is Chronic Renal Disease?
Chronic renal disease (aka chronic renal insufficiency,
chronic renal failure, chronic kidney disease) occurs when 70% of kidney
function is irreversibly destroyed. The kidneys consist of tiny units
called nephrons, which are responsible for filtering out toxins and
wastes from the blood. These toxins and wastes become concentrated in
the urine and eliminated from the body. When the kidneys no longer have
enough functioning nephrons to effectively rid the body of toxins,
uremic poisoning results.
As one of the most common causes of death in the
geriatric cat, CRD can occur as a result of:
- Kidney inflammation
- Congenital renal diseases
- Renal lesions
- Unresolved pyelonephritis (bacterial
infection of the kidney)
- Feline leukemia
- Feline infectious peritonitis
- Hypertension (high blood pressure)
- Chronic immune stimulation including
chronic oral and skin infections, inflammatory bowel disease,
- Unknown causes
The normally functioning kidney is able to
rid the body of toxins and wastes by storing them in the bladder as
concentrated urine. However, the failing kidney is unable to use a small
amount of water for the toxins (concentrated urine), and because of this
failure in water conservation, more water is needed to flush the toxins
from the body. Consequently, the most common symptoms of CRD are polydipsia
(increased drinking) and polyuria
(increased urination). These are also the two most common
signs of diabetes.
As CRD progresses, other physical signs include:
- weight loss
- dull coat
- muscle wasting
- mouth ulcers
Diagnosis of CRD can be made
by a variety of methods. Physical examination findings of abnormally
small or large kidney(s) may initiate further testing of kidney
function. Tests most commonly utilized to assess kidney function include
a urine specific gravity test to determine how well the kidney is
concentrating urine, and blood work to determine the levels of toxins in
the blood. The two most significant blood test results are the BUN
(blood urea nitrogen) and the creatinine levels. BUN is a protein
metabolite and although lab values differ, the approximate range is
between 14-36 mg/dl (5-12.9 nmol/L) for healthy kidneys. BUN is related
more to diet, and if dehydration is present, will show increased values.
Creatinine is thought to be a more reliable indicator of kidney function
as it shows how well the kidneys are filtering out the toxins and is
less dependent on dietary factors and hydration status of the cat. A
normal range for creatinine value for the healthy kidney is 1.0-2.2
mg/dl (88.4-194.5 umol/L). Additional blood values used to diagnose
renal failure include phosphorus, potassium, calcium, and packed cell
Other tests to determine kidney function include x-ray of the kidneys,
kidney ultrasound and biopsy.
Considerations for Diagnosing Diabetics
Because many of the same symptoms present in diabetes (e.g., PU/PD), are
also indicators of renal failure, CRD can be easily misdiagnosed as
poorly controlled diabetes. Elevated BUN and creatinine levels can also
occur with diabetes alone, so a diagnosis of CRD can be complicated.
This misdiagnosis results in delayed treatment and therefore faster
progression of CRD as well as mismanagement of diabetes. If the owner is
assessing diabetes control by measuring fluid intake and output only,
the cat can be inappropriately overdosed with insulin.
Because the diabetic cat is prone to CRD as well as other illnesses, it
is advisable for the cat to undergo periodic examinations including a
comprehensive blood work panel and urinalysis. If at all possible,
periodic blood pressure of the diabetic cat is also recommended as
hypertension can results from poorly controlled diabetes, and untreated
hypertension can lead to CRD.
CRD is a terminal illness. However, with specialized
treatment, many CRD cats are able to live months to years before
succumbing to the disease. The goal of treatment is to ease the work
done by the kidneys and to prevent dehydration. Thus, management to slow
the progression of the disease revolves around two mainstays of
treatment, diet and fluid therapy, both of which are controversial.
Up until somewhat recently, the recommended diet was both low in protein
and phosphorus. However, there is new evidence suggesting that the
amount of protein is of less importance than the "quality" of
the protein source. Consequently, there are now two schools of thought,
one advocating the traditional low protein CRD foods and the other
proposing a higher or moderate protein diet using high quality proteins
such as cooked eggs, boiled liver, chicken, turkey, heart, etc.
Many vets do not recommend low protein/restricted protein diets for
early, mild or moderate disease. Restricted protein can be helpful in
very severe CRD because low protein reduces nitrogenous wastes, making
it easier for the kidney to do its job of filtering blood. However, both
sides concur with one aspect of the CRD diet: it must be low in
Low phosphorus foods for CRD can be found listed at the following
For drinking water, distilled water is
recommended because tap water and bottled water with added minerals can
be hard on the kidneys.
For most CRD cats at one stage or another, the mainstay of CRD treatment
is the administration of subcutaneous fluids which can slow the
progression of the disease by helping to keep the cat consistently
hydrated. Fluid therapy is given several times a week to several
times daily depending on the needs of the cat as determined by both
renal values and overall well-being. Caution, especially in cats
with preexisting heart disease, must be used with chronic administration
of large amounts of subcutaneous fluids because of the danger of
inducing hypertension and/or congestive heart failure.
