Obstruction and Recanalization of the Ureter during Embryonic Development

Abstract

Major controversies still exist regarding the terminology, the etiology and the pathogenesis of congenital obstructive diseases of the ureter. To try to provide some additional information to this controversial subject, a comparative study of ureteral development in rat and human embryos, using light and electron microscopy, has been performed. During fetal development we observed and demonstrated the existence of obstructive phenomena, both at the level of the ureterovesical junction (Chwalla's membrane) and along the ureter. At the end of the embryonic period, the ureter undergoes a physiologic recanalization process.

Genetic and developmental basis for urinary tract obstruction

“…The detailed mechanism of ureteral valve formation is still unclear. However, it appears that a transient membrane structure (Chwalla's membrane) seals the distal end of the ureter (48). It ruptures to allow urine flow after the ureter is properly inserted into the bladder.…”

Severe congenital midureteral dilatation

“…This embryogenic hypothesis is supported by the high incidence of associated ureteric bud abnormalities such as contralateral renal dysplasia and ipsilateral ectopic ureter [3]. Embryologically, the ureteric bud appears as an evagination of the mesonephric duct at 28 days [4]. Between 28 and 35 days, the entire length of the ureter is patent somewhere.…”

Hypoplastic thymus and T-cell reduction in EECUT syndrome

“…During embryonic development, the ureter undergoes a physiological obstruction and recanalization within the 7th and 8th week of pregnancy [Alcaraz et al, 1989[Alcaraz et al, , 1991. Recanalization occurs during the time of extensive longitudinal growth and starts in the middle of the ureter [Ruano-Gil et al, 1975].…”