skip to main content

Immature renal concentrating ability — MRCPCH TAS MCQ

Instant feedback + full explanation. One question, done properly.

ModeratePhysiologyImmature renal concentrating abilityMRCPCH TAS

A 6-week-old infant becomes dehydrated quickly during gastroenteritis. Urine remains relatively dilute despite clinical dehydration. What is the most likely explanation?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Immature renal medullary concentrating capacity

Young infants have limited renal concentrating ability, partly due to an immature medullary gradient and tubular function. Complete absence of antidiuretic hormone would produce a more severe diabetes insipidus phenotype. The teaching point is that infants have less renal reserve during fluid losses.

Reference: Ganong's Review of Medical Physiology; Nelson Textbook of Pediatrics; RCPCH Theory examination syllabi