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Kidney Disease in
Dogs
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Kidney Disease in Dogs
Kidney Failure in the Dog and Cat
Chronic Renal Failure
Kidney Failure-Where to begin
Kidney
Disease in Dogs
Harvey Carruthers
www.shootingtimes.co.uk
Chronic kidney
disease is seen in dogs of all ages and breeds. The occurrence of
chronic kidney disease increases with age and dogs tend to be around seven
years old when diagnosed. The term "cronic" means that these dogs suffer
a deteriorating kidney function over months or years, rather than acute onset
disease. Some inherited kidney conditions have been reported in golden
retrievers and cockers, among other breeds.
Dogs may not show symptoms until 75 percent of the kidneys are damaged.
Once damaged, these vital organs cannot remove toxins from the blood
or conserve body water. As a result, dogs urinate large volumes, sometimes
in the home. This is accompanied by greatly increased water intake.
The gut may be damaged by the toxins, and diarrhoea and vomiting result.
Protein is also lost in the urine, leading to weight loss.
Damaged kidney cells are irreplaceable. Treatment tries to stop
further damage by improving kidney function and treating the underlying disease.
Blood pressure may be regulated and vitamins and hormones given to
improve appetite and muscle mass. Diet is an important part of the
treatment. Commercial and home made recipes aim to lower salt content
and regulate protein levels, but ultimately it depends on what the dog will
eat.
Some dogs survive for years. The outlook depends on how aggressive
the underlying disease is and how much healthy kidney remains following
long term disease. Dogs in the end stages of chronic kidney damage
may have other illnesses, the treatment of which may be complicated by the
weakened kidneys. These dogs are able to sustain much lower levels
of activity and the final stage of kidney failure comes abruptly.
reprinted with kind permission from Alastair Balmain
Deputy Editor:Shooting Times
& Country Magazine
Blue Fin Building, 110 Southwark Street SE1 0SU
Tel: 020 3148 4750
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KIDNEY FAILURE IN THE DOG AND CAT
http://www.thepetcenter.com
Kidney failure... kidney
disease in the dog and cat is a common and difficult disorder to manage.
Often called CRF... Chronic Renal Failure, it is seen most often in the
older dog or cat. Kidney failure has it origins in a wide variety of
causes. For example, some animals are born with poorly constructed
or functioning kidneys and never reach totally optimum health.
Eventually, these individuals usually fall into kidney failure at an early
age. Another type of kidney failure can occur after accidental ingestion
of antifreeze that contains ethylene glycol. These situations cause
sudden and often irreversible renal (kidney) failure. Quite commonly, kidney
failure results from low grade, long term (chronic) inflammation of kidney
tissues called chronic nephritis; the damage caused by this inflammation
renders permanent damage to delicate renal tissues that are not able to
repair themselves or heal as some other body tissues do. Eventually,
not enough normal functioning tissue remains to support the body's need
for metabolic regulation and waste elimination. The dog or cat becomes
UREMIC, a condition where body waste material builds up in the blood. These
toxins promote vomiting, poor appetite, depression, and eventually death.
Bacterial invasion of the kidneys is a common cause of chronic nephritis
and kidney failure.
Quick
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NORMAL
KIDNEY PHYSIOLOGY
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CAUSES OF KIDNEY FAILURE
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DIAGNOSIS OF KIDNEY FAILURE
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TREATMENT OF KIDNEY FAILURE
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The nephron is the
structural and functional unit in the kidney. A nephron consists of
a glomerulus in a capsule, proximal convoluted tubule, loop of Henle,
and distal convoluted tubule which leads to a collecting duct.
The collecting duct empties into the renal pelvis.
Normal kidney function involves the following responsibilities,
among others:
1.) Regulating the amount of fluid in the spaces
surrounding the body's cell. This is called extracellular fluid
volume regulation.
2.) Regulating the amounts and types of solids in
the blood in order to keep blood concentration within normal limits.
This is called blood osmotic pressure regulation.
3.) Regulating the acid-base balance of the animal
through retention or elimination of specific ions in the blood.
Common important ions
affecting the acid-base balance of dogs and cats are bicarbonate, sodium,
ammonium, potassium and hydroxyl ions. This function keeps the pH
(amount of acidity) of the blood and body fluids within strict normal ranges.
4.) Removing metabolic waste products such as uric
acid and also molecular foreign substances detoxified by liver.
5.) Reacting to Aldosterone (ADH) produced in the
adrenal glands. The major target of aldosterone is the distal tubule
of the kidney, where it stimulates exchange of sodium and potassium and
the reabsorption of water back into the blood.
6.) Production (Erythropoetin), a chemical effecting
red blood cell production.
The kidneys receive
about 20 percent of the heart's blood output and play a vital role
in keeping the dog or cat in normal metabolic balance. The glomerular
blood vessels have a large endothelial surface which allows for the active
and passive transport of many chemicals into and out of the kidneys.
KIDNEY STRUCTURE
The functional unit
of the kidney... the real mechanism whereby the kidney does most of its
prescribed tasks, is called the NEPHRON. The nephron is a delicate,
structurally complicated, microscopically small collection of tiny tubes,
capillary beds that have distinct and different blood pressure settings
at two locations along the tubes, and cell membranes that have precise
tasks to perform.
