[Establishment of an animal model of blunt scrotal trauma and evaluation of the lesion by conventional and contrast-enhanced ultrasonography].

Objective: To establish an animal model of acute blunt scrotal trauma (BST) and evaluate the types of lesion by conventional ultrasonography (CUS) and contrast-enhanced ultrasonography (CEUS).
Methods: We made acute BST models in 21 healthy male New Zealand rabbits by striking 3 - 12 times the unilateral testes randomly selected with a 0. 5 kg iron ball falling freely from a 30 cm height. Then we evaluated the lesion types in the models by CUS and CEUS and verified our evaluation against pathological results.
Results: Acute BST models were successfully established in all the 21 animals, including contusion in 10, hematoma in 6, and rupture in 5, all confirmed by pathology. CUS clearly manifested the morphology, internal echoes, and blood flow of the testes, but had a low rate of accurate diagnosis in testicular contusion for over 6 hours as well as in complex lesions. CEUS revealed an earlier perfusion of the contrast agent and shorter arriving time (AT) and time to peak intensity ( TP) in testicular contusion than in the control testes (P <0.05) , but showed no statistically significant difference between the two groups in the half time of descending peak intensity (P>0.05). For testicular hematoma, contrast agent clearly presented its outline and a delayed low enhancement in the surrounding tissue, with significant differences from the control in AT and TTP. In severe testis rupture, occasional outflow but no perfusion of contrast agent was observed.
Conclusion: BST models can be established in rabbits by repeated strikes of the unilateral testes lesion of contrast agent was observed. with a freely falling iron ball. Simple contusion injury can be induced by less than 6 strikes, while complex injuries can be inflicted by more than 10. Combined application of CUS and CEUS can improve the accuracy of diagnosis of different types of lesion.