What Is Dialysis?

A treatment used when kidneys are failing

The kidneys' purpose is to regulate the concentration of substances in the blood and turn waste into urine. Dialysis is a medical procedure that helps regulate the blood when the kidneys cannot, most often in the late stage of chronic kidney disease (CKD), called kidney failure.

This article explains what dialysis is, the different types of dialysis, and how it works.

Dialysis machine and patient
Science Photo Library / Brand X Pictures / Getty Images

What Does Dialysis Do?

When the kidneys can no longer function optimally, dialysis works to do their job artificially. Namely, dialysis treatment manually filters the waste and water from your blood. In the process, it helps control functions in your body that your healthy kidneys otherwise would.

Kidneys help your body in many ways, including:

  • Maintaining safe levels of electrolytes, like sodium and potassium
  • Making red blood cells
  • Keeping bones healthy
  • Controlling your blood pressure

Dialysis can help people whose kidneys are failing be more comfortable and live longer; however, it is not a cure for kidney failure.

Who Needs Dialysis?

Dialysis treats kidney failure (also called renal failure). Kidney failure can occur for various reasons, including:

  • Kidney damage as a result of illness or infection
  • Nephrotoxic drugs (medications that are harmful to the kidneys)
  • Certain health conditions, including hypertension (high blood pressure) and diabetes

When your kidneys begin to fail, you will typically go through stages of kidney function loss over time. CKD progresses from stages 1 through 5. However, you can have mild kidney disease (stage 1-3) without progressing to stage 5, kidney failure.

In the early stages of CKD, you can often treat complications like high blood pressure, abnormal electrolytes (minerals that carry electrical charges), and edema (body swelling) with medications and dietary changes.

If the disease progresses to stage 5, this is called kidney failure, and it requires a kidney transplant. However, transplants are not always the best option for everyone, and dialysis might be necessary while waiting for a transplant or when a transplant is not an option.

Recap

Dialysis treats kidney failure, which can occur due to illness, injury, infection, medication toxicity, and some health conditions.

Dialysis Process

Before you receive dialysis, a surgeon will create an access point for the dialysis machine. The access will be either a shunt (also called vascular access) in a vein or a catheter in your abdomen.

This access point creates a path between the dialysis machine and your blood. If you need emergency dialysis, you might receive a temporary catheter called a "vascath," placed into one of the body's large blood vessels.

Which kind of access you have depends on the type of dialysis you receive. Likewise, the dialysis process is slightly different based on whether you have hemodialysis (done through a vein in your arm) or peritoneal dialysis (done through your abdominal cavity).

Who Does Dialysis?

You can have dialysis in a dialysis treatment center, a hospital, or home. In a healthcare setting, a clinician will perform the dialysis.

If you do dialysis at home, your nephrologist (kidney specialist) and a dialysis nurse will train you for a few weeks to do the procedures yourself. Then, once you are comfortable doing it, they will let you do it at home.

Types of Dialysis

There are two types of dialysis—hemodialysis and peritoneal dialysis. You can do both types in a healthcare setting or at home.

If you do dialysis at home, you will still see your nephrologist regularly. In addition, both a nephrologist and a dialysis nurse are available for on-call troubleshooting. Sometimes a nurse might visit your home if they can't handle your situation with a phone call.

From a medical standpoint, no study has proven any type of dialysis better than the other. In many cases, it is a lifestyle choice. People usually prefer home dialysis if they can take care of themselves. This option is suitable for those who like fewer appointments or want to travel frequently.

Hemodialysis

Before your first hemodialysis, a surgeon will create access to your vein by inserting a stent. They might use your own vein (fistula) or an artificial tube or graft to make this connection.

This access point is where you or your nephrologist team will insert two needles during the dialysis treatment. One needle will take blood from the body to the dialysis machine; the other will carry clean blood back from the device.

Hemo is the Greek word for blood. "Blood dialysis" is when a machine circulates your blood through a built-in filter to replicate the kidney's filtration function.

After the blood goes through this filter, called the dialyzer, the machine returns purified blood to your body.

Hemodialysis usually takes place in a dialysis center about three times every week, for three to four hours. The exact time it takes depends on your size.

Home hemodialysis may happen as often as five to seven times per week. A kidney doctor adjusts the time for each session based on your needs.

Peritoneal Dialysis

Another kind of dialysis is called peritoneal dialysis. Peritoneum refers to the abdominal cavity. If you get peritoneal dialysis, you will not need a shunt; instead, a surgeon will insert a soft plastic tube called a catheter into your abdomen.