Glomerulus... is a ball of capillaries with a large surface
area at which multiple interchanges of fluids and dissolved elements
occurs.
Bowman’s Capsule... is the proximal end of a tubule that
surrounds glomerulus.
Proximal convoluted tubule... leads to what is called
the Loop of Henle that is situated in the medullary area of the kidney.
There is an ascending limb and a descending limb, each of which has particular
and unique functions.
Distal convoluted tubule... leads into collecting ducts.
Pelvis... is an enlargement at the distal end of the collecting
ducts that provides a common area of urine collection before the urine
passes down the ureter into the bladder.
CORTEX
The glomeruli are found
in the outer area of the kidney called the cortex. Each glomerulus is
surrounded by a "Bowman's
Capsule". Most of the fluid that passes into the Loop
of Henle in the cortex is reabsorbed in the medulla back into the blood.
MEDULLA
The medullary area
of the kidney is fed by tiny arterioles. Any damage to glomeruli
affecting efferent arteriolar blood flow will also cause damage in the
tubules located in the medulla. Anything that adversely impacts the blood
flow through the medulla can have serious consequences for the tubular
structures. The medulla is slightly less vascular than the cortex.
The renal tubules that make up most of the medullary tissue have high metabolic
rates and therefore high nutritional requirements. Tubules
are responsible for water loss and conservation. Filtered water
containing waste products (urine) are passed into the renal pelvis and
then on into the ureter. In addition to waste management the renal
medulla assists in regulation of blood pressure, the elimination of toxins
and the production of hormones such as erythropoietin.
PELVIS
The renal pelvis collects
the kidney filtrate and funnels the urine fluid into the ureter that
leads to the bladder. The pelvic area of the kidney often is the
site of kidney stones and can be a reservoir of infection once microorganisms
reach this area of the kidney.
CAUSES OF KIDNEY FAILURE
A partial list of causes of kidney failure include:
DIETARY CONSIDERATIONS
Contrary to popular
myth, diets rich in protein ("high protein diets") do not cause kidney
damage. Research done decades ago indicated that rodents were adversely
affected by diets high in protein and misguided researchers extrapolated
that data to apply to the canine. Read more under TREATMENT below
or go to an article about protein in pet diets.
HEREDITARY AND CONGENITAL ABNORMALITIES:
These types of kidney
disease are very frustrating to try to control of repair. Most
dogs and cats with abnormally constructed kidneys will develop kidney failure
and do not live anywhere near a normal life span. Ultrasound
evaluation, clinical tests and contrast x-rays (Urography) are needed
to make a correct diagnosis of the type of Inherited/Congenital disorder
that may be present.
Polycystic kidney disease (PKD) is not very common and creates
cystic areas in the kidneys where normal function and structure are
lost. Eventually, even if the dog or cat reaches maturity, gradual
increases in metabolic waste products and signs of kidney disease prevent
optimum quality of life and the animal dies or is mercifully euthanized.
Polycystic Kidney Disease is an inherited kidney disease that has been
found in Persian/Exotic cats. In dogs, Bull Terriers may be affected
more commonly than other breeds
Familial glomerulonephritis in the Bernese mountain dog.
Hereditary nephritis in the Bull Terrier.
Renal agenesis, also called kidney aplasia, occasionally occurs
and the individual is born with one or both kidneys not present.
Dogs, cats and humans can survive quite well if one normal kidney is
present and functioning.
Renal hypoplasia is a condition where the kidney(s) do not develop
completely. This is seen in German Shepherds and other breeds.
Renal cortical hypoplasia is a condition where the cortex of
the kidney(s) develops incompletely.
Renal dysplasia is a condition where the kidneys develop abnormally.
Renal failure develops with protein loss in urine.
Renal tubular dysfunction occurs when the filtering tubules of
the kidneys do not function properly. In Basenjis, glycosuria develops
and is called Fanconi syndrome.amilial glomerulonephritis in the Bernese
mountain dog.
Hereditary nephritis in the Bull Terrier.
Renal agenesis, also called kidney aplasia, occasionally occurs
and the individual is born with one or both kidneys not present.
Dogs, cats and humans can survive quite well if one normal kidney is
present and functioning.
Renal hypoplasia is a condition where the kidney(s) do not develop
completely. This is seen in German Shepherds and other breeds.
Renal cortical hypoplasia is a condition where the cortex of
the kidney(s) develops incompletely.
Renal dysplasia is a condition where the kidneys develop abnormally.
Renal failure develops with protein loss in urine.
Renal tubular dysfunction occurs when the filtering tubules of
the kidneys do not function properly. In Basenjis, glycosuria develops
and is called Fanconi syndrome.
BACTERIAL INVASION:
Infections of the urinary
tract of dogs and cats are, unfortunately, very common. 
Generally arising from gradual spread of external bacterial organisms near the
external urinary orifices, the bacteria multiply and invade the urethra,
then into the bladder (causing what is termed CYSTITIS), and occasionally
further retrograde up the ureters and eventually into the kidneys.
