Arteriovenous Fistula
An abnormal connection between an artery and a vein
Quick Facts
- Type: Vascular (blood vessel) condition
- What it is: Direct artery-to-vein connection
- Causes: Injury, congenital, or surgically created
- Common use: Created for hemodialysis access
Overview
An arteriovenous (AV) fistula is an abnormal connection between an artery and a vein. Normally, blood flows from arteries into a network of tiny vessels called capillaries before returning through the veins, which lets the body deliver oxygen and nutrients to tissues. In an AV fistula, blood flows directly from a high-pressure artery into a vein, bypassing the capillaries.
Some AV fistulas occur abnormally because of injury, a congenital condition present at birth, or disease. Others are created on purpose by a surgeon, most often in the arm, to provide reliable access for hemodialysis in people with kidney failure. A small or surgically planned fistula may cause no harm, but a large or untreated one can strain the heart and circulation. Treatment depends on the size, location, and cause.
It helps to know that not all AV fistulas are a problem. A fistula created for dialysis is a planned, beneficial connection that gives reliable access for treatment, and it is expected to have a buzzing sensation and humming sound that show it is working. An abnormal fistula from injury or disease is different and may need to be closed if it grows or causes symptoms.
Symptoms
Small AV fistulas often cause no symptoms. Larger ones can produce noticeable signs, especially when near the skin.
- A visibly swollen, bulging, or pulsating vein
- A buzzing sensation (thrill) or humming sound (bruit) felt or heard over the area
- Swelling of the affected arm or leg
- Warmth or skin color changes near the fistula
- Fatigue or, in large fistulas, signs of strain on the heart such as shortness of breath
- Lower blood pressure if a large fistula diverts a lot of blood
Surgically created fistulas for dialysis are expected to have a thrill and bruit, which show that they are working.
Causes
AV fistulas can be present at birth, occur from damage, or be created intentionally.
- Injury: A penetrating wound, such as from trauma or a needle puncture, can connect an artery and vein.
- Surgically created: A surgeon deliberately joins an artery and vein, usually in the arm, to create durable access for hemodialysis.
- Congenital: Some people are born with abnormal artery-to-vein connections.
- Medical procedures: Certain catheter procedures can occasionally cause a fistula.
Risk Factors
- Penetrating injuries or trauma to blood vessels
- Catheter-based heart or blood vessel procedures
- Kidney failure requiring dialysis (for surgically created fistulas)
- Being born with vascular malformations
- High blood pressure, which can worsen the strain a fistula places on circulation
Diagnosis
Diagnosis usually starts with a physical exam and is confirmed with imaging.
- Physical examination: Feeling for a thrill and listening for a bruit over the suspected area.
- Duplex ultrasound: A noninvasive scan that shows the abnormal blood flow and the connection between artery and vein.
- CT or MR angiography: Detailed imaging of the blood vessels to map the fistula.
- Catheter angiography: Sometimes used to define the fistula precisely, especially before treatment.
Treatment
Treatment depends on whether the fistula is harmful, harmless, or a needed dialysis access.
- Monitoring: Small fistulas that cause no symptoms may simply be watched.
- Catheter-based closure: A minimally invasive procedure to seal off an abnormal fistula from inside the vessel.
- Surgery: An operation to close or repair the abnormal connection when needed.
- Care of dialysis fistulas: Surgically created fistulas are maintained and monitored to keep them working for dialysis, and complications such as narrowing or clotting are treated.
- Managing complications: Treating swelling, clots, or strain on the heart.
Prevention
- Abnormal AV fistulas from injury cannot always be prevented, but prompt care of vascular injuries helps
- Protect a dialysis fistula: avoid heavy lifting, tight clothing, blood pressure cuffs, and blood draws on that arm
- Check a dialysis fistula daily for its thrill, and report any change to your care team
- Keep blood pressure controlled
- Attend follow-up appointments to catch problems early
When to See a Doctor
See a doctor if you notice a bulging or pulsating vein, a humming sound, or swelling and warmth in a limb. If you have a dialysis fistula, contact your care team right away if you can no longer feel the buzzing thrill, or if the area becomes painful, red, or swollen, as this may mean it has clotted or become infected. Seek emergency care for sudden severe bleeding from a fistula; apply firm pressure and call emergency services immediately.
Frequently Asked Questions
What is an arteriovenous fistula?
It is an abnormal direct connection between an artery and a vein that bypasses the small capillaries in between. Some occur from injury or are present at birth, while others are created surgically to provide access for hemodialysis.
Why are AV fistulas created for dialysis?
A surgically made fistula, usually in the arm, joins an artery and vein so the vein enlarges and develops strong blood flow. This provides durable, reliable access for the needles used in hemodialysis and is preferred for long-term dialysis.
Are arteriovenous fistulas dangerous?
It depends on the size and location. Small ones may cause no problems, but a large or untreated abnormal fistula can cause limb swelling, blood clots, and strain on the heart by diverting a lot of blood. These usually need treatment.
How do I care for a dialysis fistula?
Protect the fistula arm by avoiding heavy lifting, tight clothing, blood pressure cuffs, and blood draws on that side. Check daily that you can feel the buzzing thrill, keep the area clean, and report any change, pain, redness, or swelling to your care team.
When is a fistula an emergency?
Seek emergency care for sudden, heavy bleeding from a fistula by applying firm pressure and calling emergency services. Also contact your care team urgently if you can no longer feel the thrill or if the area becomes painful, red, or swollen, which can signal clotting or infection.
References
- Mayo Clinic. Arteriovenous fistula — Symptoms and causes.
- MedlinePlus, U.S. National Library of Medicine. Dialysis access.
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Hemodialysis.
- Society for Vascular Surgery. Arteriovenous fistula.