Phosphates are included in liver values, but they are always elevated in puppies and kids for that matter...because they are growing. A low white blood count can be caused by many things...and since he's responding to the antibiotics...that may be the sole cause of off kiltered bloodwork. Shunts are not treated with antiboitics and could actually cause the condition to become worse since all medication is filtered through the liver.
Did he have any symptoms typical of a shunt? Head pressing, circling, seizures?
You may want to contact....
The Veterinary Surgical Referral Practice of Northern Virginia