Dialysis is a life-sustaining treatment for chronic kidney disease that has progressed to kidney failure. According to the National Kidney Foundation, in 2018 more than 550,000 American received dialysis to replace kidney function.

How Does Dialysis Work?

There are two main types of dialysis — hemodialysis and peritoneal — that use different approaches to filtering waste from the body.

Hemodialysis

Hemodialysis uses a filtering machine, sometimes called an artificial kidney, to remove excess water and toxins. During hemodialysis blood flows from the body through a tube, passes through an external filter called a dialyzer and then is returned to the body.

Hemodialysis may be performed at a dialysis center or at home. Treatment at a dialysis center happens about three times a week for about four hours each time. Home dialysis may be done in shorter, more frequent treatments during the day or longer sessions overnight.

Before dialysis can be performed, health care providers must set up access to the patient’s blood stream. There are three options for hemodialysis access:

• Artery-vein fistula, the preferred access option, involves surgically connecting a vein in the arm to a nearby artery. This access option provides the best blood flow but requires several months of healing after surgery.
• Artery-vein graft involves surgically placing a soft tube between a vein and an artery.
• Central venous catheter is a soft tube surgically placed in a large vein in the neck or chest. Usually, a catheter is temporary and later replaced with a fistula or graft but may be used long-term if these options are not possible.

Peritoneal Dialysis

This type of dialysis filters blood inside the body, using the peritoneum, the tissue lining the abdomen, to remove wastes.

During peritoneal dialysis, a sterile solution is flowed into the abdomen through a soft tube called a catheter. Peritoneal dialysis is not performed at a dialysis center and can be done day or night, at home, at work or while traveling.

There are two types of peritoneal dialysis:

• Continuous ambulatory peritoneal dialysis: In this method dialysis fluid is flowed into the abdomen by hand. After a few hours, fluid and wastes are drained out of the body through the catheter and replaced with fresh solution. Each fluid exchange takes about 30 minutes and is repeated four times a day, leaving the solution in the abdomen overnight.
• Continuous cycling peritoneal dialysis: In this method, dialysis fluid is flowed into the abdomen using a machine that exchanges the fluid several times during sleep. The solution is then left in the abdomen during the day.

When Is Dialysis Needed?

Dialysis is needed when the kidneys fail. Kidney failure can occur for two reasons:

• acute kidney injury (AKI), kidney failure that occurs suddenly
• chronic kidney disease (CKD), also called end-stage renal disease (ESRD), which is kidney failure that develops after a period of worsening kidney damage

While dialysis can do some of the work normally done by healthy kidneys, it cannot cure kidney disease. In AKI the kidneys may start working again, and dialysis is only needed temporarily. In CKD or ESRD, the kidneys are permanently damaged and cannot start working again. In this, dialysis is required for a lifetime.