By Dr Ananya Mandal, MD
Dialysis is a technique in which blood is filtered through a device to clear it of excess fluid, waste and toxins when the kidneys are no longer able to do so. Dialysis may be used to treat patients chronic kidney disease or acute kidney failure.
There are two types of dialysis - hemodialysis and peritoneal dialysis. Both types involve the use of a fluid called dialysate, the medium used to carry the impurities and waste away from the blood. The toxins and fluids pass from the blood through a semi permeable membrane into the dialysate.
Types of dialysis
This describes the classical form of dialysis where blood is passed via a tube into a dialysis machine which removes excess water, waste products and toxins from the blood before returning it to the body. Each session of dialysis can last for around four hours. The filtration barrier in this type of dialysis is present inside the dialysis machine.
This type of dialysis uses the serous membrane that forms the lining of the abdominal cavity as a filter for removing the excess fluids and waste. The dialysate is pumped into the peritoneal cavity through a catheter in the abdomen where it sits and absorbs waste products before being flushed back out.
Continuous ambulatory peritoneal dialysis (CAPD) is the term used to describe when this process is carried out in 30 to 40 minute sessions, four times a day. Automated peritoneal dialysis (APD) refers to when a machine is used to carry out this process while a patient is asleep at night.
Comparing the two types of dialysis
Hemodialysis needs to be performed in a hospital setting whereas peritoneal dialysis can be performed anywhere, offering a patient more freedom. In addition, peritoneal dialysis does not require the patient to adhere to as many food and fluid restrictions as hemodialysis.
On the other hand, hemodialysis is carried out on behalf of a patient instead of them having to perform the procedure themselves, it takes less time than peritoneal dialysis and it does not need to be performed as frequently.
Reviewed by Sally Robertson, BSc
Last Updated: Jan 14, 2014