In hemodialysis, a dialysis machine and a special filter called an artificial kidney, or a dialyzer, are used to clean your blood. To get your blood into the dialyzer, the doctor needs to make an access, or entrance, into your blood vessels. This is done with minor surgery, usually to your arm. Hemodialysis treatments usually last about four hours, and they are done three times a week. Your dialysis care team will monitor your treatment with monthly lab tests to ensure you are getting the right amount of dialysis. One of the measures your dialysis care team may use is called urea reduction ratio (URR). Another measure is called Kt/V. Kt/V is a number used to quantify hemodialysis (waste removal) and peritoneal dialysis treatment adequacy.