Renal Artery Stenosis (cont.)
What functional tests are used for the diagnosis of renal artery stenosis?
The main functional tests for renal artery stenosis include the plasma renin
activity test and captopril renogram. These tests have been largely replaced by
the imaging tests described above because they are less accurate, but they may
be still performed to help establish the diagnosis of renal artery stenosis.
The plasma renin activity measures the activity of the hormone renin
(described above). Activity of renin is generally higher in the kidney with
renal artery stenosis compared to the other kidney. This response may be
exaggerated by administration of captopril
(Capoten), an ACE inhibitor medication used to
treat high blood pressure.
The renogram measures the activity of the kidneys after injection of a
radioactive material
that is taken up by the kidney. By administering captopril prior to the test,
the activity may become more enhanced on the normal kidney compared to the one
with renal artery stenosis. This may indicate a significant
renal artery narrowing on the side with less activity.
What are medical treatments for renal artery stenosis?
In bilateral (both-sided) and unilateral (one-sided)
renal artery stenosis associated with high blood pressure, controlling the blood
pressure with usual blood pressure medications is the first and the safest
treatment. ACE inhibitors
or ARB medications with or without a diuretic (water pill) may be tried first.
This approach may be associated in some patients with worsening of their kidney
function. Therefore, kidney function needs to be followed closely and if
worsening of kidney function is evident, these medications may need to be
stopped.
It is worth noting that if renal artery stenosis is found incidentally when
performing a test for another disease and there is no evidence of kidney
dysfunction or high blood pressure, then no treatment may be necessary.
Sometimes even significant stenosis may not be associated with high blood
pressure or kidney dysfunction. In these situations, periodic monitoring of
blood pressure and kidney function may be advised.
Next: What surgical procedures are available for renal artery stenosis? »
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