Arteriovenous Fistula (AV Fistula)

How a dialysis fistula works

Hemodialysis removes waste from the blood through a machine, which needs blood flow of around 300 to 500 ml a minute. Normal veins cannot provide this. A surgeon joins an artery to a vein, usually at the wrist (radiocephalic) or elbow (brachiocephalic or brachiobasilic). High-pressure arterial blood flows into the vein, which enlarges and thickens over 6 to 12 weeks ("matures") until it can be needled repeatedly.

AV fistulas are the preferred access because, compared with grafts and central venous catheters, they last longer and have lower rates of infection and clotting. Planning ideally starts months before dialysis is needed, and people with advanced chronic kidney disease are advised to protect the veins in their non-dominant arm from blood draws and IV lines.

Other types of AV fistula

• Traumatic: a penetrating injury damages an artery and vein side by side, for example in the leg or neck. See vascular injury.
• Iatrogenic: after a catheter procedure through the groin artery, such as heart catheterization, or after a kidney biopsy.
• Congenital: present from birth, sometimes as part of an arteriovenous malformation.
• Dural AV fistula: an abnormal connection in the coverings of the brain, causing pulsatile ringing in the ear, headaches or stroke-like symptoms.
• Spontaneous: rarely, an aneurysm erodes into a vein, such as an aorto-caval fistula.

Symptoms of an abnormal AV fistula

• a pulsating mass or swelling
• a buzzing feeling or a whooshing sound over the area
• swollen, bulging veins or varicose veins
• leg or arm swelling
• reduced blood supply beyond the fistula, causing coldness or pain
• fatigue and breathlessness from heart strain if the flow is large (high-output heart failure)
• pulsatile tinnitus (a heartbeat sound in the ear) with a dural fistula

Living with a dialysis fistula

Check it daily

• Feel for the thrill: a continuous buzzing vibration.
• Listen with the fistula held near your ear or with a stethoscope for the whooshing bruit.
• Look for redness, swelling, bulges or skin changes.

Protect it

• No blood pressure cuffs, blood draws or IVs in the fistula arm.
• Do not wear tight sleeves, watches or bracelets on that arm, or sleep lying on it.
• Avoid carrying heavy bags across the fistula.
• Keep the skin clean, and wash with soap and water before each dialysis.
• Exercise the arm (squeezing a soft ball) while the fistula is maturing, if your team recommends it.

After dialysis

Apply gentle, firm pressure to needle sites until bleeding stops, and keep a supply of gauze at home.

Complications

Diagnosis and treatment of problems

Doctors use physical exam, duplex ultrasound to measure flow and find narrowing, and fistulograms (X-ray dye studies).

• Narrowing: balloon angioplasty, sometimes with a stent.
• Clot: clot removal with catheter techniques or surgery, ideally quickly to salvage the fistula.
• Aneurysm: surgical repair or revision.
• Steal syndrome: procedures to reduce fistula flow or reroute blood.
• Abnormal fistulas: closed by surgery or by blocking them from inside the blood vessel (embolization or covered stents).

Frequently asked questions

What is an AV fistula used for?

An AV fistula is most often created to give access for hemodialysis in people with kidney failure. Joining an artery to a vein makes the vein larger and stronger, allowing it to be needled repeatedly and deliver enough blood flow for efficient dialysis.

How long does an AV fistula take to mature?

Most fistulas take about 6 to 12 weeks to mature enough for dialysis. Some take longer or fail to mature, and may need a procedure to help. Arm exercises and protecting the arm from injury help maturation.

What should an AV fistula feel like?

A healthy fistula has a continuous buzzing vibration called a thrill and a whooshing sound called a bruit. Check it every day. If the buzz is gone, weaker or has changed, contact your dialysis unit right away, as it may mean a clot.

What are the risks of an AV fistula?

Risks include clotting, narrowing, bleeding, infection, aneurysm formation, reduced blood flow to the hand (steal syndrome) and, with very high-flow fistulas, strain on the heart. Fistulas still have fewer infections and complications than grafts or catheters.

Can an AV fistula be closed?

Yes. A dialysis fistula may be tied off if it causes problems or is no longer needed, for example after a kidney transplant. Abnormal fistulas from injury or birth are often closed by surgery or by blocking them from inside the blood vessel.