Katie,
Brutus had bilateral adrenal work in Jan 2000 and has no recurrence of
symptoms.  As is often the case, the vet was unable to get ALL of the right
gland, so there is some left and apparently enough to prevent problems.  I
believe Dr Williams on the Ferret Health List has posted about bilateral
adrenals many times (check the archives there), and, if I'm not mistaken,
at worst the ferret might need supplemental prednisone if both glands are
totally removed.
 
I hope this helps.
cb
[Posted in FML issue 3437]