What is renal denervation?
The kidneys are connected to the nervous system by fine nerves that run in the wall of the kidney arteries. When these nerves are overactive they keep blood pressure high by holding salt and water in the body and tightening the blood vessels. Renal denervation is a procedure in which a catheter is passed into each kidney artery and gentle energy, either radiofrequency heat or ultrasound, is applied to the artery wall to quieten these nerves. Nothing is left behind in the body.
Why is it done?
It is offered to patients whose blood pressure remains too high despite taking several medications correctly, or who cannot tolerate their tablets. Lowering blood pressure reduces the long-term risk of stroke, heart attack, heart failure and kidney damage. Renal denervation is not a replacement for medication or for lifestyle measures such as reducing salt, losing weight and exercising; it is an addition that in most patients produces a modest but lasting further drop in blood pressure. Before the procedure we confirm that the readings are genuinely high, usually with a twenty-four hour blood pressure monitor, check that no other treatable cause is present, and image the kidney arteries.
What happens on the day?
You come in fasting for a day case or single overnight stay. In the catheterisation laboratory a drip is placed, the groin is numbed with local anaesthetic and you are given sedation and pain medication to keep you comfortable. A catheter is guided from the groin artery into each kidney artery, contrast dye is used to map the vessel, and the treatment catheter then delivers a series of short energy applications at several points around the artery. You may feel a deep, dull ache in the back or abdomen during the applications, which is expected and treated with additional medication. Both kidney arteries are usually treated, and the procedure takes about one to one and a half hours.
What to expect afterwards
You lie flat for a few hours so that the groin puncture seals, and blood pressure and kidney function are checked. Most patients go home the same day or the next morning, with mild backache and groin bruising that settle within a few days. Very importantly, all your blood pressure medication is continued exactly as before, and only reduced later, by your doctor, if the readings allow. The effect is gradual: blood pressure usually falls over one to six months, so follow-up visits with home or twenty-four hour monitoring are arranged to track it. Not everyone responds, and some patients see little change.
Possible complications
The procedure has a good safety record but risks exist. Common: bruising, tenderness or bleeding at the groin puncture, and back or abdominal ache for a day or two. Uncommon: injury to the kidney artery wall, including a tear, spasm or a small false aneurysm at the puncture site; a temporary rise in kidney blood tests or a reaction to the contrast dye; and a slowing of the heart during energy delivery. Rarely the kidney artery narrows in the months afterwards, which is why follow-up is important, and very rarely a clot or serious bleeding occurs. Your cardiologist will discuss the balance of benefit and risk for your own blood pressure situation.
This information does not replace a consultation. Please discuss your own risks and options with your cardiologist.