Renal Artery Stenting : Indications and Complications

Kidneys are bean shaped fist size organs present in the back, just below the ribs. They are responsible for excreting waste, maintaining salt concentration and blood pressure in the body. The kidney is supplied by an artery called renal artery. Narrowing of this artery leads to reduced blood flow to the kidney leading to build up of salts and water in the body. The kidneys release a hormone called rennin, in response to reduced blood flow. Renin causes further retention of salts and water. This leads to a type of increased blood pressure called renovascular hypertension. Renal artery stenting is a procedure by which the normal blood flow to the kidney is restored, hence treating renovascular hypertension. In United states 4% of patients with hypertension have narrowing of renal artery.

Procedure of Renal artery stenting

Renal artery stenting is a minimally invasive procedure and requires only a small incision. This procedure is done in a catheterisation lab which is equipped with special x ray machine. Before the procedure you will be given medication to help you relax. A local anaesthetic agent will be administered over your groin. After the effect of anaesthetic sets in, your surgeon will make a small incision to gain access to the artery passing through your groin. A thin tube with an inflatable balloon at its end is inserted into this artery. A contrast dye is injected during the procedure to visualise the arteries on x ray. The catheter is guided upto the diseases renal artery under x ray guidance. The catheter is then carefully guided into the narrow portion of the artery. A guide wire with a balloon at its tip is introduced into the narrow part of the artery. The balloon is carefully inflated to open the blockade. A metal stent is placed inside to artery to ensure that it remains open.

Indications for Renal artery stenting

Renal artery stenting is indicated for individuals with:

• Declining renal function
• Difficult to control hypertension with 70% narrowing of renal artery
• Renal artery narrowing seen on angiography
• Heart failure with unstable angina and renal artery narrowing.

Preparation for Renal artery stenting

To decide whether you need renal artery stenting your doctor would like to request some tests. They are:

• Duplex Doppler ultrasound: a small ultrasound producing probe is placed on your abdomen. Sound waves travel into your body and reflect back. The probe is captures the reflected sound waves and forms an image on the screen. With the help of this test your doctor tries to determine the extent of narrowing and rate of blood flow through the renal artery.
• CT Angiography: with the help of X Rays and a contrast dye (which is injected into the blood stream) your doctor gets a series of cross sectional x rays which can be processed by a computer to yield a 3 dimensional picture of the renal artery.
• MRI angiography: with the help of contrast dye and a magnetic resonance imaging machine a 3 dimensional image of the renal artery system is obtained.
• Angiography: a catheter is introduced into your groin and it travels up into the aorta to reach the renal artery. A dye is injected into the artery through the catheter and an x ray image is obtained to visualise the renal arteries.

Complications of Renal artery stenting

Renal artery stenting is a relatively safe procedure. The complications seen are:

• Bruising at the site of catheter entry
• Stent misplacement
• Damage to artery
• Allergic reaction to contrast
• Bleeding at the site of insertion of catheter
• Blood clot formation
• Kidney failure

Recovery after Renal artery stenting

After the procedure you will be prescribed blood thinning medications. You will be advised to take them until the area around the stent heals. It prevents formation of blood clots. It is important that you see your doctor for follow up appointments because there is a slight risk of development of narrowing after the surgery.

Resources

• The indications and results of percutaneous transluminal angioplasty and stenting in renal artery stenosis, Semin Vasc Surg.  1996; 9(3):188-97 (ISSN: 0895-7967), Kidney DD; Deutsch LS
• Renal artery stent placement: indications, techniques and clinical results, Indian Heart J.  1998; 50 Suppl 1:153-60 (ISSN: 0019-4832), White CJ; Ramee SR; Collins TJ; Jenkins JS