Has the vet checked to see if they can locate the retained testicle? Sometimes it is palpable and therefore, no stomach surgery is required. I have heard of testicles being manipulated down because they could be felt but hadn't dropped. It takes months to do but if that can be done, then surgery would not be invasive to get them out and off.
If stomach surgery is needed, then get the gastropexy done while it's open.
If stomach surgery is needed, then get the gastropexy done while it's open.
