Kidney stones/bladder stones/urinary tract stones/uroliths come in many
types. They have been mentioned without details in recent FML posts so
I figured this might help some people in time to save some ferrets, and
will copy the FHL.

The ones that Hilbert used to get and which Morney has gotten in the
past are cystine uroliths. Cystine stones have a few genetic causes
found in other animals but the specific genetic cause(s) in ferrets
has/have not been reported upon yet in a veterinary journal. These are
not the uroliths people most commonly read about, but are not terribly
rare in ferrets, either. For this type of urolith the person who is
feeding the ferret needs to reduce 4 of the amino acids (cystine,
ornithine, lysine, and arginine) so the best approach for them without
taking protein below safe levels is to reduce protein intake to about
35% of the diet. A very rare few need medications but careful dietary
management can be sufficient. This problem is typically found when a
susceptible individual goes onto a higher protein diet than his or her
kidneys can handle. With these stones the urine will be too acidic. In
these ferrets you want the urine pH to be higher than 5, preferably
about 6 which is ferret-normal for urine pH. Once stabilized these
ferrets need to have their urine pH monitored and to have periodic
bladder x-rays to check for any possible new stone formation though a
careful diet definitely can life- long and does perfectly from our
experience with long lives possible. The trick is surviving that first
crisis but that is incredibly difficult and sadly not always possible.

Many uroliths -- of ANY type -- in male ferrets wind up being fatal
right from the start. That is because many are not found until a ferret
completely blocks or develops hydronephrosis, and mostly because male
ferrets block much more easily than females and are harder to treat.
Surgery is often needed to correct the problem even though the ferret
is often compromised when the problem is discovered. Also, a more
extreme surgery, rerouting the urinary outflow can be needed at times
if the male has a blockage in the urethra and if repeated cystos
(removal of urine by needle) are not sufficient to let the sludge
dislodge and in the inflammation go down. The problem can be survived
if found in time, if luck is on everyone's side, and if the care at
hospital and home are very good. Loads and loads of fluids are needed
to get past the acute kidney damage, BTW. We have found that ferrets
who have needed that help for a long period tend to develop a life-long
habit of drinking more water than the rest which is good because it
keeps their kidneys healthier long-term so helps provide them with
longer lives despite their history.

The type of urolith (stone) usually read about is the struvite stone
and that is because too many places use low quality foods. With poor
quality food that have a high proportion of plant proteins the urine
becomes too alkaline (too basic) and then the components of struvite
precipitate out of the urine. Although having some plant matter in the
food will not cause the urine to get too alkaline, having too much will
so it is entirely a matter of degree -- of moderation. This is why any
ferret who is a rescue from a home or farm which used cheap food has a
decent chance of having such stones present. If you know that the
previous location was a very bad one it pays to use a urine pH strip
(You CAN use the very affordable ones for humans that show a range to
test the urine pH (which should be about 6 in ferrets and should not be
above 6.4 but also should not get too low for the reason mention in the
second paragraph. Note that 6 would be too low for a human.) If there
is a chance that sludge or a stone is present then x- ray the bladder
to be safest because the best scenario is catching a stone or sludge
before some dislodges and catches in urethra or before it can irritate
the bladder badly, or... Because there simply are places like "backyard
breeders" (not the same as "home breeders" or "private breeders"),
because some of the farms are bad, because some owners just don't care
enough, and because some other owners care but just don't know enough
this winds up being the type of urolith/stone which is most often heard
about. These are easily avoided. The ferrets who get struvite stones
tend to have urine pHs of 6.4 or above.

There was an excellent article on this in
<http://www.smallanimalchannel.com/ferrets/ferret-health/bladder-stones.aspx>
but that website is currently giving so many redirects that it can not
get through to the article which is a shame. I hope that this article
becomes available soon (and it may simply be glitch or maintenance that
will be done when you read this), and for public info on another kidney
problem I hope that a way to find the past Ferrets Magazine veterinary
article on raisins causing acute kidney failure also becomes apparent.

Calcium oxalate stones are also encountered in ferrets. As with humans
the possible best solution so far appears to be to restrict oxalate
sources in the diet. We all need calcium, ferrets included.

I do NOT know if there has been any work to find out if over-dosing of
Vitamin D in ferrets has a chance of playing a part in formation in
uroliths, nor do I know enough to know if it might even be a reasonable
scenario. At some point I have to find time to learn more on that
topic. We humans are very hard to over-dose for D and we usually don't
get enough of it. Ferrets, on the other hand, are like dogs in that
they develop hypercalcemia pretty easily from levels of D which are
lower (See recent FML digests or the FHL Archives for links on the VIN
investigation of one of the Blue Buffalo foods for this problem.) and
that can cause calcium deposits in organs. The kidney is one of the
most commonly affected organs and the heart is also often affected. I
don't know if any of these form in locations where they can dislodge
and pass through the urinary tract as a stone/ urolith.

There are other less common stones found in mammals but i do not know
how many of those have been found in ferrets; I've simply encountered
mentions of them elsewhere.

I think that I am forgetting another of the ones seen in ferrets but
sadly I failed to create my own pdf of Dr. Murray's excellent article
which was a mistake on my part for which I apologize because if I'd
done so I would be able to help others better as well as having the
reference for myself.

Sukie (not a vet)

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/
http://www.ferrethealth.msu.edu/
http://www.ferretcongress.org/
http://www.trifl.org/index.shtml
http://homepage.mac.com/sukie/sukiesferretlinks.html
all ferret topics:
http://listserv.ferretmailinglist.org/archives/ferret-search.html
"All hail the procrastinators for they shall rule the world tomorrow."
(2010, Steve Crandall)
On change for its own sake: "You can go really fast if you just jump
off the cliff." (2010, Steve Crandall)

[Posted in FML 6841]