Urine cytology: early diagnosis of induced carcinoma of the rat urinary bladder.

Transitional cell carcinoma of the urinary bladder was induced in F344 rats by intragastric intubation of the animals with the known bladder carcinogen N-nitroso-N-methyl-N-dodecylamine (NMDA). Urinary cytology was used to follow the development of bladder lesions. As early as 8 weeks after the beginning of NMDA exposure, small, but distinct, differences could be detected between the morphology of exfoliated transitional cells found in the urine if animals treated with NMDA and those of control animals. Atypia was noted in the cells from some of the NMDA treated animals at about 20 weeks, and after 32 weeks definitely malignant transitional cells were identified in the urine of all NMDA treated animals. When the NMDA treated animals were killed, at 55-60 weeks after the beginning of NMDA treatment, transitional cell carcinoma of the urinary bladder was confirmed in all animals. No abnormal cells were noted in urine from any of the control animals. Urine cytology is an excellent technique for early detection of experimental urinary bladder cancer, and may be especially useful in screening industrial workers exposed to suspect bladder carcinogens.