Ethical question regarding a dog...help!

I work at a animal hospital and took home a dog with a prolapsed penis. He was dumped at our hospital for a month and a half with this condition, and was finally legally the hospital’s property so I took him home and neutered him. The problem is the neutering did not resolve this problem. In fact, he will probably need a very expensive surgery to correct this. So I am faced with a huge financial dilemma regarding this dog. I want to do right for this dog, he is sweet and very young and deserves a good life. But I don’t think I can afford this surgery even though I took responsibility for him. I would feel foolish giving him up after all of this, but I just don’t know what to do. Advice? Criticism? I am sure there is some out there, I love animals like everyone but financially times are tough and even those in the field can’t always afford these things.