Nephrotic Syndrome in Cats
Dr. Bari Spielman
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.
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 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.