Dialysis

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Kidney anatomy

Kidney - blood and urine flow

Dialysis is a method of removing toxic substances (impurities or wastes) from the blood when the kidneys are unable to do so. Dialysis is most frequently used for patients who have kidney failure, but may also be used to quickly remove drugs or poisons in acute situations. This technique can be life saving in people with acute or chronic kidney failure.

Artificial kidneys; Hemodialysis; Peritoneal dialysis; Renal replacement therapy;

Dialysis can be performed using several different methods.

PERITONEAL DIALYSIS

Peritoneal dialysis works by using the body's peritoneal membrane, which is inside the abdomen, as a semi-permeable membrane. Special solutions that help remove toxins are infused in, remain in the abdomen for a time, and then are drained out. This form of dialysis can be performed at home, but must be done every day.

HEMODIALYSIS

Hemodialysis works by circulating the blood through special filters outside the body. The blood flows across a semi-permeable membrane (the dialyzer or filter), along with solutions that help remove toxins.

Hemodialysis requires a blood flow of 400-500 milliliters per minute (ml/min). A normal IV tube in an arm or leg will not support that volume of blood flow, so dialysis uses special ways of accessing the blood in the blood vessels.

The access can be temporary or permanent. Temporary access takes the form of dialysis catheters. These are large-size catheters (hollow medical tubing) placed in large veins that can support acceptable blood flows. Most catheters are used in emergency situations, for short periods of time. However, catheters called tunneled catheters can be used for prolonged periods of time, often weeks to months.

Permanent access is created by surgically joining an artery to a vein. This allows the vein to receive blood at high pressure, leading to thickening of the vein's wall. Now this "arterialized vein" can sustain repeated puncture and also provides excellent blood flow rates. The connection between an artery and a vein can be made using blood vessels (an arteriovenous fistula, or AVF) or a synthetic bridge (arteriovenous graft, or AVG).