URR Calculator — Urea Reduction Ratio for Dialysis
Enter the blood urea nitrogen (BUN) measured before and after a haemodialysis session to calculate the Urea Reduction Ratio (URR) — the percentage of urea removed — and check whether the session meets the KDOQI adequacy target of ≥ 65 %.
mg/dL
mg/dL
Excellent (≥ 70 %)
- 1
BUN removed
60 − 18 = 42 - 2
Urea Reduction Ratio (URR)
(42 ÷ 60) × 100 = 70A URR ≥ 65 % meets the KDOQI adequacy target for thrice-weekly haemodialysis.
Ako táto kalkulačka funguje?
URR = (BUN_pre − BUN_post) / BUN_pre × 100. A URR of ≥ 65 % meets the KDOQI adequacy target for thrice-weekly haemodialysis; ≥ 70 % is the typical clinical goal. Enter pre- and post-session BUN values (mg/dL) to check adequacy instantly.
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How this is calculated
Urea is a small, freely filtered molecule produced from protein metabolism and accumulates in renal failure. The URR measures what fraction of the pre-session urea burden was removed by dialysis: URR = (BUN_pre − BUN_post) / BUN_pre × 100. A single blood draw before and one within 5 minutes of session end (before rebound equilibration) gives the two BUN values.
The KDOQI (Kidney Disease Outcomes Quality Initiative) 2015 guidelines recommend a minimum URR of 65 % for thrice-weekly haemodialysis; most centres aim for 70 % or higher. Below 65 % is considered inadequate and is associated with higher morbidity and mortality.
URR is simpler to compute than Kt/V (the formal dialysis dose), but it ignores ultrafiltration (fluid removal), which can slightly overestimate clearance. For that reason, Kt/V is preferred in formal adequacy assessments, but URR correlates closely with Kt/V and is widely used as a quick bedside check. This calculator does not replace a full clinical assessment.
Často kladené otázky
KDOQI guidelines (2015) set a minimum URR of 65 % for thrice-weekly conventional haemodialysis. Many nephrologists aim for ≥ 70 % to provide a safety margin above the threshold.
Kt/V is the gold-standard dialysis dose metric; it accounts for urea distribution volume and ultrafiltration. URR is a simpler ratio that correlates well with Kt/V and is easy to compute at the bedside. A URR of 65 % roughly corresponds to a single-pool Kt/V of 1.2.
No. URR represents the fraction of initial BUN that was cleared, so it is bounded between 0 % (no clearance) and a practical upper limit of ~80–85 %. Values above that suggest a measurement error, a prolonged session, or an incorrect blood draw timing.
TG we-Calculate Editorial Team. (2026). URR Calculator — Urea Reduction Ratio for Dialysis [Online calculator]. TG we-Calculate. https://we-calculate.com/sk/calculator/urr-calculator
TG we-Calculate Editorial Team. "URR Calculator — Urea Reduction Ratio for Dialysis." TG we-Calculate. 2026. https://we-calculate.com/sk/calculator/urr-calculator.
TG we-Calculate Editorial Team, "URR Calculator — Urea Reduction Ratio for Dialysis," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/sk/calculator/urr-calculator
@misc{wecalculate_urr_calculator, title = {URR Calculator — Urea Reduction Ratio for Dialysis}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/sk/calculator/urr-calculator}}, year = {2026}, note = {TG we-Calculate} }
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