Testicular torsion occurs when the spermatic cord (from which the testicle is suspended) twists, cutting off the testicle's blood supply, a condition called ischemia. The principal symptom is rapid onset of testicular pain. The most common underlying cause is a congenital malformation known as a "bell-clapper deformity" wherein the testis is inadequately affixed to the scrotum allowing it to move freely on its axis and susceptible to induced twisting of the cord and its vessels.
The diagnosis should usually be made on the presenting signs and symptoms and an urgent ultrasound should only be done...