The creatinine level is less likely to be affected by
factors other than kidney disease but is slower to rise when kidney disease
is present. Knowing this, it is sometimes possible to evaluate whether
a rise in BUN is due to a non-kidney related cause or whether kidney damage
is acute rather than chronic. In addition, the creatinine levels may be
a slightly better way to monitor the kidney’s response to treatment over
the long term than BUN levels. When both the BUN and the creatinine are
elevated it is highly likely that actual kidney disease is present and
that further diagnostic efforts should be directed at finding the cause
of kidney disease rather than trying to establish whether or not it is
present.
Potassium levels usually fall with chronic kidney disease
but may rise with extremely acute kidney failure in which urine production
is decreased, such as ethylene glycol (antifreeze) poisoning. In cats,
the potassium level may fall prior to any other indication that chronic
kidney damage is occurring. It is unclear whether this fall in potassium
is harmful in some way to the kidneys and leads to further kidney failure
or whether it is just an early warning sign of damage to come. Most vets
agree that potassium should be supplemented when serum potassium levels
drop below 3.5 mEq/L, especially in cats.
Phosphorous levels in the serum are another indirect way
to measure kidney function. Rises in phosphorous levels occur as kidney
function deteriorates. Measuring phosphorous levels can help in making
decisions about control of dietary phosphorous intake and are particular
important when calcitriol therapy is being used to help in the treatment
of chronic renal failure.
There are many more specialized tests that are used to
aid in the diagnosis and management of renal disease in pets. Creatinine
clearance is a test in which the total amount of creatinine in the urine
(collected over a 24 hour period) is compared to serum creatinine level
taken during the same time period. This test is a good way to monitor response
to therapy and to figure out if kidney disease is present when there is
some indication that it is but the BUN and creatinine levels are not high
enough to be sure. Biopsy of the kidneys is often the only way to accurately
determine the cause of kidney disease. While this can be important in some
cases in managing long term kidney diseases such as amyloidosis or glomerulonephritis
there are risks involved and they must be carefully weighed prior to making
a decision to biopsy. Ultrasound exam of the kidneys can be very useful,
especially in helping to determine if conditions such as polycystic kidney
disease are present. X-rays of the kidneys can be valuable as well, helping
to evaluate the size of the kidneys, presence of kidney stones and when
combined with dye techniques to evaluate kidney function. Serologic information
may be necessary to rule out causes of kidney disease such as leptospirosis,
feline leukemia virus infection or other diseases. Sometimes it is necessary
to test for other organ system or hormonal disease, such as hypoadrenocorticism,
hypertension (high blood pressure) or liver failure, all of which can influence
the results of laboratory tests that are used to evaluate the possibility
of kidney damage.
The major fault in veterinary medicine in evaluation of
kidney disease and in monitoring progression of treatment is a lack of
aggressiveness in collecting laboratory data. This is understandable, since
lab tests can add significant costs over and above already expensive treatments.
This is true of both acute kidney disease and chronic kidney disease conditions.
In the acute disease situations having good information on the status of
the kidneys may be the difference between life and death. In chronic conditions,
especially in cats, monitoring kidney related lab values on a periodic
basis may be the difference between a life span of several comfortable
years managing the kidney disease or discomfort and a shortened life span
for the patient. When kidney disease is suspected or after it has been
confirmed, periodic lab tests are necessary to manage the kidney failure
effectively. Successful management of kidney disease is best accomplished
when an informed client works closely with their veterinarian to provide
all the information and care necessary to keep a pet comfortable.
Why Does My Cat Throw Up So Often?
One of the more difficult problems in veterinary medicine
is discerning the significance and cause of occasional vomiting in cats.
At the beginning and end of almost every examination in my office I try
to ask the question, "Is there anything else that is bothering you about
your pet’s health?" I have never stopped to add up the frequency of particular
complaints but it wouldn’t surprise me if 25% or more of my clients report
that their cat throws up sometimes. Most clients do not seem to be particularly
worried about this behavior and don’t complain about it until I ask them
if there are additional problems they wish to discuss. Clients who own
Persian rugs and light colored carpet are a little more likely to volunteer
the information on their own but even then they seem to accept it as a
normal problem associated with owning cats. So when is vomiting important
and why do cats vomit so readily?
Cats do not appear to be particularly upset by the process
of vomiting. Dogs tend to make a much bigger production out of vomiting
and often seem to be uncomfortable before or afterwards. Cats usually just
stop a moment, vomit, and move on. I think that the fact that vomiting
is easy for them makes it a more common event. The ease with which they
vomit doesn’t mean it is always unimportant, though.
Many of my clients seem to think that most vomiting relates
to "hair balls". It is undeniable that cats often vomit up hair but I truly
believe that in most cases the hair is just incidental to the vomiting
and not the cause or that it may be triggering a vomiting response but
indicative of another problem, such as skin disease. In many instances
treating for skin disease when it is present or treating for other underlying
causes of vomiting such as inflammatory bowel disease will stop hairball
related vomiting entirely, or at least reduce the incidence of it markedly.
