Tissue hypoxia occurs during acute kidney injury. MRI-based measurement of renal T2* and T2 could become a non-invasive surrogate marker of tissue oxygenation. However, the relationship between renal oxygenation and T2*,T2 is confounded by changes in the blood and tubular volume fractions, which are often accompanied by changes in kidney size (KS). We performed serial MRI scans along with clinically-realistic interventions acutely affecting renal oxygenation, applied directly while rats were in the scanner. We show that changes in KS correlate with changes in renal T2*,T2, underscoring that monitoring KS is necessary for correct interpretation of renal oxygenation derived from MRI.