Another less common means of kidney infection arises from a blood
borne dispersion of bacteria from a remote area such as an abscess or
skin infection. Leptospirosis bacteria can have a severe effect
on canine kidneys. The bite of a tick carrying the bacteria Borrelia
burgdorferi which causes Lyme Disease
is a good example of this kind of bacterial dispersion to the kidneys.
In these situations, delicate membranes of the kidney tissue can be adversely...
and permanently... damaged to the point that filtration of body waste
products and transport of those waste products into the urine cannot be
accomplished. Even after eliminating the bacteria with antibiotic
therapy there may remain permanent structural damage to vital renal tissues...
and kidney failure ensues.
FUNGAL INFECTIONS:
Systemic fungal infections such
as Blastomycosis, Coccidioidomycosis
(Valley Fever), and Histoplasmosis
can attack nearly any tissue or organ in the body. Systemic fungal
infections are notoriously tricky to diagnose and treatment can be a
challenge. Permanent damage to renal tissues can be a sequel to
any systemic fungal infection. Most systemic fungal diseases are
rather geographically oriented.
TRAUMA TO KIDNEY TISSUES:
Direct trauma to the
kidneys can result in kidney failure. Although rare, dogs and
cats that are run over by vehicles can suffer permanent and irreparable
kidney trauma. Also, sudden physical shock to the kidney tissues
from being struck by vehicles, baseball bats, kicking, or falls from a
height, etc. can result in suffusive bleeding into the kidney tissue and
permanently impair renal function.
BLOCKAGE OF URINE FLOW:
The most notable condition
seen in cats and dogs from blockage of urine flow from the 
kidneys involves kidney stones or bladder stones or urethral obstruction.
These mineral concretions (usually called struvite uroliths) can form
in the urine of the kidney pelvis or bladder and remain for long periods
of time without causing serious trouble. Easily contaminated with
bacteria, however, urinary calculi are a major nidus of bacterial proliferation
and will cause physical irritation to the kidney or bladder tissues.
These irritated tissues become thickened, scarred and prone to chronic
infection. Under certain circumstances a kidney stone can become
lodged in the ureter leading away from the kidney toward the bladder and
obstruct urine flow from the kidney. If the situation persists for
days the increased back pressure on the affected kidney will permanently
damage kidney function and cause what is termed hydronephrosis...
a kidney swollen under pressure with backed up urine. Surely this
is a life threatening situation. Generally this will occur in a single
kidney and if only one kidney is damaged and the opposite kidney is normal,
bodily waste removal needs can be met by the single remaining kidney.
Take a look at a kidney removal surgery due to an obstructed ureter.
FUS (Feline Urological
Syndrome) also sometimes called FLUTD (Feline Lower Urinary Tract Disease)
has as one of its presenting emergencies a situation where mineral deposits
obstruct the male cat's penis. The bladder eventually dilates
maximally and back pressure into the kidneys can cause death or permanent
kidney damage if relief isn't provided expediciously.
Dogs with bladderstones often obstruct when a stone passes from
the bladder but cannot be voided past the os penis... the bone present
in the male canine's penis. There is an inherent lack of room for
the urethra to dilate in the area of the os penis and small bladder stones
often dam up the urine flow at this site. Surgical intervention is
often required in these emergency urinary tract blockage cases.
Tumors, cysts, abscesses and scar tissue, if present in critical
areas of the urinary tract, can create obstructive situations where
the urine flow from a kidney is compromised. Any situation that
creates urine outflow restriction from a kidney will result in damage
to delicate kidney tissue structures, and the damage is often permanent.
If enough tissue is destroyed or its function impaired, kidney failure
will result.
CANCER:
Cancer of the kidney
is extremely rare in dogs and cats. When it is seen it usually
takes the form of secondary invasion of metastatic cancer originating
in a distant tissue. In cats and dogs with leukemia disorders,
the kidneys can be infiltrated with neoplastic leukemic cells which can
severely compromise renal function. There is a form of leukemia
in cats that targets the kidneys and crowds out normal kidney cells.
EXTERNAL TOXINS (INGESTED TOXINS):
One of the most devastating
external toxins that causes kidney failure in dogs and cats is antifreeze
that contains ethylene glycol
. It doesn't take much of this sweet tasting liquid to
prompt crystals to form in the delicate tubules of the kidney's filtration
systems. Massive doses of Vitamin D can be nephrotoxic (poisonous
to the kidneys), rodent poison such as D-Con can allow hemorrhaging into
the kidneys, the Easter Lily plant can be toxic if ingested and heavy metal
toxicity such as from lead, mercury, cadmium, and arsenic all pose a very
real threat to kidney tissue. Other renal toxins include thallium and turpentine.
There is evidence that raisins/grapes can be nephrotoxic to dogs.
ENDOTOXINS:
Endotoxins are chemicals
produced within the animal that are toxic. The most common type
is that group of poisons formed by certain types of bacteria. Clostridia
organisms are famous for causing tetanus. Many bacteria produce
toxins from their normal metabolic waste products In others, when
they die off they leave behind toxins that can have damaging effects on
delicate body tissues such as kidney structures and heart valve tissues.
