What is dialysis?

Your kidneys are two bean shaped organs located just below the rib cage on each side of the body. They help perform many functions to keep the body in optimal balance. They aid in removing waste products from the blood and in formation of urine, to excrete these wastes and excess water from the body. Other jobs that your kidneys carry out include: controlling levels of important molecules and salts such as sodium, potassium and chloride, and producing hormones. The three main hormones that the kidney produces include: erythropoietin which stimulates the production of red blood cells when the oxygen carrying capacity of the blood is reduced, renin which is involved in controlling our blood pressure and the active form of Vitamin D, which controls uptake of calcium.

In some cases, the kidneys may fail to function properly or work to their full capacity. Some people who are at risk for kidney disease include those with high blood pressure or diabetes. If your kidneys do not perform their usual functions, you may need some form of treatment to help the body get rid of excess wastes and be maintained in optimal balance.

There are three main treatment options for kidney failure: dialysis (a way to clean the blood artificially), kidney transplants and no treatment (conservative). Dialysis is a process which helps filter and remove wastes from your blood if your kidneys are failing. There are two main forms of dialysis: haemodialysis and peritoneal dialysis.

Haemodialysis is when there is a machine which acts as an ‘artificial kidney’, through which your blood is pumped into.

Peritoneal dialysis is a process which allows the blood to be cleaned inside the body – a part of the abdomen called the peritoneal membrane is used to filter your blood.

How many people receiving dialysis?

Lots of data have been collected by the Australia and New Zealand Dialysis and Transplant Registry (ANZDATA), regarding all patients receiving dialysis in Australia and New Zealand. In the year 2000, the number of people who started dialysis treatment in Australia was 92 per million people. In New Zealand, the rate was slightly higher, at 107 per million people. Looking at the amount of people already on dialysis treatment, the prevalence rates for those on dialysis were 334 per million in Australia and 348 per million in New Zealand. The increased numbers of people on dialysis are seen mainly in the older population.

Those patients who may need dialysis treatment include: diabetic patients, people with high uncontrolled blood pressure, congenital or acquired diseases of the kidney, and cases where there are insults or systemic illnesses that cause lasting, irreversible kidney damage.

When is dialysis needed?

You may need dialysis when you develop end stage or irreversible kidney failure. This usually means you have lost about 85 to 90 percent of your kidney function. There are various parameters such as the filtration rate of the kidneys that can provide a good clinical indication of the kidney function. Doctors are guided by factors such as these levels and may initiate or recommend dialysis treatment when the rates fall below a certain level. If there are any complications like build up of toxic wastes (eg urea), or malnutrition, dialysis may also be needed. Apart from kidney filtration rates, the decision to initiate dialysis may also be influenced by acute and chronic issues.

Acute indications for dialysis

  • High or life threatening levels of potassium (this is concerning because inappropriate levels of potassium can cause abnormalities in heart rhythms and other symptoms such as muscle weakness or numbness / tingling in the body);
  • Excess fluid in the body, leading to accumulation of fluid in the lungs and trouble breathing;
  • Inappropriate levels of metabolites / acids in the body;
  • Complications due to build up of urea – irritation of some of the membranes surrounding the heart, confusion, neuropathy (abnormalities of the nervous system or nerves), muscle aches / pains, fatigue, nausea, shortness of breath, itching;
  • Hyperthermia (an increase in body temperature where the body produces or absorbs more heat than it can get rid of);
  • Significant decreases in production of urine;
  • Drug overdose with a medication that can be removed with dialysis, such as lithium or aspirin.

Longer term indications for dialysis

  • Decreased kidney filtration rates (as above);
  • When you experience symptoms from your kidney failure that are both uncomfortable and interfere with your daily life;
  • Difficulty in controlling the levels of different ions and electrolytes in the body;
  • Low levels of red blood cells.

Some studies have shown that patients who start dialysis treatment earlier have a greater survival rate after the first few years. It is also recommended that when your kidney filtration rates fall below certain levels, you should have regular blood tests to monitor the progress and condition of your kidneys. This will help the doctor decide if and when you need dialysis.

It is important for you to receive sufficient information and education regarding the condition of your kidneys and the options available for treatment, so you can make an informed choice about management of your kidneys and overall health. If you opt for dialysis treatment, you should be well aware of the benefits, risks, complications and commitments that are associated with this therapy. There are many support groups and good sources of information available in the community, such as Kidney Health Australia and the Kidney Health Information Service Line.

Haemodialysis: How does it work?

