Why av fistula for dialysis?

Two types of vascular access designed for long-term use include the arteriovenous (AV) fistula and the AV graft. A third type of vascular access—the venous catheter—is for short-term use.

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An AV fistula is a connection, made by a vascular surgeon, of an artery to a vein. Arteries carry blood from the heart to the body, while veins carry blood from the body back to the heart. Vascular surgeons specialize in blood vessel surgery. The surgeon usually places an AV fistula in the forearm or upper arm. An AV fistula causes extra pressure and extra blood to flow into the vein, making it grow large and strong. The larger vein provides easy, reliable access to blood vessels. Without this kind of access, regular hemodialysis sessions would not be possible. Untreated veins cannot withstand repeated needle insertions, because they would collapse the way a straw collapses under strong suction.

Health care providers recommend an AV fistula over the other types of access because it

Before AV fistula surgery, the surgeon may perform a vessel mapping test. Vessel mapping uses Doppler ultrasound to evaluate blood vessels that the surgeon may use to make the AV fistula. Ultrasound uses a device, called a transducer, that bounces safe, painless sound waves off organs to create an image of their structure. A specially trained technician performs the procedure in a health care provider’s office, an outpatient center, or a hospital. A radiologist—a doctor who specializes in medical imaging—interprets the images. The patient does not need anesthesia for this procedure. A Doppler ultrasound shows how much and how quickly blood flows through arteries and veins so the surgeon can select the best blood vessels to use.

A surgeon performs AV fistula surgery in an outpatient center or a hospital. The vascular access procedure may require an overnight stay in the hospital; however, many patients go home afterward. A health care provider uses local anesthesia to numb the area where the surgeon creates the AV fistula.

An AV fistula frequently requires 2 to 3 months to develop, or mature, before the patient can use it for hemodialysis. If an AV fistula fails to mature after surgery, the surgeon must repeat the procedure.

At the start of a hemodialysis session, a health care provider or the patient inserts two needles into the vascular access. One needle carries blood from the body to the dialyzer. The other carries filtered blood back to the body. To tell the needles apart, the needle that carries blood away from the body is called the arterial needle. The needle that carries blood back to the body is called the venous needle. Some patients prefer to insert their own needles into the vascular access, which requires training to learn how to prevent infection and protect the vascular access. No matter who inserts the needles, the patient should know how to take care of the needle insertion area to prevent infection.

If an AV fistula does not mature, an AV graft is the second choice for a long-lasting vascular access.

An AV graft is a looped, plastic tube that connects an artery to a vein. A vascular surgeon performs AV graft surgery, much like AV fistula surgery, in an outpatient center or a hospital. As with AV fistula surgery, the patient may need to stay overnight in the hospital, although many patients can go home after the procedure. A health care provider uses local anesthesia to numb the area where the surgeon creates the AV graft.

A patient can usually use an AV graft 2 to 3 weeks after the surgery. An AV graft is more likely than an AV fistula to have problems with infection and clotting. Repeated blood clots can block the flow of blood through the graft. However, a well-cared-for graft can last several years.

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A venous catheter is a tube inserted into a vein in the neck, chest, or leg near the groin, usually only for short-term hemodialysis. The tube splits in two after the tube exits the body. The two tubes have caps designed to connect to the line that carries blood to the dialyzer and the line that carries blood from the dialyzer back to the body. A person must close the clamps on each line when connecting and disconnecting the catheter from the tubes.

If kidney disease has progressed quickly, a patient may not have time for placement of an AV fistula or AV graft before starting hemodialysis treatments.

A nephrologist—a doctor who specializes in kidney problems—or an interventional radiologist—a doctor who uses medical imaging equipment to perform operations—performs the venous catheter placement procedure in a hospital or an outpatient center. The patient receives local anesthesia and sedation to stay calm and relaxed during the procedure.

Venous catheters are not ideal for long-term use. With a venous catheter, a patient may develop a blood clot, an infection, or a scarred vein, causing the vein to narrow. However, if a patient needs to start hemodialysis right away, a venous catheter will work for several weeks or months until a surgeon can perform a long-term access surgery and the AV fistula or AV graft has time to mature.

