The ABCs of kidney dialysis

~by Jo Jordan

What are your kidneys designed to do?

Your kidneys act as a filter for your blood, taking out whatever is not supposed to be there such as the natural byproducts of metabolism, drugs, and other toxins.

The kidneys keep your blood balanced, so that it is not too acidic or too basic, they balance water and electrolyte concentrations (minerals such as potassium, magnesium, sodium, and others), and they control blood volume and pressure. Your kidneys also produce the hormone erythropoietin, responsible for creating new red blood cells, and bone health is partly managed by this pair of organs.

When is dialysis necessary?

If diabetes, high blood pressure, or other diseases progress to the point of causing kidney failure, your kidneys will no longer be able to perform all their functions or filter waste from your blood; your body will become overburdened with high levels of toxins.

Kidney dialysis – also referred to as renal dialysis and hemodialysis – is an artificial means of filtering waste from the blood. It may be used over the short-term in cases where someone has suddenly, and temporarily, lost kidney function (acute renal failure).

Dialysis is also vital to patients who are in the end stages of chronic kidney disease, and have permanently lost kidney function; it is the only way to prolong life if a kidney transplant is not an option.

What is dialysis?

Dialysis is not a perfect replacement for healthy functioning kidneys because it cannot replicate the hormonal functions of these organs. Dialysis is not a cure for kidney disease, and there are serious risks attached to it, such as infection.

Kidney dialysis works on the principles of diffusion, a process in which smaller dissolved molecules in a solution (i.e. blood) separate from the larger molecules when they flow through a semi-permeable membrane.

A dialysis machine uses this process to filter blood the way it would normally be filtered via a pair of healthy kidneys.

Types of dialysis

There are two primary types of dialysis: hemodialysis and peritoneal dialysis.


Receiving hemodialysis requires the insertion of two small tubes into the patient – one in a vein and the other in an artery. The tube in the artery removes the blood, which then enters the dialysis machine. Once filtered of waste products and adjusted for electrolyte imbalances by the machine, the blood returns to the patient via the tube in the vein.

In the United States, dialysis is typically undergone three times a week at a dialysis center. Each session requires from three to five hours.

More frequent dialysis (up to seven sessions a week, for six to eight hours daily, or while a patient sleeps) is believed to foster a better quality of life as well as reduce the risk of death from kidney failure. This, together with innovations in home dialysis equipment, is making home dialysis a more desirable option for many kidney disease patients.

Peritoneal dialysis

Peritoneal dialysis filters the blood by making use of the labyrinth of tiny blood vessels in the abdomen (also known as the peritoneal cavity). After a small, flexible tube is implanted into the abdomen, a specific solution is flushed into and drained out of the abdomen in order to remove wastes.

This type of dialysis can also be administered four or five times per day at home, as well as while overnight via an automated system known as a peritoneal dialysis or cycler machine.

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