Pulmonary hypoplasia associated with renal agenesis is characterized by which findings?

• A. Decrease in lung size and cell number
• B. Reduction of the chest cavity by external compression is the only factor that affects lung growth
• C. Severity correlates with the duration of polyhydramnios
• D. Lung hyperplasia

Answer: (A)

Pulmonary hypoplasia in the setting of renal agenesis results from oligohydramnios, so the fetal lungs fail to develop fully. With limited amniotic fluid, the lungs don’t expand adequately, leading to smaller lungs and reduced cellular development in the lung tissue. That combination—smaller size plus fewer cells—best describes the condition.

External chest compression from low fluid can contribute to reduced lung growth, but it isn’t the only factor, so claiming it as the sole cause isn’t accurate. The idea that polyhydramnios occurs here is incorrect, as this scenario involves oligohydramnios (low fluid) and the severity is tied to how long the fluid is restricted, not to excess fluid. Lung hyperplasia would mean more lung tissue, which is the opposite of hypoplasia.