In haemodialysis, an artificial kidney machine (called a dialyser) is used to remove the wastes and excess fluids from the body. For dialysis to work, there must be a difference in the concentration between the blood and the dialysate (fluid that circulates inside the dialysis machine). Solids move from areas of high to low concentration, whereas water tends to do the opposite, moving from low to high concentrations. This is because the area with a higher concentration has less water. For example, when potato slices are added to a salt solution, the water from inside the potato moves to the salt solution, which causes the potato to shrink.

What is involved in performing haemodialysis?

Haemodialysis is often performed three times a week, for 4-5 hour sessions. This often means that you will have to attend a location where there is a dialyser machine and staff to receive your treatment. In some cases, you may be able to perform haemodialysis at home – this is an option for people who are otherwise medically stable and feeling confident about dealing with the steps involved with haemodialysis at home. Special training is always provided for people who choose the option of home dialysis.

The time needed for dialysis may be influenced by: how much you weigh, how much fluid you gain between the treatments, and how much wastes you have accumulated in your body.

There are three main components required for dialysis:

  • The special dialyser machine;
  • The dialysate;
  • The blood delivery system (via certain access points).

The dialyser machine

During haemodialysis, your blood passes through a special dialyser machine, which is made of a blood pump, a filter called a dialyser, a solution known as a dialysate and various safety monitors. The dialysis machine has a membrane that both solids and water can pass through. Waste products are filtered into the dialysate solution, out of the blood.

A dialyser can be based on two main models – hollow fibre and flat plate configurations. The hollow fibre machines are more commonly seen, composed of many fine tubes inside the dialysis machine. Blood is pumped through the dialyser and flows through the tubes, which have special tubes to drain wastes and excess fluids from the blood. The dialysate fluid flows around the tubes.

During dialysis treatments, you are seated near the machine. Access to your blood is obtained through two needles placed into your dialysis access point. One of these needles takes blood to the machine to be cleaned and the other returns the filtered blood. While you are connected to the machine, you can still perform activities such as reading, writing, watching television or hold a conversation with someone, but you can not usually get up and move around too much.


Dialysate is the fluid that is circulated through the dialysis machine, which has a similar make up to the blood in your body, helping restore the blood’s normal balance. The electrolytes and chemicals in the dialysate can be altered (e.g. potassium, calcium and sodium) depending on the levels of these electrolytes in your body. For example, if you have high amounts of potassium in the body, the level of potassium in the dialysate can be lowered, to help facilitate removal of excess potassium.

There is a large amount of water that is circulated through the body during each dialysis treatment. Often the cycle is repeated about six times during each treatment. Therefore it is very important that the water used for the dialysate is prepared by a variety of processes to ensure that it is sterile and clean.

Blood delivery system

This refers to the circuit between your dialysis access point and the dialysis machine. A small amount of blood is pumped through the circuit at a time, through the dialysis machine and back into your body. The amount of waste removed from the blood is affected by factors including how fast the blood is flowing, the number of hours you are connected to the dialysis machine, and the type of machine you are using.

Dialysis access

There are three main types of access used for dialysis:

  • An arterio-venous fistula (connection between the veins and arteries under your skin to create a bigger blood vessel);
  • An artificial graft (a plastic tube used to join the artery to the vein under your skin);
  • A temporary (often short term) catheter, inserted into a large vein in the neck. This is usually used in emergency situations.

The type of access that is best suited for you depends on factors such as the state of your arteries and their flow rates, and the likely course of your kidney’s condition. It is possible for more than type of access to be present at a time, if needed.

Arterio-venous fistula

A fistula is the preferred access point, created by joining an artery to a vein to make a larger blood vessel. A needle can then be placed into this large vessel to gain access to your blood. A fistula is created for many weeks or months before dialysis is needed, to allow it to mature and strengthen. There is usually a buzzing sensation that can be felt if you put your finger on top of the fistula – this is due to blood flowing from the artery into the vein. The buzzing can give you an indication that the fistula is working well. Often, fistulas are created in your non-dominant arm, commonly located in the forearm, elbow and the hands.

Artificial grafts

In some patients, the dialysis access point may be through an artificial graft that uses a prosthetic material between the artery and the vein. This type of access is used when your own blood vessels are not strong enough to make a fistula, in situations where you have had multiple treatments and your blood vessels may be scarred, or if you have diabetes. These grafts can last from two to three years, with complications such as infection, clotting and development of swellings in the vessels potentially occurring.