Endotoxins can have systemic effects as well and play a role in triggering
shock in an animal where blood pressure declines, heart output diminishes
and body tissues become starved for oxygen and nutrients. Endotoxic
shock can leave irreversible damage in any organ of the body.
MEDICATIONS:
Some types of medications
can be nephrotoxic such as acetaminophen (analgesic), amphotericin B
(antifungal), adriamycin (doxorubicin) in cats, kanamycin (antibiotic),
neomycin (antibiotic), polymyxin B (antibiotic), cisplatin (a cancer drug),
penicillamine (chelating agent/immune modulator), Cyclosporine (immunosuppressive),
amikacin (antibiotic), and radiographic contrast agents. Especially
in older pets, medication administration needs to be employed in the light
of potential harmful effects on the patient.
AUTOIMMUNE DISEASES:
Systemic Lupus Erythematosis
(SLE)... known as the great imitator, this disorder can be difficult
to diagnose since it can manifest as a disease of the skin/mucous membranes/nails,
kidney and/or joints. As a consequence of the animal's adverse and
abnormal immune response to its own body tissues and proteins, many organ
sites can be affected, including the kidneys. As the kidneys filter the
circulating blood the abnormal immune molecules are trapped in the glomeruli
and blood vessels, causing the kidney to leak protein. A condition
called Glomerulonephritis is the result and all sorts of abnormal kidney
function can occur due to the damaged glomeruli.
Amyloidosis: Although not proven to be a result of an autoimmune
disorder, the deposition of protein called Amyloid can actually occur
in any tissue of the body. The kidneys are most commonly affected
and since the protein deposition destroys normal function, renal amyloidosis
can be particularly serious due to the fact that kidney tissue does not
repair itself. Amyloidosis is fairly common in Akitas and Chinese
Shar Pei dogs and reported in Abyssinian, Siamese, and Oriental Shorthaired
cats. Usually present in middle or older dogs and cats, amyloidosis
most often results from chronic inflammation, cancer or other diseases.
DIAGNOSIS OF KIDNEY FAILURE
One of the first signs
an animal will show when beginning to be affected by kidney failure
is an increased thirst. Polydipsia is the term used for this situation
where the animal needs to consume greater amounts of water than normal.
Increased toxins and other metabolic waste products triggers sensors in
the brain that the blood is too concentrated and through a series of
chemical reactions the animal may have a sense of dehydration... and drinks
more water to alleviate this sensation. Compounding this sense
of dehydration is actual water loss through the kidneys above normal amounts
due to the kidneys being inefficient in retaining water within the body.
Water soluble vitamins, such as the B-vitamins are washed out
of the body with this polyuria and polydipsia and the animal suffers
from hypovitaminosis.
In order to make a diagnosis of renal failure the veterinarian
will need to check two avenues of data gathering... a urine sample
and a blood sample. Checking one without the other may render
a diagnosis less accurate.
THE URINE SAMPLE
In nearly all
cases of kidney failure the kidneys are unable to concentrate urine.
That means the
Urine Specific Gravity measurement (SpG) that indicates
how concentrated the urine is compared to distilled water (SpG = 1.00)
will display a dilute reading... actually, very close to distilled
water. Since the action of conserving water while allowing undesirable
metabolites and toxins to remain in the urine is the job of the tubules
in the kidneys, whenever the tubules are damaged water conservation
is less efficient; therefore more water flows through the tubules unresorbed
and washes away in the now dilute urine. Most cases of kidney failure
display a SpG of about 1.008 to 1.012. Generally, a normal dog's
urine SpG will be 1.020 to 1.040; generally a cat's urine SpG will be about
1.025 to 1.050. If a water deprivation test is done, where the animal
has no access to water for 18 hours, the urine specific gravity goes up...
the urine becomes more concentrated. (Generally, if kidney failure
is suspected a water deprivation test is not done because it will render
the patient even more toxic.)
Many cases of kidney failure also show protein or sugar in the
urine where in most normal animals urine protein is scarce and no glucose
is present. The loss, or lack of reabsorption of protein or sugar
molecules back into the blood after an initial pass into the tubular
fluid, places the animal in a negative protein/energy balance.
This state shows up as weight loss and muscle wasting. And since
these patients have a poor appetite, the added stress of protein and
energy loss in the urine really tends to make the maintenance of normal
body weight nearly impossible.
Bacteria and blood may show up in the urine samples of chronic
renal failure patients. Infectious agents, red and white blood
cells, epithelial cells from the lining of the kidney and bladder structures,
crystals, and protein plugs called casts that arise from damaged tubules
all may be commonly observed in urine samples. Conversely, some
patients have such dilute urine and such thirst that a urine sample may
have no detectable cells or debris but simply show a low Specific Gravity
and very dilute urine.
THE BLOOD SAMPLE (See normal ranges for dog and cat
blood chemistry values here.)
When renal function is diminished, many, many toxic chemicals
build up in the patient's body. Think of the situation
as you would if there were no smoke stack on a factory and
all those burned gasses and chemicals stayed within the walls of the
factory. That's just what happens when kidney failure is present.
