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Info & Treatments for Kidney Stones & Kidney Disease

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A dialysis machine is a device used in dialysis. Dialysis is a blood treatment that replaces the natural functions of the kidneys with artificial blood purification to remove wastes and excess water. Both diffusion (the filtering out and discarding of waste products from the blood) and ultrafiltration (elimination of excess water) are natural kidney function, normally generating urine, which discards both water and waste materials.

However, when either chronic or acute renal disease leads to acute kidney failure, the kidneys are unable to perform these necessary functions normally, and so dialysis treatment is necessary to replace them. In either case, that of acute or chronic kidney disease, dialysis is a temporary measure. Acute kidney disease allows the damage to the kidney to repair itself. Dialysis is used to replace kidney functioning until the natural abilities of the kidneys are restored.

The end stage of chronic renal disease is not normally reversible, but in this case the remedy is a kidney transplant, and dialysis is used to maintain life and health until a donor kidney becomes available. On those occasions when a transplant cannot be performed for whatever reason, dialysis will be necessary for the rest of the patient's life.


Two types of dialysis treatment are in common use. Of these, hemodialysis is the one that uses a dialysis machine, properly so called. In hemodialysis, a catheter is inserted in a vein to extract the patient's blood.

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The blood is put through an artificial filtering system that is part of the dialysis machine. The entire process requires up to four hours and usually needs to be done about once a week, although recent studies have shown the benefit of more frequent dialysis treatments, up to once a day. In terms of time requirement, hemodialysis using a dialysis machine is the more efficient of the two procedures.

How Does A Dialysis Machine Work?

A dialysis machine consists of the following working parts:

1) a venous catheter to remove blood from the patient;

2) a blood plump to power the circulation;

3) two pressure monitors, one at the point where blood from the vein is pumped into the dialyzer, the other where cleansed blood is returned to the patient's body;

4) the dialyzer itself, where blood is filtered using a solution called dialysate pumped into the dialyzer from one container and pumped out of it into another container for used dialysate;

5) a heparin pump to prevent clotting, and

6) a saline drip to give the cleansed blood the proper consistency before it is returned to the patient's body.

The patient's blood is removed from the body, circulated through the dialysis machine and treated, and returned to the body in an artificial circulation. The dialyzer itself has two chambers separated by a semi-permeable membrane, one for blood, the other for dialysate.

Because the dialysate solution is completely lacking or at least low in concentration of urea, creatinine, and dissolved minerals such as potassium and phosphorous, while the blood has undesirably high concentrations of these materials, so that they pass through the semi-permeable membrane from the blood into the dialysate, removing them from the blood.

The  spent dialysate is then returned to a separate container and replaced with fresh dialysate. The exact composition of the dialysate solution varies depending on the contaminants in the patient's blood.

The principle involved in dialysis is called diffusion. This is a property of substances dissolved in water, namely that they tend to move from an area of high concentration to one of lower concentration when allowed to do so.

The liquids do not actually have to be in contact or mixed to allow diffusion to operate, but they do need to be in proximity and not separated by a completely impermeable barrier.

A dialysis machine sets up two opposite flows, blood in one direction and dialysate in the other, with a semi-permeable membrane between them. This allows the contaminants to flow across the membrane from the higher-concentration solution (the blood) to the liquid in which they are not found or found in lower concentration (the dialysate).

Dialysis Machine

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