Those are great numbers! Dogs who test that far under 100 have MVD, not a Liver Shunt. Just get him on a low protein diet, and as long as he has no symptoms, he can live a long , happy life. No further testing is needed, unless you feel the need to pursue a definite diagnosis, many owners choose not to put their pups through the additional testing. There are many MVD pups and owners on YT that manage this problem through low protein diet alone (18-22% protein).
This site explains it better:
Portosystemic Shunts FAQ
From the U of Tenn:
Do all dogs with high bile acids have shunts?
Bile acids can be increased with any liver disease. Bile acids can also be mildly increased in normal dogs, particularly in some breeds (such as Maltese) where chemicals in their blood interfere with the test. Most dogs with liver shunts have fed bile acids over 100 (normal <15-20). If the bile acids are only mildly increased or the animal seems normal, many veterinarians will simply rerun the test in 3-4 weeks.