Development of an animal model to study congenital urinary obstruction

Purpose We outline the development of a reliable model of obstructive uropathy in fetal lambs highlighting our understanding of the critical time points for interventions and the variability of any such model. We identify some discoveries that may have clinical implications. Methods The model requires 60-day-gestation fetal lambs. In lambs, glomerulogenesis is complete by 90 days gestation. (Term is 145 days.) The ability to develop a reliable method of creating bladder outlet obstruction in females, ligating both the urethra and urachus was critical. The lambs are bred to an accuracy of ±24 h. Results Creating the model at 50–60 days gestation, produces different expressions of renal dysplasia in groups of lambs undergoing identical interventions at the same stage of gestation. Early complete urethral obstruction can produce the Potter phenotype. An appropriately timed vesico-amniotic shunt preserves renal development, producing a shrunken, non-compliant bladder. Shunting the normal fetal bladder at 80 days gestation produces a similar bladder. Provision of a low-pressure valve in the shunt preserves bladder development and compliance. Using a high-pressure shunt produces results similar to non-shunted lambs. Discussion We developed a reliable animal model for obstructive uropathy. Being alert to peripheral results can lead to new findings.