The effects of overcoming experimental bladder outflow obstruction in fetal sheep

Abstract

Objective: To develop an ovine model of fetal bladder outflow obstruction and to investigate the effect on the kidney of surgical relief of the obstruction in the prenatal period.Methods:Ultrasound examination and amniocentesis were performed on 68 date-bred pregnant ewes at day 57 of pregnancy (term = 150 days). Fetal gender was determined using a molecular technique to identify singlemale fetuses. The urethra and urachus were ligated at hysterotomy on 20 of these fetuses at 75 days' gestation. Comparisons were made with six controls that did not undergo operation. Changes that occurredin fetal urinary tract appearance were detected using serial ultrasound examinations. Seven obstructed cases chosen at random had further prenatal surgery on day 94 to decompress the obstructed urinarytract by vesicostomy. The animals were killed at 110 days' gestation and post-mortem studies were performed.Results: Fourteen days after surgical obstruction, there were increases in the summedrenal lengths (33 mm vs. 28 mm, p = 0.003) and renal pelvis anteroposterior (A-P) diameters (8 mm vs. 5.5 mm, p = 0.02). In the group allocated to receive surgical decompression, 9 days' reliefof obstruction resulted in significant reductions in summed renal lengths (30 mm vs. 41 mm, p = 0.024; controls 31 mm) and renal pelvis A-P diameters (5.8 mm vs. 8.9 mm, p = 0.012; controls< 2 mm). Post-mortem histological examination in the surgical decompression group revealed an estimated number of glomeruli similar to controls and greater than in the obstructed cases.Conclusion:Surgical relief of fetal bladder outflow obstruction in ovine mid-pregnancy results in improved renal appearance on ultrasonic and histopathological examinations.