In about 2 out of 1000 persons vide untill it enters the metanephric
the lower poles of the two kidneys are blastema. Premature bifurcation of the
fused to each other, creating a U- ureteric bud results in a bifid ureter.
shaped structure called horseshoe kid- Complete duplicate ureters, ie, double
ney. The ureters pass anterior to the ureters result from the growth of two
bridge, usually without any obstruction separate ureteric buds from a meso-
to urinary flow. It has been proposed nephric duct. In such cases, the cranial
that the normal ascent of the fused kid- bud induces formation of the upper
neys is prevented by the inferior mes- pole of the kidney, whereas the caudal
enteric artery. Consequently, the bud induces the development of lower
horseshoe kidney usually lies in cthe pole of the kidney. In cases of double
hypogastrium, anterior to the lower ureter the caudal ureter opens in the
lumbar vertebrae. Wilms' tumors are bladder wall in a normal manner. The
more frequently seen in children with cranial bud, however, is carried inferi-
horseshoe kidney than in normal chil- orly and forms its final connection with
dren. • any derivative of the urogenital sinus.
In the male the ectopic ureter may