Arteriovenous (AV) Fistula
About - An arteriovenous (AV) fistula is an abnormal connection between an artery and a vein. Normally, blood flows from arteries into smaller blood vessels called capillaries before reaching the veins. An AV fistula allows blood to flow directly from an artery into a vein, bypassing the capillaries. Some AV fistulas are present from birth (congenital), while others develop later because of an injury, certain medical procedures, or disease. AV fistulas can occur in different parts of the body, including the arms, legs, lungs, brain, and other organs. An AV fistula may sometimes cause no symptoms and may be discovered during an examination or imaging test performed for another reason. However, larger or high-flow fistulas can place extra strain on the heart and may cause circulation problems or other complications. A special type of AV fistula is surgically created for hemodialysis. In this procedure, an artery and vein are intentionally connected, usually in the arm, to provide reliable access for dialysis. Unlike an abnormal AV fistula, a surgically created dialysis fistula is planned and monitored as part of treatment for kidney failure.
The symptoms of an AV fistula depend on its size, location, and the amount of blood flowing through it. Small AV fistulas may not cause noticeable symptoms. Possible symptoms include:
- Fatigue or weakness
- Low blood pressure (hypotension)
- Rapid heartbeat or palpitations
- Shortness of breath
- Swelling of the arms or legs
- Purplish or bluish skin
- Bulging or enlarged veins
- Warmth over the affected area
- A throbbing sensation in the affected area
- A continuous buzzing or humming sound over the fistula, sometimes called a bruit
- Pain or discomfort in the affected limb
- Reduced circulation to tissues beyond the fistula
When an AV fistula occurs in the brain or its surrounding blood vessels, symptoms may be different and can include severe headaches, seizures, vision problems, neurological changes, or bleeding. A large AV fistula can increase the amount of blood returning to the heart. Over time, this may place additional stress on the heart and, in severe cases, contribute to heart failure.
AV fistulas may be congenital or acquired.
Some AV fistulas develop before birth because of abnormal development of blood vessels. These may be associated with certain genetic or vascular conditions.
A penetrating injury or significant trauma that damages an artery and a nearby vein can result in an abnormal connection between them.
An AV fistula can occasionally develop after procedures that involve blood vessels, including catheter-based procedures. This is more likely when an artery and vein located close to each other are injured.
Doctors intentionally create an AV fistula in some people with advanced kidney disease who require hemodialysis. The connection provides durable access to the bloodstream for dialysis.
Certain vascular abnormalities can result in abnormal connections between arteries and veins.
Some inherited disorders can increase the likelihood of developing abnormal blood vessel connections or multiple AV fistulas.
AV fistulas can be classified according to where they occur and how they develop.
This type occurs in an arm, leg, or another peripheral part of the body. It may result from trauma, a medical procedure, or may be congenital.
A fistula can develop between arteries and veins around the brain or its protective coverings. These fistulas may cause neurological symptoms and, depending on their location and blood-flow pattern, can carry a risk of bleeding.
A pulmonary AV fistula, also called a pulmonary arteriovenous malformation (PAVM), is an abnormal connection between blood vessels in the lungs. It can allow blood to bypass normal oxygen exchange in the lungs.
A surgically created AV fistula is commonly used for long-term hemodialysis. It is usually created by connecting an artery and a vein in the arm. With time, the vein becomes stronger and larger, allowing repeated access during dialysis.
Factors that may increase the likelihood of developing an acquired AV fistula include:
- Significant trauma or penetrating injuries
- Previous vascular or catheter-based procedures
- Certain congenital vascular abnormalities
- Conditions associated with abnormal blood vessel development
- Previous surgery involving blood vessels
People who require long-term hemodialysis may have a surgically created AV fistula as their dialysis access.
A doctor may suspect an AV fistula after taking a medical history and performing a physical examination. During examination, the doctor may listen over the affected area with a stethoscope. A continuous abnormal sound, known as a bruit, may indicate increased blood flow. Depending on the location and suspected cause, tests may include:
Doppler ultrasound uses sound waves to examine blood flow through arteries and veins. It can help identify an abnormal connection and determine the direction and speed of blood flow.
CT angiography uses computed tomography and contrast material to produce detailed images of blood vessels. It may be used to evaluate AV fistulas in different parts of the body.
MRA uses magnetic resonance imaging to visualize blood vessels without conventional catheter angiography. It may be particularly useful for evaluating vascular abnormalities in the brain and other areas.
During angiography, a catheter is inserted into a blood vessel and contrast material is used to visualize the vascular system. It can provide detailed information about the location and blood-flow pattern of an AV fistula and may also allow treatment during the same procedure in selected cases.
