Kt/V & URR Calculator
mg/dL
mg/dL
minutes
litres removed during dialysis
kg (dry weight)
spKt/V
—
target ≥1.4
URR
—
% (target ≥70%)
Adequacy
—
KDOQI
Kt/V — Dialysis Adequacy Guide
Daugirdas 2nd gen spKt/V:
R = post-BUN / pre-BUN
t = session duration (hours)
UF rate = UF (L) / post-weight (kg)
Kt/V = −ln(R − 0.008×t) + (4 − 3.5×R) × UF/post-weight
URR (%) = (1 − R) × 100
R = post-BUN / pre-BUN
t = session duration (hours)
UF rate = UF (L) / post-weight (kg)
Kt/V = −ln(R − 0.008×t) + (4 − 3.5×R) × UF/post-weight
URR (%) = (1 − R) × 100
KDOQI Adequacy Targets
- spKt/V ≥1.4 per session: KDOQI 2015 minimum target for 3×/week HD. Target ≥1.2 is the minimum acceptable (older guidelines)
- URR ≥70%: Equivalent adequacy benchmark — simpler to calculate without weight data
- eKt/V (equilibrated): More accurate for short/high-efficiency dialysis — eKt/V target ≥1.2. eKt/V ≈ spKt/V − 0.6/t (hours)
How to Improve Inadequate Dialysis
- Increase session duration (most effective — from 3.5h to 4h increases Kt/V ~10%)
- Increase blood flow rate (Qb from 300 to 350 mL/min)
- Increase dialysate flow rate (Qd from 500 to 800 mL/min)
- Use high-flux dialyser with larger surface area (1.8–2.1 m²)
- Improve vascular access — recirculation from poorly functioning AV fistula reduces effective clearance
- Treat blood-side recirculation — access recirculation >10% significantly reduces Kt/V
Related Calculators
⚠ Medical Disclaimer: Kt/V calculation requires accurate BUN sampling — post-dialysis sample within 30 seconds of stopping dialysis (slow-flow sample). Kt/V is one measure of dialysis adequacy; clinical status, dry weight achievement, and phosphate/potassium control are equally important. Consult nephrology for persistently inadequate dialysis.