Renal duplication with obstructed upper renal moiety (Weigert-Meyer rule)
Duplex right kidney with obstructed upper moiety as well as mild right hydronephrosis and hydroureter with intra-vesical ureterocele as described.
Weigert-Meyer Rule: with duplex kidney and complete ureteral duplication, the upper renal and lower renal moiety have their own ureters with each ureter having its own ureteral orifice in the bladder. The upper renal moiety has ectopic insertion medial and inferior to the lower pole moiety ureter and frequently ends in a ureterocele. The lower renal moiety has orthotopic insertion lateral and superior to the ureter draining the upper pole and reflux typically occurs.