Overview of Nephrotic Syndrome in Cats
Nephrotic syndrome is characterized by the combination of protein in the urine, low protein level in the blood, high cholesterol and abnormal fluid accumulation in any part of the body (edema).
Below is an overview of Nephrotic Syndrome in Cats followed by detailed information on the diagnosis and treatment of this condition.
Dogs are affected more commonly than cats. The average age of onset varies, but middle-aged dogs are most commonly affected. Several breeds are felt to be at higher risk than average.
Two common causes of nephrotic syndrome include:
Glomerulonephritis (GN) in Cats
This is an inflammation of the kidney – specifically in the area referred to as the glomerulus.
Familial (appearing in multiple members of the same family) GN has been reported in cats.
Acquired GN is uncommon.
Amyloidosis in Cats
This is the deposition in organs and tissues of a protein called amyloid that compromise normal function.
Familial amyloidosis has been reported in the Oriental shorthair, Abyssinian and Siamese.
Acquired amyloidosis is uncommon.
The type, number, and severity of clinical signs associated with the nephrotic syndrome are variable. Signs may be associated with an underlying disease process, such as with infection and immune disease.
What to Watch For
Edema or ascites (fluid in the abdominal cavity)
Acute dyspnea (difficulty breathing) or panting
Loss of vision
Diagnosis of Nephrotic Syndrome in Cats
Complete blood count (CBC)
Urine Protein:Creatinine Ratio
Bacterial urine culture
Chest and abdominal X-rays
Abdominal ultrasound +/- kidney biopsy
Treatment of Nephrotic Syndrome in Cats
It is most important to determine whether the patient’s condition warrants admission to the hospital for treatment, or treatment at home as an outpatient. Treatment may include:
Fluid and electrolyte therapy
Treatment for concurrent high blood pressure, edema, ascites or thrombosis (blood clots)
Home Care and Prevention
Administer all medication and diet as directed by your veterinarian. Return for follow up evaluation, and/or notify your veterinarian if your pet exhibits recurrence or progression of signs.
There are no recommendations to prevent nephrotic syndrome.
In-depth Information on Nephrotic Syndrome in Cats
Nephritic syndrome is characterized by the combination of protein in the urine, low protein level in the blood, high cholesterol and abnormal fluid accumulation in any part of the body (edema). In addition, systemic hypertension (high blood pressure) and thromboembolism (blockage of blood vessels with blood clots) are commonly associated.
Nephrotic syndrome most often occurs secondary to glomerulonephritis or amyloidosis. The clinical signs associated with the nephrotic syndrome may initially be mild, but as the disorder progresses, signs can be devastating to the patient. Depending on the specific case, certain diagnostics and therapeutics are recommended and tailored to that individual.
Several diseases/disorders appear similar to the nephrotic syndrome. These include:
Severe liver disorders such as inflammation of the liver (hepatitis), cancer, infection and cirrhosis often cause severe hypoalbuminemia and in turn, ascites or edema.
Protein losing enteropathy, which are intestinal disorders that cause profound protein loss. These include inflammatory bowel disease, lymphangiectasia and cancer and can cause severe hypoproteinemia and fluid accumulation.
Proteinuria is commonly seen with inflammatory urinary tract diseases such as bacterial bladder infection, infection or inflammation within the kidney, stones within the urinary tract and cancer. These disorders are often accompanied by an active or inflammatory urinalysis. It is important to differentiate these from the nephrotic syndrome.
Proteinuria is the hallmark of glomerulonephritis and amyloidosis. These disorders are most often associated with an inactive or non-inflammatory urinalysis.
Hypertension second to other systemic disorders needs to be ruled out, including hyperadrenocorticism (Cushing’s disease), primary kidney disease and heart disease.
Thromboembolic complications need to be differentiated from other disorders that cause thrombosis, such as hyperadrenocorticism.
When the patient with nephrotic syndrome is in kidney failure, other causes of increased thirst and urination, to include hyperadrenocorticism (Cushing’s disease), diabetes mellitus and liver disease, need to be ruled out.
