What is the diagnosis?
Lack of Doppler signal is highly concerning for testicular torsion.
What is the most useful view for this diagnosis?
A comparison view (often called the sunglasses shot) where both testes are images in transverse with colour Doppler box over them (see the last image of this ultrasound for an example).
Normal Doppler trace on right. No Doppler trace on left.
Left sided reactive hydrocoele. Findings consistent with testicular torsion.