In many patients, slow and progressive loss of filtering tubules creates
a situation where these toxins very gradually build up; in other acute
kidney diseases (such as anti-freeze poisoning) the sudden and massive
damage creates immediate toxin buildup within the body. Many dogs
and cats become accustomed to very gradual toxin buildup as slowly progressive
kidney disease moves toward the critical limit where there are not enough
healthy nephrons to eliminate waste products. Eventually, outward
signs of kidney disease becomes evident.
Two of the most useful chemicals that veterinarian measure to
see if toxins are building up in the patient's body are Blood Urea Nitrogen
(BUN) and Creatinine. Normal BUN levels in dogs and cats seldom
reach higher that 25 to 30 mg/dl. (Mg/dl means milligrams of material per
100 milliliters of blood.) Many patients presented in renal failure
have BUN levels of 90 or higher! Similarly, Creatinine, a chemical
normally present in the blood at levels less than 1.0 mg/dl, may rise to
over 8 mg/dl. Blood urea nitrogen (BUN) and Creatinine (a normal product
of muscle tissue breakdown) are just two of many chemicals in the blood
that are affected by kidney failure. Most veterinarians can check these two
chemicals in the animal hospital; otherwise blood samples are sent to a veterinary
lab for analysis and the results are faxed or called in to the referring
veterinarian.
The diagnosis of kidney failure is made only after...
* A thorough physical exam
* A thorough discussion with the owner about the dog or
cat's relevant history
* A urinalysis is performed
* A blood chemistry analysis is performed
TREATMENT FOR KIDNEY FAILURE
In human medicine, dialysis and kidney transplantation are the
main methods of dealing with advanced kidney failure. Expensive
and time consuming, these methods are also employed in treating dogs
and cats but impose heavy financial and time burdens on the pet owner
and some stress on the patient who is already stressed by the disease.
Unfortunately, once the diagnosis of kidney failure is made, most patients
are so sick that response to treatment is unrewarding and slow.
The pet's owner may need to consider euthanasia in order to prevent the
long, slow, and agonizing death that comes from complete renal shutdown.
In very extreme and special circumstances, a kidney transplant may be an
animal's only hope of long term existence. See an article about KIDNEY
TRANSPLANTS here. Kidney transplantation is a controversial topic
but the science and success rate in cats and dogs has advanced greatly
in recent years.
Treating kidney failure is one of the most consistently
discouraging aspects of veterinary medical practice. The difficulty
stems from the fact that once a dog or cat has lost 75% of total renal
function, the ability to remove metabolic waste products is outweighed
by the buildup of those toxins. The animal is simply not able to keep
up with the "housecleaning" and as a result gradually becomes increasingly
more toxic. Body chemistry swings more and more acidic, important
chemicals and nutrients are lost from the body and the animal comes gradually
closer and closer to a fatal uremic poisoning. In some cases, gradual
kidney tissue loss can be present for years before the patient becomes
critical and actual "renal failure" is diagnosed.
The goal of treatment is to allow the patient to live as close
to a normal life as possible under the circumstances. Since the
kidneys do not heal or regenerate new and functioning tissue, the remaining
functional tissue carries the entire burden normally handled by two
healthy kidneys. Intravenous and subcutaneous fluids can be administered
for varying lengths of time to try to correct acid-base imbalances.
Vomiting can be controlled. Anti-ulcer medication can be given.
Bicarbonate may be administered either orally or intravenously to assist
in neutralizing acid buildup. B-vitamins are provided. Antibiotics
are employed if there is an infection present anywhere in the body...
taking into consideration that some antibiotics will also build up in the
patient if renal function is compromised. Phosphate binders and Omega
Fatty acids in correct amounts and proportions may be temporarily beneficial
for the Chronic Renal Failure patient. High quality, low protein
diets have been proven to be helpful in lessening the metabolic tasks that
must be performed by the kidneys once end stage kidney disease is present.
DIETARY CONSIDERATIONS
Contrary to popular myth, diets rich in protein ("high protein
levels") do not cause kidney damage. 
Research done decades ago indicated that rodent kidneys were
adversely affected by diets high in protein... and misguided researchers
extrapolated that data to apply to the canine. There is no evidence
that feeding dogs and cats diets rich in or "high" in protein actually
causes kidney damage or disease. Some day this myth will be finally
be put to rest. In fact, there is ample research and well documented
studies that prove that dogs and cats thrive on diets with levels of protein
consistent with a meat-eater's (carnivore) natural prey selection.
Read more about protein in dog and cat diets here.
Additionally, documented research on dogs indicates that reducing
dietary protein levels in older dogs may be unwise; however, if kidney
damage is already present to the extent that the BUN levels are 75mg/dl
or above, some restriction of dietary protein may be beneficial for metabolic
reasons... not renal reasons. "...restriction of protein intake
does not alter the development of renal lesions nor does it preserve renal
function." (See KIRKS VETERINARY THERAPY XIII, Small Animal Practice, W.
