
Depending on your Vet surgery Ultrasound/X-ray could be options, most however, opt for exploratory surgery..as to be honest Monorchidism is extremely rare!! It is much more likely to be bilateral cryptorchidism.
Mono= one ... As in there is only one(anywhere in the dog).
Crypt= hidden.. (which is more common.)
Mon/orchid/ism= one/testicle/condition of
Crypt/orchid/ism = hidden/testicle/condition of
If that makes more sense!! :D
In my breed descent can be very late and the added problem Sibes are well versed in using their cremaster muscle!.. the cold weather heritage makes them pull the testes right up into their body cavity and has fooled many a vet trying to palpate.. and very late (comparitavely) descent can still occur.
what breed is it you have?