Effect of the Urine and Calculus Formation on the Incidence of Bladder Tumors in Rats Implanted with Paraffin Wax Pellets1

A double pouch of bladder was formed by divison of the bladder of inbred Fischer 344 rats and implantation of paraffin pellets into each pouch. The upper pouch could be in contact with or isolated from the urinary stream, while the lower pouch was always in contact with the urine. No tumors formed in 99 isolated upper pouches, while 49 formed in 119 communicating upper pouches in contact with the urine. The presence of 20% 3-hydroxyanthranilic acid in the pellets made no change in the incidence of tumors. When the urine was in contact with the pouch, stone formation was evident in one-half of the pouches and, in those pouches with stone formation, the incidence of tumors approximately doubled. The technique allows comparison of the effect of the pellet in the presence or absence of urine. The data suggest that the urine may play an as yet undefined role in the production of these tumors.