In the imaging of acute testicular torsion, which of the following are true?

In the imaging of acute testicular torsion, which of the following are true?
a) Surgery is successful in 20% of patients who present between 12 and 24 hours after onset of symptoms
b) On sonography, a reactive hydrocoele is seen after 6 hours
c) Colour Doppler ultrasound may show increased blood flow in the epididymis
d) Hyperperfusion of the testicle on colour Doppler ultrasonography makes testicular torsion unlikely
e) Technetium-99m pertechnetate scintigraphy typically shows a halo of hyperactivity in the acute phase (first 6 hours)