B. Saunders, page 861). Restricting dietary protein may be helpful
to those patients whose BUN levels are rather high and that are already
in advanced kidney failure.
THE PET HEALTH LIBRARY
Kidney Failure (Chronic
Renal Failure)
What You Should Know
If My Pet Is Still Making Plenty of Urine, How Can There Be Kidney
Failure?
In chronic kidney failure, urine is usually produced in excessive
quantities. What the kidneys are failing to do is conserve water (they
are failing to make concentrated urine). The body produces numerous toxins
on a moment by moment basis. These toxins circulate to the kidneys where,
dissolved in water, they are filtered out and urinated away. An efficient
kidney can make a highly concentrated urine so that a large amount of toxin
can be excreted in a relatively small amount of water.
When the kidneys fail over a long time period, they lose their
ability to concentrate urine and more water is required to excrete the
same amount of toxin. The animal will begin to drink more and more to
provide the failing kidneys with enough water. Ultimately, the animal
cannot drink enough and toxin levels begin to rise. Weight loss, listlessness,
nausea, constipation, and poor appetite become noticeable. It is common
for animals, especially cats, to have a long history of excessive water
consumption when they finally come to the vet's office with one of the
latter complaints.
What Is my Veterinarian Reading on the Blood Panel?
If you wish to understand your pet's status with regard to
kidney failure, it is important to understand some of the parameters
being monitored.
Urine Specific Gravity - This is a measure of how concentrated
a urine sample is. Water has a specific
gravity of 1.000. A dilute urine sample has a specific gravity
less that 1.020 (often less than 1.010). A concentrated urine sample would
have a specific gravity over 1.030 or 1.040.
Blood Urea Nitrogen (BUN) - This is a protein metabolite
excreted by the kidney (it is one of the toxins we are concerned about).
In a normal animal, the BUN is 25 or so. A good goal for BUN in kidney
failure is 60 to 80. Often at the time of diagnosis, BUN is well over 150,
200, or even 300.
Creatinine- This is another protein metabolite (though this
one is less dependent on dietary protein intake than is BUN). A normal
creatinine is less than 2.0. A good goal in kidney failure is a creatinine
of 4.5 or less. BUN and creatinine will be tracked (as will several other
parameters) over time and in response to different treatments.
Phosphorus - The calcium/phosphorus balance becomes deranged
in kidney failure due to hormone changes that ensue as well as the inability
of the failing kidney to excrete phosphorus. If calcium and phosphorus
levels become too high, the soft tissues of the animal's body will develop
mineralized deposits which are inflammatory and uncomfortable. The bones
will weaken as well. If phosphorus can be maintained in the normal range
(less than 7.5), a medication called calcitriol can be used to help prevent
or slow the progression of kidney failure. Medications and special diets
can be used to help keep phosphorus levels down.
Potassium - The failing kidney is unable to conserve potassium
efficiently and supplementation may be needed. Signs of hypokalemia (the
scientific name for low blood potassium) include weakness, especially
drooping of the head and neck.
Packed Cell Volume/Hematocrit - This is a measure of red
blood cell amount. More literally it represents the percentage of the
blood made up by red blood cells. The hormone that stimulates the production
of red blood cells is made by the kidney. The failing kidney does not make
this hormone in normal amounts and anemia can result. Anemia is often worsened
by the extra fluid administrations needed to manage the kidney toxins. Sometimes
a blood transfusion is needed or, more commonly, the owner of the pet
must learn how to give hormone injections to boost the red blood cell
count.
Blood Pressure - Blood pressure is not something measured
off a laboratory result sheet but it is important to monitor in kidney
patients as there is a tendency for hypertension to develop in kidney
failure. Special medications may be needed to manage this problem should
it arise.
The owner who plans to be involved with monitoring of the pet's
condition at home should become familiar with these terms and even get
a copy of the pet's lab results for their own records.
Your veterinarian is likely to have a handwritten chart in your
pet's record showing changes in the above parameters; it's not a bad idea
to start your own folder and chart at home.
What Are the Treatment Options?
What one does to address this problem depends on its stage at the
time of diagnosis. More advanced
cases will require hospitalization for a cycle of diuresis. Fluids
are delivered intravenously for 48 to 72 hours and the above parameters
are rechecked. The goal is to stabilize the patient at a toxin level where
good life quality can be indefinitely experienced.
Milder cases can be managed with fluid administration under the
skin (subcutaneous fluids) at home. This sounds scary at first but, in
fact, it is not uncomfortable for the pet and is easy to learn.
Also available (but very expensive) are dialysis, where a machine
filters the toxins from the patient's blood, and kidney transplantation.
What Sort of Treatments Might my Pet Require at Home?
Special Diet:
Most prescription diet companies produce a diet with restricted
protein (so as to generate less BUN),
restricted phosphorus, and with other important qualities to promote
metabolic health in kidney patients. Many clinics stock K/D diet made
by Hills and Select Care Modified made by Innovative Veterinary Diets. In
some cases, simply switching to this food may be adequate treatment. There
is no preventive benefit that we know of in changing to these diets prior
to the onset of kidney failure.
