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Neonatal renal immaturity — MRCPCH TAS MCQ

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ModeratePhysiologyNeonatal renal immaturityMRCPCH TAS

A 30-week preterm infant develops fluctuating sodium levels during the first week of life. Creatinine is falling slowly and urine concentrating ability is poor. What is the most likely explanation?

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Correct answer: C — Immature glomerular and tubular renal function

Preterm infants have low glomerular filtration and immature tubular handling of sodium and water. Adult-level concentrating ability is not present, which increases vulnerability to fluid and electrolyte disturbance. The pearl is that neonatal renal physiology changes rapidly with gestation and postnatal age.

Reference: Rennie and Robertson Textbook of Neonatology; Ganong's Review of Medical Physiology; RCPCH Theory examination syllabi