Introduction to Peritoneal Dialysis (PD)

What do my kidneys do?

The main role of normal kidneys is to get rid of waste products and water in the blood. They achieve this by filtering the blood and turning the waste into urine. They also produce certain hormones.

Making Urine

The kidneys filter the blood. In this way they get rid of waste products such as urea and creatinine and excess water from the body and therefore maintain a normal balance of water and salts in the body. They also remove excess acid made in the body.

Producing hormones

The second role of the kidneys is to produce a hormone called erythropoietin or EPO. This helps the body to make and maintain a normal level of red blood cells in the bloodstream.

The kidneys convert vitamin D into an active form that is important in maintaining a normal balance of calcium in the body and, as a result, keeping teeth and bones healthy.

The kidneys also play a role in maintaining normal blood pressure. Receptors in the kidney detect falls in blood pressure and causing the kidneys to release a hormone called renin which activates a series of chemical actions in the body leading to a rise in blood pressure.

What happens when my kidneys fail?

They stop making enough urine

They fail to remove excess waste products from the blood. These products are urea, creatinine, acid and excessive amounts of potassium. Waste products, such as urea and creatinine, build up in the blood and can reach toxic levels. The symptoms vary from person to person. Some people experience all the symptoms and some experience a few. Others will not suffer any symptoms at all, however, it is important to recognise that this does not mean that their kidneys are working. Symptoms include: lack of appetite, nausea, vomiting, metallic taste in the mouth, itching, drowsiness during the day, insomnia and restlessness at night, restless legs, leg cramps. These symptoms may also be caused by imbalances in the levels of salts such as potassium in the body.

They fail to remove enough excess water. This means that too much water stays in the body, this is known as ‘fluid overload’. Fluid overload causes swelling of the feet and ankles initially. In severe overload a patient may have shortness of breath. If overload is left untreated, it may put undue strain on the heart.

production of hormones is affected

The kidneys do not produce enough EPO in order to manufacture red blood cells. This causes anaemia and patients will experience symptoms according to the level of anaemia. Some of the symptoms are: lethargy, nausea, loss of appetite, lack of concentration, shortness of breath and feel the cold.

The kidneys do not produce enough active vitamin D. This causes an imbalance between calcium and phosphate levels in the body resulting in weak and aching bones and itching.

Damage to the kidneys may cause them to overproduce renin leading to high blood pressure. This often causes headaches and if left untreated places the patient at higher risk of having a stroke.

Why do I need to have dialysis?

The only way to control the build up of excess fluid and waste products is to filter the blood using artificial means. This is called dialysis. The problems caused by the changes in production of hormones are not directly helped by dialysis but will require drug therapy, for example, EPO can be given by a regular injection, vitamin D by a tablet and any blood pressure problems can be addressed using tablets.

How do I decide what type of dialysis to have?

Once you have been told that you need long term dialysis because your kidneys are failing you will need to decide what is the best treatment for you. You will be given information about the two types of dialysis, haemodialysis and peritoneal dialysis, and the opportunity to discuss them with members of the dialysis team. Both types of dialysis provide a good treatment. Unless you have a medical problem that prevents you having a particular type of dialysis you will have a choice between them.

Generally, people make a decision based on the information they are given and how one or other treatment fits in best with their lifestyle.

What is peritoneal dialysis?

Peritoneal dialysis is a method of cleaning the blood without the blood leaving the body. A clean ‘sugar’ solution (dialysate) is run through a tube called a Tenckhoff catheter into the abdominal cavity.

A thin membrane, called the peritoneum, lines this cavity. The membrane has tiny holes (or pores) in it, through which the waste products can pass from the bloodstream into the ‘sugar’ solution (dialysate). When this fluid is drained out through the catheter, the waste products drain out with it.

There are several different types of PD that use the abdominal cavity in this way, CAPD – the most common type used, APD & CCPD. The difference between them is the equipment and time they need to put the dialysate through the catheter into the abdomen.

How does peritoneal dialysis work?

This next section provides a fairly detailed account of how it works. It is not essential to know it but it may be of interest to you.