If fistula or graft surgery is unsuccessful, then a patient will need a long-term venous catheter access. When a patient needs a venous catheter for more than 3 weeks, the surgeon will “tunnel” the catheter under the skin, rather than insert it directly into the vein. A tunneled catheter is more comfortable and has fewer problems. Even tunneled catheters, however, may become infected.

All three types of vascular access—AV fistula, AV graft, and venous catheter—can cause problems that require further treatment or surgery. The most common problems include access infection and low blood flow due to blood clotting in the access.

Infection and low blood flow happen less frequently in properly formed AV fistulas than in AV grafts and venous catheters. Still, having an AV fistula does not guarantee the access will be problem-free.

AV grafts more often develop low blood flow, an indication of clotting or narrowing of the access. The AV graft may then require angioplasty, a procedure to widen the narrow part. Another option involves surgery on the AV graft to replace the narrow part.

Venous catheters are the most likely to cause infection and clotting problems. If these problems develop, medication may help. Antibiotics are medications that fight bacteria that can cause infection. Blood thinners such as warfarin keep blood from clotting. If these treatments fail, a nephrologist or an interventional radiologist will need to replace the catheter.

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A patient can care for and protect a vascular access by:

Researchers have not found that eating, diet, and nutrition play a role in causing or preventing problems with a vascular access.

More information about eating well during hemodialysis is provided in the NIDDK health topic, Eat Right to Feel Right on Hemodialysis.

This content is provided as a service of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), part of the National Institutes of Health. The NIDDK translates and disseminates research findings through its clearinghouses and education programs to increase knowledge and understanding about health and disease among patients, health professionals, and the public. Content produced by the NIDDK is carefully reviewed by NIDDK scientists and other experts.

The NIDDK would like to thank:Michael Allon, M.D., University of Alabama at Birmingham

Filtering about 180 liters of liquid a day, kidneys serve to regulate the balance of electrolytes in the blood. When these extremely important organs fail to work at full capacity, usually starting at 10-15% of normal function, patients must begin dialysis.

Hemodialysis is the use of a machine, sometimes referred to as an artificial kidney, to clear the blood of waste and excess water from the blood as a replacement for normal kidney function. Because kidneys have such an important role in maintaining good health, dialysis must be performed regularly. The frequency and length of each dialysis treatment depend on the health of the patient's kidneys, the size of the patient, the amount of fluid retained after the previous session, and the type of artificial kidney used.

Dialysis is a major time commitment, often taking three to five hours per session and is uncomfortable for the patient. Because of its function, an artificial kidney requires entrance into the blood vessels to access the blood and chemicals it needs to filter. A physician creates an entrance into the blood vessel through minor surgery on the arm or leg.

Dialysis is performed so regularly for some patients, that it makes sense to create a permanent access point for dialysis. This often comes in the form of a fistula, or the joining of an artery and a vein in the arm, that provides a steady flow of blood that can be filtered and processed by the artificial kidney. Arteriovenous fistulas are considered the gold standard for patients who require dialysis on a regular basis.

AV fistula offer a number of advantages over the two more traditional methods of accessing blood during dialysis.

Catheters are usually used for short-term access, but can sometimes be permanent. A catheter is inserted into a large vein or artery in the neck or chest for access to the blood. Catheters are considered a poor permanent option for dialysis because they sit both sides and outside the body and are prone to infection. The catheter must also always be kept dry, so swimming or bathing are not allowed. They are also unsightly and unwieldy when getting dressed and undressed. Of the three options, catheters allow for the slowest flow of blood.

An AV graft is one superior alternative for a catheter. An arteriovenous graft is created similarly to a fistula, connecting a vein to an artery, but it employs a plastic tube that is healed over by its surrounding tissue. Hemodialysis can be performed by inserting two needles on either side of the tube--arterial and venous. The graft greatly increases the rate of blood flow during dialysis, shortening the time required to perform it. An AV graft requires the patient to take good care of the access point, as it might be prone to complications otherwise.

