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By now,
regular readers of my website are aware of my obsession with feline
chronic renal failure (CRF). The majority of cats eventually fall
victim to this disorder; it is, in fact, the number 2 cause of death in
pet cats. There have been many advances in the treatment of renal
failure in cats over the past several years. Initially, our treatments
were directed at making affected cats more comfortable while the disease
inevitably progressed. More recently, we’ve discovered that by
restricting dietary protein and phosphorus, maintaining normal potassium
levels, and controlling high blood pressure, we may be able to slow the
progression of the disease. With the exception of a kidney transplant,
it is currently impossible to improve kidney function in cats with
chronic renal failure.
The
job of the kidneys is to filter the toxins out of the blood stream and
put them in the urine. If the kidneys are unable to do this properly,
the level of toxins in the blood stream will start to rise, and the
urine will become more dilute. At my cat hospital, I recommend that all
cats age 7 and older undergo a complete blood count, serum biochemistry
panel, and complete urinalysis to make certain that all body systems,
including the kidneys, are functioning properly. The earlier we can
detect a problem, the better chance we have successfully treating or
controlling it.
Blood
and urine tests are a simple, non-invasive way to evaluate kidney
function, however, there is a major disadvantage with these tests: they
don’t detect declining kidney function until the kidneys are
significantly compromised. The first sign that the kidneys may be
having a problem doing their job is the production of urine that is not
as concentrated as it should be. Unfortunately, in dogs, this happens
when about 66% of kidney function is compromised. Soon afterward, the
level of kidney toxins in the circulation begins to rise. This happens
in dogs when kidney function declines to a point where approximately 75%
of kidney function is compromised. Similar principles apply to the
cat. No one is exactly sure what triggers the onset of renal failure in
cats. Once the process begins, however, it only gets progressively
worse. Kidney infections, inflammation, trauma, genetic factors, immune
disorders, etc. have all been shown to play a potential role in
triggering the onset of renal failure, however, the inciting cause
usually goes undetected, and by the time we detect kidney dysfunction
(either because the cat is showing clinical signs of CRF, or through
routine geriatric blood and urine tests), the damage has been done. At
that point, even a kidney biopsy is unlikely to reveal the inciting
cause. All we see is the resultant damage and scarring. It would be
ideal if there were an accurate, convenient, and affordable way to
detect renal dysfunction at a much earlier point, as this would allow
earlier intervention and would significantly increase our ability to
alter renal disease progression.
The
kidneys are selective about what they filter out of the blood stream.
Albumin is an essential protein that the kidneys normally do not let
pass through the filter. When the kidneys aren’t working quite right,
however, small amounts of albumin escape through the filter and end up
in the urine. Microalbuminuria (small amounts of albumin in the urine)
has been shown to be an accurate predictor of impending renal disease in
people with high blood pressure and diabetes. Several years ago, a
number of studies suggested that detection of small levels of albumin in
canine urine is also an early indicator of renal failure. In light of
these findings, the Heska Corporation (Fort Collins, Colorado) developed
and released their Canine E.R.D. HealthScreen, a 5-minute in-hospital
test for the detection of microalbuminuria in dog urine.
Recent reports in reputable veterinary journals have clearly
demonstrated that dogs with kidney failure that are fed low-protein,
low-phosphorus prescription diets experience a slower progression of
their kidney disease and lived significantly longer than dogs not fed
these diets. An interesting finding in that study was that instituting
the diet in dogs that were only mildly affected, i.e. earlier in the
course of disease, was still beneficial. It stands to reason that if a
new test can detect kidney disease at an even earlier stage than the
commonly used tests, we might be able to look for and treat any
underlying infectious or inflammatory diseases that could be triggering
the kidney failure, and institute measures even earlier in the course of
the disease, significantly altering the path and progression of the
disease.
Fortunately, the E.R.D
Healthscreen Urine Test is available for cats as well. It’s a simple
test that requires a small amount of urine. The test is performed in
the clinic, with results available in less than 10 minutes. A positive
test (i.e. albumin in the urine) indicates that something is “bothering”
the kidneys, and a search should be performed to detect possible causes
for microalbuminuria. High blood pressure, dental disease, chronic skin
infections, and inflammatory bowel disease are a few common conditions
that could lead to kidney inflammation and microalbuminuria. If a
medical condition is identified, it should be treated, and the E.R.D.
test repeated four weeks later. A normal result four weeks later
suggests that the kidneys are no longer being irritated, presumably
delaying the onset of renal damage in the future. By detecting kidney
damage early and treating underlying causes if possible, we may be able
to reduce the long-term impact of kidney disease and give our pet cats
extra years of good quality life.
Updated
2/9/06 |
