Kt/V Urea (Dialysis Adequacy)

Calculates single-pool Kt/V using the second-generation Daugirdas equation for hemodialysis adequacy. Kt/V is the most widely used measure of dialysis dose worldwide.

mg/dL
Blood urea nitrogen before dialysis session.
mg/dL
Blood urea nitrogen after dialysis session (obtained with slow-flow/stop-pump technique).
hours
Length of dialysis treatment in hours.
Liters
Total fluid removed during dialysis in liters.
kg
Patient weight after dialysis in kg.

References

  1. The Nitty-Gritties of Kt/Vurea Calculations in Hemodialysis and Peritoneal Dialysis — Saudi Journal of Kidney Diseases and Transplantation/PMC (2021)
  2. Second generation logarithmic estimates of single-pool variable volume Kt/V: an analysis of error — Journal of the American Society of Nephrology (1993)

Note: Equilibrated Kt/V formula: eKt/V = spKt/V * T/(T+35) for AV fistula, or T/(T+22) for venous catheter (T in minutes). Standard Kt/V (stdKt/V) should be used for more frequent dialysis (>3x/week).

Warnings & Limitations

  • Minimum spKt/V for thrice-weekly HD is 1.2 per KDOQI (equilibrated ~1.0-1.05).
  • For twice-weekly dialysis, higher Kt/V per session required but overall weekly dose may still be inadequate.
  • Post-dialysis BUN must be collected using slow-flow/stop-pump technique to avoid dilution from access recirculation.
  • Equilibrated Kt/V (eKt/V) is typically 0.15-0.20 lower than spKt/V.
  • Kt/V underestimates clearance in patients with significant interdialytic weight gain.