Hi
This condition will be something he was born with and testicles do not descend as dogs get older contrary to popular belief. Its not an emergency but if the testicle is retained in his abdomen, I have seen cases where abnormalities in later life such as cancer develop in the retained testicle. I always advise removal of a retained testicle. If you get this done whilst he's still a young dog 1-2 years old there's no risks of anything bad happening later. if you are fortunate, the retained testicle might be present in his groin and not in his abdomen, I still advise removal but it would less costly for you. As your dog matures a vet should be able to assess him re the likelihood of where the testicle is and advise you of what approach is needed.
Cathy Wickenden BVet Med MRCVS
Barton Lodge Veterinary Centre
1 Midland Road, Hemel Hempstead, Hertfordshire, HP2 5BH
Tel: 01442 216048 24 hours
[
www.bartonlodgevets.co.uk]