An arteriovenous (AV)
fistula is an abnormal connection between an artery and a vein.
Normally, your 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.
When you have an arteriovenous fistula, blood flows directly from an
artery into a vein, bypassing the capillaries. When this happens,
tissues downstream from the bypassed capillaries receive less blood
Arteriovenous fistulas usually occur in the legs, but can also develop in the brain, lungs or arms.
You can be born with an arteriovenous fistula (congenital), or you can
develop an arteriovenous fistula after some medical procedures. You can
also develop an arteriovenous fistula from an injury that pierces the
skin, such as a gunshot or stab wound. Leaving an arteriovenous fistula
untreated can eventually lead to serious complications.
For people who have severe kidney disease, arteriovenous fistulas are
sometimes surgically created in their forearms to make dialysis easier.
If you have an arteriovenous fistula created, your doctors will closely
monitor your condition to make sure you don't develop complications.
Small arteriovenous fistulas in your legs, arms, lungs or kidneys often
won't have any symptoms and usually don't need treatment other than
monitoring by your doctor. Larger arteriovenous fistulas may cause
Arteriovenous fistula symptoms may include:
* Swelling and reddish appearance on the skin surface
* Purplish, bulging veins that you can see through your skin, similar to varicose veins
* Decreased blood pressure
An arteriovenous fistula in your lungs (pulmonary arteriovenous fistula) is a serious condition and can cause:
* Bloody sputum
* Difficulty breathing, especially when exercising
* Blueness of the skin
* Clubbing of fingers
* Infections in the valves of your heart
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 can make your condition easier to
treat and may reduce your risk of developing complications, such as
blood clots or, in severe cases, heart failure.
Causes of arteriovenous fistulas include:
Cardiac catheterization. An arteriovenous fistula may develop as a
complication of a procedure called cardiac catheterization. During
cardiac catheterization, a long thin tube called a catheter is inserted
in an artery or vein in your groin, neck or arm and threaded through
your blood vessels to your heart. If the needle used in the
catheterization crosses an artery and vein during your procedure, and
the artery is widened (dilated), this can create an arteriovenous
Although this is the most common way an arteriovenous fistula may develop, it's still rare.
* Injuries that pierce the skin. It's also possible to develop an
arteriovenous fistula after a piercing injury, such as a gunshot or stab
wound. This may happen if your wound is on a part of your body where a
vein and artery are side by side.
* Being born with an arteriovenous fistula. Having an arteriovenous
fistula you're born with (congenital) is uncommon. Doctors aren't sure
what causes congenital arteriovenous fistulas.
* Genetic conditions. Arteriovenous fistulas in the lungs (pulmonary
arteriovenous fistulas) are usually caused by a genetic disease
(Rendu-Osler-Weber disease, or ROWD) that causes blood vessels to
develop abnormally throughout your body, but especially in the lungs.
* Surgical creation (AV fistula procedure). People who have
late-stage kidney failure may also have an arteriovenous fistula
surgically created to make it easier to perform dialysis. If a dialysis
needle is inserted into a vein too many times, the vein may scar and be
destroyed. Creating an arteriovenous fistula widens the vein by
connecting it to a nearby artery, making it easier to insert a needle
for dialysis and causing blood to flow faster.
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. Since your blood flows more quickly through an
arteriovenous fistula than it would if your blood flowed through a
normal course of arteries, capillaries and veins, your blood pressure
drops and your heart pumps harder to compensate for the drop in blood
pressure. Over time, the increased intensity of your heart's pumping can
weaken your heart muscle, 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 also cause you
to develop pain in your legs (claudication), or can worsen pain you
Preparing for your appointment
If you think you may have an arteriovenous fistula, make an appointment
with your family doctor. If an arteriovenous fistula is found early,
your treatment may be easier and more effective. Eventually, however,
you may be referred to a vascular or heart specialist (cardiologist).
Because appointments can be brief, and because there's often a lot of
ground to cover, it's a good idea to be prepared for your appointment.
Here's some information to help you get ready for your appointment, and
what to expect from your doctor.
What you can do
* Be aware of any pre-appointment restrictions. At the time you make
the appointment, be sure to ask if there's anything you need to do in
advance, such as restrict your diet. Since tests for an arteriovenous
fistula usually include an ultrasound, it's likely you'll need to fast
for several hours before your appointment.
* Write down any symptoms you're experiencing, including any that may seem unrelated to arteriovenous fistula.
* Write down key personal information, including previous piercing
injuries or a family history of arteriovenous fistula or other blood
* Make a list of all medications, as well as any vitamins or supplements, that you're taking.
* Take a family member or friend along, if possible. Sometimes it
can be difficult to soak up all the information provided to you during
an appointment. Someone who accompanies you may remember something that
you missed or forgot.
* Be prepared to discuss your diet and exercise habits. If you don't
already follow a diet or exercise routine, be ready to talk to your
doctor about any challenges you might face in getting started.
* Write down questions to ask your doctor.
Your time with your doctor is limited, so preparing a list of questions
will help you make the most of your time together. List your questions
from most important to least important in case time runs out. For
arteriovenous fistula, some basic questions to ask your doctor include:
* What is likely causing my symptoms or condition?
* What are other possible causes for my symptoms or condition?
* What kinds of tests will I need?
* What is the best course of action?
* What's an appropriate level of physical activity?
* What are the alternatives to the primary approach that you're suggesting?
* I have other health conditions. How can I best manage them together?
* Are there any restrictions that I need to follow?
* Should I see a specialist?
* Should my children be screened for this condition?
* Are there any brochures or other printed material that I can take home with me? What Web sites do you recommend visiting?
In addition to the questions that you've prepared to ask your doctor,
don't hesitate to ask questions during your appointment at any time that
you don't understand something.
What to expect from your doctor
Your doctor is likely to ask you a number of questions. Being ready to
answer them may reserve time to go over any points you want to spend
more time on. Your doctor may ask:
* When did you first begin experiencing symptoms?
* Have your symptoms been continuous or occasional?
* How severe are your symptoms?
* What, if anything, seems to improve your symptoms?
* What, if anything, appears to worsen your symptoms?
Tests and diagnosis
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
If your doctor hears a machinery murmur, you'll have other tests to
confirm that the murmur is caused by an arteriovenous fistula. These can
* Doppler ultrasound. Doppler ultrasound is the most effective and
common way to check for an arteriovenous fistula. In Doppler 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 Doppler ultrasound can estimate how fast blood flows by
measuring the rate of change in its pitch (frequency).
* Computerized tomography (CT) angiogram. A CT angiogram allows your
doctor to check your arteries to see if blood flow is bypassing the
capillaries. You'll 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 imaging (MRI). Your doctor may use MRI 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. During an MRI, 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.
Treatments and drugs
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.