Dialysis is the passage of a solution through a membrane. Usually this term is used to refer to renal dialysis, a procedure that removes toxins, excess fluid and salt from the blood when the kidneys can no longer perform these functions.

Kidney dialysis becomes necessary when the buildup of wastes begins to make a person ill, typically when renal function falls below 10 percent in someone with chronic kidney failure (end-stage renal disease, ESRD). Causes of chronic kidney failure include diabetes, high blood pressure, lupus, prolonged obstructions in the urinary tract, and kidney disorders such as polycystic kidney disease and some types of nephritis.

Chronic kidney failure is irreversible, and dialysis does not cure it. Treatment usually continues for life unless a kidney transplant is available, and patients may die within weeks if they discontinue dialysis. However, there have been unusual cases where kidney function improved enough that a physician could safely discontinue dialysis.

Dialysis also can be used to treat acute kidney failure, which is sometimes reversible. Causes of this sudden condition include trauma, blood loss, shock, poisoning (sometimes caused by medications such as common painkillers), heart attack, severe infections such as E. coli bacteria, dehydration, glomerulonephritis, and recent obstructions in the urinary tract due to causes such as kidney stones or prostate enlargement. Dialysis can resolve some cases of acute kidney failure and be needed only temporarily.

The kidneys are central to the body’s waste-removal system. They are composed of filtering units called nephrons, which themselves are made up of tiny blood vessels called glomeruli. Waste products in the blood pass through the glomeruli and later leave the body in urine. Protein and other needed substances are normally too big to leak through the filters.

The primary cause of kidney failure in the United States is diabetic kidney disease (diabetic nephropathy). Diabetes damages the kidneys by making them filter too much blood. After years of overwork, the glomeruli begin leaking small amounts of protein in the urine (microalbuminuria). If the condition is not caught early, it will worsen to proteinuria, the presence of larger amounts of protein in the urine. High blood pressure, often associated with diabetes, speeds up the damage. This damage can lead to chronic kidney failure and the need for dialysis or a kidney transplant.

People with diabetes can avoid or delay the need for dialysis by having their physician perform a special urine test for microalbuminuria annually upon diagnosis of type 2 diabetes or starting five years after diagnosis of type 1 diabetes. A physician may also recommend other assessments of kidney function, such as glomerular filtration rate (GFR) and waste product testing.

Dialysis patients, especially those with diabetes, may have relatives with undiagnosed kidney disease, researchers have determined. At-risk family members may also benefit from testing for microalbuminuria.

Among diabetes patients in the United States, some racial and ethnic groups are at much higher risk for chronic kidney failure and the need for dialysis, according to the American Diabetes Association:

Treatment usually continues for life, and people with kidney failure may die within weeks if they discontinue dialysis. However, in unusual cases it is possible for kidney function to improve to the point where dialysis can be safely discontinued by a physician.

Dialysis is a life-extending treatment for patients who would otherwise not be able to survive. For some patients, dialysis is not enough to sustain their lives. The U.S. Food and Drug Administration (FDA) has reported an annual mortality rate of up to 23 percent for American dialysis patients. However, some dialysis patients may live as long as people who do not have renal failure, according to the National Kidney Foundation. Researchers are investigating whether dialysis procedures can be improved to reduce that mortality rate. Better patient education also may increase the success of dialysis by encouraging patients to monitor symptoms, adhere to their treatment schedule and undergo regular testing.

Researchers are working on advances in dialysis, including improved home units and a dialysis device that can be worn like a belt.