I have several clients whose cats have allergies who use vomiting as the
gauge for when it is necessary to begin treatment for the allergy again.
Their cats are fine during the seasons that the allergies do not affect
them and they begin to vomit before they have obvious hair loss associated
with their allergies. Some of these cats respond to treatment with antihistamines,
which normally don’t help a lot with inflammatory bowel disease conditions,
so I am pretty sure that allergies are at least partially responsible for
the vomiting.
We recommend treating for vomiting when the vomiting begins
suddenly and occurs more than once or twice on the first day or when a
cat is losing weight, when vomiting is occurring more than once (or perhaps
twice) a week on a chronic basis and when the vomiting does seem to be
uncomfortable for the cat. We recommend trying to discern the cause of
the vomiting and treating for that particular condition whenever possible.
In kittens and young cats, vomiting may be related to
food sensitivities, intestinal parasites, heartworm disease, systemic illnesses
(liver or kidney failure, etc.), gastroenteritis and intestinal obstruction.
It is reasonable to test for intestinal parasites or to deworm prophylactically
in kittens.
In middle aged cats vomiting is more likely to be due
to inflammatory bowel disorders or to be related to underlying causes such
as allergies or persistent skin disease problems. Intestinal lymphoma,
a form of cancer, affects some middle aged cats and can cause chronic vomiting
for several months or longer prior to becoming life threatening. Some causes
of vomiting, such as gastroenteritis, systemic illnesses and parasite infections
are still potential problems in middle aged cats, as well. There is an
interesting illness that occurs in correlation with migrations of small
birds in which cats in the areas the birds are passing through develop
vomiting from "songbird sickness", which is actually a form of salmonella
infection. Presumably this happens because they are able to catch and eat
some of the birds during the migrations. When overweight cats stop eating
for any reason they are susceptible to a liver disease, called hepatic
lipidosis, caused by increased fat metabolism. This is an occasional cause
of unexplained vomiting in cats, as well.
In older cats, kidney failure, hyperthyroidism and inflammatory
bowel disease are much more common than other causes of vomiting, even
though most of the things that affect young or middle aged cats can occasionally
affect an older cat, too. Chronic vomiting in an older cat that is accompanied
by any weight loss should prompt an examination that includes lab testing
for kidney problems and hyperthyroidism.
Should vomiting always be treated? That is a hard question
to answer. We frequently advocate an examination for skin disease and other
possible primary causes of vomiting. It is reasonable to check for parasites
and to deworm as necessary. Once it is clear that there is not an easily
treated condition causing the vomiting it is much harder to decide how
to proceed. It is difficult to establish a diagnosis of inflammatory bowel
disease and to rule out problems like lymphoma. The only really good way
to test for these conditions is to consider intestinal biopsy, either endoscopically
or through exploratory surgery. Since these are invasive procedures that
involve anesthesia it is best to consider the overall health of the cat
in the decision about whether or not to attempt to make a specific diagnosis.
If the cat is not losing weight and otherwise is doing well I think it
is reasonable to treat for inflammatory bowel disease and to consider further
diagnostic testing if there is not a reasonable response to treatment.
However, we often try using a single antigen diet to rule out food sensitivities
and the addition of fiber to the diet since that seems to help in a few
cases since these are relatively easy things to do in many instances and
are not likely to cause harm. Many of our clients simply opt to live with
the vomiting and wait to see what happens. In most cases, the vomiting
continues but does not get worse. The cats appear to do well in most instances
but occasionally this course of action works out badly for the cat due
to important underlying causes that are missed because we didn’t look for
them. Chronic vomiting is one of those disorders for which the client must
determine how concerned they are by the overall behavior and condition
of their cat and make a conscious decision about whether or not to pursue
diagnosis and treatment. Your vet can help in the evaluation of your cat’s
overall health and in determining the necessity of lab testing to rule
out possible causes.
Frozen Waters
My children really like the story in "Fried Green Tomatoes"
in which a group of ducks fly away with a lake after it freezes suddenly
while they are swimming in it. Even though they are now teen-agers they
still ask me once in a while if I think that could ever really happen.
While I think it is unlikely, I have had several experiences with pets
and animals who managed to get frozen in ice. The case that makes my kids
almost believe in the duck story occurred when my oldest daughter was about
5 or 6 years old. Shortly after dark one evening in February, the phone
rang at the house. My wife answered it and I could hear her side of the
conversation.
