We first decided to get Miko tested when he was urinating blood and the vet told us that it wasn't a UTI...I had read that might be a symptom of LS, so we made an appt. to have him bile acid tested...The weekend before his appt. he had a bad seizure and we rushed him to the vet. They ran bloodwork and tests and later they did a bile acid test and found that he very likely had LS...We went to another vet that was very highly recommended and he did an ultrasound, but he couldn't pinpoint ONE shunt,so he said he could do further testing or go in for exploratory surgery...Miko's bile acid tests and liver enymes came back very high, so we opted for the surgery also. Like I said before, his liver shunt is intrahepatic and inoperable, so he was put on medicine and special diet.
You can have your vet do an ultrasound to see if he can find the shunt that way...
The following link will give you info on how to diagnose liver shunt, ie. radiography, ultrasound, etc.
http://www.malteseonly.com/shunt.html
This next link gives you a wealth of information on liver shunts...All this information is very important for you to know if your baby has a liver shunt.
http://www.malteseonly.com/shunt2.html