Dialysis Pro · Key Performance Indicators
KPI / Adequacy
Dialysis dose measurement, adequacy targets, ultrafiltration limits, and routine monitoring for conventional thrice-weekly hemodialysis. When a metric is off-target, see the Dose Adjustment tile.
⚠️ Clinical reference only. Targets reflect KDOQI 2015 / UpToDate guidance for conventional in-centre HD and should be individualised. Not a substitute for clinical judgment or local protocol. Developed by Dr. Abbas Deeb. Not affiliated with KDOQI, KDIGO, UpToDate, or any guideline body.
Kt/V — Preferred Dose Metric
Single-pool preferred · Fractional urea removal per session
Kt/V = dialyzer urea clearance (K) × treatment time (t, min) ÷ urea distribution volume (V ≈ total body water), corrected for ultrafiltration. Volume correction matters: in a larger patient, the same urea loss represents a smaller fraction of total body urea.
Kt/V = −ln(R − 0.03) + (4 − 3.5R) × (UF ÷ W)
R = post-dialysis BUN ÷ pre-dialysis BUN · UF = ultrafiltration volume (litres) · W = post-dialysis weight (kg)
Daugirdas second-generation formula. Little systematic error for Kt/V 0.7–2.0 — the range covering recommended goals. Most accurate for conventional thrice-weekly schedules.
Daugirdas second-generation formula. Little systematic error for Kt/V 0.7–2.0 — the range covering recommended goals. Most accurate for conventional thrice-weekly schedules.
Single-pool vs double-pool (equilibrated)
| Metric | Model / sampling | Notes |
|---|---|---|
| Single-pool (spKt/V) | One urea compartment; post-BUN drawn at session end (with slow-flow technique) | Preferred by most clinicians; practical; no outcome disadvantage vs dp |
| Double-pool / equilibrated (eKt/V) | Two compartments; requires BUN drawn 30 min post-dialysis | More accurate in theory but adds patient waiting time; eKt/V ≈ spKt/V − 0.21 |
| Standard Kt/V | Cumulative weekly dose incl. residual function | Used for frequent/home HD; allows cross-modality comparison |
The single-pool/double-pool gap (~0.21) arises because post-HD BUN keeps rising for ~30 min from extravascular urea equilibration and dissipation of access/cardiopulmonary recirculation. The gap narrows with longer treatment times.
Source: UpToDate "Prescribing and assessing adequate hemodialysis" (Apr 2026); Daugirdas JASN 1993.
Urea Reduction Ratio (URR)
Simpler alternative · Less accurate than Kt/V
URR = 1 − (post-dialysis BUN ÷ pre-dialysis BUN)
e.g. URR = 0.60 if post-BUN is 40% of pre-BUN. PRU = URR × 100 (expressed as a percentage).
URR ignores urea removed by ultrafiltration, so it is less precise than Kt/V for individuals. At a single URR value, Kt/V varies widely — one study found median URR 0.62 ≈ median Kt/V 1.12, but Kt/V both <1.0 (under-dialysis) and >1.30 occurred at that same URR. A large UF requirement alone can raise Kt/V by ~0.2.
Estimating equations are most accurate when Kt/V is 0.7–1.3 (URR ≈ 40–65%), session time is 3–5 h, and total body water is 50–60% of weight. URR cannot compare patients dialysed more than 3×/week. Its effect on survival is mitigated by serum albumin (a marker of inflammation/protein-energy wasting).
Source: UpToDate "Prescribing and assessing adequate hemodialysis" (Apr 2026).
Post-Dialysis BUN Sampling Technique
Errors here directly distort Kt/V and URR
Post-HD BUN is artificially low at the moment dialysis ends because of access and cardiopulmonary recirculation, then rises over ~30 min. Correct sampling technique is essential — a falsely high post-BUN lowers the calculated Kt/V.
Single-pool Kt/V — slow-flow method (KDOQI 2006 / European / Canadian)
1
Slow the blood pump to 100 mL/min for 15 seconds — this clears recirculated blood from the access.
2
Stop the blood pump.
3
Draw the post-dialysis BUN sample immediately.
For double-pool (equilibrated) Kt/V: draw the BUN from a sample obtained 30 minutes after dialysis ends, to allow full urea reequilibration. Reserved for short high-efficiency HD where equilibration matters.
Source: UpToDate "Prescribing and assessing adequate hemodialysis" (Apr 2026); Depner urea modelling, Kidney Int 1994.
Dose Targets — Conventional 3×/week
Target high enough to ensure the minimum is delivered
Target spKt/V
1.4
per session — prescribed
Minimum spKt/V
1.2
per session — CMS floor
Adequate URR
~65%
approximate equivalent
Standard Kt/V
~2.3
per week — frequent HD
Why target 1.4 to deliver 1.2? Delivered dose is routinely less than prescribed. Aiming for spKt/V ~1.4 ensures the CMS-mandated minimum of 1.2 is actually achieved. Equilibrated Kt/V ≥1.05 ≈ single-pool ≥1.2.
More is not better. The HEMO study showed targeting spKt/V >1.4 does not improve survival or reduce hospitalisation. Very high Kt/V (>1.6) is associated with increased mortality — likely reflecting low V (reduced muscle mass / malnutrition) rather than benefit from extra clearance.
High-flux membranes are recommended (KDOQI) where adequate water treatment exists — meta-analysis showed reduced cardiovascular mortality vs low-flux, despite no overall all-cause mortality difference in HEMO.
