Arteriovenous fistula

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at January 27, 2016
StartDiseasesArteriovenous fistula

Arteriovenous fistula or AV fistula is an abnormal connection between arteries and veins. It can occur at any point in the body, be of any size, and vary in length and number. It refers to both the surgical procedure done for dialysis and a symptom of disease or trauma.

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Definition & Facts

Normally blood flow begins in the arteries and travels to the veins through the capillaries, whereas AV fistulas bypass the capillaries. This can result in reduced blood supply to the tissues. AV fistula can also be created surgically and used during dialysis for people with kidney failure. Dialysis requires access to the cardiovascular system and over half of the people who need it use AV fistulas, which creates a larger and tougher blood vessel that can tolerate multiple needle punctures needed for dialysis. AV fistula, whether created surgically or caused by disease or trauma, should be monitored carefully since it can lead to severe complications.

Symptoms & Complaints

Small AV fistulas will not have any symptoms at all. However if they increase in size, symptoms will be experienced depending on which part of body they occur in. Some of these symptoms include:

Causes

AV fistula can be caused by a variety of factors such as:

  • Surgically: They are intentionally created for dialysis to make blood flow easily. They are usually done on the forearm.
  • Congenital disorder: Arteries and veins for some unclear reason may not develop fully in the womb. A child is thus born with the condition. These usually don't require any treatment only monitoring since they heal on their own.
  • Cardiac catheterization: This is a procedure where a catheter is inserted into the body via a vein or artery. If the long thin tube used crosses a vein and an artery an AV fistula will be formed.
  • Skin injury: If an injury pierces skin occurs at the point where a vein and artery are next to each other, an AV fistula may form.

Diagnosis & Tests

When blood flows through an AV fistula it makes a humming or click sound known as a murmur. Diagnosis is done by using a stethoscope to listen to the blood flow on the suspected area and detect a murmur. Early detection makes the condition easier to treat and reduces the risk of complications developing. Once confirmed, additional tests are done to verify its existence. These tests might include:

  • CT Angiogram: A dye-like substance is injected in the body and a CT scan takes images of the suspected arteries and can show if blood flow is bypassing any capillaries.
  • Duplex ultrasound: Transducer that produces high-frequency sound waves is pressed over the suspected area. Speed of blood flow is then measured against the rate of change in frequency.

Treatment & Therapy

Depending on the size of the AV fistula, various forms of treatment can be recommended. When small, they don't cause health problems and a doctor may suggest monitoring. However, treatment may include:

  • Ultrasound-guided compression: This is a simple procedure carried out in 10 minutes and done when the AV fistula can be easily seen on ultrasound. The fistula is compressed by the ultrasound probe and blood flow to the damaged blood vessels is blocked. Unfortunately it only works in one out of three people.
  • Catheter embolization: This involves inserting a catheter in an artery that's close to the AV fistula. An X-ray and other imaging techniques then guide the catheter to the fistula and a small coil or plug is placed there to reroute blood flow. It is a short procedure that may only require an overnight stay in hospital.
  • Surgery: This is the last resort and used to treat fistulas that can't be treated using other methods. The type of surgery depends on location and size of the fistula.

Prevention & Prophylaxis

This condition is often caused by genetics and thus prevention is not usually possible. Other options for dialysis include AV graft, where an artificial blood vessel is inserted or a venous catheter.