On obstetric ultrasound at 20 weeks, a foetus is found to have bilateral renal agenesis. Which of the following is NOT a component of Potter sequence associated with this finding?

• A Oligohydramnios
• B Pulmonary hypoplasia
• C Polyhydramnios due to impaired swallowing ✓
• D Characteristic facial features (low-set ears, retrognathia, flat facies)

Explanation

Potter sequence (oligohydramnios sequence) results from bilateral renal agenesis or severe renal dysfunction leading to oligohydramnios. Reduced amniotic fluid causes: pulmonary hypoplasia (restricted chest expansion), characteristic Potter facies (low-set ears, epicanthal folds, retrognathia), and limb deformities due to compression. Polyhydramnios results from impaired swallowing (oesophageal atresia, CNS anomalies) and is the opposite of what is seen in Potter sequence.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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