Source: UpToDate "Prescribing and assessing adequate hemodialysis" (Apr 2026); HEMO study NEJM 2002; CMS Conditions for Coverage.
Minimum Time & Frequency
Time matters independently of Kt/V
Sessions / week
≥3
minimum
Time / session
≥4 h
author preference (Grade 2C)
KDOQI 2015 floor
3 h
if residual fn <2 mL/min
A minimum of 3 sessions/week and ≥4 h/session is suggested irrespective of Kt/V. KDOQI 2015 sets a 3 h/session floor for patients with little/no residual function (<2 mL/min), but longer sessions are better tolerated — shorter sessions concentrate fluid removal and provoke cramps, fatigue, and intradialytic hypotension.
More time on HD (longer sessions or higher frequency) is associated with better outcomes: the FHN frequent-HD trial showed reduced mortality and better BP/phosphate control; observational data favour sessions >4 h. Exceptions: short daily home HD, and incremental HD in selected patients with significant residual function.
In practice, patients resist longer sessions (the TiME trial failed to achieve a meaningful time difference between arms). Adherence is the real-world limiting factor.
Source: UpToDate "Prescribing and assessing adequate hemodialysis" (Apr 2026); FHN trial; KDOQI 2015.
Ultrafiltration Rate Limits
Rapid fluid removal causes harm — including below the CMS threshold
CMS quality threshold
13
mL/h/kg
>10 mL/h/kg
+22%
mortality risk
>13 mL/h/kg
+31%
mortality risk
Harm from rapid ultrafiltration begins even below 10 mL/h/kg. DOPPS data: UFR >10 mL/h/kg → higher intradialytic hypotension and all-cause mortality; each 1 mL/h/kg increase → ~22% higher mortality risk. Mechanisms include hemodynamic instability and myocardial stunning; higher UFR also linked to atrial fibrillation, heart failure, and cognitive deficits.
Weight-scaled UFR thresholds may worsen outcomes in higher-body-weight patients — interpret the 13 mL/h/kg figure as a quality measure, not a hard physiological cutoff. The fix for high UFR is to lengthen time or add frequency, not to push fluid off faster.
Source: UpToDate "Prescribing and assessing adequate hemodialysis" (Apr 2026); DOPPS; CMS quality measure.
Volume Control & Target Weight
Normalising extracellular volume is a primary goal of dialysis
Interdialytic gain
1–1.5 kg
target limit
Sodium intake
<2000 mg/d
to reduce thirst
Target ("dry") weight = the weight at which the patient has neither fluid overload (hypertension, pulmonary/pedal oedema) nor volume depletion (orthostatic symptoms, tachycardia). Poorly controlled BP may be the only sign target weight is set too high.
Mitigate interdialytic gain: restrict sodium <2000 mg/day, continue diuretics if residual urine output. For persistently large gains, increase session time or frequency to allow a lower UFR — rather than removing more fluid faster.
Source: UpToDate "Prescribing and assessing adequate hemodialysis" (Apr 2026); KDOQI 2015.
Monthly Monitoring
Standard assessment in stable HD patients
Most clinicians assess the regimen once per month in stable patients (though evidence for monthly vs 6-weekly intervals is limited — one Canadian study found no outcome difference).
| Parameter | Why |
|---|---|
| Kt/V | Confirm delivered dose meets target |
| Ultrafiltration requirement per session | Track UFR and fluid load |
| Intradialytic haemodynamic stability | IDH frequency, tolerance |
| Blood pressure control | Volume status surrogate |
| Clinical volume status & target weight | Reassess dry weight |
| Intra-/interdialytic symptoms | Cramps, fatigue, recovery time |
| Anaemia, mineral-bone, electrolytes | Lab review (see Dose Adjustment tile) |
| 24-h urine (incremental HD only) | Monitor residual kidney function |
Source: UpToDate "Prescribing and assessing adequate hemodialysis" (Apr 2026).
Limitations of Kt/V
Do not use Kt/V as the sole indicator of adequacy
Kt/V measures only urea clearance. It does not capture protein-bound toxins (indoxyl sulfate, p-cresyl sulfate), middle molecules (β2-microglobulin), or guanidines — all removed less efficiently than urea and linked to adverse outcomes.
The volume (V) problem. A high Kt/V can reflect either high clearance (Kt) or low V. Small or malnourished patients may be under-dialysed if time is cut because of a "good" Kt/V. Some argue Kt alone may be a better measure. Very high Kt/V (>1.6) correlates with worse nutrition and higher mortality.
Kt/V also doesn't account for missed/shortened treatments, frequency benefits beyond delivered Kt/V, volume control, haemodynamic stability, or symptoms — all of which independently affect outcomes. Single-pool formulas lose accuracy outside conventional thrice-weekly schedules.
Source: UpToDate "Prescribing and assessing adequate hemodialysis" (Apr 2026).
Dialysis Pro — KPI / Adequacy · Sourced from UpToDate "Prescribing and assessing adequate hemodialysis" (literature current through May 2026), KDOQI 2015, HEMO study, DOPPS.
Developed by Dr. Abbas Deeb. For clinical reference only. Targets are for conventional in-centre HD and must be individualised. Not affiliated with KDOQI, KDIGO, UpToDate, or any guideline body.
Developed by Dr. Abbas Deeb. For clinical reference only. Targets are for conventional in-centre HD and must be individualised. Not affiliated with KDOQI, KDIGO, UpToDate, or any guideline body.