Urea Reduction Ratio (Renal PatientView)

Urea Reduction Ratio [URR]

URR is used to measure how effective a haemodialysis treatment is. It is based on tests of blood urea, by measuring the levels before and after treatment, to show how much has been removed. Kt/V is another test of haemodialysis effectiveness: some units use URR, some use Kt/V, some use both.

In the UK the agreed target URR is a minimum of 65%. This applies to someone receiving dialysis three times each week. If your own kidneys are still working a bit, a slightly lower URR may be acceptable.

Lower values are associated with shorter survival on dialysis. Of course other things affect how long you will live too. A single low value is nothing to get too worried about if all other values are over 65%.

Causes of low URR include

Dialysis too short; stopped early or interrupted on the day URR was measured? Problems that day? Or prescription too short?
Problems with blood flow or recirculation at fistula or line
Artificial kidney too small

How to improve URR and/or dialysis dose - possibilities include

Longer dialysis
Better access (fistula or line)
A larger artificial kidney may help if blood flow is good
More frequent dialysis (e.g. 4 times per week instead of 3)

More information about URR and Kt/V from the NIDDK (USA) - detailed and thorough

More information about URR and Kt/V from ikidney.com - a bit easier