Artery Stenosis - What is it?
Narrowing of the main blood vessel running to one or both of your kidneys.
Why does Renal Artery Stenosis Occur?
Renal artery stenosis is occasionally seen in young people, when it is caused by muscular bands in the artery to the kidney. However, it is much more common in older people with hardening of the arteries.
“Hardening of the arteries” or arteriosclerosis develops in very many of us as we get older. As well as becoming thicker and harder, the arteries develop fatty deposits in their walls which can cause narrowing. If the kidneys are affected there is generally also arterial disease in other parts of the body a history of heart attack or stroke, or poor blood supply to the lower legs.
Arteriosclerosis is a consequence of fat in our diet, combined with other factors such as cigarette consumption, high blood pressure and genetic factors. It may develop faster if you also have diabetes.
What are the Symptoms?
Normally there are no symptoms. The arterial narrowing does not cause pain, and urine is passed normally. Therefore this is usually a problem detected when other tests are done for example, routine blood tests to measure the kidney function.
What are the Complications of Renal Artery Stenosis?
- Kidney failure If the kidneys are starved of blood, they may stop working. This can occur if the artery blocks off suddenly, or more gradually if there is a serious narrowing. In its early stages, kidney failure does not cause symptoms, but is only detected in blood tests. The prevention of kidney failure is one of the main aims when doctors treat renal artery stenosis.
- High blood pressure One of the jobs the kidneys normally perform is to control the blood pressure. If they are starved of blood, this can cause high blood pressure. This puts a strain on the rest of the circulation, so that using drugs to control the blood pressure can be very important. Good blood pressure control reduces the risks of stroke, heart attack and kidney failure.
- Fluid retention Renal artery stenosis can lead to fluid retention. This may cause ankle swelling, or sometimes cause fluid to accumulate in the lungs. If you get fluid in the lungs, this can cause a sudden attack of breathlessness.
How do doctors confirm the diagnosis?
Normally the kidneys are checked with an ultrasound scan in the X-Ray department which measures the size of the kidneys. If one kidney is smaller than the other, this can give a clue to arterial narrowing. Another simple test uses an injection of radioisotope into the vein, to measure the overall level of blood flow to the kidneys.
More complex X-ray machines can take pictures of the arteries to the kidneys most hospitals use either a CT scanner or MRI scanner. Both these machines require you to lie down for a few minutes while the scanner moves over your body. It may be necessary to have a small injection of fluid to highlight the arteries on the scanner. These scans can be performed as an out-patient procedure.
Another way of outlining the arteries is to have an angiogram. In this, a narrow plastic tube is passed into the artery in the groin and up the abdomen to the area of the kidneys. X-ray dye is injected, which shows in detail the outline of the arteries to the kidneys. The procedure is similar to angiograms to look at the heart or the legs, which some patients with renal artery stenosis have previously had. An angiogram requires you to have a hospital bed for a short stay.
What is the Treatment of Renal Artery Stenosis?
Doctors try to relieve the narrowing in the artery and improve the blood flow to the kidney. The simplest way to do this is by placing a small balloon in the artery during an angiogram, and inflating it so that the narrowing is stretched up. This procedure is called angioplasty. It is normally very successful, but follow-up tests are needed to be sure that the narrowing does not come back. To help prevent the narrowing coming back, a wire tube (called a stent) is usually placed into the artery at the same time as the angioplasty.
If someone with kidney disease is having an angioplasty, there is a risk of complications. One of these is a reduction in kidney function. The risk of this can be reduced by giving fluids through a drip before and during the procedure. Anyone having this procedure should make sure that the drip is not forgotten, if it is needed in their case. There is also a small risk of damage to the blood vessels as tubes are passed up and down from the groin to the kidneys.
It is also possible for a surgeon to operate on the artery and to relieve the narrowing, often by using a piece of vein from the leg as a bypass graft. Surgery can be done if angioplasty fails, or is often performed if another arterial operation has to be performed. This surgery is quite major, and requires careful checks of the heart and lungs beforehand.
Although it may be possible to perform an angioplasty procedure, a large trial (called Astral) has shown no clear cut benefit from angioplasty in reducing the rate of decline of renal function. Therefore your specialist will not advise that an angioplasty should be performed just because a narrowing is present in the renal artery. A decision as to the best treatment will be made on an individualised basis.
What about diet and cholesterol and other treatment?
There some other things you can do which may help not only the arteries to your kidneys, but any other arteries in your body affected by arteriosclerosis.
- Smoking if you smoke, this puts strain on the arteries and you will be better off stopping
- Diet a healthy diet without too much saturated fat or salt is advisable. A dietician can give you advice on this
- Cholesterol the level of cholesterol (fat) in the blood should be measured. If this is too high despite a good diet, it may help to take extra drugs to lower the cholesterol level.
- Aspirin some of the problems in renal artery stenosis are due to tiny blood clots around the arterial hardening. Taking a small aspirin tablet daily reduces the tendency for this to happen.
- Exercise regular moderate exercise will be good for you, but of course you should discuss this with your doctor in case you also have heart disease.
- Blood pressure - high blood pressure will continue to damage your kidneys and put strain on the heart and other blood vessels. Your doctor will measure the blood pressure and may prescribe drugs to bring the level down.
Are there any drugs to avoid?
The are two types of drug that may cause particular complications in renal artery stenosis and should be avoided if possible.
The first is a class of drug commonly used to treat high blood pressure or heart failure. These are called ACE inhibitors and have names ending in -opril. Examples are captopril (also called 'Captopen'), lisinopril (also called 'Zestril'), ramipril, fosinopril. These are to be avoided because they can cause kidney failure in renal artery stenosis. Occasionally your doctor will advise that is safe to stay on these drugs.
Anti-inflammatory drugs for arthritis should be used with caution because they can cause fluid retention and reduction in kidney function. There are many types of these, common ones are 'Brufen' and 'Voltarol'. 'Nurofen', available over the counter at your chemist, is also one of this type of drug. They should not be used without discussing the risks and benefits with your doctor.
Adapted from a leaflet written by Rob Higgins, Renal Consultant, Walsgrave Hospital, Coventry, 1998
The National Kidney Federation cannot accept responsibility for information provided. The above is for guidance only. Patients are advised to seek further information from their own doctor.