Mark,
 
By far the most common cause of a swollen vulva in a female spayed ferret is
an adrenal tumor.   I have seen many ferrets this age and younger with
adrenal tumors.  It is also possible, though unlikely, that there could be
retained ovarian tissue present from an incomplete spay.  Ultrasound usually
does not give a definitive answer and is expensive.  The treatment of choice
is exploratory surgery.  No matter what the cause is, and even if the
ultrasound gives a diagnosis, the only treatment for either of these
conditions is surgery.  It is important to have a vet experienced in ferret
surgery do the exploratory (an unexperienced surgeon may not know the size of
a normal adrenal gland).
 
In a case like this exploratory surgery is highly recommended.   It is much
more likely that this ferret has an adrenal tumor;  however, if there is
ovarian tissue present, it should be removed ASAP or the ferret may develop
life-threatening bone marrow suppression.
 
Good Luck,
 
Dr. Weiss
301-299-4142
[Posted in FML issue 1288]