Blunt trauma to testes with rupture:

This 25 yr. old male came to me with a history of severe blunt injury to the left scrotum. On inquiring further, he reported that the part of a heavy machine hit him squarely without causing any bleeding. However, the left scrotum was moderately swollen and markedly painful.
Ultrasound imaging of the scrotum revealed (see ultrasound video clip below):

 Observe the large hypoechoic (dark) inhomogenous area in the left testis. This is a typical appearance of an intratesticular hematoma. But is that all? The right half of the video shows partial rupture of the outer covering of the left testis (tunica albuginea). Do we see anything more? There is some spillage of the lateral part of the testicular parenchyma outside the confines of the testicular capsule.
See some more color Doppler ultrasound videos of this testicular trauma- below:

Observe normal vascularity (blood flow) of the main testicular tissue (in the above long section of the left testis). This is a good sign and shows that the injured left testis is viable and does not need to be removed surgically. However, the lower pole of the left testis does show vessels entering the tissue that has spilled out of the capsule of the testis. This confirms that seminiferous tubules from the testis have been pushed out of the rupture site (of the left testicular fibrous capsule). In addition, there is a moderately large hemorrhagic fluid collection in the left scrotum (left hematocele).
Visit this link to read more on this topic:
http://www.ultrasound-images.com/acute-scrotum.htm#Testicular_trauma_%28rupture_of_testes_or_fracture_testes%29:_
We have one more color Doppler ultrasound video (this time a transverse section of the left testis):

 

Observe the linear strip of tissue hanging (or floating) within the hematocele in the left scrotum. This could be left testicular tissue with part of the body of the left epididymis.

Here are the ultrasound/ color Doppler images of this case of testicular trauma:

This last image is a transverse section section of the testis showing the site of rupture of the tunica albuginea, using Power Doppler imaging. The intratesticular hematoma is also seen.