Chronic Renal Failure

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Chronic Renal Failure

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Introduction
Chronic renal (kidney) failure (CRF) is a common
problem in all cat breeds. The digestion of food produces
waste products, which are carried by blood to the kidneys
to be filtered and excreted in the form of urine. When the
kidneys fail, they are no longer able to remove these waste
products, and toxins build up in the blood producing
clinical signs of kidney disease.


Anatomy of the kidney
(from Wikipedia)
Renal
capsule
: The membranous covering of the kidney.

Cortex: The outer layer
over the internal medulla. It contains blood vessels,
glomeruli (which are the kidneys’ “filters”) and urine
tubes and is supported by a fibrous matrix.

Hilus: The opening in
the middle of the concave medial border for nerves and
blood vessels to pass into the renal sinus.

Renal column: The
structures which support the cortex. They consist of lines
of blood vessels and urinary tubes and a fibrous material.

Renal sinus: The cavity
which houses the renal pyramids.

Calyces: The recesses
in the internal medulla which hold the pyramids. They are
used to subdivide the sections of the kidney. (singular –
calyx)

Papillae: The small
conical projections along the wall of the renal sinus. They
have openings through which urine passes into the calyces.
(singular – papilla)

Renal pyramids: The
conical segments within the internal medulla. They contain
the secreting apparatus and tubules and are also called
malpighian pyramids.

Renal artery: Two renal
arteries come from the aorta, each connecting to a kidney.
The artery divides into five branches, each of which leads
to a ball of capillaries. The arteries supply (unfiltered)
blood to the kidneys. The left kidney receives about 60% of
the renal bloodflow.

Renal vein: The
filtered blood returns to circulation through the renal
veins which join into the inferior vena cava.

Renal pelvis: Basically
just a funnel, the renal pelvis accepts the urine and
channels it out of the hilus into the ureter.

Ureter: A narrow tube
40 cm long and 4 mm in diameter. Passing from the renal
pelvis out of the hilus and down to the bladder. The ureter
carries urine from the kidneys to the bladder by means of
peristalsis.

Function of the
kidneys


The kidneys have five primary functions:

• Filtering waste products from the body (primarily urea
and creatinine).

• Regulating electrolytes (potassium, calcium, phosphorus
and sodium).

• The production of erythropoietin, which helps to
stimulate the bone marrow to produce red blood cells.

• The production of renin, an enzyme that controls blood
pressure.

• Production and concentration of urine

CRF affects all breeds of any age, although older pets are
commonly affected, as the prevalence increases with age.
The average age of diagnosis in cats is nine years. Breeds
thought to be more susceptible include Abyssinians and
Persians. CRF affects almost every body system causing many
changes throughout the body and usually results in the
following:

Abnormal filtration of blood and retention of waste
materials

Failure of hormone production (including substances that
stimulates the production of red blood cells
[erythropoeitin])

Disturbance of fluid, electrolyte and acid-base balance


Causes


CRF can be caused by several different processes. These may
include diseases, some of which can be secondary to other
disease processes or trauma, that may have caused acute
kidney failure such as:

• Toxins

• Poor blood flow and lack of oxygen (ischemia)

• Inflammatory disease

• Infections

• Cancer (neoplasia)

• Immune system abnormalities

Clinical
signs


• Increased thirst

• Excessive drinking

• Lethargy

• Vomiting

• Bad breath

• Anorexia

• Weakness

• Lack of coordination when walking

• Depression

• Increased urination (sometimes noted as pet using the
litter box more frequently, urinating in abnormal places in
the house or increased weight of the litter box)

Diagnosis
Diagnostic tests are needed to recognize CRF and
exclude other diseases. These tests may include:

• Complete medical history

• Complete physical examination

• Blood tests

• Urinalysis

• X-rays

• Ultrasound

Treatment
Although there is no cure, early detection can
slow the progression of the disease. CRF can be a life
threatening condition that requires hospitalization and
treatment for stabilization in extremely ill pets.
Treatments may include:

• Fluid therapy for dehydrated pets

• Management of blood abnormalities such as hyperkalemia or
hypokalemia (abnormal potassium blood levels), metabolic
acidosis and hyperphosphatemia

• Dietary therapy with protein a phosphorus restriction

• Free access to water

• Supportive care and careful monitoring of urine output

• Control of vomiting with diet and drug therapy as needed

• Management of anemia if needed

Summary

Chronic renal failure is life-threatening, and if you
suspect your pet has this condition, you should see your
veterinarian as soon as possible. Follow-up with your
veterinarian for examinations, laboratory work and
urinalysis. Blood and urine analysis should be repeated
within five to seven days after discharge.

Feed your pet the diet recommended by your veterinarian.
Provide free access to fresh clean water at all times. Some
owners can administer subcutaneous fluid to their pets at
home, if necessary. Your veterinarian can provide
instructions when indicated.

Administer any prescribed medications as directed by your
veterinarian. Drug therapy may include: phosphate binders;
potassium supplementation; or drugs for vomiting (such as
cimetidine or famotidine); or anabolic steroids for some
patients. Epogen may be given for anemia two to three times
weekly.

Prevention

There are no specific recommendations for prevention of
chronic renal failure. However, general suggestions
include:

• Providing frequent attempts to urinate and free access to
fresh clean water.

• Avoiding exposure to ethylene glycol and toxic plants
(such as Easter lily) that can cause acute kidney damage.