My border Terrier is now 16 months old and when he had his annual check up the vet said he only had one desended testical.  Her advice was that if the other one hasn't dropped within the next six months then I should have him x-rayed to find the hidden one and have it removed.  I have consulted his breeder and he says to leave it as it should come down naturally.  Don't know what to do, confused, can anyone give me some advice....

I think your breeder might be being a bit hopeful.  There is no getting away from the fact that retained testicles happen.  I would do just as your vet says as giving it another 6 months seems like plenty time to me.

I bred a dog that is now 2 years 3 months old and sadly his second testicle never did drop. I think after the age of close to a year the chances are extremely small it will drop.

Unfortunately I would say it's not going to come down now.  Not that I've had any but if anyone queries on here etc. I usually say wait until they are 12 months before doing anything.  What a wonderful vet you have many want to gt them out before they are 6 months if only ones down!!

I am not sure about this so please dont take it has gospel.   Is there not something that happens after a year old that stops it coming down, does something close of or tighten up.. just can't remember where I heard of read it.  Could someone please confirm if they know for sure so I don't confuse anyone :-)

Our border collie had the same problem and it stayed up. My cocker had one at 6 months and two at 8 months so he escaped the knife!!

My boy had a retained one and accidently mated my bitch(did have her injected so no puppies to pass the gene onto)but it still didnt come down so had him castrated when he was just over 2 years.