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Page 1 of 3 CHRONIC RENAL INSUFFIENCY
The progressive
deterioration of your cat's kidneys, and what you can do. Sometimes
this problem is called "age-appropriate" in cats. That's because so
many older cats do have to deal with this progressive condition. The
age at which it can be considered appropriate is debatable - some
eighteen year old cats show no signs of kidney disease despite other
age-related problems, yet many twelve year old cats are already
diagnosed with "fading kidneys".
This is a syndrome. We can
demonstrate on blood and urine tests that the kidneys are no longer
functioning but in most cases, we cannot say WHY or what caused or is
causing the problem. The initial cause - a parasite, bacterial
infection, toxin exposure, or whatever event led to decreased blood
flow to the kidneys - may have happened a long time before the
diagnosis of CRI is made. There may not even be a cause, other than
"age" - that syndrome of genetically programmed cellular deterioration
that happens to all of us - and we all "age" differently. The rate at
which the kidneys fail varies significantly from cat to cat, and many
cats do live for years after the diagnosis is made. This
is a CHRONIC syndrome, that is, it takes time - months, years, to
develop and progress. It is important to differentiate this diagnosis
from ACUTE renal failure, pyelonephritis (kidney infection), and other
kidney problems that require an entirely different therapeutic approach.
There
are two kidneys. They have several very important functions for
sustaining life and so have what we call a large "reserve capacity" -
in other words, your cat can appear to be doing just fine on only .5 a
kidney, never mind the other 1.5 that stopped doing anything. (This is
why we can donate a kidney, provided the other is healthy). About 75%
of the kidneys are non-functional when blood and urine tests first
indicate there is a problem. That is why the earlier we pick up the
problem, the more helpful the lifestyle changes and treatments are
likely to be - there is more kidney to work with. Kidneys cannot
regenerate or regain function - lost kidneys are lost kidneys. All our
management and treatments are aimed at conserving the remaining kidney
function for as long as possible, and ensuring a comfortable life.
For
this article, I am going to discuss the failing kidneys function by
function - what the doctor looks for on the blood and urine tests, what
is happening to your cat, and what can be done about it.
1. Concentration urine, maintaining hydration
Kidneys conserve the body's water by making the urine much more
concentrated than the blood that is filtered. As they lose this
ability, your cat will produce more dilute urine. Your cat will feel
thirsty, drink more, and produce more urine. Eventually your cat cannot
drink enough to compensate for the body's loss of water, and becomes
dehydrated. Many cats hover on subclinical dehydration, which speeds up
the rate of kidney decline. More severe dehydration can be rapidly
fatal.
The veterinarian assesses "urine concentrating ability"
by checking Urine Specific Gravity. During the physical exam, the
veterinarian will assess oral mucus membranes, skin turgor, coat
quality and overall body condition to give a subjective grade of
dehydration. Dehydrated cats will show relatively increased
haematocrit, total serum proteins, serum creatinine on blood tests -
these values drop when the cat is rehydrated.
Early on, you
can encourage your cat to drink more water. Later on, this is not
enough, and we maintain hydration by treatment with subcutaneous fluids
- called SQ fluids - this is a balanced isotonic intravenous (IV)
electrolyte solution that can be injected under the skin. It is
absorbed over a few hours. This technique is easy to learn, most cats
tolerate and seem to appreciate the beneficial routine, and how often
it needs to be done depends on the cat. Many people learn to do this
treatment at home. If this is not possible at home, it does help to
have it done weekly or as often as possible at the vet's.
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