Influence of irradiated volume on ureteral injury after intraoperative radiation therapy: experimental study in dogs.

Abstract

To investigate the role of irradiated volumes at intraoperative radiation therapy in the development of ureteral injury in dogs. Sixteen beagle dogs were randomized to receive 30 Gy of intraoperative radiation therapy in the right ureter. Lead shielding ensured that different volumes were irradiated. Six dogs received a 4 x 12-cm field, five dogs a 4 x 8-cm field, and five dogs a 4 x 4-cm field. Follow-up included magnetic resonance (MR) imaging, clinical examination, and resting sequential renography. Twelve months after irradiation, the animals were killed, and autopsy was performed. Functional outcome was defined as MR imaging and renography findings and was evaluated statistically by using the Cochran-Armitage test at a.05 significance level. Twelve months after therapy, ureteral obstruction with consecutive hydronephrosis of the right kidney was observed in four of six animals that received the largest volume of irradiation. Two dogs that received the medium volume developed ureteral obstruction. None of the five dogs that received the smallest volume showed abnormal findings (P <.05). The irradiated parts of the ureters in all dogs showed abnormal histopathologic findings, such as fibrosis. The probability of ureteral obstruction following intraoperative radiation therapy increases with the irradiated partial volume of the ureter.