An AV fistula is the preferred long-term access for haemodialysis. This guide explains what it is, how the operation works, what helps it to work well and what to watch for afterwards. It does not replace the advice of your own surgeon or nephrologist.
What is an AV fistula?
Arteries carry blood from the heart to the body, quickly and under pressure. Veins carry it back, slowly and close to the skin. Usually the two are not directly joined. In an arterio-venous (AV) fistula, a surgeon connects an artery to a vein.
The reason is simple. Blood from the artery now flows through the vein at high speed and pressure, and over several weeks the vein grows larger and stronger. It becomes big enough for the dialysis needles to be placed in it and connected to the dialysis machine.
Fistula or dialysis line?
Some patients start dialysis through a dialysis line (a central venous catheter) while a fistula is being made and is maturing. The two are different:
- A dialysis line is a soft tube placed in a large vein deep in the body, in one of a few possible sites. It can be used straight away, but it cannot stay in for long and tends to develop problems after a few months.
- A fistula uses your own blood vessels, in the arm. It cannot be used straight away, because it needs at least 6 to 8 weeks to mature, but if it is looked after well it can last several years.
Where is a fistula made?
A fistula is made in the upper limbs, so there are only two places to choose from: the left arm and the right arm. There may be two or three usable points on each arm.
The operation
The operation is done under local anaesthesia. You stay awake throughout, and it takes about an hour. In outline:
- You lie down
- The area is cleaned
- You are covered with sterile drapes, leaving only the area to be used
- An injection numbs the area
- The skin is opened and the surgeon connects the artery and the vein
What helps a fistula to mature
Several things decide whether a fistula works out well. Your surgeon will assess them with you:
- A healthy artery that is wide enough. A healthy artery carries blood easily, while one with hardened, narrowed walls carries much less
- A healthy vein that is wide enough, with a thin wall that can expand over time
- No blockage in the veins along the way
- Enough blood pressure to push blood through the fistula. Low blood pressure can make it harder for a fistula to mature, so please follow your doctor's advice and never change your medicines on your own
Protect your veins
Frequent blood tests and drip lines left in a vein for many days can damage it and make its wall thick, so that it no longer expands well. If you may need a fistula, ask for blood samples and drips to be taken from the other arm or from the back of the hand, and tell the staff that you need to protect your veins.
When the operation is more difficult
- Higher body weight: the vessels may lie deeper under the skin, and sometimes a second small operation is needed later to bring the fistula closer to the surface so that it can be used easily
- Small or very slim build: the vessels in the arm are smaller
- Young patients: in teenagers and children the vessels are small, and a fistula operation is often not possible
Early problems after the operation
Most problems that happen in the first 6 to 8 weeks, while the fistula is maturing, can be treated if they are noticed early.
- Bleeding: some bleeding from the wound can occur in the first few days. Your care team will tell you how often to change the dressing
- Infection: the area becomes painful and bleeds, or produces a yellowish or creamy discharge
- Swelling of the whole arm: the arm becomes swollen and tense, which can happen when a vein further up is narrowed, for example after an earlier dialysis line
A fistula that is ready to use
Once it has matured, a fistula usually feels like a firm, pen-sized vein just under the skin, and you can feel a gentle buzzing over it. A matured fistula is the one your dialysis nurses will use for the needles.
Problems once the fistula is in use
Problems that happen after the fistula has matured and is in use for dialysis, usually from about 2 months onwards, include:
- Bleeding after dialysis: a lot of blood can come out of the needle sites if they are not pressed properly afterwards. If the bleeding has not stopped before you leave the dialysis unit, or it restarts at home, go back to the hospital
- A blocked fistula: a blood clot can form inside the fistula so that blood no longer flows well, and the dialysis machine cannot draw blood properly. This usually happens after the fistula has been used for a while, often when too much pressure is applied to it after dialysis. Careful handling by you and by the nurses each time lowers the risk
- A ballooned fistula: a part of the fistula wall becomes thin and balloons out into a swelling that keeps getting bigger. This must be reviewed by the surgeon within days, because if it is left it can burst and cause serious blood loss. It is usually treated in theatre
- Needle problems: if a dialysis needle goes into the artery lying beside the fistula, there can be heavy bleeding and the arm becomes very painful. Tell the dialysis staff at once if you have sudden, severe pain in the arm during dialysis
When to go back to the doctor
- The dressing is soaked with blood, or the wound keeps bleeding
- Bleeding from the needle sites does not stop
- Pain, redness or discharge at the wound
- The arm becomes swollen and tense
- A swelling that is growing along the fistula
- You can no longer feel the buzzing in the fistula, or dialysis is not running well
- You are worried about your fistula for any other reason
If you have heavy bleeding that does not stop, go to the nearest hospital or clinic immediately.
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This article gives general information and does not replace advice from a doctor. To discuss your own situation, please book a consultation.