My two ferrets were also diagnosed by a lab.  as this post had stated.
Specifically, they had G.I. biopsis done when the vet did surgery for
other reasons (one, insolinoma; the other, adrenal disease).  Labs came
back with high numbers that indicated, to the vet, various degrees of
inflammation in the gut, bowel, stomache.  So, they were being treated
with drugs that had in the past shown the potential for reducing these
numbers.  For one, Linus, it worked, as far as getting these numbers down
to close to normal.  He still has the issue of hepatitis, however.  For
the other, Zooey, the vet succeeded in reducing these numbers but not as
much.  Both ferrets had monthly lab tests for a year before Zooey died
and Linus reached stability.  His recent lab tests indicate whatever is
causing the inflammation in his g.i. tract is still being controlled.
 
Minta & ferrets
[Posted in FML issue 3888]