Objective: The objective was to evaluate urethral tissue heat injury in a rabbit model. Histopathology analysis was used to determine the minimum temperature required to achieve urethral tissue injury following interstitial radiofrequency ablation (RFA).
Methods: A total of 37 healthy rabbits were divided into 6 groups randomly and treated with interstitial RFA in the penial parenchyma. The temperatures of urethra were monitored and controlled to 48ºC, 49ºC, 50ºC, 51ºC 52ºC and 53ºC respectively. The urethral tissue acute heat injury (48 hours after heating) was assessed by HE staining, TUNEL staining and quantitative analysis in tissue sections.
Results: Histologically, the main feature of acute heat damage was necrosis or vascular congestion or thrombosis of blood vessels of the urethral wall. This occurred only in one out of five cases at 49ºC and 50ºC heating, but in four out of five cases at 52 and 53 degrees. The percent necrosis was significantly different at tissue temperature of 52ºC and above. Quantitative image analyses of TUNEL staining demonstrated a significant increase in the positive staining for apoptotic cell at tissue temperatures of 50ºC and above. It indicated that the TUNEL staining was more sensitive than routine histology in detecting cell death.
Conclusion: The results from this in vivo study indicate that 50ºC and 5 minutes heating of rabbit urethra during interstitial RFA is the minimum temperature for heat injury of the normal rabbit urethra as measured at 48 hours after treatment.