Kidney Week

Abstract: FR-PO0055

AKI Risk and Hydration Biomarkers Following Mild Dehydration in Young and Older Women

Session Information

• AKI: Epidemiology, Risk Factors, and Prevention
  November 07, 2025 | Location: Exhibit Hall, Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Acute Kidney Injury

• 101 AKI: Epidemiology, Risk Factors, and Prevention

Authors

• Domeier, Christin, Cardiovascular and Applied Physiology Laboratory, Florida State University, Tallahassee, Florida, United States

Christin Domeier, MS, MSc

• Robinson, Austin, Kinesiology, Indiana University, Bloomington, Indiana, United States

Austin Robinson, PhD

• Babcock, Matthew C., Geriatric Medicine, University of Colorado-Anschutz, Aurora, Colorado, United States

Matthew C. Babcock, PhD

• Smith, Kyle, Institute of Sports Sciences and Medicine, Florida State University, Tallahassee, Florida, United States

Kyle Smith, PhD, RD

• Watso, Joseph C., Cardiovascular and Applied Physiology Laboratory, Florida State University, Tallahassee, Florida, United States

Joseph C. Watso, PhD

Background

Dehydration increases acute kidney injury (AKI) biomarkers in young male and female adults. Percent change in body mass, spot urine specific gravity (USG), and urine osmolality after 24 hours of fluid deprivation all predicted AKI risk. However, it is unknown whether aging affects the utility of these hydration markers for predicting AKI risk or whether 24-hour USG and urine osmolality predict AKI risk after milder dehydration. Therefore, we tested the hypothesis that 24-hour urinary hydration biomarkers predict AKI risk among young (YF) and older females (OF).

Methods

We assessed change in body mass, 24-hour USG, 24-hour urine osmolality, and plasma osmolality after three days of euhydration and dehydration completed in a random crossover fashion among 17 YF (22[4] years, median[IQR]) and 9 OF (64[12] years). We assessed AKI risk using urinary insulin-like growth factor binding protein 7●tissue inhibitor of metalloproteases-2 (IGFBP7●TIMP-2) set at ≥0.3 (ng/ml)²/1000 and used receiver operating characteristic curves to determine diagnostic accuracy (AUC) and optimal cutpoints for hydration biomarkers. The discriminatory ability of hydration measures was interpreted as AUC≤0.5 none, 0.5<AUC<0.7 poor, 0.7≤AUC<0.8 acceptable, 0.8≤AUC<0.9 excellent, and AUC≥0.9 outstanding.

Results

Percent change in body mass was a significant predictor of AKI risk but showed poor discrimination in both age groups (AUC=0.52-0.55, p<0.001 for both). 24-hour USG showed excellent to outstanding discrimination among YF and OF groups (AUCs=0.82-0.93, p≥0.57 for both), but was not significant. 24-hour urine osmolality showed excellent discrimination in YF (AUC=0.84[0.67-1.00], p<0.001) with an optimal cutpoint of 543 mOsm/kg H₂O, and outstanding discrimination in OF (AUC=0.95[0.84-1.00], p<0.001) with an optimal cutpoint of 591 mOsm/kg H₂O. Plasma osmolality showed poor discrimination in YF (AUC=0.62[0.40-0.84], p<0.001) with an optimal cutpoint of 290 mOsm/kg H₂O, and acceptable discrimination in OF (AUC=0.76[0.52-1.00], p<0.001) with an optimal cutpoint of 298 mOsm/kg H₂O, respectively.

Conclusion

Following mild dehydration, 24-hour urine osmolality had the greatest ability to discriminate elevated urinary IGFBP7*TIMP-2 within YF and OF. This non-invasive biomarker could assist in identifying those at risk for AKI from mild dehydration.

Funding

• Other NIH Support – JCW has received speaking honoraria from Danone, a beverage company. JCW provides education/consulting at Watso Health LLC.

Digital Object Identifier (DOI)

• doi: 10.1681/ASN.2025cn0gp661