What is Dialysis?

Dialysis is a treatment method that replicates the function of the kidneys when they are failing. In healthy individuals, the kidneys work to filter and remove waste products, excess fluid, salts and toxins from the blood.

However, in cases of kidney failure, this mechanism fails and individuals need to undergo dialysis. Dialysis can be used to treat people with chronic or acute kidney disease.

Duration of dialysis

In individuals with chronic kidney disease, the build up of urea and other waste products in the blood (uremia) leads to several symptoms such as vomiting, itching, swelling of the feet, legs and body and extreme weakness. If left untreated, symptoms can be severe and the uremia may even lead to death.

In the case of chronic renal failure, the kidneys do not improve and people need dialysis for the rest of their lives, unless they are a suitable candidate for kidney transplant. Some cases of acute kidney disease, however, can be treated and dialysis may only be required in the short term.

Types of dialysis

There are two types of dialysis which include:


This is the classical form of dialysis where the blood is carried via a tube into a dialysis machine which contains a semi permeable membrane. Inside the machine, blood is filtered through the membrane to remove excess water, waste products and toxins before being passed back into the body.

Each session of dialysis may last for around four hours and needs to be performed three times a week.

Peritoneal dialysis

With this type of dialysis, the peritoneal lining of the abdominal cavity is used as the membrane through which the blood is passed to filter out substances. A catheter is attached to the abdomen and a dialysis fluid (dialysate) is pumped into the peritoneal cavity. There, the dialysate sits and absorbs waste from passing blood before being flushed out. The process usually needs to be carried out four times a day with each session lasting around 30 to 40 minutes.

Reviewed by Sally Robertson, BSc

Further Reading

Last Updated: Jan 14, 2014



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