Final answer:
Hemodialysis is a medical procedure used to filter blood externally through a machine to remove waste products and excess water in patients with kidney failure. It is done multiple times a week to maintain the balance of waste products and fluid levels in the body.
Step-by-step explanation:
Hemodialysis is a medical procedure used to filter blood externally through a machine to remove waste products and excess water in patients with kidney failure. It is typically done 3 times a week for 3 to 4 hours each session. The frequency of hemodialysis is necessary because the patient's kidneys are no longer functioning properly, so the blood needs to be continuously cleaned to maintain the balance of waste products and fluid levels in the body.