Page last reviewed: 13/07/2011
Dialysis is a type of treatment that replicates many of the functions of the kidneys. It is often used to treat cases of kidney failure, which is also known as end-stage renal disease. This is where the kidneys have been severely damaged and lost almost all of their ability to function.
The functions of the kidneys
The kidneys are two bean-shaped organs that are located at the back of the abdomen behind the liver and the intestines.
Every day, your kidneys filter your blood, removing waste products that are collected as part of your normal bodily functions, along with any excess fluid. The waste products and excess fluid become urine, which is stored in the bladder until you go to the toilet.
If the kidneys fail, an excess of waste products can build up in your blood, leading to a range of symptoms including:
- itchy skin
- swelling of the feet, hands and ankles
Without treatment, such as dialysis, kidney failure will eventually prove fatal.
Types of dialysis
There are two types of dialysis:
- peritoneal dialysis
Haemodialysis is the type of dialysis that most people are aware of. It involves inserting a needle, which is attached by a tube to a dialysis machine, into a blood vessel. Blood is transferred from your body and into the machine, which filters out waste products and excess fluids. The filtered blood is then passed back into your body.
Peritoneal dialysis is a less well known method of dialysis, although it is becoming more common. Peritoneal dialysis involves using the peritoneum as a filter.
The peritoneum is a thin membrane that lines the inside of the abdomen, and surrounds and supports the abdominal organs, such as the stomach and the liver. Like the kidneys, the peritoneum contains thousands of tiny blood vessels, making it useful as a filtering device.
During peritoneal dialysis, a small flexible tube known as a catheter is attached to an incision in your abdomen, and a special fluid, known as dialysis fluid, is pumped into your peritoneal cavity. The peritoneal cavity is the space surrounding the peritoneum.
As blood moves through the peritoneum, waste products and excess fluid are moved out of the blood and into the dialysis fluid. The dialysis fluid is then drained out of the cavity.
Dialysis use in Ireland
In Ireland, an estimated 1600 people are receiving haemodialysis, and an estimated 200 people are receiving peritoneal dialysis.Haemodialysis is available in all 4 regions of the HSE. Because of the way peritoneal dialysis is performed, it does not require regular visits to a dialysis unit.
Living with dialysis can be challenging because the treatment is associated with side effects including fatigue and weight gain. However, there is plenty of help and support available, and many people achieve a good quality of life while living with dialysis.
Page last reviewed: 13/07/2011
The kidneys contain millions of tiny filters known as nephrons. As blood passes through the kidneys, nephrons filter out excess fluid and waste products from the blood. These are then released from the body as urine.
However, if the nephrons become damaged, the kidneys can lose their filtering abilities and dangerous levels of fluid and waste products can build up.
Kidney failure occurs once the kidneys have lost around 90% of their filtering ability. Left untreated, the amount of waste products in the blood will build up to a dangerous level, resulting in coma and then death.
The ideal treatment for kidney failure is a kidney transplant, but many people have to wait several months, or years, before a suitable donated kidney becomes available. Therefore, dialysis is used to prevent death until a suitable kidney becomes available.
Some people are not suitable for a kidney transplant because they have another serious health condition, such as heart failure or cancer. This usually means that they will be unlikely to survive the transplant procedure. People who are not suitable for a kidney transplant will require dialysis treatment for the rest of their lives.
Causes of kidney failure
Diabetes is a condition where the body either does not produce enough insulin (type 1 diabetes), or does not make effective use of it (type 2 diabetes). Insulin is vital because it breaks down the glucose (sugar) in our blood in order to produce carbohydrate, which provides us with energy.
If you have diabetes that is not properly controlled, too much glucose (sugar) can build up in your blood. The excess glucose can damage the nephrons (tiny filters), which affects the ability of your kidneys to filter out waste products and fluids.
Blood pressure is a measurement of how much pressure is required by your heart to pump the blood around your veins and arteries. Too much pressure, known as high blood pressure or hypertension, can damage your body's organs and lead to heart disease.
The causes of 90% of cases of hypertension are unknown, although there appears to be a link between the condition and general health, diet and lifestyle.
