(1) Simply put, hemodialysis is the process of drawing blood out of a patient and transporting it through a machine to a special “artificial kidney” (i.e., a dialysis machine) where the blood is “cleaned” (with treated water and concentrated dialysis fluid) to remove toxins and excess water from the blood and then transfused back into the patient. The blood is then transfused back into the patient. (2) The dialyzer acts as a “sieve”, with the blood flowing through the sieve and the dialysate flowing in the opposite direction outside the sieve, removing toxins and water from the blood through the sieve holes and into the dialysate. This type of purification is called “hemodialysis”. (3) Another purification method is called “hemofiltration”, in which water is added to the sieve, and toxins are removed through the sieve holes with this water. (4) Another purification method is “hemoperfusion”, which is similar to the principle of gas mask, in which the blood is passed through activated carbon or resin particles to adsorb the toxins. Hemoperfusion has a much wider range of toxin removal. (5) Generally, patients with uremia undergo dialysis 2 to 3 times a week for 4 to 5 hours each time.