"Well, I wouldn’t get too close to it. You know they can
be pretty dangerous," she was telling someone. "Yes, I know its a problem,
but you have to be careful, " she said, followed by "I’ll ask him if he’s
willing to come out and help but I can’t promise he will." By now, I was
pretty curious and trying to get her to hand me the phone. "I’ll explain
the situation to him and have him call you back." This is my wife’s way
of getting a few minutes to talk me out of something she doesn’t want me
to do. She told me that the caller was concerned about a great blue heron
that seemed to be trapped in the ice on a frozen creek. It isn’t all that
common for the brackish water in the marshy creeks along the Chesapeake
Bay in our region to freeze and it is less common for them to freeze hard
enough to walk on them. She didn’t like the idea of trying to rescue a
heron, with its sharp and dangerous beak while walking on thin ice. Of
course she was right, but I am not always adverse to risk taking so I got
the directions from her and headed out into the night. "Please call them
back and tell them I’m coming," I said, as I left.
My veterinary truck had a really bright spotlight that
plugged into the cigarette lighter. As I approached the area the heron
was supposed to be, I started to use the spotlight to find it. Almost immediately
I could see a group of people on each bank of a creek that was about 20
feet wide and a heron, standing, but obviously frozen into the ice. As
the light hit it, the bird flapped its wings but didn’t go anywhere. I
pulled off the road alongside the creek and parked near the bird.
In our area, just falling through the ice isn’t the biggest
risk. Often, the water depth is only a foot or two but underneath of that
there will be five or six feet of really soft mud. It mires legs so quickly
that movement is sometimes nearly impossible. Lots more people have to
be rescued from the mud in our area than have to rescued for falling through
ice. Someone had already put a ladder out on the ice and it was holding
that much weight. I asked if anyone had tried going out for the bird but
there was general agreement that this was a situation that called for "an
expert". I am pretty sure that word is used in place of "idiot" in some
instances. I tied my lariat around my waist, gave the other end to the
biggest spectator and laid down on the ladder. As I made my way toward
the heron I was mentally reviewing all I knew about herons, including reports
of one-eyed wildlife biologists and veterinarians who have had close encounters
with herons and cranes. I decided that I was going to have to risk at least
kneeling on the ice to get ahold of its head first.
Surprisingly, grabbing the heron went really well. I grabbed
its neck just below its head in one quick movement and the heron didn’t
resist at all. But then, the ice broke all around us and I was instantly
immersed in the cold water and mud. Almost as quickly the crowd at the
other end of the rope started a rapid and vigorous attempt to pull me out,
resulting in me being propelled toward the shore on my back with the bird
on my chest. Fortunately, my head stayed above water the whole way. But
I was really cold now. I said a quick good-bye to the crowd, assured them
that I would bring the heron back there when it was well, and left.
It is hard to drive a car in the winter when you are soaking
wet. The windows fog up so thickly that the defroster just can’t handle
it. So I drove the four or five miles home with my head out the driver
side window, one hand on the wheel and one hand holding the heron down
between the front seats by its neck. It didn’t struggle the whole way.
My house and my clinic were on the same property at that
time. I went to my house first, carrying the heron. It had not struggled
at all the entire trip. I felt like it must have been caught for some time
and felt comfortable setting it down on the couch while I went to change
clothes. I think that would have been an OK decision if my cat hadn’t taken
a sudden interest in the bird, jumping up on the arm of the couch right
next to it. Startled, the heron started running around my house full speed,
flapping its wings and getting airborne at times for short periods. My
wife and I were chasing it and telling the kids to stay in their rooms
and gathering up the three dogs who had now joined in the chase all at
the same time. We caught the heron pretty quickly but not before it had
deposited a couple of large smelly reminders of its presence.
I took the heron out to the clinic and checked it over
carefully. It was thin and needed to be fed and rehydrated but it seemed
to be otherwise unaffected by its adventure. It was apparent that it could
not fly but we could not find any particular reason why not. We fed it
for several days and took it back to the creek which had warmed up enough
to be free of ice by then. I asked the neighbors if they knew it couldn’t
fly.
"We’ve been feeding it for several years, Doc. It never
leaves during the winter but it has done OK as long as we fed it." They
insisted it could fly. I guess it could, technically, but it couldn’t go
more than 20 or 30 feet at a time. It seemed reasonable to leave it there
where they were used to taking care of it.
For several years after that, I would always look for
the heron as I drove past the creek. He was there for a long time before
disappearing one day for good. I do not know if he finally decided to fly
or if something happened to him. It surprised me that he would adapt to
living on handouts in the winter time but it probably shouldn’t have. I
wouldn’t have been surprised if he had been a seagull!
As always, we sincerely appreciate your support
of the VetInfo Digest and the VetInfo Web Site. It is much easier to provide
these services with your help.
Thanks!
Copyright, TierCom, Inc., 1998
Tiercom, Inc.
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The opinions expressed in this newsletter are solely those of
the author, Michael Richards, DVM, unless otherwise noted in the text.
Michal Justis is our web designer and graphic artist.
This page was last edited 06/15/04
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