zero. In long slow overnight dialysis, if simplified equations are used, the URR also underestimates the amount of dialysis due to urea generation during the long dialytic session. For this reason, the kinetically modeled Kt/V is always recommended as the best measure of dialysis adequacy. The Kt/V, even that derived by formal modeling, is primarily based on the URR, and so it contains little additional information in terms of the amount of dialysis that was delivered. Since the URR and Kt/V are so closely related, their predictive power in terms of patient outcome is similar. However, use of Kt/V and urea modeling in general allows for comparing expected with predicted dose of dialysis, which can be used to analyze dialysis treatments and dialyzer clearances and in troubleshooting and quality control activities. Also, Kt/V permits calculation of the urea generation rate, which can give clues about a patient's protein intake. Minimally adequate dose in terms of URR In the standard 3x/week hemodialysis schedule a URR of 65% is considered the minimum acceptable dose, corresponding to a minimum Kt/V of 1.2 When dialysis is given more frequently than three times a week, the minimum acceptable URR is lower; because more dialysis treatments are given over the week, the dose of dialysis for each treatment does not need to be as large. Also minimally acceptable values for URR (and Kt/V) can be reduced in patients who have substantial amounts of residual renal function. References External links Hemodialysis Dose and Adequacy - a description of URR and Kt/V from the Kidney and Urologic Diseases Clearinghouse. Calculators Kt/V calculator - (estimating equation) Medindia Kt/V calculator - (Full kinetic model) hdcn.com Renal dialysis