An arteriovenous (AV) fistula is an abnormal connection between an artery and a vein. Normally, blood flows from your arteries to your capillaries, and then on to your veins. Nutrients and oxygen in your blood travel from your capillaries to tissues in your body.
With an arteriovenous fistula, blood flows directly from an artery into a vein, bypassing some capillaries. When this happens, tissues below the bypassed capillaries receive less blood.
Arteriovenous fistulas usually occur in the legs, but can develop anywhere in the body. Arteriovenous fistulas are often surgically created for use in dialysis in people with severe kidney disease.
A large untreated arteriovenous fistula can lead to serious complications. Your doctor monitors your arteriovenous fistula if you have one for dialysis.
Small arteriovenous fistulas in your legs, arms, lungs, kidneys or brain often won't have any signs or symptoms and usually don't need treatment other than monitoring by your doctor. Large arteriovenous fistulas may cause signs and symptoms.
Arteriovenous fistula signs and symptoms may include:
- Purplish, bulging veins that you can see through your skin, similar to varicose veins
- Swelling in the arms or legs
- Decreased blood pressure
- Heart failure
A significant arteriovenous fistula in your lungs (pulmonary arteriovenous fistula) is a serious condition and can cause:
- A bluish tinge to the skin
- Clubbing of fingers (the fingertips spread out and become rounder than normal)
- Coughing up blood
An arteriovenous fistula in your gastrointestinal tract can cause bleeding in your digestive tract.
When to see a doctor
If you have any of these signs and symptoms and think you might have an arteriovenous fistula, make an appointment to see your doctor. Early detection of an arteriovenous fistula may make your condition easier to treat. It also may reduce your risk of developing complications, including blood clots or heart failure.
Causes of arteriovenous fistulas include:
- Injuries that pierce the skin. An arteriovenous fistula may occur if you have a piercing injury, such as a gunshot or stab wound, on a part of your body where a vein and artery are side by side.
- Being born with an arteriovenous fistula (congenital). The exact reason why isn't clear, but in some babies, the arteries and veins don't develop properly in the womb.
- Genetic conditions. Arteriovenous fistulas in the lungs (pulmonary arteriovenous fistulas) can be caused by a genetic disease (Osler-Weber-Rendu disease, also known as hereditary hemorrhagic telangiectasia) that causes blood vessels to develop abnormally throughout your body, but especially in the lungs.
- Dialysis-related surgery. People who have late-stage kidney failure may have an arteriovenous fistula surgically created in the forearm to make it easier to perform dialysis.
In addition to certain genetic or congenital conditions, the following risk factors may make you more likely to develop an arteriovenous fistula:
- Being female
- Cardiac catheterization, especially if the procedure involves blood vessels in your groin
- Certain medications, including some blood thinners (anticoagulants) and medications used to control bleeding (anti-fibrinolytics)
- High blood pressure
- High body mass index (BMI)
- Older age
Left untreated, an arteriovenous fistula can cause complications, some of which can 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 normal blood vessels. As a result, your heart pumps harder to make up for the increase in blood flow. Over time, the increased workload on your heart can interfere with how the heart works, leading to heart failure.
- Blood clots. An arteriovenous fistula in your legs can cause blood clots to form, potentially leading to deep vein thrombosis, a painful and potentially life-threatening condition if the clot travels to your lungs (pulmonary embolism). Depending on where your fistula is, it can lead to a stroke.
- Leg pain. An arteriovenous fistula in your leg can cause pain in your leg (claudication), or can worsen pain you already have.
- Bleeding. Arteriovenous fistulas may lead to bleeding in your gastrointestinal system.