Dialysis Adequacy Family
The last group of tests measured kidney function. If the kidneys fail, there are also tests to measure the dose of dialysis. The next two tests we'll talk about are only for people who are on dialysis.
Test Your Knowledge
Here's a quick true/false statement for you: Everyone on dialysis gets the same amount of treatment.
True
False
Nope! A one-size-fits-all approach would mean that some people would not get enough dialysis to stay healthy. Try again!
You're right! Dialysis is prescribed by a doctor, just like medicine. The prescription depends on body weight, amount of wastes to be removed, and other factors. If you want to learn more about how to get enough dialysis to feel your best, read Module 10—Getting Adequate Dialysis.
Remember the blood urea nitrogen (BUN) test? It measures the amount of urea in your blood. In people on HD, the BUN is used to tell if the minimum dose of dialysis is being given. This is called hemodialysis adequacy.
Once a month, BUN level is measured before an HD treatment. It's measured again after the treatment. Then the two levels are compared. This is called the urea reduction ratio (URR). This number tells you if you got the minimum dose of dialysis—for this one treatment only.
If you are on standard in-center HD and your clinic uses URR, your level should be at least 65% or higher. Higher is better, because more dialysis is better!
What's the Formula for URR?
In case you want to figure out your own URR, the formula is:
(Predialysis BUN - Postdialysis BUN)/Predialysis BUN x 100
For example:
(96 - 31)/96 x 100 = 67.7%
URR is easy to calculate. But it doesn't take body weight into account—or the time needed to remove fluid during HD. Another measure of HD adequacy called Kt/V (kay-tee-over-vee) does both:
- K = dialyzer clearance in mL/min
- t = length of the dialysis treatment in minutes (time)
- V = volume of water in the body that contains urea
To figure out your Kt/V, a BUN level and weight are checked before and after a treatment. The results are put into a formula.
On standard in-center HD, your level should be at least 1.2 or higher. Your minimum prescribed dose should be at least 1.3. Again, higher is better, because more dialysis is better!
If you use peritoneal dialysis (PD), a form of Kt/V is used to measure your PD dose. Instead of looking at just one treatment, a weekly Kt/V is calculated, because PD is done continuously. Your PD should give you a weekly Kt/V of at least 1.7.
