Fetal hydrops in experimental obstructive uropathy resolves after vesicostomy formation: is this cause and effect?

The association of obstructive uropathy and hydrops is rare but often fatal. Hydrops has been observed in our fetal lamb model with obstructive uropathy. We created a vesicoamniotic shunt 21 days after creating the obstruction to explore the effect of relieving the obstruction on the hydrops. Fetal lambs underwent urethral and urachal ligation at 60 days gestation. We created a vesicostomy (female) or urethrostomy (male) in 12 lambs to release the pressure 21 days after creating the obstruction. The fetuses were delivered at term (145 days), and the urinary tract was removed for histological examination. Six fetuses had severe hydrops at the time of the vesicostomy (group A), and six had no hydrops (group B). Only two lambs from group A survived (33%), and four lambs survived from group B (66%). Three lambs miscarried, and one was stillborn from group A. Two lambs from group B miscarried. In our fetal lamb model, hydrops appears to be associated with massive urinary ascites. We hypothesize that a connection exists between urinary ascites and hydrops. Vesicostomy, by bypassing the obstruction, may allow the lambs to recover from their hydrops. However, it is possible that by 21 days after creation of the obstruction, the damage created by the hydrops is irreversible.