Researchers found that, as compared with normal dogs, there is evidence of oxidate damage taking place in the liver of dogs with portosystemic shunts (PSS). It can be surmised that antioxidant therapy might slow down the progression of the disease in dogs that are not surgical candidates. This project will provide the foundation for possible future study to measure the benefit of antioxidant therapy for dogs with PSS. The ultimate goal of this research would be to identify improved medical therapies for dogs whose shunts cannot be surgically corrected. Also known as a liver shunt, PSS is a congenital abnormality, seen in all breeds, in which blood from the stomach and intestines bypasses the liver and is carried directly into to the blood stream. Surgery is the treatment of choice, but some shunts are not surgically treatable. This project studied the levels of oxidative stress in the livers of ten dogs with PSS.