In this radiology lecture, we discuss the imaging appearance of duplicated collecting system and ureterocele, with attention to US and VCUG. Key points include: * Weigert-Meyer rule: Remember the mnemonic “DUMI.” * With duplex kidneys and complete ureteral Duplication, ureter draining Upper pole inserts ectopically into bladder Medially and Inferiorly to ureter draining lower pole. * Lower pole moiety inserts orthotopically. * Upper pole moiety often ends as an ectopic ureterocele. * Upper pole moiety tends to obstruct, and lower pole moiety is prone to reflux. * Obstructed upper pole moiety causes mass effect with resultant inferior displacement of the lower pole moiety and the “drooping lily” sign.