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 degrees , 49 degrees , 50 degrees , 51 degrees 52 degrees and 53 degrees C 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 49 degrees C and 50 degrees C heating, but in four out of five cases at 52 degrees and 53 degrees C. The percentage of necrosis was significantly different at tissue temperature of 52 degrees C and above. Quantitative image analyses of TUNEL stain sections demonstrated a significant increase in the positive staining for apoptotic cell at tissue temperatures of 50 degrees C 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 50 degrees C 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.