Hypertension causes damage by putting strain on the small blood vessels in the kidneys. This prevents the filtering process from working properly.
Other causes of kidney failure include:
- polycystic kidney disease, which is a genetic (inherited) condition where cysts (fluid-filled sacs) develop inside the kidneys
- repeated kidney infections
- glomerulonephritis, which is a poorly understood condition that causes inflammation inside the kidneys
Page last reviewed: 13/07/2011
Dialysis is usually recommended if you begin to show symptoms that suggest that your kidneys have lost most of their filtering abilities, and the levels of waste products in your blood are dangerously high. The medical term to describe this situation is uremia.
Uremia is a Greek word that means 'urine in the blood'. However, if you have uremia, you do not literally have urine in your blood, but your blood will contain many of the waste products that are usually passed out during urination.
Initially, uremia usually develops with symptoms of:
- prolonged fatigue
You may then experience symptoms that affect the skin, such as:
- very itchy skin
- dry and flaky skin
Other symptoms of uremia include:
- an unpleasant metallic taste in your mouth
- an unpleasant ammonia smell on your breath(ammonia is a chemical that smells like stale urine)
- loss of appetite
- muscle cramps
- sleeping problems
- mental confusion
- seizures (fits)
In some cases, if testing shows that your kidneys have lost much of their filtering ability, dialysis may be recommended, regardless of whether you have begun to experience the symptoms of uremia.
This is often recommended for people with diabetes whose pre-existing illness may make it dangerous to delay treatment until the symptoms of uremia begin. This is because the combination of uremia and diabetes could potentially lead to serious complications, such as nerve damage or malnutrition.
The filtering abilities of the kidneys are assessed using a measurement that is known as the glomerular filtration rate (GFR). The GFR measures how many millilitres of blood your kidneys are able to filter over a given time.
Using a blood test, GFR can be estimated to a reasonably high degree of accuracy. A person with healthy kidneys would have a GFR of 90, or above. A GFR of below 15 suggests kidney failure, or near kidney failure, and dialysis treatment will probably be recommended.
Page last reviewed: 13/07/2011
Deciding on a dialysis plan
If dialysis is recommended for you, you will have to decide whether you want haemodialysis or peritoneal dialysis.
Both methods have the same levels of clinical effectiveness, so the choice is usually a case of personal preference. However, there may be some circumstances in which peritoneal dialysis is not recommended, for example, where a person is visually impaired or has dementia.
It should be stressed that any decision you make about which treatment method to have will not be final, and you can choose to move from one treatment option to another.
Haemodialysis usually involves using the dialysis machine three times a week, with each dialysis session usually lasting for about four hours.
One disadvantage of haemodialysis is that you will have to plan your life around your dialysis sessions. For example, if you travel to another country you have to pre-arrange access to dialysis facilities.
Another disadvantage of haemodialysis is that your diet and the amount of fluid you drink needs to be restricted. For example, many people receiving haemodialysis have to avoid foods that are high in potassium, such as bananas, chocolate and crisps, and are usually advised not to drink more than a couple of cups of fluid a day.
See Dialysis - how it is performed for more detailed information about diet and fluid intake.
The main advantage of haemodialysis is that, unlike with peritoneal dialysis, you will be able to have four 'dialysis-free' days a week.
Haemodialysis - home or hospital?
If you decide to choose haemodialysis, you have the option of having a haemodialysis machine installed in your home. This means that you will not have to make regular visits to a dialysis unit.
There are several criteria that usually have to be met for home haemodialysis to be considered a suitable treatment option. Home haemodialysis will be considered if:
- you are physically and mentally capable of operating the dialysis equipment
- previous sessions of dialysis have stabilised your symptoms
- you are free of complications and do not have any other significant health conditions
- there are no problems associated with using a catheter to gain access to your blood
- you have a carer who has made an informed decision to assist you with the dialysis
- there is enough space in your home for a haemodialysis machine and the associated equipment
If you fulfil these criteria, you still may not necessarily want to have home haemodialysis, and you will certainly not be forced to have it if you don't want it.
