Pain in the testis may radiate to abdomen and may lead to vomiting
It may be due to torsion of testis where testis gets twisted.
You should go for Colour doppler scrotum
instead of ultrasound
But,the Colour doppler scrotum should be taken immediately after pain
The pain may be relieved after derotation.
Sometimes,the testis has to be explored by surgery.Consult a urologist