A juvenile animal model to study the growth potential of bowel segments in the urinary tract

A juvenile animal model has been developed to study the growth potential of ileum in the urinary tract. Patch ileocystoplasties of known surface area were constructed in dogs of Group 1. Nonrefluxing ileal nipple valves of known length were created to replace one ureter in dogs of Group 2. After the juvenile animals grew and at minimum doubled their weight, they were reoperated and augmentation surface areas were remeasured at various physiologic intravesical pressures. Nipple valve lengths were remeasured after cystograms ruled out reflux. Results show that the bowel augmentation and an identical control segment increased in surface area proportionate to animal growth and that hydrostatic dilation caused further surface area increase. Nipple valves did not grow and in fact shortened, but remained nonrefluxing. The conclusion is that in the pediatric population, consideration should be given to downscaling the size of bladder augmentations or diversions in anticipation of future bowel growth, but that one should not shorten the ileal nipple valves.