The most common method used today is to place an oil or gel on the scrotum and move a pen like probe across the testes in the scrotum as an ultrasound picture is projected on a screen. Still frames of the picture can be taken as desired by the sonographer.
The ultrasound shows the structure, density and any cysts, tumours or other abnormalities of the testes and epididymis (sperm collecting tubes) that surrounds it. If necessary, a cyst may have a needle passed into it under ultrasound control to drain it and determine what was in it.
The ultrasound process is completely painless and at worst merely tickles.
In previous years, older ultrasound machines examined the testes in a different way. The man lay face down on a table, which had a strategically paced hole in it so that the testicles and scrotum dangled through the hole into a small bath of water. The ultrasound waves were passed through the water and reflections of the sound waves were picked up by a detector to produce an image.
Rarely, it may be necessary to perform an x-ray of the testicles or penis, but the use of x-rays in this area is usually kept to a minimum because of the risk of damage to the testes.