Domino has one descended & one in the inaugural canal (I can feel it & it's quite a bit smaller than the other one.)
Previously my vet has recommended leaving it & keeping an eye on it in case it causes a problem; however I saw another vet at the practice who suggested removing it whilst Domino is a young, fit dog & would therefore recover from the op. better than if it had to be removed if & when he became ill from it, but leaving the 'sound' testicle where it was so that his coat would still be the same; also he tends to lack a bit of confidence with other dogs so I feel that castrating him could make him even more fearful.
I must admit I can see where he is coming from with this so I probably will have it removed.