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Dialysis dose Kt/V

Optimizing treatment quality

Chronic hemodialysis must be viewed as a medication whose dose must be adjusted to the individual requirements of the patient. Large international studies [1; 2; 3; 4; 5; 6] have shown that the administered dialysis dose affects the long-term prognosis of the patient.

Indicator for dialysis dose

The elimination of urinary excreted substances from the entire organism is crucial for the assessment of the adequacy of dialysis treatment. Urea is used as an indicator substance because of it‘s characteristics:

  • distributed in all water in a patient's body
  • balances out quickly any differences in concentration in different compartments
  • can be almost completely eliminated in the dialyser due to its molecular size.

The elimination of urea from the organism during treatment therefore reflects dialysis adequacy.

There are different methods to quantify urea clearance:

URR (Urea Reduction Ratio)

is the simplest way to determine the dialysis dose.


spKt/V (single-pool Kt/V)

takes both urea generation during dialysis and the effect of ultrafiltration into account.


eKt/V (equilibrated Kt/V)

takes also urea rebound into consideration.



List of abbreviations:

Ct = Urea concentration at the respective treatment instant;

C0 = Urea concentration pre-treatment; In = natural logarithm;

R = Ct/CO; T = Dialysis time in hours;

UF = Ultrafiltration volume in kg;

W = Weight after HD in kg



List of literature:

[1] Greene T, Daugirdas J, Depner T, Allon M, Beck G, Chumlea C, Delmez J, Gotch F, Kusek JW, Levin N, Owen W, Schulman G, Star R, Toto R, Eknoyan G; Hemodialysis Study Group. Association of achieved dialysis dose with mortality in the hemodialysis study: an example of "dose-targeting bias". J Am Soc Nephrol. 2005 Nov;16(11):3371-80. Epub 2005 Sep 28.

[2] Depner T, Daugirdas J, Greene T, Allon M, Beck G, Chumlea C, Delmez J, Gotch F, Kusek J, Levin N, Macon E, Milford E, Owen W, Star R, Toto R, Eknoyan G; Hemodialysis Study Group. Dialysis dose and the effect of gender and body size on outcome in the HEMO Study. Kidney Int. 2004 Apr;65(4):1386-94.

[3] Port FK, Ashby VB, Dhingra RK, Roys EC, Wolfe RA. Dialysis dose and body mass  index are strongly associated with survival in hemodialysis patients. J Am Soc Nephrol. 2002 Apr;13(4):1061-6.

[4] Wolfe RA, Ashby VB, Daugirdas JT, Agodoa LY, Jones CA, Port FK. Body size, dose of hemodialysis, and mortality. Am J Kidney Dis. 2000 Jan;35(1):80-8.

[5] Held PJ, Port FK, Wolfe RA, Stannard DC, Carroll CE, Daugirdas JT, Bloembergen WE, Greer JW, Hakim RM. The dose of hemodialysis and patient mortality. Kidney Int. 1996 Aug;50(2):550-6.

[6] Yang C-S, Chen S-W, Chiang C-H, Wang M, Peng S-J, Kan Y-T. Effects of increasing dialysis dose on serum albumin and mortality in hemodialysis patients. Am J Kidney Dis. 1996 Mar;27(3):380-6.