Dialysis removes from the blood waste products and excess water, which are retained in people with kidney failure. It can be a temporary treatment for acute kidney failure or a long-term measure used in end-stage kidney failure. There are two forms: peritoneal dialysis, in which the peritoneal membrane in the abdomen is used as a filter; and haemodialysis, in which a kidney machine filters the blood.
In peritoneal dialysis, the peritoneum, the membrane that surrounds the abdominal organs, is used instead of the kidneys to filter the blood. A procedure called an exchange is carried out four times a day at home. During an exchange, dialysis fluid that was infused into the abdomen 4–6 hours earlier is drained out of the peritoneum through a catheter in the abdominal wall. The fluid is replaced with fresh solution, then the equipment is disconnected and you can carry out normal activities. Between exchanges, wastes and excess water pass from the peritoneal blood vessels into the dialysis fluid.
In haemodialysis, blood is pumped by a kidney machine through a filter attached to the side of the machine. Inside the filter, blood flows on one side of a membrane and dialysis fluid flows on the other. Waste products and water pass from the blood across the membrane and into the dialysate fluid, and the filtered blood returns to the body. Each treatment takes 3–4 hours and is usually repeated three times a week.
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.