Description, Causes and Risk Factors:
An arteriovenous fistula is an abnormal connection between an artery and a vein. Normally, blood flows from your arteries to your capillaries 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 supply. 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.
Congenital arteriovenous fistulas are uncommon. Acquired arteriovenous fistulas can be caused by any injury that damages an artery and a vein that lie side by side. Typically, the injury is a piercing wound, as from a knife or bullet. The fistula may appear immediately or may develop after a few hours. The area can swell quickly if blood escapes into the surrounding tissues.
The factors that cause these errors are unknown. Potential exogenous causes, such as viral infections, toxins, and drugs, have been implicated but not yet proven. The most common etiology for acquired arteriovenous fistulas is penetrating trauma. Arteriovenous fistula also can occur from non-traumatic causes, such as erosion of an aneurysm into a neighboring vein or following surgery for therapeutic purposes (eg, access for hemodialysis).
Many complications can result with an arteriovenous fistula, such as bleeding, infiltrations, poor blood flow, aneurysm, stenosis and thrombosis.
Purplish, bulging veins that you can see through your skin, similar to varicose veins.
Swelling in the arms or legs.
Decreased blood pressure.
Myocardial infarction (heart failure).
Swelling and reddish appearance on the skin surface.
To diagnose an arteriovenous fistula, your doctor will use a stethoscope to listen to the blood flow through the area where he or she thinks you may have a fistula. The blood flow through an arteriovenous fistula makes a sound similar to clicking or humming machinery (machinery murmur).
If your doctor hears a machinery murmur, you will have other tests to confirm that the murmur is caused by an arteriovenous fistula. These include:
Computerized tomography (CT) angiogram. A CT angiogram allows your doctor to check your arteries to see if blood flow is bypassing the capillaries. You will receive an injection of a dye that shows up on CT images, and the doughnut-shaped CT scanner will be moved to take images of the artery your doctor believes is narrowed. The images are then sent to a computer screen for your doctor to view.
Magnetic resonance angiography (MRA). Your doctor may use MRA if he or she thinks you may have an arteriovenous fistula in an artery that's deep under your skin. This test allows your doctor to see the soft tissues in your body. It uses the same technique as magnetic resonance imaging (MRI), but also includes the use of a special dye that helps create images of your blood vessels. During an MRI or MRA, you lie on a table inside a long tube-like machine that produces a magnetic field. An MRI machine uses the magnetic field and radio waves to create pictures of your body's tissues. Using the images from the test, your doctor may be able to see an arteriovenous fistula.
Digital angiography is helpful in identifying the arteries feeding the fistula and in elaborating a vascular map for endovascular treatment.
Duplex ultrasound. Duplex ultrasound is the most effective and common way to check for an arteriovenous fistula in the blood vessels of the legs or arms. In duplex ultrasound, an instrument called a transducer is pressed to your skin. The transducer produces high-frequency sound waves, which bounce off red blood cells. A duplex ultrasound can estimate how fast blood flows by measuring the rate of change in its pitch (frequency).
Blood gas analysis in an arteriovenous fistula (AVF) reveals higher oxygen saturation in the venous blood immediately distal to the fistula as compared with normal venous blood.
It is possible your doctor may suggest only monitoring your arteriovenous fistula, especially if it is small and does not cause any other health problems. Some small arteriovenous fistulas close without treatment. Except for very small arteriovenous fistulas (AVFs), all other acquired arteriovenous fistulas (AVFs) need to be treated to prevent complications of distal limb ischemia, continued large flow of blood with eventual heart failure, and rarely infection, such as endocarditis. Recurrence is a complication of inadequate or incomplete 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.
Surgery. Large arteriovenous fistulas that cannot be treated with catheter embolization may require surgery. The type of surgery you will need depends on the size and location of your arteriovenous fistula.
Ultrasound-guided compression. If you have an arteriovenous fistula in your legs and it is easily visible on ultrasound, treatment with ultrasound-guided compression may be an option for you. In this treatment, an ultrasound probe is used to compress the fistula and block blood flow to the damaged blood vessels. This procedure only takes about 10 minutes. But, it only works for about one in three people.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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