Hypercalcemia (High Blood Calcium) in Cats

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Overview of Feline Hypercalcemia 

Hypercalcemia refers to an abnormally high blood concentration of calcium. Blood calcium concentrations are measured in milligrams (mg) per deciliter (dl). One hundred milliliters equals one deciliter. Normal values for blood calcium concentration vary slightly from one laboratory to another but approximately 9.0 to 11.6 mg/dl is considered normal in adult cats. Blood calcium concentrations above 13.0 mg/dl are abnormal and warrant diagnostic evaluation and treatment.

Below is an overview on hypercalcemia in cats followed by detailed information on the diagnosis and treatment of this condition. 

Some relatively common (and benign) situations can cause erroneously high blood calcium concentrations to be reported by the laboratory depending on the analyzer used. Examples include blood samples with high fat content (lipemia) due, for example, to collection of blood soon after a meal or release of hemoglobin from the red blood cells during processing of the blood (hemolysis). Certain anticoagulants and detergents used to clean laboratory glassware also may cause erroneously high blood calcium concentrations to be reported. In these situations, the blood calcium concentration should be determined again using a properly collected blood sample that is free of lipemia and hemolysis.

Dehydration is a common clinical situation that can result in mildly increased blood calcium concentration. Blood calcium concentration should be re-evaluated after the patient has been rehydrated by intravenous or subcutaneous (under the skin) administration of fluids.

What to Watch For

  • Loss of appetite
  • Increased urine production
  • Increased water consumption
  • Vomiting
  • Weakness
  • Lethargy
  • Dehydration
  • Diagnosis of Hypercalcemia in Cats

    A thorough diagnostic evaluation of the cat is necessary if hypercalcemia persists after correction of lipemia, hemolysis and dehydration, because high blood calcium concentration can be a marker of some serious underlying disease processes including several different types of cancer. Routine laboratory testing provides information about the total concentration of calcium in the blood. It also may be necessary, however, for your veterinarian to have the laboratory measure the active component of blood calcium (ionized calcium). This component contributes to many of the clinical symptoms and physiologic consequences of hypercalcemia.

    The symptoms of hypercalcemia are nonspecific. Diagnostic tests are needed to recognize hypercalcemia and exclude other diseases causing similar symptoms. Tests may include:

  • A complete medical history and physical examination. The medical history will include questions about changes in water consumption and urination, change in appetite, weight loss, previous illnesses, medications being given, and exposure to toxins such as vitamin D-containing rat poison, vitamin D-containing topical ointments or toxic plants. Physical examination may include palpation of the abdomen to evaluate for enlargement of the liver or spleen, palpation of lymph nodes located under the skin to detect enlargement, palpation of the anal sacs to detect masses because one important cause of hypercalcemia is cancer of anal sac glands, and listening to the chest with a stethoscope.
  • A complete blood count (CBC) to evaluate red blood cell count and rule out anemia and blood protein concentration
  • Serum biochemistry tests to evaluate your cat’s general health and determine the effects of hypercalcemia on other body systems, especially the kidneys
  • Urinalysis to evaluate the effects of hypercalcemia on the ability of the kidneys to concentrate urine
  • Blood ionized calcium concentration to evaluate the biologically active form of calcium
  • Treatment of Hypercalcemia in Cats

    Treatment for hypercalcemia is determined by the underlying cause and the severity of your cat’s hypercalcemia and its effects on kidney function. Emergency treatment may be necessary when blood calcium concentration is very high. This may include hospitalization for intravenous fluid therapy and drug treatment.

    Serious damage to the kidneys and mineralization of soft tissues can occur if very high blood calcium concentration is allowed to persist.

    Home Care and Prevention

    Administer any medications prescribed by your veterinarian. Follow-up with your veterinarian for physical examinations and repeated testing of blood calcium concentration.

    If the underlying cause of hypercalcemia is not identified on initial evaluation, or if your cat responds inadequately to treatment, further diagnostic evaluation and treatment will be necessary.

    Make sure your cat has free access to ample amounts of fresh drinking water. Avoid exposure of your cat to toxins known to cause hypercalcemia such as vitamin D-containing rat poisons, topical ointments containing vitamin D-like compounds like calcipotriene, and plants such as day-blooming Jessamine (Cestrum diurnum), Solanum malacoxylon and Trisetum flavescens.

    In-depth Information on Hypercalcemia in Cats

    Several serious medical conditions can result in hypercalcemia. It is important to identify the underlying cause of hypercalcemia in your cat so that effective treatment can be instituted. Disorders that can cause hypercalcemia include:

  • Lymphosarcoma, a type of cancer
  • Chronic kidney failure sometimes caused by hereditary kidney disease
  • Primary hyperparathyroidism, which is overactivity of the parathyroid gland usually due to a benign tumor called an adenoma
  • Hypoadrenocorticism, also known as Addison’s disease, which is a hormonal disorder caused by insufficient production of steroid hormones by the adrenal glands
  • Apocrine gland adenocarcinoma of anal sac, or a cancer of the glands of the anal sacs
  • Vitamin D intoxication caused by consumption of vitamin D-containing rat poison
  • Vitamin D intoxication caused by consumption of vitamin D-containing plants such as day-blooming Jessamine (Cestrum diurnum)
  • Vitamin D intoxication caused by consumption of topical ointments containing calcipotriene used to treat psoriasis in people
  • Multiple myeloma, which is a cancer of antibody-producing cells called plasma cells
  • Other cancers including squamous cell carcinoma, thyroid adenosarcoma, nasal adenocarcinoma, mammary gland adenocarcinoma, and others
  • Acute kidney failure
  • Granulomatous diseases, which refer to a specific type of inflammation, such as blastomycosis (fungal infection). In these diseases, inflammatory cells (called macrophages) are thought to produce vitamin D-like chemicals
  • Osteomyelitis, bacterial infection of bone
  • Overactivity of the parathyroid glands due to nutritional disturbances
  • Dehydration with increased blood concentrations of albumin, a major protein of the blood
  • Hypercalcemia can occur normally in young growing cats
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