Once your chronic kidney failure impairs your body’s functioning too severely, your nephrologist – kidney specialist – will advise you that dialysis has become necessary.
What is dialysis?
Dialysis is basically a method of artificially doing the work that your kidney would do. It filters certain chemicals, created during metabolism, out of your blood, as well as making sure your body has an optimal fluid balance, so it also gets rid of excess water.
Are there different types of dialysis treatments available?
Yes. You can either have hemodialysis or peritoneal dialysis.
How do these different forms of dialysis work?
With hemodialysis (HD), special filters in the dialysis machine do your kidney’s job of cleaning your blood. A lot of blood needs to be circulated through these filters, so the dialysis machine uses a strong pump. Your blood is sucked out of your bloodstream and circulated through the filters before being pumped back into your body.
With peritoneal dialysis (PD), the peritoneum – the sac around your abdominal organs – is used to do your kidney’s work. This is achieved with the help of a dialysis catheter that runs a bag of special fluid into your peritoneal cavity. Once there, your peritoneum works its magic and the fluid is drained out. It sounds almost too easy, but it really is as miraculous as that.
I need hemodialysis. What can I do to make sure it works?
You only need one thing really: access to a large amount of blood.
How do I get connected to a dialysis machine?
Two ways. With a hemodialysis catheter, which is a thick, specialised pipe that gets inserted into a blood vessel, or with a surgically created AV-fistula. The first option is only really suited for short-term use because there’s a high risk of infection. Hemodialysis catheters also tend to cause severe, and permanent, damage to your big blood vessels in which they’re placed. If you’ll need long-term hemodialysis treatment, your best option would be an AV-fistula.
So what is an AV-fistula exactly and how does it work?
The sole aim of creating an AV-fistula is to create a blood vessel that’s easily accessible for needling during hemodialysis. Needling is the practice where the dialysis sister sticks two thick steel needles (connected to plastic pipes which are in turn connected to the dialysis machine) into the fistula. This allows the dialysis machine to suck a vast amount of blood very quickly and also to pump it back into the body once it is filtered.
We have only two types of blood vessels in our bodies. Arteries, taking the blood from the heart to the tissues, and veins, which take the blood back to the heart. We could never needle arteries, although it has more than enough blood flow to allow for excellent dialysis, the damage done to these vessels would lead to major blood loss and even limb loss. Needling a thick vein in your arm will not work either because the blood flow is not fast enough.The dialysis machine will simply choke as it sucks all the blood away in less than a second.
AV stands for arterio-venous and fistula means an abnormal connection in the body. So an AV-fistula for hemodialysis is when your surgeon connects an adequately sized vein in your arm to an artery. This increases the flow in the vein 10-fold and the pressure also increases dramatically. The minute this join is created, we don’t call the vein used a vein any longer, we now call this blood vessel a fistula. Suddenly, there is more than enough blood in the vein to feed the hungry dialysis machine. Over a period of 6 weeks, the increased pressure causes the fistula to become wider and develop a thick, strong wall. After 6 weeks, needles can be placed through this tough wall into the fast-flowing blood, allowing adequate flow for the dialysis machine.
Does a surgeon always use my own veins to create an AV-fistula?
No. Sometimes a special pipe made from an artificial material, called a graft, is used if your veins are too small or if they are clotted up.
I’ve heard of people whose AV-fistula surgery failed. How can I know mine will be successful?
Many variables need to be taken into consideration when planning an AV-fistula operation.
The blood vessels (veins) need to be big enough, if not a graft should be used.
The outflow blood pipe should be wide open. This is often a problem with people who’ve had previous dialysis lines that have damaged their big veins. To assess this, a venogram should be performed. This is a simple examination in the X-ray department where dye is injected into the veins of your arm. Lastly, an experienced fistula surgeon should perform the operation to ensure technical perfection.
It’s also important to remember that all successful fistulas will eventually fail. This is because every time a needle is inserted for dialysis some weakening of the wall will occur. A good fistula will last you no more than 3 years and an exceptional one, seldom more than 5.
I’ve had an upper-arm fistula that’s come to the end of its lifespan. Must I have a graft next?
No, not necessarily. Most people have a beautifully developed vein running next to the artery of their upper arm. This vein can be used to create a new and very robust fistula. As part of the procedure, the vein is tunnelled in a new pathway close to your skin but far away from the main artery and nerves of your arm. This is called a brachio-basilic transposition fistula.
I’ve heard of people having problems with their catheters during peritoneal dialysis. Is this a common problem?
It’s true. Peritoneal dialysis catheters need to be very carefully managed to prevent infection. A lot can be done to pre-empt PD catheter problems with careful placement by way of a small operation using keyhole surgery. This way the surgeon can also make sure that the tip is in exactly the right place. He can also use some techniques to ensure the catheter’s tip doesn’t move later on. Lastly, he can do a lot to prevent the catheter from ever blocking up. If you’re going to have peritoneal dialysis, this is definitely the preferred method of PD catheter placement.