A sterile dialysis solution is infused into your abdomen where it remains for some time, usually between 4 and 12 hours. It is then drained, bringing out waste products and excess water from the body.
This procedure is either repeated 3-5 times every day [continuous ambulatory peritoneal dialysis (CAPD)] or is performed overnight with the help of a machine [automated peritoneal dialysis (APD)].
You will perform this treatment at home; there is no need to be in a hospital or clinic, apart from for the initial insertion of the tube.
How peritoneal dialysis works
Approximately 2 litres of dialysis solution are infused into the abdomen through a special tube called a peritoneal catheter. This process is called 'infusion.' The removal process uses the peritoneal membrane in your abdomen as a natural filter. Waste products and excess water are extracted from your body into the dialysis solution through the peritoneal membrane.
After 4-12 hours (dwell time), this fluid is drained from your abdomen in a process called 'drainage', which takes about 20-30 minutes. After that, a new sterile solution is infused into your abdomen, and the process starts all over again. The process of draining out the old solution and infusing with a new one is called an 'exchange' and is done mainly using gravity. Except during these exchanges — which take on average 30-40 minutes, and occur 3-5 times a day — you are free to do whatever you want during the rest of the day (e.g., work, study or even travel).
Inserting the catheter
Peritoneal dialysis requires access to the abdomen via a PD catheter. A PD catheter is a thin plastic tube, about the size of a pencil, inserted through the abdominal wall into the abdominal cavity. It is inserted by a surgeon or a nephrologist under general or local anaesthesia. It is permanently connected to your body, with just a small part of it exiting through the skin for connection to the transfer set and the PD bags during exchanges. The PD catheter is the same for CAPD and APD. It is desirable to wait at least two weeks after catheter insertion before starting PD.
Keeping the catheter and the area around it clean is very important. You will be trained in how to do this and avoid infections.
Combining peritoneal dialysis with your daily life
When on peritoneal dialysis, you can go on doing most of the things you did before you started this treatment and your residual renal function may be preserved for longer. This allows for fewer diet restrictions, such as limiting fluid intake and salt. As part of the process, you will be able to discuss these matters with your renal team.
Automated Peritoneal Dialysis (APD)
APD follows the same basic principles as CAPD, but exchanges occur while the patient sleeps, with the help of a 'cycler' machine. Patients thus have their daytime free and most people learn how to use the machine in about 10 days.
How does APD work?
The cycler measures the fluids needed for each exchange and times the delivery, dwell and drainage carefully and automatically, removing metabolic waste and excess water from the body over 8-10 hours.
Just before the patient disconnects from the machine in the morning, a 'last fill' solution can be infused into the peritoneal cavity where it remains during the day, possibly requiring an extra exchange before the night time dialysis.
Machines and equipment
The cycler is the size of a small wheeled suitcase and easily portable. It is designed to adapt to normal sleeping patterns and allows treatment to be interrupted to enable the patient to leave their bed if necessary.
Cyclers have programmable data cards containing prescribed treatment details which can capture data from each dialysis session. The newest machines also allow online monitoring and are currently available at Diaverum UK, Germany and Poland. As with CAPD, some space is needed at home for storage of the APD device and dialysis supplies.
Continuous Ambulatory Peritoneal Dialysis (CAPD)
CAPD is a peritoneal dialysis modality which is carried out by the patient, with 3-5 exchanges each day. CAPD can be done at home or any other place, putting some normality into daily life.
How CAPD works
Approximately 2 litres of dialysis solution is infused into the abdomen through a unique tube called a PD catheter. This process is called 'infusion'. The cleaning process uses the membrane in your abdomen as a natural filter. Waste products and excess water are removed from your body into the dialysis solution through the peritoneal membrane. After 4-12 hours, this fluid is drained from your abdomen in a process named 'drainage', which takes about 20-30 minutes. After that, a new sterile solution is instilled into your abdomen, and the process starts all over again. This process of draining out the old solution and introducing a new one is called an 'exchange' and is done mainly by gravity. Except for the time spent during these exchanges — on average 30-40 minutes, 3-5 times a day — the rest of the day you are free to do whatever you want (e.g., work, study or even travel).
Supplies for CAPD
All the dialysis solutions, lines, and other supplies will be delivered to your home periodically. Your prescription will inform you how often and when you should use the different dialysis fluids.
Glucose – the driving force for water removal
To extract the adequate amount of water from your body, you need to have the right strength of the dialysis fluid. The dialysis fluid most commonly consists of a glucose solution that pulls water out of your body into the peritoneal membrane. This process is called 'ultrafiltration'.
To be able to perform your exchanges yourself, you need to be trained on how to connect and disconnect properly. You will learn how to do the exchange procedure and how to identify and cope with any potential problems. The training usually takes a week and takes place in the dialysis clinic or hospital where you perform the first treatments.