S1E36 Renal Reality Check: Decoding Kidney Function Tests

Not all kidneys fail loudly. Sometimes the earliest signs are hidden in the labs — if you know where to look. In this episode, we go deep into renal function testing, breaking down how to spot trouble early, stage chronic kidney disease accurately, and make sense of the numbers that don’t always tell the full story. Whether you're monitoring a dialysis patient or picking up subtle trends in a post-op patient, this episode equips you with the clinical insight to interpret renal labs with confidence.

Key Topics Covered:

• GFR (Glomerular Filtration Rate):

  • Why it’s the gold standard

  • Estimated vs measured GFR

  • Creatinine vs cystatin C

  • Limitations and influencing factors (age, muscle mass, etc.)

• KDIGO CKD Staging:

  • GFR and albuminuria categories

  • Clinical relevance in guiding treatment

• Creatinine and BUN:

  • What they measure and what they miss

  • BUN/Cr ratio and what it tells you about prerenal vs intrinsic causes

• Albuminuria/Proteinuria:

  • Spot urine vs 24-hour collection

  • Why microalbuminuria matters

• Urinalysis (UA):

  • Key elements: Specific gravity, pH, protein, casts, sediment

  • Clues for glomerular vs tubular vs post-renal pathology

• Tubular Function Tests:

  • Fractional excretion of sodium (FeNa), urine osmolality, and concentrating ability

• Clinical Pearls:

  • How hydration, medications, and diet can skew results

  • When to question the numbers and what to do next

  • Nursing implications for trending renal labs, fluid management, and alerting providers