How does kidney dialysis work? --- Thomas, Oakley, California
A kidney dialysis machine is basically an artificial kidney. It pumps blood out of the patient, removes the toxins from blood and pumps it back into the patient.
The machine uses a porous membrane to do the removal. Blood flows on one side of the membrane, and a clean plasma-like fluid (called dialysate) flows on the other. The pores in the membrane are small enough to keep the red blood cells and platelets in, but big enough to let the plasma pass freely. All the toxins in the blood's plasma get diluted in the dialysate, leaving the blood clean.
For lots more details, please see this blog post that I created for you: How Kidney Dialysis Works