Cross-posted from the Ferret Health List...
 
 --- In Ferret-Health-list, katharine <shurcool@t...> wrote:
>Am taking a chance that someone can offer advice.  Champ (will be 4 y.o.
>in May) recently had right adrenal surgery, had a UT infection within 3-4
>days, and is now in renal failure.
>
>...Any suggestions, assistance, clues?  I really don't understand this
>renal failure stuff.  Apparently the type he has is not the common type
>that ferrets normally have (of course).  I guess I'm trying to find out
>if anyone has any other suggestions for him.
 
Dear Katharine:
 
While I'm afraid that I don't have any useful suggestions regarding
the treatment of chronic renal failure in ferrets save for the protein
restricted diet which you are currently pursuing, perhaps I may be able
to shed some light on chronic renal failure that may explain why treatment
is so difficult.
 
The kidney, like several other tissues in the body (such as heart and
brain) does not have a good ability to regenerate following injury.  Once
kidney tissue wears out following aging or injury, it is replaced by scar
tissue, not by new kidney tissue.  So it is essentially a non-renewable
resorce.  There are some exceptions, which are lumped together in a
syndrome called acute renal failure - this is usually the result of
one-time antibiotic administration or short term hypoxia, as might be
seen in shock.
 
Chronic renal failure occurs when the functional kidney mass falls below
25%.  Recent investigations suggests that the kidneys may be able to work
adequately and not fail in some conditions when up to 90% of the kidney
is lost.  When kidneys fail, two things occur - they lose the ability to
concentrate urine, so urine is generally dilute (and the animal tends to
urinate frequently and in large amounts) and it cannot excrete the normal
substances which the kidney is responsible for removing from the body.
 
Diagnosis of chronic renal failure is based on the combination of measuring
the concentration of the urine and measuring the concentration of several
compounds in the blood (in most cases, BUN, creatinine, and occasionally
phosphorus.) Failing kidneys don't excrete them properly, so they build up
in higher than normal levels.  So we look at bloodwork and a urinalysis.
If the urine is dilute and remains dilute even in the face of dehydration,
and the leve of the BUN and creatinine is significantly elevated (mild BUN
elevations may be seen in dehydration in animals with normal kidneys), a
diagnosis of chronic renal failure is given.  Some practitioners may
diagnose chornic renal failure based on bloodwork alone, which may lead
to a small number of errant diagnoses, as other conditions may cause
elevations of the compounds mentioned above.
 
As you haven't mentioned the tests that were done or the levels that
indicated chronic renal failure, I can't comment specifically on this case.
 
Unfortunately, as the kidney has limited regenerative capability, when
chronic renal failure occurs, a cure is not possible - there is nothing
left but scar tissue.  The kidneys become small, contracted, and hard.
As another function of the kidney is to elaborate a hormone called
erythropoetin, which stimulates bone marrow production of red blood cells,
another potentially life-threatening complication of chronic renal failure.
 
It has been shown that naimals on protein-restricted diets tend to have
better renal function over their lifetime than those with higher levels of
protein.  While the benefits of a restricted protein diet have not truly
been established in animals with chronic renal failure, the theory that
protein restriction may prolong remaining function in failing kidneys,
coupled with the fact that there is little else that we can truly do to
treat this condition, has made protein-restricted diet a primary mode of
therapy in the treatment of CRF in domestic animals.
 
With kindest regards,
Bruce Williams, DVM
[Posted in FML issue 3339]