Amphojel/Phosphate Binders:
Amphojel is an antacid caplet used for stomach upset in
people. It also binds phosphates in the diet when it is given with food.
This reduces the phosphorus intake from the GI tract and helps normalize
the blood phosphorus level.
Calcitrol: This medication actually represents activated
vitamin D. Vitamin D is not a vitamin in the way other vitamins are or
in the way we think of vitamins; vitamin D is actually a hormone. It plays
an important role in calcium phosphorus balance and is beneficial in preventing
the progression of kidney failure when it is administered while phosphorus
levels are still normal. Our experience with this medication has been
excellent and we recommend its use in appropriate patients whole-heartedly.
The doses that are used are exceedingly small and must be compounded by
a special pharmacy. If your pet qualifies to take this medication, special
instructions on how to obtain it will be given to you.
Epogen/Erthropoeitin: In older times, anabolic steroids
were used to address the anemia (low red cell count) of chronic kidney
disease. With the advent of genetic engineering, the actual hormone the
kidney has stopped producing can be given by injection. This is done usually
at home 2 to 3 times a week along with an oral iron supplement. This treatment
has helped many patients dramatically as the anemia that goes with kidney
disease can be very debilitating. The downside to this treatment is that
the product commercially available for use is of human origin and pets will
ultimately produce antibodies against it (and worse still against their own
remaining hormone). For this reason, this hormone is not used until anemia
is more advanced and the patient really needs this treatment.
Amlodipine (brand name Norvasc): It is difficult to find
a blood pressure medication that is not also toxic to the kidneys. Amlodipine
is a calcium channel blocker type medication commonly used in hypertensive
cats with renal failure. It also must be compounded specially in cat sized
doses.
Fluids Under the Skin: This technique is important to learn
as most pets in kidney failure require this treatment either right away
or following hospitalization. If this process is recommended for your
cat, you will receive lessons on how this technique is performed.
Kidney failure is a complicated disease with
many facets. Please do not hesitate to contact your veterinarian should
you have questions or problems at home. You will periodically be contacted
when it is time for your pet to have monitoring tests.
You Are Not Alone: Further Resources
Chronic renal failure is a common disease and there are many
pet owners just like you all sharing thoughts, tips, and information
over the internet. If you are interested in exploring these resources,
here is what is available:
A large information area has been structured at http://www.felinecrf.com/ by the owner
of Avatar, a cat who ultimately succumbed to his kidney failure. While
this site is especially geared for cat owners, its information is certainly
applicable to dog owners as well.
For those with America On-Line subscriptions, there is a weekly
feline chronic renal failure chat to which all are welcome. This chat
is held on Sundays from 5 to 6 pm Pacific Time in the private room called
"crf." (Click on "People Connection," click on "Private Room," type in
"crf.")
There is also an on-line mailing list (a listserv) for owners of
cats with chronic renal failure. To subscribe go to http://groups.yahoo.com/group/Feline-CRF-Support/.
Please do not hesitate to ask your veterinarian if you have any
questions or problems regarding your pet's condition.
Copyright 2001 - 2007 by the Veterinary
Information Network, Inc. All rights reserved.
This work was originally published by Veterinary Information Network,
Inc. (VIN)
and is republished with VIN's permission.
Kidney Failure:
Where to Begin
The Vocabulary of this
Disease
“Chronic” means long term. “Renal” means kidney. “Failure” means
inability to perform a task adequately.
Chronic renal failure, also called chronic kidney failure, refers
to the situation where the kidneys have not been able to perform at least
one of their many tasks adequately for some time (months to years). Because
the word failure evokes such a sense of doom, many clinicians opt for the
term chronic renal insufficiency, as many cases can be treated successfully
and can look forward to months or often years of quality life.
The terms renal failure or renal insufficiency imply that a condition
called azotemia is present. Azotemia is the condition where toxins have
built up in the bloodstream and lab tests are definitely abnormal. It
does not necessarily mean the patient is experiencing reduced life quality
as a result of these abnormal lab findings. The term uremia means that
the patient is experiencing uremic poisoning. In other words, not only
are the tests abnormal but the patient is feeling the effects of the toxic
build up. Our goal in treatment is to prevent, postpone, or resolve uremia.
Resolving azotemia may not be realistic.
In most cases, by the time the diagnosis of kidney failure has been
made, the initial disease that started the kidneys on their path to failure
is long gone, leaving a progressive loss of function to march unrelentingly
onward. Our goal is to stop that march, and get to a stage where the patient
does not feel the consequences of the disease. We cannot make failed kidneys
become normal again, but we may be able to re-balance our patient’s metabolism
so that he or she feels as though we did. What makes a case hopeless or
hopeful depends on the patient’s ability to respond to therapy nearly as
much as it depends on the stage at which the condition is discovered.
Many people have no idea what our kidneys do for us beyond that
they have something to do with urine production. In fact, the kidneys
are involved in conservation of water, stimulating red blood cell production,
regulating blood pressure, balancing salts, activating Vitamin D, and more.
Any of these functions may be failing in the renal failure patient.