PD works by the process of the movement of water and particles across a semi-permeable membrane, the peritoneum, allowing excess water and waste products to be removed from the bloodstream.

This is possible because the theory behind peritoneal dialysis exploits two essential principles of physics and chemistry.

Firstly, diffusion. All molecules and ions, the particles referred to above, move continuously, whether in liquid, gas or solid form and they spread out throughout any substance they are in. If there is a barrier in the way such as a ‘semi-permeable’ membrane that allows smaller particles to pass but blocks larger particles, the small particles will pass through it and spread out, but the larger particles will not. (Imagine a sheet of cling film with holes in it and household sugar & salt on it. The smaller salt crystals can go through the holes but larger granulated sugar ones are too big, then imagine similar sized particles in a fluid trying to pass through the cling film). So if there is a liquid with more particles on one side (a higher concentration) than the other to start with, eventually, the particles that can pass through the membrane will be spread out evenly on both sides.

In PD, you place a fluid with no waste products in the abdominal cavity. The water is separated from the bloodstream by the peritoneum, a membrane that is semi-permeable allowing waste products to pass through it, but not larger particles and elements in the blood. The waste products diffuse into the dialysis fluid which is then drained out.

Secondly, osmosis. Osmosis is the movement of water through a membrane which allows the solutions on side of the membrane to be balanced with another. So, if particles are unable to pass through the membrane and diffuse out, then the water can and will move until the solutions on either side of the membrane are balanced equally.

In PD the fluid used to attract particles in it, is also a highly concentrated ‘sugar’ solution. The ‘sugar’ slowly passes through the peritoneum into the bloodstream, but in order to create balance, the water in the blood quickly crosses the membrane into the solution, weakening it until it is the same sugar concentration as the blood. Therefore, when you drain out the fluid, you get more than you put in because water, excess to overall body needs, is removed.

What is CAPD?

CAPD stands for:

Continuous – you are having dialysis all the time

Ambulatory – you are able to walk around while dialysing

Peritoneal – the inside of your tummy is used for dialysis

Dialysis – the process by which waste products and fluid are removed from the blood/body

In CAPD, the movement of water and waste products across your peritoneal membrane takes place over a period of several hours while the fluid stays in your peritoneal cavity. After a specific period of time the fluid reaches saturation point, full of water and waste products. At this time, the fluid is drained out and exchanged for fresh dialysis fluid. This will take place 4 times a day, for example, at breakfast, lunch, teatime and before going to bed.

The exact time that you choose to change your bag is entirely up to you, in order to allow you to fit dialysis around the planned activities of the day. You do need to space out exchanges evenly throughout the day, but there is room for flexibility.

What is APD?

APD stands for

Automated – a machine is used

Peritoneal - the inside of your tummy is used for dialysis

Dialysis – the process by which waste products and fluid are removed from the blood/body

In APD, a machine is used to perform the exchanges of dialysis fluid. Dialysis takes place overnight so that all the patient has to do is set up and programme the machine. During the night, the machine carefully measures and controls the amount of fluid passing in and out of the patient.

This form of PD is better suited to some patients than others because some patients receive better dialysis when the dialysis fluid is left inside them for a shorter period of time. This is achieved most easily during the night using a machine. Doing it during the day would require the patient to perform extra bag exchanges.

When will I have the Tenckhoff catheter inserted?

We aim to plan and prepare access for peritoneal dialysis before the time of dialysis arrives. You can find out more about Tenckhoff insertion if you read the leaflet on Access for Peritoneal Dialysis. It does require time off work and in a small number of cases an overnight stay in hospital is necessary.

After you have had a Tenckhoff inserted, you will be followed up by your renal consultant until the time has arrived for you to commence PD training

What does PD training consist of?

The length of time it takes to learn how to change peritoneal bags and the problem solving that goes with it can take between 1 and 2 weeks, depending on the individual. You will not be rushed and training sessions are taken at your own pace. At present, most PD training takes place in one of the PD training rooms on B5 at UHW. In the near future, patients who are medically fit will be trained at home, with the PD nurses coming to your home and teaching you in your own environment.

What happens when the PD training is completed?

