon angioplasty or stent placement?
- What are the risks and benefits of the treatment
plan prescribed for me?
Back to top
Reviewed by:
Timothy Clark, MD
January, 2003
|
