proventriculus

I am new to this forum. I have already been to a VET multiple times. I am struggling with how much $ I have already spent and my bird is still not better. Looking for opinions/advice and personal experiences. I will attach xray images. I don't know what or if I should do any further...

my vet did an x ray contrast dye on my cockatiel and discovered that he had a distended proventriculus and ventriculus. She suspects Borna virus. She also said that another cause could be ingestion of metals. Are there any other causes for the proventriculus and ventriculus to be distended...