Am going through a similar thing with my 15 month old GSD. It is a long, tedious process with steps to be taken. I am at the stage where we are on the pancrezyme to be used at each feeding. He's taking 2 (crushed) tablets per feeding which I am feeding him 3 times per day. I was told to leave it for 10 to 15 minutes so it can set in and adhere to the food.
Prior to that I had a TLI Test that came back normal for EPI but neverhteless can be misdiagnosed. He did come back with a high count in Folate suggesting that there was an overgrowth of bacteria. We also did fecal lab test for Giardia twice and came back negative. Presently I have made another appt. to get full blood work and urinalysis done to rule out any other possible issue.
Meantime they have put him on prescription ID both bland and kibble to mix in the pancrezyme (two tablets each meal, which I crush into powder) and here we are. One of my vets told me that if he's doing fine with the ID then it's best to leave him on it. So far, in the past week he has picked up 2.7 lbs. He is not by any means emancipated but just ribby. He looks a lot better in just one week on the pancrezyme and I'm praying that this will be the cure.
The reason why I suspected it was EPI is because he eats voraciously and was losing weight accompanied by sometimes diarrea and soft stools. Those were my GSD's symptoms. He was on two different antibiotics; metrozindole (can't spell it) which helped for a couple of days but then he relapsed. 2nd antiobiotic was amoxicillin which didn't completely get rid of it but helped a lot. It seemed like the antibiotics would work for 2 days and then they would stop working. weird....
I am seeing 2 different vets to get different perspectives. I too, did extensive research about EPI, SIBO you name it! I just hope this pancrezyme works and helps him lead a happy, normal life.
He acts and behaves super normal the only difference I could see was the voracious eating and losing weight.
I would so appreciate it if you could post your results and what happens and I will too as soon as we do the blood tests. EPI apparently is prevelent in German Shepherds and young ones at that. And that it can be misdiagnosed. So, the more info we are armed with the better off we are.
Good luck to you and your doggie and let me know what happens and I will do likewise.