Vivian, these are called uroliths.

There are a very large number of types of such urinary stones/
crystals/sludge. Today our service provider is having trouble with
web access so I can't check for updates but the Louis Herring Lab
has a number of pages of photos of many types of stones. Try
http://www.herringlab.com/photos/29-56 to start and then you can
navigate from there. Like I said, though, I can't check to day to see
if the address has been updated.

In ferrets the most common type of urolith is struvite. In fact, there
is a ferret struvite stone among the pages of photos at Louis Herring
Lab. These happen when there is too much vegetable matter in the diet
for the ferret. The urine is alkaline. For those stones the diet has
to be changed to involve more animal matter, and a urine acidifier may
be needed. Usually, cheap food is involved.

Second most common urolith in ferrets is cystine stones.

Dr. Michelle Hawkins (Yes the same vet who has a team that is
studying genetic vulnerabilities in ferrets and their contribution
to endocrinological diseases like adrenal disease and insulinoma,
beginning with MEN, Multiple Endocrinological Neoplasia, genetics.)
began a team studying cystine stones in ferrets two or three years
ago after it was noticed that the rate of such stones in ferrets had
markedly increased as per the specimens sent to their urolith lab at
U.C. Davis.

Cystine stones are not tested for often enough. It is always important
to remember that not all ferret urolliths are struvite ones. Cystine
stones tend to involve some sort of genetic vulnerability. There are
several types of such vulnerabilities known in other mammals currently.
We personally have two ferrets who have had to have cystine stones
removed. Hilbert's situation was very complicated and he nearly died.
Mornie's was easier. With cystine stones the problems are with too much
of any of four amino acids (the building blocks of proteins); too much
of any of that "C.O.L.A. group" cause cystine to drop out and
crystalize. With cystine stones the OPPOSITE approach is needed
compared to struvite stones. The urine is too acidic, and the protein
levels need to be reduced. You can see why knowing WHICH stone type
can make all the difference for survival since the two most often seen
types need opposite approaches. Quite a number of people who have
encountered cystine stones in ferrets have noticed exactly what we have
among survivors; many do just fine as long as the protein levels in the
diet are not over 35% so those individuals need to be tackled in the
same way as ferrets with chronic kidney disease by giving a reduced
protein diet containing high quality protein, but they don't need the
phosphorous control that ferrets with chronic kidney disease need. For
a low number of ferrets who get cystine stones medication is needed; on
that score two vets can consult: Dr. Tom Kawasaki and Dr. Mike Dutton
since both have been very successful on that score.

Most ferrets do well on higher protein, but it is essential to know
that there are exceptions and that those individuals are being noticed
more now.

On a very rare basis (maybe 2 or 3 times so far in 6 years) there have
been reports of far less common urolith types sent to the FHL.

So, when uroliths are present always test for the stone TYPE and always
check the urine pH.

It also pays to monitor urine pH at home for a while afterwards, and
if a PU is needed but no one locally has experience doing those in
ferrets then (Pulling from my email copy of my links list.):
http://www.petcarevabeach.com/ferretservices.html Pet Care Veterinary
Hospital: multiple ferret health articles including Urethrostomy and
Penile Amputation to Treat Urethral Obstruction

Finally, one trick that can sometimes prevent the need for a PU once
the cause of the stones has been determined and it is sure no new
sludge or crystals are being created is to leave the ferret in the
hospital and have the health professionals there repeatedly do cystos
(emptying the bladder by needle) until the urethra has time to go down
again. That sounds awful but our ferret who was saved by them (Hilbert)
adores our vet so it can't be as bad as the pain he had without them.

   ------

[A later P.S.]:

We just got back web access

Go here for the photos:

http://www.herringlab.com/

and then just click on the kidney stone photographs link. There are
currently 84 photos of varied types and then some other pages of
specific types. The ferret struvite stone is on the first page. I
don't think that they have any of the other types of stones found
in ferrets pictured.

  ------

Sukie (not a vet)
Current FHL address:
http://groups.yahoo.com/group/ferrethealth
Recommended ferret health links:
http://pets.groups.yahoo.com/group/ferrethealth/
http://ferrethealth.org/archive/
http://www.afip.org/ferrets/index.html
http://www.miamiferret.org/fhc/
http://www.ferretcongress.org/
http://www.trifl.org/index.shtml
http://homepage.mac.com/sukie/sukiesferretlinks.html

[Posted in FML 5600]