Many people who are suitable for home dialysis still prefer to visit a dialysis unit because they find the attention and supervision of the staff both comforting and reassuring.
Also, many people find that having the haemodialysis machine in their house can be an unwelcome reminder that they have a serious health condition.
Before making a decision, you may wish to discuss the option of home haemodialysis further with your family, partner and/or other household members.
The obvious advantage of peritoneal dialysis is that, unlike haemodialysis, it does not require regular visits to a dialysis unit or, in the case of home haemodialysis, having a bulky machine installed in your house.
Also, the equipment that is used in peritoneal dialysis is portable, allowing you more freedom to travel than haemodialysis patients. There are two main types of peritoneal dialysis equipment. One type is roughly the size of a hat stand on wheels, and the other type is the size and weight of a small suitcase.
Another advantage of peritoneal dialysis is that there are fewer restrictions on diet and fluid intake compared with haemodialysis. People having haemodialysis are given a strict limit on the amount of fluids that they can drink. See Dialysis - how it is performed for more information.
One of the main disadvantages of peritoneal dialysis is that you need to perform it every day, whereas haemodialysis is usually only performed three days a week.
Another major disadvantage of peritoneal dialysis is that it increases the risk of your peritoneum becoming infected with bacteria (peritonitis). Peritonitis causes symptoms that include:
- abdominal pain
- chills (episodes of shivering and cold)
Repeated episodes of peritonitis can damage the peritoneum and surgery may be required to repair it.
Another drawback of peritoneal dialysis is that the dialysis fluid that is used in peritoneal dialysis can cause a reduction in protein levels, which can lead to a lack of energy and, in some cases, malnutrition.
Some people using peritoneal dialysis also experience a raise in their blood cholesterol levels, which can increase their risk of developing a cardiovascular disease, such as heart attack or stroke.
Weight gain is another side effect of peritoneal dialysis that affects some people.
Continuous and automated peritoneal dialysis
There are two types of peritoneal dialysis:
- continuous ambulatory peritoneal dialysis (CAPD)
- automated peritoneal dialysis (APD)
CAPD does not involve using a machine. A set of portable equipment is used, which includes a dialysis bag containing fluid and a number of tubes.
With CAPD you carry out regular dialysis sessions during the day. These sessions are known as exchanges because clean fluid is exchanged with fluid that contains waste products. Most people using CAPD have four exchanges a day, with each exchange lasting between 30 and 40 minutes.
APD involves using a dialyser machine, although the machine is much smaller than the one used in haemodialysis. Dialysis is performed during the night as you sleep, with a session lasting between 8 and 10 hours.
The main advantage of using CAPD is that the equipment is portable. This gives you more freedom to travel away from your house. For example, you may be able to take your CAPD equipment to your workplace. However, you will need to spend at least two hours a day performing dialysis.
The main advantage of using APD is that your days are 'dialysis free'. However, you need to keep and maintain a dialyser machine (and the associated equipment) in your house, which does not suit some people.
Page last reviewed: 13/07/2011
If you choose to receive haemodialysis, the first step usually involves creating an arteriovenous fistula (AV fistula).
An AV fistula is a surgically modified blood vessel that is created by connecting an artery to a vein. The fistula is usually created in your wrist and upper arm.
Joining the vein and artery together to create the fistula results in making the blood vessel stronger and larger. This makes it easier to transfer your blood into the dialysis machine and then back again.
The operation to create the AV fistula is usually carried out six weeks before haemodialysis begins because this allows the tissue and skin surrounding the fistula to heal.
If your blood vessels are too narrow to create an AV fistula then you may be given an alternative operation known as an AV graft. This involves using a piece of synthetic tubing, known as a graft, to connect an artery to a vein.
As a short-term measure, or if haemodialysis is suddenly required because of a medical emergency, you may be given a neck line. This involves inserting a small tube into a vein in your neck. Once the AV fistula has been created and had time to heal, the neck line can be removed.
The haemodialysis process
Most people require three sessions of haemodialysis a week, with each session lasting for four hours.
