Continuous ambulatory peritoneal dialysis ( CAPD )
What is peritoneal dialysis?
The principal role of the kidneys is the filtration and removal of waste products and excess fluid from the blood. Dialysis is a way of replacing kidney function in people whose kidneys have failed. There are two main forms of dialysis: in haemodialysis, blood is taken from the patient’s circulation, passed through an artificial kidney, and returned to the patient; in peritoneal dialysis, the internal lining of the abdomen acts as the artificial kidney. The abdomen is lined by a thin membrane called the peritoneum, which has a rich supply of tiny blood vessels (capillaries). If the peritoneal membrane is bathed in fluid, waste products can pass from the capillary blood vessels into that fluid, which removes them from the blood. During peritoneal dialysis, fluid is drained into the peritoneal cavity, allowed to sit there for several hours whilst it absorbs waste products, and then drained out. This process, repeated several times a day, can effectively replace kidney function and – because it is a continuous process which allows you to carry on with normal activities – it is known as continuous ambulatory peritoneal dialysis (CAPD).
How does CAPD work?
A permanent soft flexible plastic tube (catheter) is inserted in the abdomen under local or general anaesthetic. You may be required to stay in hospital for 24-48 hours following this procedure and may have some dialysis during your stay. About a week to ten days after your discharge, a nurse will take out your stitches and you will be shown how to keep the area around your catheter (known as the “exit site”) clean and how to put on a new dressing. The exit site dressing will need to be changed regularly. Two or three weeks later, the catheter will be ready for use and CAPD can commence. One to three litres of dialysis fluid are run via the catheter into the peritoneal cavity (Figure 1), and remain in the cavity for several hours before being drained out into an empty bag by gravity. This is called an exchange procedure. The waste products normally removed by the kidney are contained in the drained fluid, which is disposed of into the toilet. A new bag of fluid is then drained into the peritoneal cavity. The exchange procedure is usually performed four times a day, every day, and takes about 30-45 minutes.