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Renal artery stenosis: when high blood pressure is caused by a narrowed kidney artery
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Renal artery stenosis is a narrowing of the blood vessel that carries blood to a kidney. It can raise blood pressure (renovascular hypertension) and gradually impair kidney function. However, a narrowing that has been found is not always the cause of high blood pressure, and only some patients need stenting: for most, medicines remain the mainstay of treatment.
What renal artery stenosis is and why it raises blood pressure
The most common cause of the narrowing is atherosclerosis: the plaque usually sits at the origin of the renal artery, more often in older people with atherosclerosis in other arteries. About 10% of cases are fibromuscular dysplasia, a non-inflammatory disease of the artery wall that is more common in younger women.
When less blood reaches the kidney, it releases substances that raise blood pressure. Long-standing narrowing can gradually impair kidney function. At the same time, a narrowing found during tests is not always the cause of hypertension: it may be a “bystander” in a person with ordinary high blood pressure (essential hypertension). The narrowing itself usually causes no symptoms: it is suspected from how blood pressure behaves, blood tests and ultrasound.
When to suspect that high blood pressure comes from the kidneys
- Blood pressure does not come down despite three or more medicines, one of them a diuretic (water pill)
- Blood pressure that used to be well controlled has suddenly worsened
- High blood pressure at a young age, especially in women (fibromuscular dysplasia is possible)
- Worsening kidney function tests (creatinine) after starting an ACE inhibitor or an angiotensin receptor blocker (ARB, “sartan”)
- Kidneys of different sizes on ultrasound
- Repeated attacks of sudden shortness of breath due to fluid in the lungs (pulmonary edema) while the heart is working normally
When it is urgent
Sudden severe shortness of breath or a feeling of suffocation; very high blood pressure (180/110 mm Hg or higher) with chest pain, a severe headache or vision problems; sudden weakness or numbness of an arm, a leg or one side of the face, or difficulty speaking: call an ambulance (103 in Ukraine). This may be pulmonary edema, a hypertensive crisis with organ damage, or a stroke; these conditions are treated as emergencies in hospital. Signs of stroke need an ambulance whatever the blood pressure — even if they pass within a few minutes.
Tests: renal artery ultrasound, CT or MR angiography
If the reason for testing is blood pressure that will not come down, doctors first make sure it is truly uncontrolled: home readings or 24-hour ambulatory monitoring, and a check that all pills are taken regularly. The first test of the renal arteries is a duplex ultrasound: it is safe and uses no contrast or radiation, but it is technically demanding and depends on the doctor's experience. CT or MR angiography is used to confirm the diagnosis and plan treatment. Catheter angiography is done only immediately before a procedure.
Kidney function tests (creatinine, albumin in the urine) and the size of the kidney also matter: if the kidney has already shrunk considerably, restoring its blood flow usually does not help it.
Treatment: medicines for most, a procedure only for clear indications
The mainstay of treatment is blood-pressure-lowering medicines (chosen by the doctor, who also monitors kidney function tests), antiplatelet medicines, statins for atherosclerosis, and stopping smoking. Large studies (ASTRAL, CORAL) have shown that in atherosclerotic stenosis, stenting plus medicines did not reduce the risk of kidney or cardiovascular complications compared with medicines alone — even when the narrowing was severe; blood pressure was on average only about 2 mm Hg lower. So if blood pressure is controlled with medicines and kidney function is stable, a stent is not placed, whatever the degree of narrowing.
A procedure is considered in specific situations: fibromuscular dysplasia with high blood pressure that responds poorly to treatment; repeated attacks of sudden pulmonary edema with narrowing of both renal arteries or of the artery to a single kidney; blood pressure that does not come down despite three or more medicines, with a severe narrowing; rapid decline in the function of a kidney that is still viable. These indications are based on expert opinion and small studies, so the decision is made individually, weighing the risks of the procedure. Even after a successful procedure, blood pressure pills are usually still needed.
Fibromuscular dysplasia: balloon angioplasty without a stent
In fibromuscular dysplasia the narrowing is usually in the middle part of the artery and looks like a “string of beads” on angiography. The mainstay of treatment is blood pressure medicines and an antiplatelet medicine. If a procedure is needed, balloon angioplasty is performed; a stent is placed only if a complication occurs during the procedure. Dysplasia can also affect other arteries, so the arteries from the head to the pelvis are imaged once.
How the procedure is done and what happens afterward
Renal artery angioplasty and stenting are performed through an arterial puncture under local anesthesia and X-ray guidance. The amount of contrast is limited to protect the kidneys. Like any procedure on an artery, it carries risks: bleeding or a hematoma (a collection of blood under the skin) at the puncture site, injury to the renal artery and worsening kidney function. That is why it is done only for clear indications.
After the procedure, blood pressure medicines and an antiplatelet medicine are continued, plus a statin for atherosclerosis; blood pressure and kidney function are checked regularly. The artery can narrow again, so follow-up tests are needed according to the doctor's plan.
Bleeding from the puncture site or a swelling that grows quickly: press on the puncture site and call an ambulance (103 in Ukraine). Lie down and keep pressing firmly on the puncture site with your palm until the ambulance arrives.
Frequently asked questions
I have been told I have renal artery stenosis of over 70%. Do I have to get a stent?
No. If blood pressure is controlled with medicines and kidney function is stable, a stent is not placed: large studies have shown that in atherosclerotic stenosis, stenting plus medicines does not improve outcomes compared with medicines alone, even with a narrowing of over 70%. A procedure is considered only in particular circumstances: blood pressure that does not come down despite three or more medicines; repeated attacks of sudden shortness of breath due to pulmonary edema; rapid decline in kidney function; fibromuscular dysplasia with blood pressure that responds poorly to treatment.
Can I stop taking blood pressure pills after stenting?
In most cases, no. With atherosclerotic narrowing, blood pressure may fall after the procedure, but the pills are usually still needed. In fibromuscular dysplasia the chance of normal blood pressure without medicines is higher, especially in younger patients whose high blood pressure started recently, but even then only a minority achieve it — roughly one in three or fewer. More often blood pressure becomes lower and easier to control with medicines.
Can I take ACE inhibitors or ARBs (sartans) if a renal artery is narrowed?
These medicines are often exactly what is recommended, but with narrowing of both renal arteries or of the artery to a single kidney they are prescribed with caution, with regular creatinine checks. Do not stop or start these medicines on your own.
Which test is better: renal artery ultrasound or CT angiography?
Testing starts with a duplex ultrasound of the renal arteries: it is safe and uses no contrast or radiation, but it depends on the doctor's experience and the conditions of the scan. CT or MR angiography is used to confirm the diagnosis and plan treatment.
Why isn't a stent placed for fibromuscular dysplasia?
Balloon angioplasty is usually enough, and in dysplasia a stent in the mobile renal artery offers no benefit and may later fracture or cause the artery to narrow again. It is placed only if a complication occurs during angioplasty.
Is a scan with contrast safe if my kidneys are already not working as well?
The risk is assessed in advance from a creatinine blood test. If kidney function is reduced, the amount of contrast is decreased, other methods are chosen (ultrasound, MR angiography), or CO₂ angiography is used during the procedure.
Book a consultation
Vascular surgeon consultation at the Shalimov Center, 30 Akademika Shalimova St, Kyiv. Booking and questions go through the contact doctor, Yurii Vahis. Patients from other cities and abroad can arrange an online consultation.