Massively Dilated Lower Pole Ectopic Megaureter with Involuted Lower Pole Renal Moiety and Collecting System: An Exception to the Meyer-Weigert Rule.

Duplicated collecting systems have a predictable draining pattern that is described by the Meyer-Weigert rule. When there are abnormalities associated with duplicating collecting systems, the upper pole moiety drains inferomedially (most commonly associated with obstruction), and the lower pole moiety drains superolaterally (most commonly associated with vesicoureteral reflux). We present a case of an infant with a duplicated collecting system that violates the Meyer-Weigert rule with lower pole megaureter with massive dilation, ectopic insertion, and associated involuted lower pole renal moiety. To our knowledge, this is the only reported case of a lower pole ectopic ureter with an involuted lower pole renal moiety.