A key finding in an infant with acute renal failure includes which laboratory abnormality?

• A. Hypercalcemia
• B. Elevated Creatinine
• C. Hypophosphatemia
• D. Hyperkalemia

Answer: (B)

Acute kidney injury reduces the glomerular filtration rate, so waste products that the kidneys would normally excrete accumulate in the blood. Creatinine is a waste product of muscle metabolism that is ordinarily filtered out by the kidneys, so a rise in serum creatinine directly reflects decreased filtration and is a hallmark of ARF in infants. While high potassium can occur because the kidneys can’t excrete it well, elevated creatinine more precisely identifies impaired renal function. Phosphate tends to accumulate (hyperphosphatemia) rather than drop, and calcium often decreases (hypocalcemia) rather than increases, so these are less consistent with the typical lab pattern.