Composite urinary reservoir in dogs: histological findings

This animal study was designed to investigate whether the composite urinary reservoir might lessen the premalignant histological alterations observed after bladder augmentation performed with a gastric segment or large bowel.

Composite urinary reservoirs were created using gastric and colonic segments simultaneously in 8, 3-month-old female beagle dogs by augmenting half the native bladder. Two dogs with gastrocystoplasty and 2 with colocystoplasty served as controls. Biopsies were taken from the native bladder, and the gastric and colonic segments at augmentation, and endoscopically 4 and 8 months postoperatively. The dogs were sacrificed and open biopsied 12 months postoperatively. Tissue specimens were examined with routine hematoxylin and eosin, reaction and immunohistological staining for PCNA.

At the creation of composite reservoir and gastrocoloplasty or colocystoplasty all specimens showed normal histology. At 12 months postoperatively dysplasia was found in 1 gastric segment, 2 native bladders and 3 colonic segments in the composite reservoir group. There was a single carcinoma in situ in 1 gastric segment in the composite reservoir group. In the control groups 1 colonic segment and 1 native bladder dysplasia were detected at the end of 12-month followup. There was an in situ carcinoma in 1 gastric segment in the composite reservoir.

A composite reservoir did not decrease premalignant changes in dogs during 12 months of followup. Laboratory investigations, molecular studies and longer followup are needed to approach the question of early malignant alterations after augmentation cystoplasty in animals and patients.