About

In hemodialysis, Kt/V is the primary parameter used to quantify treatment adequacy. It represents the fractional clearance of urea from the patient's body volume. Achieving a target Kt/V (usually ≥ 1.2) is strongly correlated with reduced morbidity and mortality in End-Stage Renal Disease (ESRD) patients.

This tool utilizes the Daugirdas Second Generation formula, which is widely preferred over the single-pool model because it accounts for urea generation during the dialysis session and the volume contraction due to ultrafiltration. This results in a more accurate reflection of the dialysis dose actually delivered to the patient.

Formulas

The Daugirdas II formula corrects for volumetric changes and urea generation:

Kt/V = -ln(R − 0.008 × t) + (4 − 3.5 × R) × UFW

Where:

R = Ratio of Post-BUN to Pre-BUN (BUN_post / BUN_pre)
t = Session duration in hours
UF = Ultrafiltration volume (weight loss) in kg/L
W = Post-dialysis weight in kg

Reference Data

Parameter	Target (Minimum)	Target (Optimal)	Risk Level
Single Session Kt/V	1.2	1.4+	< 1.2 (Inadequate)
URR (Urea Reduction)	65%	70%	< 65%
Weekly Kt/V (3x/wk)	3.6	4.2+	Low clearance

Frequently Asked Questions

According to KDOQI guidelines, the minimum delivered Kt/V for hemodialysis (3 times/week) should be at least 1.2. A target of 1.4 is often set to ensure the minimum is consistently met.

URR (Urea Reduction Ratio) is simpler but ignores two critical factors: the urea produced by the body *during* the dialysis session, and the concentration of urea caused by removing water (ultrafiltration). Daugirdas II accounts for both, making it significantly more accurate.

Clearance (K) and Time (t) are directly proportional. Increasing blood flow rate, dialyzer surface area, or session duration will improve Kt/V. Conversely, a higher body volume (V) lowers the ratio.