Dilatation and stenting of renal artery

Renal artery stenting is a procedure which is used to open the renal arteries when they have become blocked due to renal artery stenosis.

Renal artery stenosis (RAS) is a narrowing of one or more arteries that carry blood to the kidneys (renal arteries). The renal arteries are responsible for carrying oxygen-rich blood to your kidneys, which helps the kidneys rid your body of waste and excess fluid. Over time, RAS can lead to high blood pressure, edema and kidney damage.

Renal artery stenosis can have a variety of different etiology, but the two major causes are atherosclerosis and fibromuscular dysplasia. Atherosclerosis is causing the RAS in more than 90% cases, it’s a process in which plaque made up of fats, cholesterol and other substances builds up on the walls of renal artery and as those deposites get larger, they can reduce blood flow, cause kidney scarring and eventually narrow the artery. Rarely, renal artery stenosis can be caused by condition called fibromuscular dysplasia in which the muscle in the artery wall grows abnormal. It’s more commonly seen in women and younger people and it is potentially curable.

Risk factors for renal artery stenosis are:

RAS can develop in both, men and women. Its more common in older adults, and those who develop hypertension before the age of 30. Other risk factors are similar to those of other forms of atherosclerosis, such as: diabetes, family history of heart disease, high cholesterol, obesity, sedentary lifestyle or lack of exercise, smoking.

Symptoms of renal artery stenosis

Renal artery stenosis usually doesn’t cause any specific signs or symptoms, until its advanced. The condition may be discovered incidentally, during other clinical testing. Sometimes, the first sign of RAS is high blood pressure (hypertension) that is extremely hard to control, along the worsening of previously well controlled high blood pressure, or elevated blood pressure that affects other organs in the body. As RAS progresses other signs and symptoms may include:

• Fluid retention and swelling in your body tissues
• Elevated protein levels in the urine
• Decreased or abnormal kidney function
• Worsening kidney function during treatment of high blood pressure

Diagnosis of renal artery stenosis

If your doctor suspects that you have renal artery stenosis, they may order tests to either confirm suspicions or rule it out. These include:

• Blood tests and urine tests to evaluate kidney function
• Kidney ultrasound, which uses sound waves to show the size and structure of the kidney
• Doppler ultrasound, which measures blood-flow speed in arteries to the kidney
• Magnetic resonance ( arteriogram ) and CT angiography, imaging studies that use a special dye (contrast medium) to produce a 3-D image of the kidney and its blood vessels
• CT angiogram to provide detailed images of the heart and the blood vessels that go to the heart, lung, brain, kidneys, head, neck, legs, and arms

How is renal artery stenosis treated?

Treatment for RAS depends on a combination of medications and lifestyle changes. Certain medical procedures may also be necessary. One of the first ways to treat this condition is with medications. Your doctor may prescribe medications to help relax blood vessels so they don’t narrow. Options include: angiotensin II receptor blockers (ARBs), calcium channel blockers, angiotensin converting enzyme (ACE) inhibitors, alpha-beta-blockers and beta-blockers can also help by decreasing blood vessel dilation, diuretics to reduce swelling and fluid retention. 

Also the doctor may recommend certain lifestyle changes such as getting regular exercise, losing or maintaining weight, if necessary, quitting smoking, cutting back on alcohol or caffeine, consuming less sodium, managing stress, getting adequate sleep.

Procedures

If medication and lifestyle changes aren’t enough to limit the effects of RAS, the condition may progress. Eventually, your kidneys could become damaged. In such cases, your doctor may recommend certain procedures that improve arterial function, such as angioplasty, often with stenting or surgery.

Renal artery stenting is done during the procedure called angioplasty, which involves inserting a small catheter in the diseased renal artery. An angioplasty catheter has a balloon on its end In order to inflate or dilate the narrowed area. Angioplasty is a minimally invasive procedure, which means that it is performed through small incision in the thigh. Angioplasty is performed in a room equipped with special X-ray and imaging machines. Before the procedure, you will receive medication to help you relax, but you will be awake. You are also given a contrast dye that makes your arteries easier to see on the imaging equipment. You may feel some discomfort during the procedure, but it is generally not painful.

During the angioplasty:

• A catheter, a flexible hollow tube, is inserted through a tiny incision, or opening, in your groin.
• Using the imaging equipment, the doctor carefully guides the catheter through the femoral artery to the narrow part of renal artery.
• The doctor then places a guide wire with a balloon on its tip through the catheter to the spot in the artery and inflates the balloon to open the blockage.
• The stent, a fine mesh tube, is then pressed into the artery wall. The stent is left in the artery to keep it open to maintain blood flow.

During the procedure, a series of X-rays, called fluoroscopy, is used to help the doctor visualize the catheter and stent inside the artery. The procedure lasts 30 to 90 minutes, depending on the severity of the narrowing. Angioplasty and stenting is performed using local anesthesia and sedation. Your doctor determines how long you stay in the hospital based on your medical history and overall health. Some people are able to go home the day of the procedure. 

After returning home, you can expect to resume your usual activities within two days. Most people are placed on an antiplatelet medication, such as aspirin or clopidogrel, to prevent platelets in the blood from sticking to the stent, causing clots.

What are the risks of renal artery stenting?

The risks of renal artery stenting include:

• Bruising where the catheter was inserted.
• Bleeding in or around the insertion site.
• Damage to the artery.
• Blood clots.
• Allergic reaction to the dye used during the procedure.
• Stent misplacement.
• Kidney failure.

When should I call my doctor?

Call your doctor if any of the following occur:

• You have a fever.
• You have problems breathing.
• You develop a rash.
• The area where the catheter was inserted becomes red, swollen, and
  painful, or it oozes blood.
• The leg in which the catheter was inserted becomes painful, cold, pale, or weak.
• You notice new pains in the abdomen or the flank on the side of the treated kidney.
• You become lightheaded and have a very low blood pressure