Kt/V Calculator Daugirdas

Created by Łucja Zaborowska, MD, PhD candidate
Reviewed by Steven Wooding
Based on research by
Daugirdas J. T. Simplified equations for monitoring Kt/V, PCRn, eKt/V, and ePCRn Advances in renal replacement therapy (October 1995)See 2 more sources
Sternby, J.; Daugirdas, J. T. Theoretical basis for and improvement of Daugirdas' second generation formula for single-pool Kt/V The International journal of artificial organs (December 2015)Breitsameter, G., Figueiredo, A. E., Kochhann, D. S. Calculation of Kt/V in haemodialysis: a comparison between the formulas Jornal brasileiro de nefrologia : 'orgao oficial de Sociedades Brasileira e Latino-Americana de Nefrologia (March 2012)
Last updated: Jul 28, 2022

The Kt/V calculator allows you to assess your patient's dialysis or peritoneal dialysis efficacy and adequacy, using both the urea reduction ratio (URR) and the Daugirdas Kt/V formula.

A short read below will furnish you with the basic definitions used in dialysis evaluation and the Kt measurements. We'll also explain the complicated maths that stands behind our simple tool. ⏳

We try our best to make our Omni Calculators as precise and reliable as possible. However, this tool can never replace professional medical advice.

What does Kt/ V stand for in dialysis?

The Kt/V in dialysis is used for the measurement of the dialysis efficacy. It describes the rate of removal of the excessive fluids/substances (K) in a given treatment (t) of a given patient (V). This index is probably the most popular system to assess the dialysis dose.

The abbreviation itself stands for:

This value is dimensionless - is not based on any unit and cannot be calculated using its separate parts and their units.

Note that the Kt/V system may disadvantage women and smaller people and result in worse dialysis results in these patients. This difference is caused by the variances of their body water content.

Want to know more? How about checking our other kidney-related tools?

What is normal Kt/V?

  • The dialysis is considered efficient when Kt/V is greater or equal to 1.2. That's the minimum value that must be kept at all times. All the values that fall below that range are a sign of the flawed process of hemodialysis therapy.

  • The peritoneal dialysis target Kt/V is equal to 1.7 weekly (according to the International Society of Peritoneal Dialysis).

However, the patient's treatment should be adjusted to the Kt/V values of more than the recommended target!

It's a precaution used to ensure that the process is indeed of appropriate quality - it's crucial since this variable is directly related to the patient's future outcomes and is correlated to survival!

💡 Current guidelines recommend the weekly Kt/V in Acute Kindey Injury to be at least 3.9!

The Kt/V calculator displays your results along with its basic efficacy evaluation.

Our tool requires you to know three fundamental lab findings:

  • Kt/V urea - both pre and post dialysis levels of urea;
  • Volume of removed ultrafiltrate.

You may read some more about these values using:

Difference between Kt/ V and URR

Kt/V is considered to be of a better value and more accurate than the URR.

Why is Kt/V better?

Even though both of these values are closely related, the Kt/V system takes into account two additional variables:

  • Urea removed with the fluid during the dialysis;
  • Urea produced by the body during dialysis.

The measurement of fluid removed during dialysis using the Kt/V is also essential because the excessive amount of fluids accumulated in the patients' bodies might cause inevitable harm to their cardiovascular system.

The KDOQI guidelines recommend Kt/V to be the primary measure of adequacy.

How to calculate Kt/V in dialysis?

Our standard Kt/V calculator uses the following equation:

Kt/V = -ln((Post BUN/Pre BUN)- (0.008 * Dialysis duration)) + (4 - 3.5 * (Post BUN/Pre BUN)) * (UF/Weight),

where:

  • Post BUN means the level of post-dialysis blood urea nitrogen, given in milligrams per deciliter (mg/dL).

  • Pre BUN means the level of pre-dialysis blood urea nitrogen, given in milligrams per deciliter (mg/dL).

  • Dialysis duration should be given in hours.

  • UF stands for the volume of removed ultrafiltrate, given in liters (L).

  • Weight stands for the post-dialysis weight of a subject, given in kilograms (kg).

  • ln stands for the logarithm with the base of 2 → the natural logarithm.

Remember: all multiplications and divisions have a priority over adding and subtractions and should always be calculated first.

Łucja Zaborowska, MD, PhD candidate
Pre-dialysis BUN
mg/dl
Post-dialysis BUN
mg/dl
Duration of dialysis
hrs
Volume of removed ultrafiltrate
liters
Post-dialysis weight
lb
Kt/V
URR
%
💡 If you're looking for more information on the URR, try the URR calculator.
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