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. 2025 Jun 1;15(11):1408.
doi: 10.3390/diagnostics15111408.

The Urea-Creatinine Ratio as Marker of Catabolism Is Affected by Continuous Renal Replacement Therapy

Andreas Markl-Le Levé  1 , Petra Hillinger  1 , Simon Woyke  1 , Marco Ronzani  1 , Stefan Schmid  1 , Janett Kreutziger  1 , Christopher Rugg  1
Affiliations

The Urea-Creatinine Ratio as Marker of Catabolism Is Affected by Continuous Renal Replacement Therapy

Andreas Markl-Le Levé et al. Diagnostics (Basel). .

Abstract

Background: An elevated urea-creatinine ratio (UCR) is used as a surrogate for catabolism and elevated protein metabolism in critically ill patients. This study investigated the effect of continuous renal replacement therapy (CRRT) on UCR. Methods: In this retrospective single-centre study, ICU patients from 2011 to 2022 with an ICU stay >2 days before CRRT and a CRRT duration of ≥4 days were included. Patients were grouped by UCR at CRRT initiation into high (UCR ≥ 75 mg/dL:mg/dL) and low groups and compared to matched controls not requiring CRRT. Propensity score matching considered age, sex, bodyweight, SAPS3, SOFA score, and UCR values on baseline and pre-baseline days. Results: In the high UCR group, UCR significantly decreased after CRRT initiation, reaching a significant difference from controls on day 2 (85.0 [IQR: 69.5-96.4] vs. 94.4 [IQR: 83.0-115.2]; p = 0.036) and falling below the threshold of 75 by day 3. In the low group, UCR increased post-CRRT initiation, but was less pronounced than in controls, with significant differences on day 1 (44.0 [IQR: 34.2-59.8] vs. 40.6 [IQR: 32.1-52.5]; p = 0.024). Conclusions: CRRT significantly affects UCR in critically ill patients, showing a marked decrease when compared to matched controls.

Keywords: acute kidney injury; catabolism; continuous renal replacement therapy; creatinine; urea; urea–creatinine ratio.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Study flow chart.
Figure 2
Figure 2
Trends in serum urea, creatinine, and urea–creatinine ratio during the observation period. Graphical presentation via generalized additive models with 95% confidence interval. Baseline day 0 is defined as the day of CRRT initiation in treatment groups and the corresponding day on ICU in matched controls. The low group is defined as an UCR < 75 and the high group as an UCR ≥ 75 on the day of CRRT initiation.
Figure 3
Figure 3
Trends in daily calorie and protein intakes per kg during the observation period. Graphical presentation via generalized additive models with 95% confidence interval. Baseline day 0 is defined as day of CRRT initiation in treatment groups and the corresponding day on ICU in matched controls. The low group is defined as an UCR < 75 and the high group as an UCR ≥ 75 on the day of CRRT initiation.
See this image and copyright information in PMC

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