At the beginning of the session, a measurement of your blood pressure, skin temperature and pulse will be taken. If you choose to receive home dialysis, you will be trained to take these measurements yourself.
Two thin needles will be inserted into your AV fistula, or graft, and then taped into place. One needle will slowly take blood out of your body and transfer it to a machine known as the dialyser. The dialyser contains a series of membranes that act as filters and a special liquid called dialysate.
The membranes filter out waste products from your blood, which are passed out into the dialysate fluid. The 'dirty' dialysate fluid is then pumped out of the dialyser, and the 'clean' blood is passed back into your body through the second needle.
As it would be too dangerous to remove large amounts of blood in one go, only 40-50ml (two fluid ounces) of blood is removed from the body at any one time. This is why dialysis sessions take at least four hours to complete.
During your dialysis sessions you will sit or lie on a couch, recliner or bed. During the sessions you will be able to read, listen to music, use your mobile phone or sleep. Children who have haemodialysis often find that playing on a mobile games console is an enjoyable way to pass the time.
Haemodialysis is not painful, although some people experience symptoms of nausea, dizziness and muscle cramps during dialysis. This is because of the rapid changes in blood fluid levels that occur during dialysis.
Once the dialysis session is complete, the needles are removed and a plaster applied to prevent bleeding.
Haemodialysis and fluid intake
If you are receiving haemodialysis, the amount of fluid that you can drink will be severely restricted. This is because your kidneys are not working properly. The haemodialysis process itself also limits the amount of fluid you can drink.
Over the course of a day, healthy kidneys constantly remove excess fluid from the body. However, during the haemodialysis process, 2-3 days' worth of fluid is removed over the course of four hours.
If you drink too much, the dialyser is unable to remove all of the fluid, and excess fluids will build up in your blood, tissues and lungs. Potentially, this can be very serious and lead to:
- breathing difficulties
- high blood pressure (hypertension)
- heart disease
The amount of fluid that you are allowed to drink will depend on your weight and your body size. Most people are only allowed to drink between 1,000 and 1,500ml (2-3 pints) of fluids a day.
You will also have to avoid eating foods that have a high fluid content such as:
- ice cream
Many people who are having haemodialysis find that the restriction on drinking fluids is one of the most challenging aspects of living with dialysis. You may find that chewing gum or sucking an ice cube can help with symptoms of thirst.
Haemodialysis and diet
As well as removing waste products, the kidneys help to regulate the amount of minerals that are in the body such as:
- sodium (salt)
These minerals are removed during haemodialysis, but the levels of each mineral can build up rapidly between dialysis sessions, particularly if you eat foods that are high in potassium, phosphorus or sodium.
Excess levels of any of these minerals can be dangerous:
- excessive levels of sodium (hypernatraemia) can cause seizures and coma
- excessive levels of potassium (hyperkalaemia) can cause an irregular heart beat (arrhythmia) and, in the most serious cases, sudden death
- excessive levels of phosphorus (hyperphosphataemia) can cause weakness of the bones (osteoporosis)
It is likely that before having haemodialysis you will be referred to a dietitian so that a suitable diet plan can be drawn up for you.
Diet plans will differ from person to person, but it is likely that you will be asked to avoid foods that are high in sodium, potassium and phosphorus.
Foods that are high in sodium include:
- ready-to-eat meals (including ready-to-eat sandwiches)
- smoked fish
You will also be advised not to add salt to your meals.
Foods that are high in potassium include:
- baked potatoes
Foods that are high in phosphorus include:
- dairy products, such as cheese
- baked beans
- bran cereals
As with haemodialysis, the first stage in peritoneal dialysis is to create an access point. This is so that the dialysate fluid can be passed through your peritoneal cavity.
This is done by making an incision in your abdomen, usually just below the navel (belly button), and inserting a piece of equipment called a Tenckhoff catheter into the incision.
A Tenckhoff catheter is a thin piece of tube that is around 10cm (four inches) long. The dialysate fluid is passed through the catheter and into the peritoneal cavity. When a dialysis session is finished, the end of the catheter is sealed. You will be given training in how to keep the catheter clean in order to prevent peritonitis occurring (infection of the peritoneum).
