Overview of Acute Kidney Failure in Cats
Acute kidney failure (acute renal failure or ARF) is characterized by an abrupt decline in kidney function that leads to changes in the chemistry of the body including alterations in fluid and mineral balance. The changes that arise as a result of ARF affect almost every body system.
Below is an overview of Acute Renal (Kidney) Failure in Cats followed by in-depth information about the diagnosis and treatment of this serious condition.
The kidneys filter blood, remove the waste products of metabolism, and eliminate them in the urine. The kidneys also regulate the volume and composition of body fluids (including mineral concentrations and acid base balance), and produce hormones that stimulate the production of red blood cells (erythropoietin) and regulate calcium balance (calcitriol).
Acute kidney failure can be caused by toxic injury to the kidneys, decreased blood flow and oxygen delivery to the kidneys, infections, obstruction of the kidneys and prevention of urine elimination caused by a ruptured bladder.
The recent recognition of kidney failure is not necessarily the same as acute renal failure, since some animals with chronic kidney failure tolerate it for some time before symptoms are apparent.
There is no specific breed predilection but older animals are thought to be at greater risk for acute kidney failure. Acute kidney failure is more common in the fall and winter due to pet exposure to anti-freeze which contains ethylene glycol. Cats that are allowed to roam outside without supervision potentially have increased exposure to ethylene glycol.
The symptoms of ARF, although often severe, are not specific. Even with intensive management, ARF is a very serious disorder and often is fatal.
What to Watch For
Decreased urine production
Straining to urinate
Loss of appetite
Changes in water consumption and urination
Diagnosis of Acute Renal Failure in Cats
Your veterinarian will take a complete medical history specifically questioning exposure to ethylene glycol (anti-freeze), recent surgery or anesthesia (possibly causing decreased blood flow to the kidneys), exposure to drugs toxic to the kidneys (aminoglycoside group of antibiotics and non-steroidal anti-inflammatory drugs) and previous illnesses. The following diagnostic tests may also be necessary to recognize acute kidney failure and exclude other diseases. Tests may include:
Complete physical examination
Serum biochemistry tests
Complete blood count
X-rays of the abdomen
Culture of the urine
Ethylene glycol test
Blood tests for certain infections
Treatment of Acute Renal (Kidney) Failure in Cats
ARF is a life-threatening serious condition that requires hospitalization and intensive treatment. Treatment consists of identification and correction of life-threatening problems while searching for the underlying cause of ARF. Treatment for ARF may include one or more of the following:
Drugs that encourage urine production
Management of blood electrolyte abnormalities
Monitor urinary output
Control of vomiting
Management of anemia
Peritoneal dialysis or hemodialysis
Treatment with 4-methylpyrazole (Antizol®) or ethanol
Acute renal failure is a life-threatening condition and there is no effective home treatment. If you suspect your pet has this condition, or if you even suspect your pet may have consumed even a small amount of anti-freeze, you should call your veterinarian immediately. Your veterinarian may instruct you to induce vomiting before bringing your pet to the hospital.
Administer any medications prescribed by your veterinarian. Follow-up examinations and laboratory tests are important to assess your pet’s response to treatment. Allow free access to fresh clean water.
Avoid exposure to ethylene glycol (anti-freeze), and avoid exposure to drugs known to be toxic to the kidney (e.g. aminoglycoside antibiotics and non-steroidal anti-inflammatory drugs). Don’t allow cats to roam outside unattended.
In-depth Information on Acute Renal (Kidney) Failure in Cats
Acute renal failure (ARF) is a life-threatening disorder that can affect cats of any age.
Acute renal failure may be caused by decreased blood flow to the kidneys (called ischemia) or exposure to certain drugs or chemicals that are toxic to the kidneys.
