Measuring Urethral Tissue Heat Injury Temperature Of Healthy Male Rabbits During Interstitial Radiofrequency Ablation

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). Materials and 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 48, 49, 50, 51 52 and 53C respectively. The urethral tissue acute heat injury (48 h after heating) was assessed by HE stain, Terminal Deoxylnucleotidyl Transferase Mediated-dUTP Nick End Labeling (TUNEL) stain 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 49C and 50C heating, but in four out of five cases at 52 and 53C. The percentage of necrosis was significantly different at tissue temperature of 52C and above. Quantitative image analyses of TUNEL stain sections demonstrated a significant increase in the positive staining for apoptotic cell at tissue temperatures of 50C and above. It indicated that the TUNEL stain to detect cell death was more sensitive than routine histology. Conclusion: The results from this in vivo study indicate that 50C and 5 min heating of rabbit urethra during interstitial RFA is the minimum temperature for heat injury of the normal rabbit urethra as measured at 48 h after treatment.