Renal artery stenosis is a narrowing of the arteries that supply blood to the kidneys, often caused by atherosclerosis. It can lead to kidney failure and high blood pressure. Diagnosis is through imaging and function tests. Treatment includes monitoring, medication, and surgery in severe cases.
Renal artery stenosis is a narrowing of the arteries that supply blood from the heart to the kidneys. When the renal arteries decrease in diameter, blood flow to the kidneys is restricted. If both renal arteries are affected, the function of the kidneys can be impaired, eventually leading to kidney failure. High blood pressure is a common result of renal artery stenosis affecting only one of the arteries.
Most cases of renal artery stenosis are caused by atherosclerosis, which means that the blood vessel wall hardens and narrows from within. This is similar to what can happen to the arteries in the heart. Advanced age, cigarette smoking, and diabetes are all risk factors that increase the chance of atherosclerosis. Patients with high cholesterol levels and high blood pressure are also at increased risk of blood vessel problems.
There are typically no specific symptoms associated with renal artery stenosis. Severe hypertension that begins before age 30 or after age 50 and does not respond well to typical blood pressure medications may be suspect. Often, renal artery stenosis is detected incidentally through other tests when a doctor discovers that one of a patient’s kidneys is smaller than the other.
If a doctor suspects renal artery stenosis, they will do imaging tests, function tests, or a combination of the two to confirm the diagnosis. Imaging tests show the artery itself so a doctor can determine if it has narrowed, and if so, how much. Functional tests help determine if the narrowing of the arteries is enough to cause kidney failure or high blood pressure.
The most accurate imaging test is an angiogram, but it’s not commonly used due to the risk of complications from the invasive procedure. An angiogram involves a catheter inserted through the groin into the heart and down the renal arteries. A dye is then injected and x-rays are taken to analyze the degree of narrowing of the arteries. Magnetic resonance angiography (MRA) or computed tomographic angiography are less invasive. They are done by injecting a dye into the body and then analyzing pictures of the kidney arteries to determine if a narrowing is present.
Functional tests include the captopril renogram and plasma renin activity test. The captopril renogram measures kidney activity following an injection of a radioactive substance. If the activity is more pronounced in one kidney, it may indicate that the function of the other is impaired due to renal artery stenosis. A plasma renin activity test analyzes whether one kidney shows higher activity of the hormone renin than the other kidney, as higher renin activity generally indicates that renal artery stenosis is present.
In mild cases, no treatment may be needed, and a doctor may choose to simply monitor a patient’s blood pressure and kidney function on a regular basis. High blood pressure caused by renal artery stenosis is usually treated with the same blood pressure medications as any other patient. In cases where the renal artery or arteries have narrowed by more than 75%, surgery may be required to widen the blood vessel.
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