When you have completed your training, you will be discharged home. In some instances, a district nurse will call to change the Tenckhoff dressing and record blood pressure for those unable to manage these procedures themselves.

Your first outpatients appointment will be 2 weeks after discharge from training. Most appointments, when established and settled on CAPD vary at intervals of between 1 and 3 months.

Will I need to restrict the fluids and the food I eat?

One of the purposes of dialysis is to remove excess water from the body because the kidneys are no longer able to do this. However, the amount of fluid that can be removed is limited and so you will be required to restrict your fluid intake.

The amount that you need to drink will be calculated when you start your PD training. You will be asked to complete a 24 hour urine collection, from which your fluid restriction will be worked out depending on how much urine you have passed.

The food you eat is as important as the dialysis itself. You will be seen by the renal dietitian who will discuss your dietary needs in detail with you and give you a comprehensive diet sheet and dietary advice. Generally, a PD diet needs to consist of high protein, low sugar, low cholesterol and moderate amounts of fibre. We strongly advise asking the dietitian if you have any concerns about your diet.

Will I be able to bathe or shower

You will be able to have a bath, but you must ensure that the bath is clean and the bath water is below the level of the catheter exit site. A shower is preferable to a bath as the water is fresh and running.

Will I be able to go on holiday?

Yes, you will be able to go on holidays in this country and abroad. You will be required to contact the Home Dialysis Administrators who will arrange for deliveries of fluids and stock to your hotel or holiday accommodation. Between 6 to 12 weeks notice is required in advance depending on where you are going. UK holidays can be arranged with about 2 weeks notice.

Will I be able to go swimming?

Yes, swimming is possible for people on PD, but only in a swimming pool, not in the sea. If you would like to go swimming please ask your PD trainer about it who will give you instructions about how this can be undertaken.

What are the possible complications of PD?

Catheter or exit site infections

These can occur and are best prevented by cleaning the exit site on alternate days. Infections that do occur are treated with antibiotics.


This is an infection of the peritoneum. It is the major drawback with PD. The signs and symptoms are cloudy drainage fluid, temperature, pain, nausea and vomiting. Peritonitis is treated with antibiotics taken by mouth or given directly into the dialysate bags before running them into the abdomen. In some instances, if the infection is severe and does not respond, the catheter may need to be removed. Haemodialysis is used until a new catheter is inserted.

Peritonitis can be avoided by maintaining good standards of personal hygiene and hand washing.


This may occur when the catheter is first used. It means that the catheter is not fully healed into the skin. The catheter will be rested for another 10-14 days before trying PD again.

Poor drainage

Sometimes drainage of fluid out of the abdomen during exchanges is poor. This may be caused by the catheter end pointing up in the abdomen as opposed to down towards the pelvis. It is also caused by constipation. Drainage may improve after the successful use of a laxative.

What are the main advantages and disadvantages of PD?

The main advantage of PD is mobility. It can be performed at home, work or on holiday. You do it on your own without help. You can do it at the times that most suit you and you don't need a machine and if you are using a machine overnight, it is easily portable. PD patients are independent and need only visit the hospital every 8 weeks or if there is a problem.

There are fewer dietary restrictions on PD than haemodialysis because the dialysis is continuous.

The main disadvantages are the complications associated with infection, particularly peritonitis, that it disrupts your daily routine and the time off work required for Tenckhoff insertion and training.

Some people who have undergone abdominal surgery can not have PD because the peritoneum has been scarred by surgery and cannot function as an effective semi-permeable membrane.

Can I have a kidney transplant?

You may be suitable for a kidney transplant. If you are interested in this option then you will need to discuss it with your consultant. You may do this before you start on dialysis and at anytime after you have started dialysis. You will be referred to a transplant surgeon for an assessment in outpatients clinic. Routine tests will be arranged to see if you are medically suitable. If you are suitable, your name will be placed on a transplant waiting list and when a kidney which matches your blood group and tissue type becomes available you will be given it.

It is important to realise that the length of time you are on the waiting list depends on the availability of a suitable kidney and not how long you have been waiting.

Some people may have relatives who wish to make a kidney donation. In this case you will need to discuss it with your consultant and an assessment for you and your potential donor will be arranged.

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