1) Ectopic ureter draining into the genital system is a rare entity and results from a more cranial origin of the ureteral bud
from the mesonephric duct with resultant ureteral stump opening in the mesonephric duct derivatives (seminal vesicles, ejaculatory ducts, or vas deferens).
The possible reasons for renal agenesis include the lack of induction of the metanephric blastema by the ureteral bud
, primary absence of the caudal nephrogenic core, ureteral bud
malformation, and dysplasia of mesonephric duct [4-6].
On the other hand, bifurcation of a single ureteral bud
proximal to the ampulla gives rise to a duplex kidney with a bifid pelvis or ureter3.
sup] The mesonephric anomaly with the absence of the Wolffian duct opening into the urogenital sinus and therefore of the ureteral bud
sprouting, justifies the blind vagina and unilateral renal agenesis.
Moreover, it is well-demonstrated that if an embryological insult occurs before 7 weeks' gestation, when the ureteral bud
separates from the mesonephric duct, SV agenesis may be associated with renal agenesis.
The ureteral bud
originates from the caudal end of the mesonephric duct at approximately gestational week 4, and proper interaction between the mesonephric duct and urogenital sinus results in the correct anatomical placement of the ureteral orifice on the bladder trigone.
4) The mechanism of development is similar to that of renal dysplasia in which the abnormality develops at the juncture of the mesonephnc duct derivative, the ureteral bud
, with the metanephrogenic mesenchyme.
In a duplex system this is inevitably the upper pole ureter, presumably due to its budding from the mesonephric duct later than the lower pole ureteral bud
As a result of the interaction between the ureteral bud
and the mesonephric duct during embryogenesis, many associated anomalies were observed.
2) There are several theories to explain the occurrence of supernumerary kidney: a) bifurcation of ureteric bud with independent penetration into metanephrogenic blastema that develop and divide in two kidneys; b) two independent ureteral buds
that penetrate the metanephrogenic blastema that divides into two and c) fragmentation of metanephrogenic blastema due to linear infarcts.
Ectopic ureters are always associated with a duplicated system--two ureteral buds
exit from the mesonephric duct, and one ends up positioned ectopically.
Throughout the embryonic development, 2 ureteral buds
rarely develop separately from a single mesonephric duct, giving rise to a duplex kidney with ureteral duplication.