The development of tumors in experimental gastroenterocystoplasty

Bladder augmentation with segments of the gastrointestinal tract is commonly used to treat patients with small or noncompliant bladders. Reliable data on the incidence of tumors in patients with enterocystoplasty are not available. In the small number of cases reported in the literature the mean latency period is approximately 18 years. We designed a study in Sprague Dawley rats to try to determine the risk of carcinogenesis in different types of augmentation cystoplasty and its possible relationship with infected urine, and to investigate the possibility of detecting the tumors by cytological analysis. We performed 30 gastrocystoplasties, 35 sigmoid cystoplasties, 30 ileocystoplasties and 10 sham operations, and used 10 nonoperated animals as controls. The animals were sacrificed upon completing 1 year of followup and bladder urine samples were collected at the time of sacrifice. Of 115 animals 86 were available for histological evaluation (26 gastrocystoplasty, 22 sigmoid cystoplasty, 18 ileocystoplasty, and all sham and control animals). Mean followup was 11.2 months in the gastrocystoplasty, 11.8 months in the sigmoid cystoplasty, and 12 months in the ileocystoplasty, sham and control groups. Multifocal or superficial transitional metaplasia was found in 65.4% of the gastrocystoplasty, 50% of the sigmoid cystoplasty and 55.5% of the ileocystoplasty animals. Proliferations that we classified as papillary hyperplasia were present in 53.8% of the gastrocystoplasty, 40.9% of the sigmoid cystoplasty and none of the ileocystoplasty rats. The proliferations occurred either at or close to the anastomosis between the bladder and the gastric or colonic patch, or in areas of transitional metaplasia. Cytological urinalysis was negative for neoplastic cells in all cases. No correlation was found between the occurrence of papillary hyperplasia and urinary infection. These data indicate that in rats transitional metaplasia is common in gastrocystoplasty, sigmoid cystoplasty and ileocystoplasty, and that papillary hyperplasia may occur near or at the anastomosis, or in areas of transitional metaplasia in either gastrocytoplasty or sigmoid cystoplasty. In contrast to other studies, we observed no examples of papillary hyperplasia in the ileocystoplasty group in this series. No transitional cell carcinomas or adenocarcinomas were identified in this study. It is not known if these papillary lesions have an increased malignant potential, thus further studies with longer followup are warranted.