Focal epididymitis:

This color Doppler ultrasound video shows a long section of the right testis- observe the lower pole.

The right tail of epididymis definitely appears inflamed. Now observe this transverse section color Doppler video clip through the right testis panning from the upper to the lower poles.

 There is a small right hydrocele which outlines the head and body of the right epididymis. The diagnosis in this case is focal right epididymitis involving primarily the tail.
Here is the still ultrasound image of the affected right testis:

And the color Doppler image of the same case: (right testis and epididymis):

And the still ultrasound image of the normal left testis (above).
For more on this topic see: http://www.ultrasound-images.com/scrotal-infections.htm