If this isn't surgically corrected by the time the boy is 2, the testes may be permanently damaged. Immediate medical attention is required to restore blood flow to the testicle. It's also possible that your husband had testicular cancer, the most common solid cancer in men younger than 25. Testicular cancer is a serious problem, but it can almost always be successfully treated if detected early through self-exam. Not only should your husband doing them at least once a month, but as your sons grow older he should teach them how to examine themselves.
Testicular cancer does tend to run in families.
To examine himself, he should grasp his testicle between his thumb and first two fingers, with the thumb behind. On the back, where his thumb is, will be a normal lump called the epididymis, where sperm mature and wait for their journey up the spermatic cord. You might also watch for signs of varicocele, which can affect fertility. To find it at an early stage, your husband should take a warm shower to relax his scrotum. When he steps out of the shower, he should flex his pelvic muscles as if he's trying to have a bowel movement.