Experts understand renal artery stenosis as a narrowing of the artery that supplies the kidneys with oxygen-rich blood. What symptoms can cause a narrowing in the blood vessel and how a renal artery stenosis can be treated.
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Quick Overview: Renal Artery Stenosis (NAST)
What is renal artery stenosis (NAST)? Renal artery stenosis is a narrowing of the blood vessel that supplies blood to the kidney. NAST can be caused by a congenital disease or by vascular calcification as part of an unhealthy lifestyle.
Symptoms of renal artery stenosis: The main symptom of NAST is high blood pressure that is difficult to treat and can manifest itself in the form of dizziness, headaches, ringing in the ears and blurred vision.
Treatment options for NAST: A stenosis of the renal artery is treated with blood pressure-lowering drugs, often drugs that lower blood lipids are also used. A PTA can also be useful. A balloon catheter is inserted into the vessel and it is expanded. A stent is placed to keep the artery wide.
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What is renal artery stenosis?
Renal artery stenosis (NAST) is a narrowing (or stenosis) of the artery that supplies the kidney with oxygen-rich blood. In some cases, the narrowing of the renal artery (arteria renalis) is on one side, in other cases both sides are affected. As a rule, the bottleneck is located in the kidney vessel at about abdominal level, directly behind the branching of the main artery (aorta).
The kidneys serve primarily as an excretory organ, filtering toxins from the blood and excreting them through the urine. In addition, it is involved in the regulation of blood pressure and water balance. The kidneys are extremely sensitive to a drop in blood pressure. They provide hormones such as renin to increase blood pressure as part of the so-called renin-angiotensin-aldosterone system (RAAS) and thus ensure adequate blood flow.
If the renal artery is narrowed, the blood pressure in the kidneys drops and renin is released: The result is permanent high blood pressure throughout the body. In this case, experts also speak of renovascular hypertension.
Long-term increased pressure in the vessels damages them. Organs such as the kidneys themselves are also damaged. Therefore, a narrowing of the renal arteries increases the likelihood of secondary diseases such as renal insufficiency.
Renal artery stenosis: Symptoms appear late
At the beginning, when the renal artery is not too narrow, there are no signs of the disease. As the vessel narrows, for example from a stenosis degree of 60 percent, high blood pressure usually develops, which is difficult to control and can manifest itself through various symptoms, including:
- Headache (especially in the morning after getting up)
- dizziness
- tinnitus
- nosebleeds
- insomnia
Visual disturbances are also possible in severe cases.
What are the causes of renal artery stenosis?
There are two different causes of renal artery stenosis. Arteriosclerosis (hardening of the blood vessels) is the reason for the narrowing of the renal arteries in around 80 percent of cases. Older people are more likely to be affected, and the stenosis is usually only on one side. There are a number of risk factors for the development of arteriosclerosis in general, for example:
- Smoking
- high blood pressure
- Fat metabolism disorders (e.g. increased cholesterol levels)
- diabetes
- overweight
An accumulation of cardiovascular diseases in the family is also considered a risk factor.
In younger people, the cause of renal artery stenosis is usually a disease of the vessel wall, known as fibromuscular dysplasia (FMD). There is locally increased growth of individual arterial wall layers. In the majority of cases, both sides are then narrowed stenotically.
Diagnosis of renal artery stenosis
The suspicion of a narrowing of the renal arteries is particularly obvious for doctors when there is arterial high blood pressure that is difficult to control with medication (hypertension that is refractory to therapy). The sudden onset of arterial hypertension before the age of 30 can also be an indication of renal artery stenosis.
A physical examination follows after an anamnesis interview, in which possible pre-existing conditions such as diabetes, information on lifestyle and precise symptoms are clarified. In the case of renal artery stenosis, a flow noise in the abdomen can often be heard when listening with the stethoscope.
Diagnosis is made using a variety of tests, including:
Blood pressure measurement: The blood pressure values are usually determined via a long-term measurement. If there is a severe narrowing of the renal arteries, the blood pressure is permanently elevated and does not drop even at night.
Blood test in the laboratory: Reduced renal blood flow can lead to impaired renal function. Laboratory tests that provide information about renal artery function are the determination of creatinine and urea in the blood. Both compounds are excreted in the urine. If they are present in the blood in increased concentrations, this indicates a restriction of kidney function. In addition, the hormones renin and aldosterone are measured in the blood.
Imaging methods: Some examinations help to visualize the vessel and the corresponding constriction. Special ultrasound methods such as duplex or Doppler sonography are used. This allows the artery to be imaged and blood flow analysis to be performed. In addition, various examinations of the vessel with contrast media (angiography) can take place. Magnetic resonance angiography (MRA) or computed tomographic angiography (CT) are possible.
Treatment options for narrowed renal artery
The treatment method depends on the underlying cause. In general, patients with NAST should ensure a healthy lifestyle and avoid risk factors, such as stopping smoking and treating relevant previous illnesses such as dyslipidemia and diabetes mellitus. If you are overweight, weight loss is recommended. Arterial hypertension is controlled with antihypertensive drugs.
Vascular dilatation by PTA
If the blood pressure cannot be reduced sufficiently or if fibromuscular dysplasia is present, doctors recommend a minimally invasive procedure to remove the constriction: the so-called percutaneous transluminal angioplasty (PTA). A small tube, the catheter, is inserted into the femoral artery and advanced to the renal vessel. There the bottleneck is widened, usually with the help of a small balloon. As a rule, a small tube, a stent, is inserted, which permanently keeps the renal artery wide.
Not all vascular constrictions or occlusions are suitable for this treatment method. However, around 90 percent of those suffering from FMD can be helped in this way. Kidney function improves and blood pressure drops.
Only rarely does a renal artery stenosis need to be operated on in an open vascular surgical procedure (such as a bypass). This is necessary, for example, if it is impossible to carry out the PTA or if there are complications.
course and prognosis
If left untreated, renal artery stenosis will continue to progress. The consequences are permanently elevated blood pressure values, which increase the risk of cardiovascular diseases such as a heart attack or stroke, as well as damage to the kidneys. In the worst case, kidney failure occurs.
If the narrowing of the renal arteries is widened with the help of an intervention and a stent is placed, regular check-ups follow. In the case of fibromuscular dysplasia, the prognosis is often favorable and the vasoconstriction can be permanently corrected. In some cases, the stenosis recurs, which requires further surgery. In addition, additional drug-based blood pressure treatment is often indicated.
If arteriosclerosis is the cause of the vascular stenosis, the chances of recovery are poorer. NAST often continues to progress despite treatment, leaving blood pressure elevated and further damaging the kidneys.
How can renal artery stenosis be prevented?
The renal artery narrowing caused by arteriosclerosis can be prevented by avoiding the risk factors. For example, nicotine is a strong vascular pollutant, it causes narrowing of the vessels. The tobacco ingredients also worsen the metabolism. People who smoke often have a significantly higher cholesterol level, which promotes the development of arteriosclerosis.
No causes are known for the development of fibromuscular dysplasia, so no preventive measures can be derived.
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