Method of rinsing back blood to hemodialysis patient

A method of automatically rinsing back blood from a dialyzer to a patient, said method performed in a dialysis machine having a dialyzer, a dialysate circuit and an extracorporeal circuit having arterial and venous blood lines connected to a patient and a blood pump, the method comprising the steps of:

• pumping dialysate from said dialysate circuit through said dialyzer into said extracorporeal circuit;
• pumping blood in said extracorporeal circuit our of said arterial and venous lines back to said patient;
• monitoring with optical sensors the concentration of blood in said arterial and venous lines as said blood is being pumped from said extracorporeal circuit back to said patient;
• and
• ceasing the flow of blood back to said patient when the concentration of blood in said arterial and venous lines drops to a predetermined threshold level indicative of substantial dilution of said blood with said dialysate, thereby preventing excess fluids from being returned to said patient.