The kidneys remove toxic wastes from our bodies and when these substances
cannot be adequately removed, we develop excess thirst, nausea, pain,
weakness, appetite loss, intestinal bleeding, even seizures. Our goal in
early stage patients is to postpone or even fully prevent the development
of uremia. Our goal in later stage patients is to resolve the uremia and
bring the patient back to an earlier stage of disease.
Let’s begin with some of the relevant lab values that come up in
the course of screening a pet’s kidney function. It is helpful to become
familiar with these terms so you can understand what your veterinarian
is tracking:
Urine Specific Gravity
One of the kidney’s most important jobs is the conservation of the
body’s water. The kidney must excrete the toxic by-products created by
the body’s metabolism but it will want to do so in the least amount of
water possible. The healthy kidney is able to make very concentrated urine.
When we analyze a urine sample, one of the most important parameters
is the specific gravity. This is a measure of how concentrated a urine
sample is. Water has a specific gravity of 1.000. A dilute urine sample
has a specific gravity less that 1.020 (often less than 1.010). A concentrated
urine sample would have a specific gravity over 1.030 or 1.040. A failing
kidney by definition cannot make concentrated urine and the patient must
drink excessively to get enough water to excrete the day’s toxic load.
Blood Urea Nitrogen (BUN)
This is a protein metabolite excreted by the kidney (it is one of
the toxins we are concerned about, though it may be more of a marker
for other toxins that are less easily measured). In a normal animal,
the BUN is 25 mg/dl (milligram per deciliter) or so. Often at the time
of diagnosis, BUN is well over 150, 200, or even 300. We’d like to keep
the BUN no more than 60 to 80 mg/dl. BUN is influenced by dietary protein
(including the patient’s own blood that has bled into the intestine), something
which becomes important in certain situations.
Creatinine
This is another protein metabolite (though this one is less dependent
on dietary protein intake than is BUN). A normal creatinine is less than
1.4 mg/dl, certainly less than 2.0. Patients begin to feel sick when
values meet or exceed 5.0 so we try to keep the value at 4.5 or less.
BUN and creatinine will be tracked (as will several other parameters)
over time and in response to different treatments.
Phosphorus
The calcium/phosphorus balance becomes deranged in kidney failure
due to hormone changes as well as the inability of the failing kidney
to excrete phosphorus. If calcium and phosphorus levels become too high,
the soft tissues of the animal's body will develop mineralized deposits
that are inflammatory, uncomfortable, and often cause intestinal bleeding.
The bones will weaken as well, in some cases actually becoming rubbery.
Keeping phosphorus levels in the low normal range has been correlated with
improved survival.
Potassium
The failing kidney is unable to conserve potassium efficiently and
supplementation may be needed. The sign of hypokalemia (the scientific
name for low blood potassium) is weakness, especially drooping of the
head and neck.
Packed Cell Volume / Hematocrit
This is a measure of red blood cell amount. More literally it represents
the percentage of the blood made up by red blood cells. The hormone which
stimulates the production of red blood cells is made by the kidney. The
failing kidney does not make this hormone in normal amounts leading to
a reduction in red blood cells, in turn leading to weakness, poor appetite,
and overall poor life quality.
Blood Pressure
Blood pressure is not something measured off a laboratory result
sheet but it is important to monitor this parameter in kidney patients
as there is a tendency for hypertension to develop in kidney failure. Special
medications may be needed to manage this problem should it arise.
Urinary Protein
One of the functions of the kidney is to prevent loss of the body’s
proteins, in particular the blood proteins. The kidney’s filtering mechanism
that enables it to remove toxins is designed to leave larger molecules
(such as proteins) inside the body where they belong. But if holes develop
in the filter, protein can be lost. If this complication cannot be controlled,
survival time is dramatically shortened.
If you are a hands-on kind of pet owner, it is a good idea to request
copies of monitoring lab work so you can make a chart of these parameters.
In this way you can see how the disease is progressing or improving and
what the problem areas are.
IRIS Staging
The International Renal Interest Society (IRIS) has posed the following
staging criteria for pets with kidney failure based on creatinine value
in mg/dl.
|
Stage I
(pre-failure)
|
Stage II
(mild failure)
|
Stage III
(moderate failure)
|
Stage IV
(severe failure)
|
Dog
|
<1.4
|
1.4-2.0
|
2.1 - 5
|
>5
|
Cat
|
<1.6
|
1.6-2.8
|
2.8 – 5
|
>5
|
Most of what we discuss here will pertain to treating patients in
Stage III and Stage IV but there is also a great deal of room to help
patients still in Stage II.
Copyright
2007 - 2007 by the Veterinary Information Network, Inc. All rights reserved.
This work was originally published by Veterinary Information
Network, Inc. (VIN) and is republished with VIN's permission.
Join
k9kidneydiet/
or
k9kidneys/
For information and support.Everyone on these lists knows what
it is to have a dog in some stage of renal failure.
The advice comes from experience, the people are caring and
nonjudgmental.
The above information is simply informational.
It's intent is not to replace the advice of a veterinarian nor to assist
you in making a diagnosis of your pet. Please consult with your own veterinarian
for confirmation of any diagnosis. Your pets life may depend on it.