Low blood flow to the kidneys may occur during anesthesia and surgery, and some drugs such as the non-steroidal anti-inflammatory agents like ibuprofen may also cause ARF by reducing blood flow to certain parts of the kidneys. Other causes of reduced blood flow to the kidneys include severe dehydration, shock, poor heart function, heat stroke and overwhelming infection (sepsis).
Many toxins can damage the kidneys and lead to ARF. Probably most important is ethylene glycol, which is the active ingredient of anti-freeze. Some antibiotics, especially a class of injectable antibiotics known as aminoglycosides, can cause damage to the tubules of the kidney and ARF. High blood calcium concentration likewise can damage the kidneys. Heavy metals (e.g. lead, arsenic), contrast dyes used for certain X-ray procedures, and some anesthetics also can damage the kidneys. An important toxin that specifically affects the kidneys of cats is the Easter Lily. Cats should never be allowed access to this group of plants. Some older drugs used to treat heartworms (thiacetarsamide) and fungal infections (amphotericin B) also are toxic to the kidneys.
Acute bacterial infection of the kidneys (called pyelonephritis) also can produce ARF.
Rare causes of ARF include glomerulonephritis (acute inflammation of the microscopic filtering devices of the kidney called glomeruli), glomerular amyloidosis (deposition of an insoluble type of protein in the kidney), disseminated intravascular coagulation (a body-wide clotting disorder), obstruction by blood clots of the arteries going to the kidneys, and hemolytic-uremic syndrome (liver and kidney failure caused by a specific strain of the bacteria E. coli).
Urinary obstruction is a type of reversible ARF that is treated by relieving the obstruction.
The most common causes of death during treatment of ARF are high blood potassium concentration, acid-base disturbances, very high concentrations of waste products in the blood that do not improve with fluid therapy and excessive administration of fluids with fluid accumulation in the lungs.
Animals unable to produce urine despite medical treatment have little chance for survival without peritoneal dialysis (infusion and removal of fluid into the abdominal cavity to remove waste products from the body). Hemodialysis can be performed in animals but is only available at selected referral hospitals and is very costly.
The prognosis for recovery of kidney function in ARF depends on the severity of the kidney damage, the underlying cause of ARF and supportive treatment.
Other medical problems can lead to symptoms similar to those encountered in ARF. A thorough medical evaluation is needed to diagnose ARF including laboratory testing and diagnostic imaging (X-rays or ultrasound). Warning signs that owners may see in pets with ARF include complete loss of appetite, marked lethargy, and vomiting. Unfortunately, these symptoms are very non-specific and may be caused by many other disease conditions. If is important to consult your veterinarian promptly.
Veterinary care should include diagnostic tests of kidney function, including blood tests and urinalysis, and subsequent treatment recommendations.
Diagnostic tests may be needed to recognize ARF and to exclude other diseases. Tests may include:
A complete medical history and physical examination
A complete blood count (CBC) to evaluate for signs of infection, inflammation, anemia or clotting abnormalities
Blood biochemistry tests to identify the presence of kidney failure. Commonly used tests to identify kidney failure include blood urea nitrogen (BUN), serum creatinine, and serum phosphorus. These test results are abnormally high in patients with kidney failure but these tests alone do not identify whether the kidney failure is acute or chronic. The veterinarian must use other tests and diagnostic reasoning to determine if the kidney failure is acute or chronic.
Urinalysis. Protein, blood or glucose may be observed in the urine of patients with ARF. The presence of microscopic crystals (such as calcium oxalate) can support a diagnosis of ethylene glycol (anti-freeze) poisoning. Microscopic casts of the kidney tubules often are seen with acute injury of the kidney, and white blood cells or casts may be found when kidney infection is present.
Additional diagnostic tests may be recommended for individual pets, including:
Kidney ultrasonography to determine if the kidney failure is acute or chronic and to help identify some specific causes of ARF (e.g. anti-freeze poisoning). Kidneys of patients with ARF typically are normal-sized to large. The presence of small, irregularly-shaped kidneys more often suggests a chronic kidney disease. Cats that drink anti-freeze often have kidneys that have increased density on ultrasound within a few hours of consuming anti-freeze.
