Urea is considered a surrogate to other small molecular weight uremic toxins and is easy to measure in the blood pre and post hemodialysis.
Although its use has limitations, it is an easily measured and useful marker of hemodialysis adequacy.
Kt/Vurea has helped standardize dialysis dosage based on urea clearance. It provides a tool to avoid grossly inadequate dialysis.
Its routine monitoring may help to identify problems of dialysis delivery such as access recirculation.
Urea reduction ratio (URR= 1-postdialysis BUN/predialysis BUN) is a less optimal measure of dialysis adequacy as it does not account for ultrafiltration during dialysis and assumes that V is constant during dialysis.