urea and other waste products from the blood. To find
out how well dialysis is working, you will have blood tests that look at the
level of urea in your blood. Usually these tests are done once a month, at the
beginning of your session and again at the end. Two measures
show how well dialysis is working: urea reduction ratio (URR) and
Urea reduction ratio
One way to measure how well
hemodialysis is removing urea from the body is to measure
blood urea nitrogen (BUN) level. The BUN is measured
before and after your treatment session. Then the two numbers are compared to
see how much the urea level in the blood has decreased. This difference is
called the urea reduction ratio (URR), and it is usually expressed as a
percentage. An adequate dose of hemodialysis should result in an average URR of
Another way to measure the effectiveness of
hemodialysis is to compare the amount of fluid that is cleared of urea during
each dialysis session with the amount of fluid that exists in the body. This is
called the Kt/V.
Kt represents the amount
of fluid that is cleared of urea during each dialysis session. It is measured
in millilitres per minute (mL/min).
represents the volume of water a person's body contains.
The Kt/V is the most accurate measure of hemodialysis,
because it also measures the amount of urea removed with excess fluid and takes
into consideration other factors, such as weight loss during dialysis. An
adequate dose of hemodialysis should result in an average Kt/V of 1.2.
What to think about
An adequate dose of dialysis can usually be
delivered in 3 to 5 hours.
ByHealthwise Staff Primary Medical ReviewerAnne C. Poinier, MD - Internal Medicine Donald Sproule, MDCM, CCFP - Family Medicine Adam Husney, MD - Family Medicine Specialist Medical ReviewerTushar J. Vachharajani, MD, FASN, FACP - Nephrology