An AVF is an abnormality of blood vessels, consisting of a direct connection between an artery and a vein. An AVF can be present at birth (congenital) or develop after birth, sometimes due to an injury (aquired).

An arteriovenous fistula can occur anywhere in the body. The communication between the high pressure artery and the low pressure vein results in an increase in the volume of blood flowing through that region. This typically results in enlargement of the artery and vein involved. Thus, a patient with an AVF typically has some swelling or prominent pulsations that can be felt. A bruit or continuous murmur are sounds that can be heard when placing a stethoscope over the site of the arteriovenous fistula. A thrill or sensation of vibrations can sometimes be felt by placing the hand over the location of the arteriovenous fistula or the draining vein.

A congenital AVF is typically present at birth, although it may not be noticed until later. Arteriovenous fistulas can occur anywhere in the body. The most common locations include the head, neck, spine and the liver. The following are some of the most common forms.

• Pial or cerebral arteriovenous fistula occurs in the brain. A large cerebral AVF can cause heart failure at or even before birth. A smaller cerebral AVF can result in damage to the brain surrounding the arteriovenous fistula, because blood flow is diverted away from the brain tissue and into the draining vein. Treatment should be carried out as soon as possible in order to minimize the amount of brain damage that occurs. Some cerebral AVFs can rupture, causing intracranial bleeding.
• Dural arteriovenous fistula occurs outside of the brain, in the dura or lining of the skull. A dural AVF can cause symptoms at birth, or it can remain undiagnosed until later in childhood. A large dural AVF can cause cardiac failure at birth. Smaller ones can cause increase in the pressure in the veins inside the head, causing hydrocephalus or enlargement of the cerebral ventricles (fluid containing spaces within the brain). A dural AVF can also cause a bruit or pulsatile noise that the patient can hear, headaches and less commonly, bleeding or damage to the brain tissue.
• Vein of Galen arteriovenous fistula is usually seen in infancy or early childhood. It drains into the vein of Galen, or deep venous system of the brain. It can result in cardiac failure, hydrocephalus or damage to the developing brain.
• Arteriovenous fistula in the face or neck causes swelling and abnormal pulsations. In extreme cases, it could cause some overload of the heart in infancy. It usually does not cause any serious problems with brain development.
• Spinal arteriovenous fistula. An AVF can occur in the spinal cord or beside it, within the spine, or outside the spine in the adjacent muscles. It can cause compression of the spinal cord, leading to numbness or weakness.
• Peripheral arteriovenous fistula. An AVF that occurs outside of the head, neck and spine is called a peripheral arteriovenous fistula. The most common type present at birth occurs in the liver (hepatic AVF). There are several types of hepatic AVF. A fistula between the hepatic (liver) artery and the hepatic vein is called a hepatic AVF. A fistula between the hepatic artery and the portal vein (vein that conducts blood from the veins draining the bowel to the liver) is termed an arterioportal fistula. Both types of AVF can occur within an infantile hemangioma.

An acquired AVF is one that is not present at birth but develops or is caused later in life. It is usually caused by passage of a sharp object through the tissues of the body, such as during a gunshot or stabbing injury The fistula can rarely result from a medical procedure, in which a needle or other instrument passes through both an artery and a vein during its course.

Most arteriovenous fistulas are treated by transcatheter embolization. In this procedure, a catheter is inserted into an artery (usually the femoral artery in the front of the hip) and guided, under a fluoroscopic or x-ray imaging, to the location of the fistula. Contrast medium is injected to identify the location of the AVF. A device is then placed precisely at the junction between the artery and the vein to stop the blood flow. Embolization devices that are used to treat an arteriovenous fistula include coils, detachable balloons, embolization glue or large devices such as a vascular plug. Once the connection between the artery and vein is closed completely, the arteriovenous fistula is cured and usually does not reoccur.

Occasionally, when the fistula occurs between the side of an important artery and the vein next to it, a covered stent (a wire mesh tube with a fabric cover) can be inserted into either the artery or the vein, across the defect. This technique can also result in cure of the arteriovenous fistula with preservation of the artery and vein.

If neither embolization or stent closure is appropriate, surgical closure of the fistula with arterial repair can be performed.