Final answer:
Dialysis is the medical procedure that patients must undergo when the kidneys can no longer remove waste, salt, and excess water from the body. It involves using a machine called a dialysis machine to filter waste materials from the blood.
Step-by-step explanation:
When the kidneys can no longer remove waste, salt, and excess water from the body, a patient must undergo dialysis. Dialysis is a medical process of removing wastes and excess water from the blood using a machine called a dialysis machine. The blood is pumped through a fake kidney in the machine, where waste materials are filtered out and the filtered blood is then returned to the patient's body.