Temporary Causes of Lower eGFR in Young Patients
In young patients, temporary decreases in eGFR are most commonly caused by physiologic stressors including acute illness, dehydration, vigorous physical activity, and medications—particularly ACE inhibitors, ARBs, and SGLT2 inhibitors which can cause transient reductions up to 25% due to altered glomerular hemodynamics rather than true kidney injury. 1
Physiologic and Reversible Causes
Hemodynamic Alterations from Medications
- ACE inhibitors, ARBs, and SGLT2 inhibitors cause transient eGFR reductions of up to 25% through changes in glomerular hemodynamics, not intrinsic renal disease 1
- This decline typically stabilizes over time and should not prompt discontinuation if the clinical condition is stable or improving 2
- These medications maintain their clinical efficacy despite the initial eGFR drop 2
Physiologic Stressors
eGFR is influenced by multiple temporary conditions 1:
- Acute illness (intercurrent infections, volume contraction) 1
- Dehydration status 1
- Vigorous physical activity 1
- Hormonal influences including puberty, pregnancy, menopause, and andropause 1
- Vasodilation (e.g., from sunburn) 1
Pre-renal Azotemia
- Volume depletion from any cause can temporarily reduce eGFR and is often effectively managed with treatment of the precipitating cause 1
- Temporary discontinuation of RAS blockade and NSAIDs may be needed during acute illness 1
Important Clinical Considerations
Timing of Measurement
- In younger children, measured GFR evaluations should be delayed at least 2 weeks after any intercurrent illnesses, particularly when GFR is being used for critical decisions like transplant listing 1
- Patients may not be in steady state during acute or subacute illness, making eGFR interpretation unreliable 1
Dilute Urine Samples
- Very dilute urine samples can lead to false-negative results if not normalized to urine creatinine 1
When to Suspect True Kidney Disease vs. Temporary Reduction
Refer to nephrology if 1:
- Abrupt sustained decrease in eGFR >20% after excluding reversible causes 1
- Features suggestive of diagnoses other than prerenal azotemia or acute tubular necrosis 1
- eGFR expected to be <30 mL/min/1.73 m² after intervention 1
Common pitfall: In young adults (18-39 years), even eGFR values at the 10th percentile for age (which may still appear "normal" by standard cutoffs) are associated with increased adverse outcomes and may represent true kidney disease rather than temporary reduction 3