Introduction
The stenosis of the renal artery is an end effect of several other medical conditions that often result in reduced renal perfusion. A reduction in renal perfusion means that the fluid that passes through the ducts of the kidney would be less due to reduced blood pressure. The effect of renal stenosis is seen as reduced renal perfusion leading to ischemic atrophy (atrophy due to the lack of blood supply) and, secondly, an indirect effect due to the activation of renin-angiotensin-aldosterone and the sympathetic nervous system. It is seen as systemic hypertension, complications in the cardiovascular system, and end-organ damage, including glomerulosclerosis (a condition in which the glomerulus, the filtering part of the kidney, is damaged).
What Is Renal Artery Stenting?
Renal stenting is done to remove the blockage or narrowing of the renal artery. The renal artery is the main artery supplying the kidneys. The condition where the renal artery gets blocked or narrowed is called renal artery stenosis. Atherosclerosis, or fibrous disease of the artery, is the main cause of arterial stenosis. When fats, cholesterol, and other materials build up on the walls of the artery, it is called atherosclerosis. When an artery is clogged, the blood supply of the artery is reduced. Arterial stenting is helpful in such conditions. The stenting of the artery widens the artery, thereby increasing the blood flow.
The kidneys maintain the salt and water balance of the body by filtering the blood and producing urine. When the blood is not able to reach the kidneys for the process, it results in fluid retention in the body. Furthermore, the kidneys also release a hormone called renin. Renin is a hormone that promotes the retention of water and salt in the body and also causes the walls of the blood vessels to become more rigid. Altogether, it can cause an increase in blood pressure called renovascular hypertension. This puts additional strain on the heart and other organs. This can also be a cause of renal failure, requiring dialysis or even a kidney transplant.
What Are the Indications for Renal Artery Stenting?
Refractory hypertension and progressive renal insufficiency are the two main indications for the procedure.
How to Know if a Renal Artery Stent Is Required?
Tests that are done to know if one requires a renal artery stent include:
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Angiography: A catheter is inserted into the aorta in this procedure. (The aorta is the main artery in the body). As the catheter advances to the renal artery, a dye is released. X-rays are taken to know about the blood flow and the width of the artery wall.
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Magnetic Resonance Angiography: This procedure works similarly to magnetic resonance imaging (Magnetic resonance imaging uses a large magnet, radio waves, and a computer to get clear images of the body). In magnetic resonance angiography, a contrast dye is injected into the blood so that better images are easier to understand, as the area of interest stands out due to the presence of the dye.
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Computed Tomography Angiography: Computed tomography uses a series of X-rays to produce clear three dimensional images of the body in a computer. In computed tomography angiography, a contrast dye is injected into the blood so that the renal arteries stand out.
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Duplex Doppler Ultrasonography: In this procedure, sound waves are used to know the width of the arteries and the speed of blood flow within the renal arteries.
What Are the Risks Associated With Renal Artery Stent?
The risks associated usually outweigh the benefits after the procedure is done. However, the patient should be aware of the risks associated with the procedure. The risks associated with a renal artery stent can include:
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An allergic reaction to the dye used.
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Infection at the site where the dye is injected.
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Bruising at the site where the catheter is inserted.
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Bleeding at the insertion site.
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Blood clots.
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The procedure may become a failure in very rare cases.
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Stent misplacement.
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Damage to the renal artery.
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Very rarely, stenting done in the renal arteries can cause difficulty or an obstruction in the other arteries.
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Very rarely, kidney failure.
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Very rarely, death.
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An extremely less chance of cancer in the area. The probability depends on the number of images taken.
How Is the Procedure Done?
A renal artery stenting is done as a part of angiography. In angiography, a catheter is inserted into the affected renal artery. A catheter used in angiography has a balloon at its end, which inflates to widen the narrowed artery. It is usually a minimally invasive procedure. The patient will be awake during the procedure, and a contrast dye will be given, which makes the area being imaged stand out. There can be mild discomfort during the procedure, though it is not very painful.
The catheter is inserted through a very small incision made in the groin. The catheter is directed toward the renal artery using images produced on the computer. A guide wire with a balloon at its tip is placed on the area of stenosis, and the balloon is inflated to remove the blockage or widen the narrow area. The stent, which is a fine wire mesh, is then passed through the catheter and pressed on the walls of the artery. The stent is left behind to leave the artery open for blood flow.
Anticoagulants, which are medicines to thin the blood to maintain the blood flow around the area where the stent is placed, will be given for a few days. There are chances for a new blockage to form in some other area of the renal artery. Another complication can include the recurrence of the narrowing, called restenosis. Hence, review visits should be done regularly till the area is healed.
Conclusion
Renal artery stenting is the most common endovascular intervention for renal artery stenosis. Renal artery stenosis can be commonly caused by atherosclerosis and fibromuscular dysplasia( a rare systemic vascular disease that usually affects the carotid and renal arteries). The procedure helps to widen narrowed arterial walls and remove any blockages present. Recent studies show that the procedure may not cure renal artery stenosis completely but can slow down the process.
