Cryptorchidism
Cryptorchidism is a condition where the one or both of the testicles fails to descend into the scrotum. The testicles should be fully descended by 2 months old and absence of palpable testes at this age is presumptive evidence of cryptorchidism. Prevalence in cats is reported to be 1.7%, with a higher prevalence seen in Persians and unilateral (one side) cryptorchidism is more common. This is considered to be a heritable problem but the genetics have not yet been fully determined.

The testicles are formed in the abdomen and then descend through a small hole in the abdomen called the inguinal ring. They then descend further and should eventually end up in the scrotum. Cryptorchidism is classified into two categories:
a) Abdominal Testicles: the testicle has not descended through the inguinal ring. These will require surgical opening of the abdomen to remove the testicle. The testicle can be located with the aid of ultrasound.
b) Inguinal Testicles: the testicle has descended through the inguinal ring but has not fully descended into the scrotum. These can usually be palpated and may be removed surgically without the need to enter the abdomen.

Cats with one affected testicle can show normal libido (sex drive) and still be fertile as one testicle is still functioning normally. Those with bilateral cryptorchidism will have decreased libido and are likely to be sterile.

There is no specific means of correcting this problem. It is strongly advisable to have the cat castrated as the condition is heritable and can therefore be passed on to subsequent generations. Testicular cancer in cats is rare and cryptorchidism does not appear to increase the risk.<