A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 2-day-old male infant, born at 38 weeks' gestation, presents with difficulty breathing and facial abnormalities. Prenatal ultrasounds showed oligohydramnios. Physical examination reveals a flattened nose, limb deformities, and clubfoot. Renal ultrasound shows bilateral cystic kidneys with no detectable urine output. Which embryologic disruption is most likely responsible for these findings?
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A
Fusion of the metanephric blastemasIncorrect. Metanephric blastema fusion produces horseshoe kidney, which still produces urine and would not cause oligohydramnios.
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B
Incomplete ascent of the kidneysIncorrect. Incomplete ascent causes pelvic kidney, which typically functions and produces urine.
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C
Failure of metanephric duct inductionCorrect. Failure of metanephric induction by the ureteric bud causes bilateral renal agenesis/dysplasia leading to Potter sequence.
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D
Aberrant renal artery developmentIncorrect. Aberrant renal artery development does not by itself cause anuria and Potter sequence.
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E
Malformation of the ureteric budIncorrect. Ureteric bud malformation could cause dysplasia but does not typically produce complete bilateral anuria as seen here.
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Answer: C. The vignette describes Potter sequence, indicated by oligohydramnios, facial abnormalities, and limb deformities. These are due to bilateral renal agenesis or severe dysplasia, which is linked to failure of metanephric duct induction. This disrupts kidney formation and urine production, explaining the oligohydramnios. 'Malformation of the ureteric bud' could lead to cystic kidneys but wouldn't necessarily explain the complete lack of urine output. 'Fusion of the metanephric blastemas' describes a horseshoe kidney, which typically still produces urine.