In some dialysis machines, the urea clearance during dialysis is estimated by testing the ability of the dialyzer to remove a small salt load that is added to the dialysate during dialysis.
2.
Urea generation during such a session results in a slightly lower URR ( by about 0.10 ) than expected as a result of urea clearance, due to the fact that urea is being added to the body by generation during the dialysis session.