NAVLE（北美执业兽医考题）Day 517

An intact male whippet presents with an acute onset of swelling and pain in one of his testicles. A post-op image shown below. Which one of the following tests is helpful to diagnose the cause of the swelling before surgery? 

一只未去势的雄性惠比特犬表现出一侧睾丸的急性肿胀和疼痛。 术后图如下所示。 以下哪项检查有助于诊断手术前肿胀的原因？