Vascular access catheter

In cases where dialysis is required urgently, or where another access procedure (i.e. arteriovenous fistula or graft) is not feasible, a vascular access catheter may be used. This is a special type of tube with two channels that can be inserted into a large vein in your neck. It provides temporary access until another form of access can be gained. There is an increased rate of infection and clotting associated with these catheters, thus they are only used for a short period of time.

What is peritoneal dialysis?

Peritoneal dialysis is another form of dialysis where your blood is cleaned inside the body. The peritoneal membrane that lines the abdominal cavity is used as a filter, to clean out excess wastes and fluids from the blood. This membrane usually covers organs in the body such as the stomach, intestines and liver.

During treatment sessions, the abdomen is filled with dialysate. Extra fluids and wastes are drawn out of the body, into the dialysate. After a certain period of time, the dialysate containing all the wastes and excess fluid is drained out of the abdomen and replaced with fresh dialysate. The amount of fluid exchanged each time varies from 2-3 litres, depending on your weight, age and other medical problems that you may have. Apart from differences in concentration between the blood and the dialysate, the rate at which wastes and other solids are transferred across the peritoneal membrane can also be affected by factors such as your physical position, exercise, drugs like beta blockers or calcium channel blockers (used in high blood pressure, heart failure) and the presence of infection.

There are different forms of peritoneal dialysis, including:

  • Continuous ambulatory peritoneal dialysis (CAPD);
  • Continuous cyclic peritoneal dialysis (CCPD);
  • Nocturnal intermittent peritoneal dialysis (NIPD).

Continuous ambulatory peritoneal dialysis

CAPD is one of the main types of peritoneal dialysis, where 2-3 litres of a dialysate solution are circulated through and drained from your abdomen during the day. At night, a certain amount of solution is placed in the abdomen, which remains in place throughout the night.

This is the only type of peritoneal dialysis that doesn’t use any machines. Gravity is used to drain the dialysate from the abdomen once it has been inside your body for about 4-5 hours.

Continuous cycling peritoneal dialysis

CCPD is usually performed during the night, when you are connected to a machine called a cycler. A series of four to five exchange cycles occurs, where dialysate is circulated into and out of your abdomen. In the morning, you are disconnected from the machine and can attend to your normal activities during the day.

Nocturnal intermittent peritoneal dialysis

NIPD is when cycles of exchange occur for about ten hours during the night, when you are asleep. The composition of the dialysate fluid can be altered depending on your electrolyte balance and needs. A standard solution contains set amounts of sodium, calcium and magnesium, which are similar to your body’s normal levels. A certain amount of glucose is also present in the fluid, to help direct flow of the solution.

Certain substances such as insulin or antibiotics can also be added if you have diabetes or an infection. To access the abdominal cavity, a plastic tube called a catheter can be put into the body. This tube stays in place during dialysis treatments. It allows the transfer of dialysis fluid into and out of the body. Catheters can be for short or longer term use – temporary (acute) catheters are used in emergency settings to allow immediate access. However, they are associated with an increased risk of infection. Chronic, longer term catheters can consist of one or two cuffs and are associated with lower risks of infection and leakage.

How do I choose between haemodialysis and peritoneal dialysis?

Haemodialysis and peritoneal dialysis are two different forms of dialysis treatment. The choice to commence on one type over another depends on many factors. Some of these include: your personal health and any co-existing medical or surgical conditions, the availability of types of dialysis treatment and lifestyle factors, and your individual preferences.

If you have had many operations on the abdomen or conditions affecting the bowel such as inflammatory bowel disease or diverticulitis, haemodialysis may be the preferred mode of dialysis. This is because peritoneal dialysis uses the peritoneal membrane a filter, and if you have any of these conditions, there may be scarring or adhesions which may interfere with peritoneal dialysis. You may experience side effects from peritoneal dialysis or repeated infections (peritonitis), or find it difficult to perform peritoneal dialysis exchanges, requiring a trial of haemodialysis.

Looking at peritoneal dialysis, this type of dialysis can be more lifestyle friendly, allowing you to perform most of your usual activities of daily living. You can attend school or work, with automated dialysis exchanges performed overnight. Peritoneal dialysis may also be more suitable if you have medical conditions such as heart failure and angina (chest pain), as changes in your fluid balance and blood pressure are more controlled and stable.

Studies have investigated the effects of peritoneal dialysis versus haemodialysis and shown that your kidney function may be better preserved with continuous ambulatory peritoneal dialysis. A study performed in 2002 in over 500 dialysis patients revealed that kidney function declined at a greater rate amongst haemodialysis patients than in those who received peritoneal dialysis. However, if side effects such as low blood pressure and dehydration were avoided, this decline could potentially be avoided. The benefits and risks of each type of dialysis needs to be extensively discussed with your doctor and any family members or friends who may be involved as part of your dialysis treatment.

