Individualizing Kt by sex and body surface area - implications for survival in hemodialysis patients

Sep 29, 2026

Dialysis dose adequacy is essential for effective hemodialysis (HD) and patient survival, and Kt serves as a key dose indicator with targets based on sex (Kt-Sx) and body surface area (Kt-BSA). This retrospective multicenter study (2022–23) analyzed 1,829 prevalent patients across 15 HD centers and 317,842 HD sessions. Meeting at least Kt-Sx related to lower 24-month mortality, and meeting both targets showed an even stronger reduction. Failure to meet both targets clustered with male sex, older age, shorter HD duration, higher comorbidity, low BMI, catheter use, shorter sessions, conventional HD, low flow rates, and small membranes.

LanguageEnglish

CategoryHealthcare

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Pages9

Reading Time23 min

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Introduction

Clinical Kidney Journal, 2025, vol. 19, no. 1, sfaf369 [https:/doi.org/10.1093/ckj/sfaf369](https:/doi.org/10.1093/ckj/sfaf369) Advance Access Publication Date: 3 December 2025 Original Article ORIGINAL ARTICLE Individualizing Kt by sex and body surface area: implications for survival in hemodialysis patients María Luz Sánchez-Tocino 1 ,2 ,3 , Antonio López-González4 , María Lorena Iglesias-González1 , Silvia Villoria-González1 , Julia Audije-Gil 1 , Jose Luis Fernández-Martín 5 , David Hernán 1 , Paula Manso 1 , Fabiola Dapena 1 and María Dolores Arenas-Jiménez 1 ; Grupo de Trabajo de la Fundación Renal Española 1 Unidad de Investigación, Fundación Renal Española, Madrid, Spain, 2 Departamento de Enfermería y Fisioterapia, Universidad de Salamanca, Salamanca, Spain, 3 Instituto de Investigación Biomédica de Salamanca (IBSAL), Salamanca, Spain, 4 Servicio de Hemodiálisis, Complejo Hospitalario Universitario A Coruña, Spain and 5 Servicio de Medicina Interna, Hospital Universitario Central de Asturias, Oviedo, Asturias, Spain Correspondence to: Julia Audije-Gil; E-mail: [julia.audije@fundacionrenal.es](julia.audije@fundacionrenal.es) ABSTRACT Background. The administration of an adequate dialysis dose is a critical aspect for ensuring the effectiveness of hemodialysis (HD) treatment and improving survival. Kt is a key indicator to evaluate the dose, with two targets: based on sex (Kt-Sx) and body surface area (Kt-BSA) . Methods. This retrospective study (2022–23) was conducted across 15 HD centers analyzed 1829 prevalent patients and 317 842 HD sessions. Results. It was found that 65.9% met both Kt targets, 21.2% met only Kt-Sx and 12.9% met neither. Failure to meet both of the targets was associated with being male, older age, shorter time on HD, higher comorbidity, low body mass index, use of a catheter, shorter sessions, conventional HD, low flow rates and small membranes. Meeting at least the Kt-Sx target was associated with a 41.6% reduction in 24-month mortality risk, and an even more favorable association was observed when both targets were met, reducing the risk by 61.7% . Conclusions. These findings highlight the importance of personalizing dialysis considering both sex and BSA, particularly in overweight or obese patients, to improve survival. Received: 13.5.2025; accepted: 3.11.2025 © The Author(s) 2025. Published by Oxford University Press on behalf of the ERA. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License ([https://creativecommons.org/licenses/by-nc/4.0/](https://creativecommons.org/licenses/by-nc/4.0/)), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact [reprints@oup.com](reprints@oup.com) for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site-for further information please [contact](contact journals.permissions@oup.com)[ journals.permissions@oup.com](contact journals.permissions@oup.com) 1 GRAPHICAL ABSTRACT |
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Individualizing Kt by sex and body surface area:
implications for survival in hemodialysis patients | | | | | --- | --- | --- | --- | --- | |
Adequate dialysis dose is essential for patient survival. Two Kt targets are used in clinical practice: Kt–Sx, based on sex (≥ 40 L women, ≥ 45 L men) and Kt–BSA, adjusted by body surface area. | | | | | | Methods | | | | Results | | Multicenter retrospective study | | | Kt-SX and
Kt-BSA
61.7%
|

Kt-Sx only

Male sex
Older age
Higher
comorbidity Shorter time on HD
Lower BMI

| | | | Prevalent HD patients n = 1829
HD sessions n = 317,842
Achieving Kt–Sx and Kt–BSA targets
24-month mortality | | | Conclusion: Personalizing dialy

FAQs

What are the two Kt targets evaluated in the study?

The study evaluates Kt targets based on sex (Kt-Sx) and body surface area (Kt-BSA). These targets are used to assess dialysis dose adequacy in clinical practice.

What proportion of patients met both Kt targets?

Among prevalent HD patients, 65.9% met both Kt targets, 21.2% met only Kt-Sx, and 12.9% met neither.

Which factors were associated with failing to meet both Kt targets?

Failure to meet both targets was associated with male sex, older age, shorter time on HD, higher comorbidity, low BMI, catheter use, shorter sessions, conventional HD, low flow rates, and small membranes.

Sep 29, 2026

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