Certain diagnostic tests must be performed to diagnose the nephrotic syndrome and exclude other disease processes that may cause similar symptoms. A complete history, description of clinical signs, and thorough physical examination are all an important part of obtaining a diagnosis of nephrotic syndrome. In addition, the following tests are recommended:
A complete blood count (CBC) may be within normal limits, although it may be helpful in evaluating for concurrent disorders, such as low red blood cell count (anemia) or elevations in white blood cell count consistent with inflammation or infection.
A biochemical profile will assess the level of hypoproteinemia and hypercholesterolemia, and may reveal elevations in kidney enzymes or electrolyte abnormalities if the patient is in concurrent kidney failure.
A urinalysis generally reveals proteinuria, and may contain casts, which are tubular shaped rafts of protein.
A urine protein:creatinine ratio confirms and quantitates proteinuria. The magnitude of proteinuria generally correlates with the severity of disease, making this test a useful parameter to assess response to therapy or progression of disease. It is a very simple urine test that can be performed by your veterinarian.
Abdominal X-rays are an important part of any baseline work-up. Although they may be within normal limits, they may reveal ascites, changes in kidney size, or they may rule out other diseases and causes of clinical signs.
Abdominal ultrasound may be helpful in evaluating the kidney. Although ultrasound does not diagnose the nephrotic syndrome, it may facilitate a diagnosis by allowing the ultrasonographer to obtain a kidney biopsy. Ultrasound itself is a noninvasive procedure, but there are some minor risks associated with a guided kidney biopsy; this test should be performed by one with expertise.
Your veterinarian may recommend additional tests to exclude or diagnose concurrent conditions. Since cases of glomerulonephritis and amyloidosis can occur secondary to chronic infectious or inflammatory disorders, additional testing is sometimes helpful and rewarding. These tests are not necessary in every case, but they may be of benefit in certain individuals, and are selected on a case-by-case basis. These include:
Blood pressure evaluation is extremely important, as many animals with the nephrotic syndrome are hypertensive.
Thoracic X-rays are indicated in some of these patients, as they assess for fluid in the chest cavity or edema. They may be helpful in documenting lung thrombosis (clots), and/or help assess other disease processes.
Evaluation for infectious disorders such as Lyme disease or heartworm disease may be indicated in certain endemic areas.
Antithrombin III is a substance that prevents a hypercoagulable state or tendency to produce blood clots. Levels are often recommended, and are most often low.
A kidney biopsy may be indicated in some patients, as it is necessary to document whether the underlying cause is glomerulonephritis or amyloidosis. This differentiation may help formulate a therapeutic plan and more accurate prognosis. This procedure is not without risks, so patient evaluation and selection is critical. This is an invasive procedure that may be performed with the guidance of ultrasound, and may necessitate exploratory surgery in certain cases.
Stable patients can be treated as outpatients as long as they are monitored closely for response to therapy. Patients who are in kidney failure, have severe edema, have thromboembolic disease, or are profoundly hypertensive should be hospitalized. It is very important that all recommendations by your veterinarian are followed very closely, and any questions or concerns that arise during the treatment protocol are addressed immediately.
Correction of any underlying predisposing factor is imperative to treatment. If the underlying cause cannot be identified and corrected, these individuals are treated symptomatically and generally progress to kidney failure, hypertension and fluid accumulation.
Dietary modification is recommended in these patients. A low-salt, low-protein diet is recommended.
Intravenous fluid therapy may be necessary in patients who are in kidney failure.
If hypertension is not controlled by sodium restriction, medical therapy is indicated.
Treatment for edema and/or ascites should be instituted only if the pet is uncomfortable or in distress. Paracentesis and/or diuretics to remove fluid from the body should be used as directed by your veterinarian.
Anti-thrombotic therapy, such as low-dose aspirin, is sometimes recommended as a preventative measure in some patients.
Follow-up Care for Cats with Nephrotic Syndrome
Optimal treatment for your pet requires a combination of home and professional veterinary care. Follow-up can be critical, especially if your pet does not rapidly improve. Diagnostic follow-up is extremely important in these patients.
Urine protein:creatinine ratios, blood pressure, body weight, protein, and kidney values should be checked on a regular basis as directed by your veterinarian. Administer all prescribed medication and alert your veterinarian if you are experiencing problems treating your pet.
Avoid using drugs that are harmful to the kidneys. Affected animals of breeds with suspected familial disorders should not be bred. Long term prognosis is guarded.