An arteriovenous fistula (AV fistula) is the connection of a vein and an artery, usually in the forearm, to allow access to the vascular system for hemodialysis, a procedure that performs the functions of the kidneys in people whose kidneys have failed. Connecting the vein and artery is a surgical procedure. The fistula develops over a period of months after the surgery.
An arteriovenous fistula is an abnormal channel between an artery and a vein
- Although doctors may be able to hear the distinctive sound of blood flow though a fistula by using a stethoscope, imaging tests are often needed.
- Fistulas can be cut out or eliminated with laser therapy, or sometimes substances are injected into the fistula to block the blood flow.
Normally, blood flows from arteries into capillaries and then into veins. When an arteriovenous fistula is present, blood flows directly from an artery into a vein, bypassing the capillaries. A person may be born with an arteriovenous fistula (congenital fistula), or a fistula may develop after birth (acquired fistula).
Symptoms And Diagnosis
When congenital arteriovenous fistulas are near the surface of the skin, they may appear swollen and reddish blue. In conspicuous places, such as the face, they appear purplish and may be unsightly.
If a large acquired arteriovenous fistula is not treated, a large volume of blood flows under high pressure from the artery into the vein network. Vein walls are not strong enough to withstand such high pressure, so the walls stretch and the veins enlarge and bulge (sometimes resembling varicose veins). In addition, blood flows more freely into the enlarged veins than it would if it continued its normal course through the arteries. As a result, blood pressure falls. To compensate for this fall in blood pressure, the heart pumps more forcefully and more rapidly, thus greatly increasing its output of blood. Eventually, the increased effort may strain the heart, causing heart failure. The larger the fistula, the more quickly heart failure can develop.
With a stethoscope placed over a large acquired arteriovenous fistula, doctors can hear a distinctive “to-and-fro” sound, like that of moving machinery. This sound is called a machinery murmur. Doppler ultrasonography is used to confirm the diagnosis and to determine the extent of the problem. For fistulas between deeper blood vessels (such as the aorta and vena cava), magnetic resonance imaging (MRI) is more useful.
Small congenital arteriovenous fistulas can be cut out or eliminated with laser coagulation therapy. This procedure must be done by a skilled vascular surgeon, because the fistulas are sometimes more extensive than they appear to be on the surface. Arteriovenous fistulas near the eye, brain, or other major structures can be especially difficult to treat.
It's possible your doctor may suggest only monitoring your arteriovenous fistula, especially if it's small and doesn't cause any other health problems. Some small arteriovenous fistulas close without treatment.
If your arteriovenous fistula requires treatment, your doctor may recommend catheter embolization. In this procedure, a catheter is inserted in an artery near the site of your arteriovenous fistula. Doctors use X-ray and other imaging techniques to guide the catheter to your fistula, and a small coil or stent is placed at the site of your fistula to reroute your blood flow. Many people who have catheter embolization stay in the hospital for 24 hours or less and can resume all their daily activities within a week.
Large arteriovenous fistulas that can't be treated with catheter embolization may require surgery. The type of surgery you'll need depends on the size and location of your arteriovenous fistula.
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