A urine culture to identify urinary tract infection
Blood gas analysis to identify acid-base disturbances
Arterial blood pressure should be monitored because high blood pressure can complicate ARF. Central venous pressure may be monitored with a catheter in the jugular vein, especially if an inadequate volume of urine is produced.
Ethylene glycol testing to diagnose this toxicity; a special test kit is required for this purpose.
Kidney biopsy may be necessary to determine the cause of ARF and to guide treatment and prognosis.
Treatments for ARF may include one or more of the following:
Treatment of ARF must be individualized based on the cause and severity of the condition, as well as other conditions and complications identified by your veterinarian. Of great importance is the ability of the pet to produce urine. Low urine output or complete absence of urine production is a very serious finding.
Prognostic signs are poor if the pet does not respond to initial drug and fluid therapy. The ultimate goal of ARF management is to provide supportive care while allowing the kidneys time to recover. Your veterinarian should identify and correct the most life-threatening body chemistry problems while searching for the cause of ARF. Drugs that may be contributing to ARF should be discontinued. Dehydration is corrected by intravenous administration of fluids.
Vomiting may be induced if a kidney toxic agent has been ingested within the past few hours and the cat has not yet vomited. This is especially important in anti-freeze poisoning in which time is critical. Always call your veterinarian immediately if you believe your pet has consumed even the smallest quantity of anti-freeze.
Fluid therapy is important to increase kidney blood flow, correct and prevent dehydration and control abnormalities in serum electrolytes. Care must be taken to avoid overhydration, because the kidneys may not be able to produce sufficient urine to eliminate excess fluid. Overhydration can lead to fluid accumulation in the lungs (pulmonary edema) which may be life-threatening. Nevertheless, fluid therapy is extremely important initially, and drug therapy may be required to encourage urine production.
Fluid therapy may aid kidney function and encourage urine production. Diuretics may be used after rehydration. Mannitol and furosemide are diuretic agents that may be given, often in combination with dopamine. Dopamine is a chemical that causes dilation of the renal arteries and potentially can increase filtration in the kidneys when administered at low dosages.
Management of hyperkalemia (high blood potassium concentration) is important because potassium is toxic to the heart. Treatment may include sodium bicarbonate, glucose and insulin, calcium, or dialysis. An electrocardiogram should be monitored during treatment.
Acid base imbalance is corrected by administration of sodium bicarbonate.
Abnormally high blood phosphorus concentration may be treated with intestinal phosphorus binders such as aluminum hydroxide.
Cats with ARF may vomit frequently and several different drugs may be used to control this symptom.
Anemia due to blood loss can be treated with blood transfusion.
Ethylene glycol poisoning may be treated with 4-methylpyrazole (Antizol) or 20 percent ethanol.
Close patient monitoring is vital. Monitoring may include serial body weight (to facilitate proper fluid therapy), measurement of urine output (often with a urinary catheter), packed cell volume (an indication of the percentage of the blood that consists of red blood cells), and total plasma proteins to monitor fluid volume. Serial determination of serum biochemistry tests is necessary to determine if the animal is responding to treatment.
Treatment for ARF may require several days or as long as two to three weeks depending on the underlying cause of ARF and the response of the individual animal to treatment. This prolonged hospitalization can be frustrating for all concerned, because it frequently is impossible to predict the outcome. If conservative medical treatment fails, peritoneal dialysis (or in exceptional circumstances hemodialysis) may be a treatment possibility. Referral to a specialist or 24-hour critical care facility is required for dialysis treatment.
Euthanasia must be considered for pets that do not respond to treatment.
Follow-up Care for Cats with Acute Renal Failure
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical. Administer prescribed medications as directed by your veterinarian and be certain to contact your veterinarian if you are experiencing problems treating your pet. Specific instructions for home therapy vary on an individual pet basis.