Partial unilateral ureteral obstruction in newborn mice: magnetic resonance imaging and pathology studies.

Purpose: The mechanism underlying the evolution of congenital obstructive hydronephrosis in humans is still unclear. Although partial unilateral ureteral obstruction has been extensively explored in rats, studies in neonatal mice may lead to new insights into underlying cellular mechanisms, especially with the availability of mutant mice. We developed a model of partial unilateral ureteral obstruction in newborn mice.

Materials And Methods: Mice were operated on by the fifth day of life. We created 3 groups, namely partial unilateral ureteral obstruction (embedding the ureter in the psoas muscle), complete unilateral ureteral obstruction (ligating the ureter) and sham (exposing the ureter). We studied pelvis diameter and kidney length on magnetic resonance imaging, and kidney weight, inflammation, apoptosis and fibrosis on histological assessment during the second (early) and fourth weeks (late) postoperatively.

Results: Magnetic resonance imaging showed enlarged pelvis diameter in late partial unilateral ureteral obstruction, and in early and late complete unilateral ureteral obstruction. Pathological studies revealed parenchyma atrophy in early and late partial unilateral ureteral obstruction. Apoptosis occurred early in partial unilateral ureteral obstruction and decreased later. Macrophage infiltration was enhanced in early and late partial unilateral ureteral obstruction. Fibrosis increased in late partial unilateral ureteral obstruction. All of these results were significantly intermediate between mice with complete unilateral ureteral obstruction and sham operated mice.

Conclusions: It is possible to create renal lesions in newborn mice specific to partial ureteral obstruction. Magnetic resonance imaging of morphological changes demonstrated specific features of partial unilateral ureteral obstruction. Being noninvasive, this approach opens the way for further studies to investigate prognostic parameters after partial ureteral obstruction. In the future this model could be used in knockout mice to study the pathogenesis of renal lesions secondary to obstruction.