THE EXPERIMENTAL MODEL OF CONGENITAL URINARY TRACT OBSTRUCTION

Abstract

In an attempt to produce experimental models of congenital urinary tract obstruction, we operated on fetal rabbits.
Sixteen pregnant rabbits were operated on between 22 to 24 days of gestation under the general anesthsia with GOF and intravenous administration of ketamine. In case of ureteral ligation, one hind limb of the fetus was fixed to the uterine wall with small stay sutures to prevent excessive loss of amniotic fluid. A ureter was exposed through a flank incision, and was ligated either with a clip or with the suture material. Care was taken to keep the fetus wet and warm.
Thirty-two fetal rabbits were operated on in this experiment: urethral ligation in 14, ureteral ligation in 10, bladder neck ligation in 3, and an incision of fetal skin without any manipulation of the urinary tract (sham operation) in 5. Twenty-nine of the 32 rabbits were born alive through cesarean section after the period of ligation from 3 to 6 days. Fourteen unoperated rabbits were considered to be controls. Vesical overdistention was evident in 6 rabbits with urethral ligation and one with bladder neck ligation. The upper urinary tracts were normal in these animals. Hydronephrosis was apparent in 7 rabbits: it was marked in 3 ureters ligated with the suture material and moderate in 4 ligated with a clip.
All of the operated newborns were markedly underweight in compared with the unoperated controls. Significant decrease of lung weight/body weight was evident in rabbits with successful urethral ligation.
Microscopic findings of the kidney and the ureter were evaluated and compared with the control materials. Histologic section of the kidney from the control showed a nephrogenic zone with a few S-shaped glomeruli in the outer cortex. The specimens of the severe hydronephrosis from ureteral ligation revealed marked renal atrophy. There were remarkable dilatation of tubules and ducts in the whole parenchyma. Small glomerular cysts, in which Bowman's capsule is dilated and the glomerular tuft is compressed to the corner, were evident in the subcapsular zone. There were no striking changes of the glomeruli in the deep cortex. The kidneys of the urethral-ligation group were normal under the microscope. The ureter and renal pelvis were markedly dilated above the obstruction in the animal of urethral ligation. The epithelial layer was overstretched, and there was a slight increase in the amount of collagen fibers in the submucosal layers. Musclar hypertrophy and hyperplasia were observed in these specimens.