Complications associated with dialysis

There are both short and long term complications experienced by patients undergoing dialysis treatment. These vary according to the type of dialysis performed.

Short-term complications


  • Hypotension (low blood pressure) is one of the most commonly seen side effects during dialysis. Often, this is because excess amounts of fluid are drained from the body. Apart from fluid depletion, factors such as excessive heat from the dialysate solution causing a rise in body temperature can lead to dilation of blood vessels and a drop in blood pressure. Occasionally, more serious causes of low blood pressure such as a heart attack, insufficient blood supply to the heart, abnormal heart rhythms or collection of fluid or blood inside the sac surrounding the heart must be ruled out.
  • Your access site for haemodialysis is also susceptible to clotting or becoming infected. A condition called septicaemia can result if bacteria spreads throughout your body.
  • Allergic reactions to parts of the dialysis solution and other medications given during dialysis can result in symptoms such as shortness of breath, chest pain and nausea.


  • One of the most serious complications of peritoneal dialysis is an infection of the peritoneal cavity inside the abdomen (peritonitis). This is commonly due to bacteria found in the abdomen, bowel and urinary tract. You may experience symptoms such as fever, a change in the colour or cloudy appearance of dialysate and abdominal pain. It is very important to seek medical attention if any of these symptoms occur.
  • Infections can also occur where your catheter exits the skin.
  • A catheter leak or occlusion may also be experienced.
  • If you do not comply with fluid restrictions, you may gain excess fluids. This can result in complications such as shortness of breath and a need for adjustment to your dialysis regime.

Longer term complications

  • If you have any disease of the blood vessels such as build up of fat and hardening of the arteries (also known as atherosclerosis), this may become progressively worse with dialysis treatment. This is particularly important in diabetic and elderly patients.
  • You may also acquire cysts in the kidney, which can result in bleeding and the development of malignancies in the kidney.
  • A condition associated with abnormal deposits of protein (called dialysis associated amyloidosis) can occur after many years of treatment with dialysis. This may be associated with pain in the shoulders, tingling in the fingers, fractures of the bones and cysts.

What is my likely outcome with dialysis?

A number of studies have looked at the survival rates between the two different types of dialysis. Some studies have found that in the first couple of years of dialysis, there is a survival advantage for patients receiving peritoneal dialysis compared to haemodialysis. After this period, the mortality is lower in haemodialysis patients. However, there are many factors that may contribute to these different outcomes, including different study methods and co-existing medical problems in patients who receive dialysis. Therefore, these different studies should be interpreted with caution.

Although there is a definite improvement in the quality of life and survival rates for patients receiving dialysis therapy, there are risks such as infection and heart problems associated with kidney failure patients. This results in an increased rate of mortality. If you have any risk factors such as high blood pressure, diabetes and poorly controlled blood sugar levels, high cholesterol levels and pre-existing heart disease, these should be well controlled. Your nutritional status has also been shown to be very important in ensuring you remain healthy and well.

Ongoing management of dialysis patients

Once you have started dialysis treatment, you may be advised to make a few changes to your lifestyle and diet to ensure that your body is well cared for and remains in optimal balance. Your recommended diet may change over time, as your kidney condition changes. Some areas of your diet that may need to be monitored and adjusted include your protein, salt, potassium, phosphate, calcium and/or fluid intake. It is recommended that an adequate amount of protein is consumed, and the amounts of salt, potassium, phosphate and calcium are restricted in the diet. Fluid intake should be carefully recorded and adjusted depending on your body’s fluid status. Often your health care team and dietician will give you more specific instructions on how to adjust your diet and fluid intake, to best suit your kidney condition. You will be advised about regular blood tests that have to be performed. Generally, if you are receiving haemodialysis, these blood tests can be taken through the dialyser machine you are connected to. On a monthly basis, levels of your red blood cells, ions such as sodium, potassium, calcium, bicarbonate and urea are monitored. Every three months, levels of iron, Vitamin B12, cholesterol and blood sugars are taken. Six monthly screens for infections and conditions such as hepatitis and HIV may be carried out. You will also need to be followed up by the kidney specialists, who can review you in clinics in the hospitals or medical practices. If you experience any difficulties or complications during dialysis treatment, you may need to be reviewed sooner.


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