The Tenckhoff catheter is permanently attached to your abdomen, and many people find this upsetting. Many people soon get used to the catheter, but some people do not. If this is the case, it is possible to have the catheter removed and to switch to haemodialysis.
Continuous ambulatory peritoneal dialysis (CAPD)
The equipment that is used to perform continuous ambulatory peritoneal dialysis (CAPD) consists of:
- a bag containing the dialysate fluid
- an empty bag used to collect waste products
- a series of tubing and clips used to secure both bags to the catheter
- a wheeled stand that you can hang both bags from
CAPD involves exchanging new dialysate fluid with dialysate fluid that contains waste products and excess fluids.
An exchange begins by draining out the old fluid into the waste bag. The new fluid is then drained into your peritoneal cavity. This process is painless and takes around 30 to 40 minutes to complete.
The new fluid is left in the peritoneal cavity for a number of hours (you will be advised about what is the best length of time for you).
As blood passes through the peritoneum, special chemicals contained in the dialysate fluid draw out waste products and excess fluid from the blood into the fluid.
After the set number of hours has passed, you will begin the process again, exchanging the old fluid for the new fluid.
Most people using CAPD require four exchanges a day.
You will be given full training in how to perform each type of draining, as well as detailed instructions about how to keep all the equipment clean in order to prevent peritonitis (infection of the peritoneum).
Automated peritoneal dialysis (APD)
Automated peritoneal dialysis (APD) works on the same principles as CAPD, except that a machine is used to control the drainage of the fluid.
You fill the APD machine with fluid before you go to bed. As you sleep, the machine automatically performs a number of exchanges.
You usually have to be attached to the APD machine for between eight and ten hours. You then usually have one last fill of fluid which you keep in your cavity all day before it is drained away the next evening. An exchange can be temporarily interrupted if, for example, you need to get up to go to the toilet.
Some people who have APD worry that a power cut or other technical problem could be very dangerous. However, it is usually safe to miss one night's worth of exchanges as long as you resume treatment within 24 hours.
If you experience technical problems contact a member of your hospital care team immediately.
Peritoneal dialysis and fluid intake
While fluid intake is less restricted for peritoneal dialysis than for haemodialysis, you will still need to limit the amount you drink.
Your recommended fluid intake will be determined by how much additional fluid is removed when you drain your peritoneal cavity, and how much fluid you pass when urinating. You will be given training in how to take these measurements.
Recommended fluid intakes can vary from person to person, but they are usually in the range of between 2,000 and 3,000ml (4-5 pints) a day.
Peritoneal dialysis and diet
Most people who have peritoneal dialysis are advised to eat a high-protein diet. This is because proteins that are usually stored in your body can be passed out into the dialysate fluid and then removed from your body.
Proteins are required to maintain normal tissue growth, so if you do not replace the missing proteins, you may be at risk of becoming malnourished. Malnutrition is where you do not receive all the nutrients you need in order to maintain a good standard of health.
Foods that are high in protein include:
You are also likely to experience weight gain once you begin peritoneal dialysis. This is because the dialysate fluid contains dextrose, which is a type of sugar that is high in calories.
Calories do not help to maintain tissue growth so, although it may sound contradictory, it is possible to experience both weight gain and malnutrition at the same time.
To minimise the weight gaining effects of dextrose, avoid eating foods that have a high fat content because they are also high in calories.
High-fat foods include:
- meat pies
- sausages and fatty cuts of meat
- hard cheese
- cakes and biscuits
As with haemodialysis, you will probably be advised to avoid foods that have a high sodium or phosphorus content. However, you should not have to avoid foods that have a high potassium content because a build-up of potassium is not usually a problem for people receiving peritoneal dialysis.
It is likely that you will be referred to a dietitian who will be able to discuss the above dietary information in more detail and help you to draw up a diet plan.
Page last reviewed: 13/07/2011
Both haemodialysis and peritoneal dialysis cause side effects. This is because of the way dialysis is carried out, and because dialysis can only compensate for the loss of kidney function to a certain extent.
