Arteriovenous Fistula -

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 fistula

An arteriovenous (AV) fistula is an irregular connection between an artery and a vein. Blood flow avoids tiny blood vessels (capillaries) and moves directly from an artery into a vein.

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
Fatigue
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.

To diagnose an arteriovenous fistula, a health care provider may use a stethoscope to listen to the blood flow in the arms and legs. The blood flow through an arteriovenous fistula makes a sound like humming.

If your provider thinks you have a fistula, other tests are typically done to confirm the diagnosis. Tests to diagnose an arteriovenous fistula can include:

Duplex ultrasound. Duplex ultrasound is the most effective and common way to check for an arteriovenous fistula in the legs or arms. In duplex ultrasound, sound waves are used to evaluate the speed of blood flow.
Computerized tomography (CT) angiogram. This imaging test can show if blood flow is bypassing the capillaries. Dye (contrast) is given by IV for this test. The dye helps blood vessels show up more clearly on the images.
Magnetic resonance angiography (MRA). This test may be done if you have signs of an arteriovenous fistula deep under the skin. Like an MRI, an MRA uses a magnetic field and radio waves to create pictures of the body’s soft tissues. Dye (contrast) is given by IV to help blood vessels show up better on the images.

If an arteriovenous fistula is small and doesn’t cause any other health problems, close monitoring by a health care provider may be the only treatment needed. Some small arteriovenous fistulas close by themselves without treatment.

If an arteriovenous fistula requires treatment, your provider may recommend:

Ultrasound-guided compression. This may be an option for an arteriovenous fistula in the legs that’s easily seen on ultrasound. In this treatment, an ultrasound probe is push down on the fistula for about 10 minutes. The compression destroys blood flow to the damaged blood vessels.
Catheter embolization. In this procedure, a thin, flexible tube (catheter) is inserted in an artery near the arteriovenous fistula. Then, a small coil or stent is placed at the site of the fistula to reroute blood flow. Many people who have catheter embolization stay in the hospital for less than a day and can resume daily activities within a week.
Surgery. Large arteriovenous fistulas that can’t be treated with catheter embolization may require surgery. The type of surgery needed depends on the size and location of the arteriovenous fistula.

References

Loscalzo J, et al., eds. Arterial diseases of the extremities. In: Harrison’s Principles of Internal Medicine. 21st ed. McGraw Hill; 2021. https://accessmedicine.mhmedical.com. Accessed March 18, 2022.
Sidawy AN, et al., eds. Acquired arteriovenous fistulas. In: Rutherford’s Vascular Surgery and Endovascular Therapy. 9th ed. Elsevier; 2019. https://www.clinicalkey.com. Accessed March 18, 2022.
Eidt J, et al. Acquired arteriovenous fistula of the lower extremity. https://www.uptodate.com/contents/search. Accessed March 18, 2022.
Cameron AM, et al. Pseudoaneurysms and arteriovenous fistulas. In: Current Surgical Therapy. 13th ed. Elsevier; 2020. https://www.clinicalkey.com. Accessed March 18, 2022.
Gossage JR, et al. Pulmonary arteriovenous malformations: Clinical features and diagnostic evaluation in adults. https://www.uptodate.com/contents/search. Accessed March 18, 2022.
Medical review (expert opinion). Mayo Clinic. May 1, 2020.

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Arteriovenous Fistula