Subcutaneous Fluids To Your Cat is an excellent site for
illustrating the technique of home administration of subcutaneous
IV fluid therapy, usually given in the veterinary hospital, is often
administered to cats with dangerously high renal values. These cats will
have severe symptoms and are gravely ill. Once the cat has been
stabilized, subcutaneous fluids will be continued at home.
Other CRD Treatments
there is increasing evidence that Calcitriol (vitamin D3) will delay
progression of CRD by restoring calcium balance. Some experts are
promoting the use of Calcitriol as long as a parathyroid hormone test
determines that the cat is a candidate. If the calcium value multiplied
by the phosphorus value exceeds 70, Calcitriol should not be
supplementation: in CRD, potassium depletion is
common. Many experts believe that potassium supplementation should be
initiated before the potassium values reach the low end of the normal
range. The most widely used potassium supplement is Tumil-K, available
in tablet, powder and gel form. Potassium added to sub-q fluids is also
an option but often causes discomfort to the cat during fluid
binder (Alternagel, Alucaps) may be used to bind
phosphates in the diet, reducing phosphorus intake and normalizing blood
is a common result of CRD and must be treated so that strokes,
heart disease and blindness are prevented. Currently, the drug of choice
for hypertension in CRD cats is the calcium channel blocker amlodipine (Norvasc).
The ace inhibitor, benazepril (Lotensin), is also gaining in popularity.
CRD progresses, anemia results due to erythropoietin deficiency.
Erythropoietin is made by the kidneys and is responsible for stimulating
red blood cell production by the bone marrow. In chronic renal failure,
erythropoietin is depleted causing anemia as reflected in a low packed
cell volume value. Severe anemia is life threatening, as there are not
enough red blood cells to deliver oxygen to the body tissues.
Unfortunately, because the only erythropoietin drug available (Epogen)
is human based, some cats develop antibodies to it causing the packed
cell volume to fall even lower. Therefore, erythropoietin therapy is not
initiated until the packed cell volume falls dangerously low (under
is common in the CRD cat. Appetite stimulants are often given to help
promote appetence and help the cat maintain a stable weight. Drugs to
stimulate appetite most commonly prescribed are Valium and
Cyproheptadine. Valium (diazepam) has been know to cause serious liver
and kidney damage in a small percentage of cats, so discuss the use of
this drug with your veterinarian before administration
distress: To counteract gastric upset in the CRD
cat, small amounts of Pepcid-AC can be given.
Many CRD and diabetic cats suffer from chronic
constipation due to dehydration. Lactulose is often recommended as it
can also theoretically aid the kidneys by helping to eliminate
nitrogenous wastes through the digestive tract, thereby decreasing the
load on the kidneys.
Considerations for Treating Diabetics
Diabetes and CRD are
intricately involved; the progression of one impacts the progression of
the other which makes control of each disease difficult to manage. CRD
puts immeasurable stress on the catís body, making diabetes regulation
difficult, if not impossible. In turn, poorly controlled diabetes will
contribute to an accelerated progression of CRD, especially if
hypertension and urinary tract infections (UTIs) are present and
inadequately addressed. In the diabetic cat with or without CRD, it is
important to have regular screenings and treatment for any UTIs and
periodic blood pressure testing if at all possible.
The diet typically indicated for CRD cats can be contraindicated in the
diabetic. Diabetes experts recommend feeding a high protein diet, which
can significantly reduce blood glucose levels. However, many high
protein foods are also high in phosphorus, so for difficult to regulate
diabetics, a decision must be made as to which diet to choose. A good
compromise may be to offer a low phosphorus diet with the addition of a
high quality protein source such as boiled chicken, turkey, liver, or
Ask your vet what he or she recommends concerning screening for CRD in
the diabetic cat. Especially if your catís diabetes is well controlled
and you still see signs of PU/PD, have a blood panel done to rule out CRD
(as well as other diseases such as hyperthyroidism)
as well as a urinalysis for urine specific gravity and to check for any
concurrent urinary tract infections.
If your cat is diagnosed with CRD, ask your vet about his beliefs
concerning diet and home administration of subcutaneous fluids.
Discussing the other treatments for CRD would also be advisable.
If your vet does not have access to blood pressure monitoring equipment,
see if he will refer you to a vet with this capability.
This page has been designed to give an overview of chronic renal failure
in the diabetic cat. For more comprehensive information, please visit
the sites listed below.
There are several excellent resources on the Internet for CRD
The information on the page was provided by Melissa,
who has both CRD and CRD-diabetic cats. This page is in memory of her
Copyright. All rights reserved.
This site is for information purposes only.
Please consult your veterinarian.