Duplex Kidney — RACP Adult Medicine MCQ

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ModerateNephrologyDuplex KidneyRACP Adult Medicine

A 35-year-old woman with recurrent UTIs is found to have a duplex kidney on ultrasound. She has recurrent pyelonephritis affecting the upper moiety. What anatomical variant is responsible for the upper moiety reflux/obstruction?

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Correct answer: C — Pelviureteric junction obstruction

In a duplex kidney, the Weigert-Meyer rule describes the anatomy: the upper pole ureter inserts ectopically (medial and inferior to the lower pole ureter) into the bladder and is prone to obstruction (often from an ectopic ureterocele), while the lower pole ureter inserts more laterally and is prone to vesicoureteric reflux. This explains why upper moiety infections/obstruction occur. Assessment with MR urography and MCUG guides management, which may include endoscopic ureterocele incision, ureteric reimplantation, or upper pole heminephrectomy for a non-functioning moiety.

Reference: eTG – 2025 – Nephrology