What is Hemodialysis

Hemodialysis (also known as haemodialysis) is the most common treatment for kidney failure and has been in regular use since the 1960s - this is what most people think of when they hear about dialysis. When patients refer to "a dialysis machine" or a "kidney machine", they are usually talking about hemodialysis. The first dialysis machine was constructed in 1943, by Willem Kolff, but was not really accepted as a reliable treatment for patients with severe problems as it did not remove excess fluids. However later improvements gradually lead to hemodialysis becoming much more common.

Hemodialysis can be carried out in a hospital, in a separate clinic, in a self-care centre or even in your own home in some cases. The process takes about four to five hours. The patient usually lies on a couch or sits in a chair while connected to the kidney machine, and can pass the time reading or watching tv. Or even browsing the web nowadays.

First, a pair of access points are created by your doctor, usually in the forearm. These are permanent access points and the surgery to insert them can be done quite some time before the patient starts the actual treatment - the first image below shows a fistula in place, clicking reveals the full image. Using these, blood is transferred, at a low flow rate, from your body to the kidney machine (second image below) through one such point. In the machine, heparin is added to the blood to prevent clotting occurring, and the blood is passed into the dialyser (third image) where the waste products and toxins are removed. The cleaned blood is then returned to the body via the second access point.

A fistula in the forearm Diagram of a dialysis machine Close-up of a dialyser Hemodialysis machine

For a full-sized view of any of the images above, just click on them.

In the dialyser are thousands of fine fibre tubes that mimic the body's own glomeruli and filter the blood as it flows through them. They are semi-permeable and allow the small molecules of fluids and soluble wastes to move through tiny holes in the membrane into the surrounding canister which is continuously flushed with dialysis fluid. This fluid is what carries away the waste products. The much larger red and white blood cells and the rest of the blood's constituents however cannot move through the semi-permeable membrane and are returned to the body, having been cleansed.

Doctors recommend hemodialysis in preference to peritoneal dialysis for people who have had recent abdominal wounds, abdominal surgery or scars from either of these events.

A continual problem with hemodialysis is that the demand for treatment always seems to be much greater than the number of machines available at clinics. The result is that some elderly patients, as was the case with the author's own father, are denied treatment. Please support charties which fund the purchase of these machines.