Fatigue is a common side effect in people who have used both haemodialysis and peritoneal dialysis on a long-term basis. It is thought that fatigue is caused by a combination of:
- the loss of normal kidney function
- the effects that dialysis can have on the body
- the dietary restrictions associated with dialysis
- the overall stress and anxiety that many people with kidney failure experience
There are several treatment options that may be of some use in helping to improve the symptoms of fatigue.
First, you may want to consult your dietitian because your diet may need to be adjusted in order to boost your energy levels.
Second, research has shown that regular aerobic exercise can improve the symptoms of fatigue.
Aerobic exercise is a type of low-to-moderate exercise that is designed to improve how your body makes use of exercise. Examples of aerobic exercise (apart from aerobics) include:
Your dialysis care team and/or your GP will be able to advise you about the type of exercise that is most suitable for you.
Side effects of haemodialysis
Low blood pressure
One of the most common side effects of haemodialysis is low blood pressure (hypotension). Low blood pressure can be caused by the drop in fluid levels that occurs during dialysis. Low blood pressure can cause nausea and dizziness.
The best way to minimise the symptoms of low blood pressure is to ensure that you stick to your daily fluid intake recommendations. If symptoms of low blood pressure persist, consult your dialysis care team because the amount of fluid used during dialysis may need to be adjusted.
Some people experience muscle cramps, usually in the lower legs, during a haemodialysis session. It is thought that this is because the muscles react to the fluid loss that occurs during haemodialysis.
If these muscle cramps become particularly troublesome, consult your dialysis care team. Medication may be available that can help you cope better with the symptoms.
Many people receiving haemodialysis experience itchy skin. It is thought that this is due to a build-up of potassium in the body. Avoiding potassium-rich food can help reduce the frequency and severity of this symptom.
Some people have also found that using moisturising cream can minimise the discomfort caused by itching.
Side effects of peritoneal dialysis
A common side effect of peritoneal dialysis is that the peritoneum becomes infected with bacteria (peritonitis). Peritonitis can occur if the dialysis equipment is not kept properly sterilised (free of germs). Bacteria that may be present on the equipment can be passed into the peritoneum.
Lack of appetite and nausea are the initial symptoms of peritonitis. These are quickly followed by abdominal pain. The pain usually begins as a dull ache in your abdomen before progressing into a steady, severe pain.
Other symptoms of peritonitis include:
- chills (episodes of shivering and cold)
- a high temperature (fever) of 38°C (100.4°F) or above
- rapid heartbeat (tachycardia)
- feeling thirsty
- not passing any urine, or passing much less than normal
Peritonitis is treated with injections of antibiotics (intravenous antibiotics). The antibiotics are usually injected directly into the tissue of the peritoneum.
The most effective way to prevent peritonitis is to keep your dialysis equipment clean. You will be given training in how to do this.
A hernia occurs when an internal part of your body, such as an organ, pushes through a weakness in the muscle or surrounding tissue wall. People using peritoneal dialysis have a greater risk of developing a hernia because holding fluid inside the peritoneal cavity for many hours places strain on the muscles of the abdomen.
The main symptom of a hernia is the appearance of a lump in your abdomen. The lump may be painless and may only be discovered during a check-up.
In some people, certain activities can cause a hernia to become painful. These activities include:
- bending over
- lifting heavy objects
- having sex
Surgery is usually needed to repair a hernia. During surgery, the surgeon will place the protruding intestine, or tissue, back inside the abdominal wall. The muscles of the abdominal wall will then be strengthened with a synthetic mesh.
Page last reviewed: 13/07/2011
How successful dialysis proves to be in the treatment of kidney failure depends on your age, whether you have any other chronic health conditions, such as heart disease or diabetes, and the underlying causes that led to your kidney failure.
Unfortunately, dialysis can only compensate for the loss of kidney function to a certain extent, and not having kidneys that work properly can place a tremendous strain on the body.
The average life expectancy of a person on dialysis who hasn't received a kidney transplant is four years. However, many people on dialysis survive for much longer than this (up to 25 years).