Experimental irradiation of the rat ureter: the effects of field size and the presence of contrast medium on incidence and latency of hydronephrosis.

Following X-irradiation of a 1.5 cm length of rat ureter, hydronephrosis developed after doses down to 10 Gy. The estimated ED50 was 11.8 Gy. In the dose range 37.4 Gy to 17.5 Gy there was a significant increase in latency with decreasing dose, but at lower doses the latency did not increase further. Reducing the length of ureter irradiated to 0.5 cm or 0.8 cm caused a decrease in incidence of hydronephrosis and longer latency periods. The ED50 for rats irradiated to 0.5 cm of ureter was 29.6 Gy. The possibility that secondary radiation produced as a result of interaction between X-radiation and iodinated contrast medium might affect the radiation induction of hydronephrosis was investigated. No difference was found between groups of rats irradiated with or without injection of contrast media.