The most common sign of testicular torsion is sudden, severe pain on one side of the scrotum.
The testes should be about the same size. If one side quickly becomes larger than the other, this can be a problem. Change in scrotum color, especially redness or darkening, is also a problem. Early on, there may not be swelling. But very shortly after, the scrotal skin will swell and turn red. You may also feel nauseous and vomit.
Testicular torsion is a medical emergency. Since all blood for the testicle comes through the spermatic cord, the blood supply is cut off with a twist. The testicle will shrink ("atrophy") if the blood supply isn't restored within 6 hours. With no blood, the testicle could die (or "infarct"). When the testes die, the scrotum will be very tender, red, and swollen. Often the patient won't be able to get comfortable.
Any pain or discomfort in the testes is a sign to get medical help right away. Call your doctor even with no swelling or change in skin color.
Slow-onset pain in the testicle, over many hours or days, can be a sign of torsion. This is less common. Problems with urination, such as burning or having to go often are not normal signs of torsion. Torsion tends to happen on the left side more than the right. Most often, torsion is only on one side. Only 2 in 100 men with torsion have it in both testes.