An arteriovenous (AV) fistula is an irregular connection between an artery and a vein. Usually, blood flows from the arteries to tiny blood vessels (capillaries), and then on to the veins. Nutrients and oxygen in the blood travel from the capillaries to tissues in the body.
With an arteriovenous fistula, blood flows directly from an artery into a vein, avoiding some capillaries. When this happens, tissues below the avoided capillaries receive less blood.
Arteriovenous fistulas usually occur in the legs but can develop anywhere in the body. An arteriovenous fistula may be surgically created for use in dialysis in people with severe kidney disease.
Symptoms of arteriovenous fistulas depend on where they form in the body. A large untreated arteriovenous fistula can lead to serious complications. Treatment for arteriovenous fistulas includes monitoring, compression, catheter-based procedures and, sometimes, surgery.
Small arteriovenous fistulas in the legs, arms, lungs, kidneys or brain often won't have any signs or symptoms. Small arteriovenous fistulas usually don't need treatment other than monitoring by a health care provider. Large arteriovenous fistulas may cause signs and symptoms.
Arteriovenous fistula signs and symptoms may include:
- Purplish, bulging veins seen through the skin, similar to varicose veins
- Swelling in the arms or legs
- Decreased blood pressure
- Heart failure
A significant arteriovenous fistula in the lungs (pulmonary arteriovenous fistula) is a serious condition and can cause:
- Pale gray or blue lips or fingernails due to lack of blood flow (cyanosis)
- Fingertips to spread out and become rounder than normal (clubbing)
- Coughing up blood
An arteriovenous fistula in the digestive tract can cause gastrointestinal (GI) bleeding.
When to see a doctor
If you have signs and symptoms of an arteriovenous fistula, make an appointment to see your health care provider. Early detection of an arteriovenous fistula may make the condition easier to treat. It may also reduce the risk of developing complications, including blood clots or heart failure.
Arteriovenous fistulas may be present at birth (congenital) or they may occur later in life (acquired). Causes of arteriovenous fistulas include:
- Injuries that pierce the skin. An arteriovenous fistula may result from a gunshot or stab wound that occurs on a part of the body where a vein and artery are side by side.
- Congenital arteriovenous fistulas. In some babies, the arteries and veins don't develop properly in the womb. It's unclear exactly why this happens.
- Genetic conditions. Arteriovenous fistulas in the lungs (pulmonary arteriovenous fistulas) can be caused by a genetic disease that causes irregular blood vessels throughout the body, but especially in the lungs. One such disease is Osler-Weber-Rendu disease, also known as hereditary hemorrhagic telangiectasia.
- Dialysis-related surgery. People who have late-stage kidney failure may have a surgery to create an arteriovenous fistula in the forearm to make it easier to perform dialysis.
Certain genetic or congenital conditions increase the risk of arteriovenous fistulas. Other potential risk factors for arteriovenous fistulas include:
- Older age
- Female sex
- Cardiac catheterization, especially if the procedure involves blood vessels in the groin
- Certain medications, including some blood thinners (anticoagulants) and medications used to control bleeding (antifibrinolytics)
- High blood pressure
- Increased body mass index (BMI)
Left untreated, an arteriovenous fistula can cause complications. Some complications may be serious. These include:
- Heart failure. This is the most serious complication of large arteriovenous fistulas. Blood flows more quickly through an arteriovenous fistula than it does through typical blood vessels. The increased blood flow makes the heart pump harder. Over time, the strain on the heart can lead to heart failure.
- Blood clots. An arteriovenous fistula in the legs can cause blood clots to form. Leg blood clots may lead to a condition called deep vein thrombosis (DVT). DVT can be life-threatening if the clot travels to the lungs (pulmonary embolism). Depending on where the fistula is, it may lead to a stroke.
- Leg pain due to lack of blood flow (claudication). An arteriovenous fistula can block blood flow to muscles, causing leg pain.
- Internal bleeding. Arteriovenous fistulas may cause bleeding in the stomach and intestines.