Treatment depends on the location, size, blood flow, symptoms, and risk of complications.
Small AV fistulas that do not cause symptoms or significant complications may sometimes be monitored regularly by a doctor.
Some AV fistulas can be treated using minimally invasive techniques. A doctor may insert a catheter into a blood vessel and use devices such as coils, plugs, or other materials to reduce or block abnormal blood flow.
Surgical repair may be recommended when an AV fistula is large, symptomatic, difficult to treat with an endovascular procedure, or associated with complications.
If the AV fistula is associated with another vascular or genetic condition, treatment may also be directed toward the underlying disorder.
A surgically created dialysis AV fistula is not usually treated as an abnormal fistula because it is intentionally created for medical treatment. However, it requires regular monitoring for problems such as narrowing, clotting, infection, or inadequate blood flow.
An untreated or complicated AV fistula can sometimes cause serious problems. Possible complications include:
- Heart failure, particularly with large or high-flow fistulas
- Low blood pressure
- Swelling of the affected limb
- Reduced blood supply to tissues
- Blood clots
- Bleeding
- Enlarged or damaged veins
- Skin changes
- Infection
- Neurological complications when the fistula involves blood vessels around the brain
- Brain hemorrhage in certain high-risk cerebral or dural fistulas
The risk of complications varies considerably depending on the location and characteristics of the fistula.
Consult a healthcare professional if you notice:
- Unexplained swelling of an arm or leg
- New or unusually prominent veins
- A persistent throbbing sensation in a limb
- A continuous buzzing or whooshing sound over a blood vessel
- Unexplained shortness of breath or fatigue
- Persistent low blood pressure
- Symptoms that develop after a vascular procedure or significant injury
Seek urgent medical attention for sudden severe headache, seizures, loss of consciousness, sudden weakness or numbness, difficulty speaking, severe shortness of breath, chest pain, or significant bleeding.
Depending on the location and cause of the AV fistula, you may be referred to:
- Vascular Surgeon – for AV fistulas involving peripheral blood vessels and for surgical treatment
- Interventional Radiologist – for diagnosis and minimally invasive/endovascular treatment of selected AV fistulas
- Neurosurgeon – for certain AV fistulas involving blood vessels of the brain or surrounding structures
- Nephrologist – for patients with kidney disease who have or require a dialysis AV fistula
The appropriate specialist depends on the type and location of the fistula.
Congenital AV fistulas generally cannot be prevented. However, some acquired fistulas may be avoided by taking appropriate precautions during medical procedures and by promptly treating significant vascular injuries. People with a surgically created dialysis AV fistula should follow their healthcare team’s instructions to protect the access site and attend regular examinations.
An arteriovenous fistula is an abnormal connection between an artery and a vein that allows blood to flow directly from the artery into the vein without passing through the normal capillary network.
An AV fistula may be harmless when it is small and causes no symptoms, but some fistulas can lead to complications. Large or high-flow fistulas may affect circulation and put extra strain on the heart.
An AV fistula may be present from birth or develop after trauma, vascular procedures, catheterization, surgery, or certain blood-vessel abnormalities. AV fistulas are also intentionally created for hemodialysis.
Yes. A large or high-flow AV fistula can increase the amount of blood returning to the heart. In some people, this increased workload may contribute to heart failure.
Depending on its location, an AV fistula may cause a throbbing or pulsating sensation, warmth, swelling, or prominent veins. A healthcare professional may be able to detect a continuous buzzing sound over the fistula.
Diagnosis may involve a physical examination and tests such as Doppler ultrasound, CT angiography, magnetic resonance angiography, or conventional angiography.
Treatment depends on its location, size, blood flow, and symptoms. Options may include observation, endovascular treatment, or surgery.
No. A dialysis AV fistula is intentionally created by a healthcare professional to provide vascular access for hemodialysis. An abnormal AV fistula develops unintentionally or as a result of a vascular condition or injury.
A vascular surgeon or interventional radiologist may treat many AV fistulas. Cerebral or dural fistulas may require evaluation by specialists such as a neurosurgeon or interventional neuroradiology team. A nephrologist may manage dialysis-related AV fistulas.
Some small acquired AV fistulas may close spontaneously, particularly after certain procedures or injuries. However, this cannot be assumed. Medical evaluation and appropriate follow-up are important.
This information is provided for general educational purposes only and should not be considered a substitute for professional medical advice, diagnosis, or treatment. Symptoms and treatment requirements can vary from person to person. Always consult a qualified healthcare professional for an accurate diagnosis and appropriate treatment. If you experience severe or sudden symptoms, seek immediate medical attention.
