What KT/V value is considered adequate?

KDOQI guidelines recommend a minimum single-pool KT/V of 1.2 for three-times-per-week hemodialysis. Values above 1.4 are considered optimal. This calculator uses the Daugirdas second-generation formula, which closely approximates the more complex two-pool model.

How is effective clearance (K) estimated?

After calculating spKt/V from measured BUN values, the tool rearranges Kt/V = K × t / V to obtain an effective K. This is not a dialyzer KoA or flow-based performance calculation.

What is URR and how is it used?

Urea Reduction Ratio (URR) = (pre-BUN − post-BUN) / pre-BUN × 100. A URR ≥ 65% is the minimum KDOQI threshold for adequacy. The calculator shows URR alongside KT/V so you can verify both markers.

Is this tool a substitute for clinical judgment?

No. This calculator uses simplified models and population-average kinetic assumptions. Always confirm adequacy with laboratory-measured BUN and consult a nephrologist for clinical decisions.

What units should I enter?

Session time in minutes, ultrafiltration volume in liters, BUN in mg/dL, and patient weight in kilograms.

Dialysis Clearance Calculator

Calculate spKt/V and URR from pre/post BUN, duration, ultrafiltration, and weight, with a derived effective clearance estimate.

Session Parameters

Session Duration minutes

Ultrafiltration Volume (UF) L

Pre-dialysis BUN mg/dL

Post-dialysis BUN mg/dL

Patient Weight (post-dialysis) kg

KT/V Adequacy

—

0 Min 1.2 2.0+

Dialyzer Clearance (K)

—

mL/min

URR

—

% (target ≥65%)

Volume of Distribution (V)

—

liters

Session Time (T)

—

hours

Daugirdas Second-Generation Formula

KT/V = −ln(R − 0.008 × t)

+ (4 − 3.5 × R) × UF / W

R = post-BUN / pre-BUN • t = session time (hours) • UF = ultrafiltration (L) • W = post-dialysis weight (kg)

Summary

This tool calculates Daugirdas second-generation single-pool Kt/V and URR from measured session data, then derives an effective K from Kt/V = K × t / V. It does not model dialyzer KoA, blood flow, or dialysate flow and is not a dialysis prescription.

How it works

Enter session duration, ultrafiltration volume, pre/post BUN, and body weight.
Provide ultrafiltration volume removed during the session.
Enter pre-dialysis and post-dialysis BUN values along with patient dry weight.
The tool computes urea reduction ratio (URR) from BUN values.
Effective clearance K is derived algebraically from the calculated Kt/V, estimated volume, and session time.
KT/V is computed via the Daugirdas second-generation logarithmic formula and compared to KDOQI targets.

Use cases

Biomedical engineers verifying dialyzer performance against manufacturer specs.
Nephrology nurses checking session adequacy before documenting monthly KT/V.
Students learning dialysis kinetics and mass-transfer equations.
Researchers comparing clearance across different dialyzer membrane configurations.
Home hemodialysis patients reviewing session logs with their care team.
Technicians troubleshooting unexpectedly low URR results.

Frequently Asked Questions

Last updated: 2026-09-30 · Reviewed by Nham Vu