Acute Kidney Injury or Physiological Response? Interpretation of Serum Creatinine Elevation After Strenuous Exercise Using Functional and Structural Kidney Biomarkers: A Narrative Review

Abstract

Background. Serum creatinine commonly rises after strenuous exercise and does not always reflect impaired kidney function. This raises the question of whether post-exercise elevation represents acute kidney injury (AKI) or a transient physiological response.

Aim. To examine post-exercise creatinine elevation and whether additional kidney biomarkers may clarify its significance.

Materials and methods. A narrative review of studies on exercise-related changes in serum creatinine, cystatin C, and kidney injury and stress biomarkers was conducted, considering exercise and hydration.

Results. Post-exercise creatinine elevation may be influenced by muscle mass, muscle metabolism, muscle damage, and hydration and does not always indicate structural kidney injury. Cystatin C is less influenced by muscle mass but reflects filtration rather than structural injury. KIM-1, NGAL, and other biomarkers may add information, although they can also change transiently after exercise and depend on exercise conditions, hydration, and sampling time.

Conclusions. A rise in serum creatinine after strenuous exercise is insufficient evidence of structural kidney injury. Interpretation should consider the time course of changes, hydration, exercise type and intensity, urinalysis, and additional kidney markers when available. No single biomarker can currently make this distinction reliably.