Dialysis fluid then goes into the abdominal cavity, which is left for a few hours to clean the blood and balance electrolytes. Then, you drain the liquid and add another round (called an "exchange").

You repeat this cycle a few times, using a machine called the "cycler." Then, finally, you unhook the cycler and put a cap on the catheter.

There are two sub-types of peritoneal dialysis: continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis. The main differences are that you do CAPD manually, by hand, while a machine does the automated type, usually while you sleep.

Hemodialysis
  • Stent as access point

  • Machine removes blood from body to filter it

  • Sessions last around 4 hours

  • One session on treatment days

Peritoneal
  • Abdominal catheter as access

  • Machine pumps dialysis fluid into abdomen to filter it

  • "Exchange" takes around 30 minutes

  • Multiple sessions on treatment days

Recap

There are two types of dialysis: hemodialysis and peritoneal dialysis. Hemodialysis removes blood from your body and filters it before returning to the body. Peritoneal dialysis inserts dialysis fluid into the abdominal cavity to clean blood before it's drained.

How To Prepare

Your nephrologist will monitor you closely in the months leading up to dialysis. In addition, they will likely recommend that you modify your diet to ensure you don't overload on fluids.

Also, during your treatment, you will need to care for your access site, including:

  • Washing the area daily and before treatments
  • Avoiding picking any scabs
  • Checking the site for infections signs
  • Checking for a thrill (vibration) over the access site to ensure blood flow
  • Avoiding trauma, pulling, or pressure on the site
  • Controlling bleeding when you move needles

While you receive dialysis, you will receive regular blood tests and weight checks to ensure the dialysis appropriately affects your body.

Outcomes

Remember, dialysis is not a cure for kidney failure, but it is a treatment that can improve your quality of life until you can receive a transplant.

Some people may receive dialysis for a few years until they receive a transplant. Others, stay on dialysis for decades. Some people choose to transition from receiving treatment in a healthcare setting to doing it themselves at home.

Around two in 1,000 Americans live with end-stage kidney disease.

In 2018, older Americans with CKD on Medicare had higher mortality rates than those without CKD— 96 per 1,000 compared to 46 per 1,000.

However, the trends in mortality are improving. For example, between 2009 and 2018, mortality rates for those receiving hemodialysis decreased by 15% and 20% for those receiving peritoneal dialysis.

Warnings and Contraindications

When you receive dialysis, some complications can occur, including:

  • Access site infection
  • Access site clotting or scarring
  • Muscle cramps
  • Hypotension (low blood pressure)
  • Blood loss
  • Hernia (when abdominal organs protrude through weak muscles, a risk with peritoneal dialysis)
  • Weight gain (with peritoneal dialysis)

In addition, dialysis is not a cure and is intended to improve your quality of life. Therefore, some people, like those who are frail or have other serious health problems like dementia, heart failure, or cancer may determine that the burden of dialysis is greater than its benefit.

Summary

Dialysis is a treatment for end-stage kidney disease. It is not a cure for kidney failure, but it can improve your quality of life until you receive a kidney transplant. It is also a longer-term treatment option for those unable to obtain a transplant. Depending on your condition, there are different types of dialysis that you can have at a dialysis center or home.

Hemodialysis is a process where the blood is pulled from the body into a machine for cleaning. The machine then returns clean blood to the body. This process happens a few times each week, depending on your needs. Peritoneal dialysis involves the placement of fluid into an abdominal catheter to filter your blood.

A Word From Verywell

If you are trying to decide which type of dialysis is best for you, remember that each has pros and cons. The best way to determine which is right for you is to discuss the options with a healthcare provider. In fact, dialysis isn't for everyone. Some people choose conservative management, which includes palliative care and hospice (end of life care) instead.

Was this page helpful?
7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. National Institute of Diabetes and Digestive and Kidney Diseases. Your kidneys and how they work.

  2. National Institute of Diabetes and Digestive and Kidney Diseases. Hemodialysis.

  3. National Kidney Foundation. Quick reference guide on kidney disease screening.

  4. U.S. National Library of Medicine, MedlinePlus. Chronic kidney disease.

  5. National Kidney Foundation. Your dialysis care team.

  6. Zee J, Zhao J, Subramanian L, et al. Perceptions about the dialysis modality decision process among peritoneal dialysis and in-center hemodialysis patientsBMC Nephrol. 2018;19(1):298. doi:10.1186/s12882-018-1096-x

  7. National Institute of Diabetes and Digestive and Kidney Diseases. Peritoneal dialysis.