The third option is the arteriovenous fistula, deemed the best option by most doctors. Rather than using a plastic tube, a fistula is created by connecting an artery directly to a vein. Once it has matured and grown, a fistula is a natural part of the body and requires less attention and care than an AV graft. A mature fistula that has grown bigger and stronger can provide good blood flow for decades. Because it is a natural part of the body, patients can "exercise" the fistula and make it grow through exercises like squeezing a rubber ball.

The AV fistula is preferred over grafts or catheters by most doctors for a number of reasons. It tends to offer the greatest amount of blood flow, so patients are in dialysis and uncomfortable for the shortest amount of time. Because they are a natural part of the body, they last much longer and are less expensive to maintain than a graft or catheter. They also offer a much lower risk of infection or clotting, which means fewer complications for patients who are already dealing with regular dialysis.

Some doctors believe that those who already have an AV graft or a catheter implanted might still be good candidates for an AV fistula and should be reevaluated. A strong initiative has begun to persuade physicians and patients alike to choose an arteriovenous fistula.

There are few risks for an AV fistula, but it might result in infection, clotting of the vessels, narrowing of the blood vessels in the fistula, or an aneurysm due to the weakening of those blood vessels. Bleeding might occur in some patients.

A major complication may be that the fistula takes too long to heal or never heals properly at all.

Furthermore, not every person suffering from kidney disease is a good candidate for an AV fistula. Patients with highly compromised vascular systems may not have the ability to heal a fistula and are therefore unsuitable for an AV fistula.

Some patients prefer not to get AV fistula for cosmetic reasons, as they result in an unsightly bulge in the arm.

If your kidneys fail, you will need to start dialysis to do the job of your kidneys unless you receive a kidney transplant. Before you can start dialysis, a surgeon will need to create what is called a vascular access. A vascular access is where the dialysis machine will connect to your bloodstream.

During dialysis treatments, the dialysis machine cleans your blood then moves it back into your body. The three most common types of vascular access for hemodialysis are an artery vein fistula, an artery vein graft and a catheter.

An artery vein fistula (AV fistula) is a connection between your artery and your vein that is created by a surgeon. This surgery creates a large blood vessel that has lots of blood flowing through it.

An AV fistula is usually located in your arm between your wrist and elbow. During dialysis treatments, the technician inserts needles into the AV fistula to get access to your bloodstream.

An artery vein graft (AV graft) is a soft rubbery tube that a surgeon implants (i.e., surgically places) into your arm. An AV graft is usually implanted in your arm but may also be implanted in your leg or chest. During dialysis treatments, the technician inserts needles into the tube to get access to your bloodstream.

A catheter (or venous catheter) is a tube placed into a vein, usually in your neck or upper chest. Catheters are usually temporary and used only for a short time. For example, you may need a catheter if you need dialysis right away and the surgery to create an AV fistula or AV graft is still healing.

AV fistula and AV graft are used for permanent, long-term access to your bloodstream, and can last for years. AV fistulas and grafts are under your skin, so they are less likely to cause infections and blood clots than catheters.

A HeRO (Hemodialysis Reliable Outflow) device is for people on dialysis who have problems with their AV fistula or AV graft. It allows more blood to flow in and out of the body compared to a catheter.

There are other types of vascular access, such as a PICC line or IV, that are not used for dialysis.

AV fistulas are considered the best kind of vascular access because they:

If you are on dialysis, your vascular access allows you to get this lifesaving treatment. Taking care of your vascular access will keep it healthy and free of problems that can disrupt your dialysis treatments–such as infections or blood clots.

Ask your dialysis care team or vascular access nurse (a specialist trained in vascular access care) to teach you how to take care of your vascular access. If you notice any signs of infection (such as redness or swelling) or any problems with your vascular access, contact your doctor, nurse or dialysis center right away.

Here are some tips to help you care for your vascular access:

To keep your AV fistula or graft working well:

Keep it clean at all times

Check it every day

Be careful with it

Use your other arm for medical tests

Your doctor will give you a prescription for supplies you willneed to care for your catheter. You can get these at a pharmacy or medical supply store. To care for your catheter:

Keep it clean, dry and covered

Take care of it

Check it every day

AV fistula is the best way to receive dialysis because it's a long term solution for dialysis patients and carries a low risk of infection.