An intravenous urogram in a child shows the lower pole pelvicalyceal system displaced inferolaterally, resembling a drooping flower, while the upper pole system is not opacified. Ultrasound confirms a duplex right kidney with a markedly hydronephrotic non-functioning upper moiety. Which anomaly best explains this 'drooping lily' appearance?

• A Renal cell carcinoma arising in the upper pole
• B Vesicoureteric reflux into the lower moiety
• C Obstructed upper moiety ureter with ectopic insertion or ureterocele ✓
• D Horseshoe kidney with malrotation

Explanation

In the Weigert-Meyer rule, the upper pole ureter inserts inferomedially and tends to obstruct, while the lower pole ureter inserts superolaterally and tends to reflux. Obstruction of the upper moiety produces a hydronephrotic, non-opacifying upper pole whose enlarged collecting system displaces the functioning lower pole calyces downward and laterally, giving the drooping lily sign. Reflux affects the lower moiety rather than causing this displacement pattern, and tumour would show a soft tissue mass rather than a dilated moiety.

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

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Written and medically reviewed by the StethoPrep medical team.