[High-frequency ultrasonography for evaluation of the urethral stricture model in rats]

To explore the methodology for the establishment of the urethral stricture model in rats, the methods of end-point imaging evaluation of the model establishment and their efficiency.

Twenty-four adult male rats were randomly divided into a blank control (n = 6) and a model group (n = 18), and the model was established by cutting the penile segment of the urethra to induce incomplete urethral rupture. Then the model rats were treated by injection of transforming growth factor-β1 (the TGF group, n = 6) or mesenchymal stem cells (the MSC group, n = 12) into the urethral cavernosum. At 4 weeks after modeling, the urethral condition of all the rats was evaluated blindly using high-frequency ultrasound combined with water bath, followed by comparison among different groups.

Compared with the blank controls, the model rats showed evident urethral stricture, with more significant urethral fibrous tissue hyperplasia in the TGF than in the MSC group. Ultrasonography revealed significantly narrowed echo strips (P < 0.01), decreased echo intensity and blurred echoes in some strips. The grouping of the model rats according to the assigned values to the ultrasonographic changes was consistent with the actual condition. The area under the ROC curve for distinguishing between the TGF and MSC groups was 0.972, with a sensitivity of 100.0% and a specificity of 83.3% when ultrasound assignment score was 7.5.

High-frequency ultrasonography combined with water bath is effective for evaluating urethral stricture in rats and may give some guidance in the establishment of the urethral stricture model.