lumps

Question
my budgie has a swelling between his legs, like a sack of fluid,we took him to vet who say they are'nt sure what the problem is.There is a slight smell to him now as well

Answer
Hi again, Meg.

Is this vet you took your bird to an avian veterinarian?  If the vet is a cat/dog vet, they don't know anything about birds.  You need an avian vet...one who treats exotic animals, like snakes, lizards, iguanas, etc.  

Budgies can develop fatty liver tumors as a result of being on all-seed diets.  This could also be a fatty deposit indicating your bird is overweight, but it could also be a cancer tumor.  A foul odor would indicate to me a possible medical problem.  If your bird is female, this could be swelling of the reproductive system if she's ready to or has laid eggs.

You really need to consult an avian veterinarian.

Chrys