Haemodialysis is a treatment for those patients whose kidneys cannot function anymore. It is a way of cleansing the blood of toxins, extra salts and fluids through a dialysis machine called "artificial kidney".
themodialysis is the process of the state of being removal of the urea and the nitrogenous wastes from  blood by a man made artificial procedure . 
    process :-
 - blood is drained out slowly and passed through dialyzer . 
 - heparin mixed 
 - dialyzer contains network of cellophane tubes inside an isotonic medium devoid of nitrogenous wastes 
  - dialyzer sucks out the wastes based on simple diffusion .
  - down the concentration gradient 
  - purified blood is pumped back to a suitable vein . 
  - anti-heparin mixed .

we know that ,  the kidney removes the harmful wastes ( metabolic wastes ) . 
    then the hemodialysis  helps to the patients  by purifying the blood for who are suffering from kidney infections , whose kidneys are dead . 

feedbacks  - hemodialysis has being a painful process the people who dialyses their blood for 2 times in a weak and they are not agree to go third time and there is many chances of blood infection too because heparin is not completely help to fight with infection  .