Hypocalcemia in Cats
The term "hypocalcemia" refers to abnormally low levels of calcium in the blood. This mineral plays an important role in vital bodily functions such as bone and teeth formation, blood clotting, milk production, muscle contraction, heart pumping, vision, and in the metabolism of hormones and enzymes. Therefore, calcium deficiency is a serious condition that requires immediate treatment.
Symptoms and Types
Symptoms vary depending on the underlying cause and severity of the problem. However, some of the more common symptoms include:
- Muscle twitching and trembling
- Uncoordinated or stiff gait
- Face rubbing against objects
- Lack of appetite
In mild cases, no symptoms may be observed until total calcium level fall well below normal (6.7 mg/dL).
Albumin is a protein found in the blood and significant fraction of calcium remains bound to albumin along with free calcium in the blood. If the level of albumin falls (hypoalbuminemia) due to some other problem or disease, it also affects the total calcium level. Although it accounts for more than 50 percent of hypocalcemia cases, low levels of calcium associated with hypoalbuminemia are not generally associated with any symptom.
Hypocalcemia may also be due to:
- Kidney failure (acute or chronic)
- Poor calcium absorption in the gut
- Alkalosis (condition in which the body fluids have excess base alkali)
- Hypoparathyroidism (Inadequate secretion of parathyroid hormone resulting in abnormally low levels of calcium in the blood)
- Hypoparathyroidism secondary to surgical removal of the thyroid gland (thyroidectomy)
- Nutritional secondary hyperparathyroidism
- Oxalate toxicity (e.g., lily, philodendron, etc.)
- Hypomagnesaemia (low levels of magnesium in the blood)
- Acute pancreatitis (inflammation of pancreas)
- Rickets (early age disease caused by deficiency of vitamin D and sunlight associated with impaired metabolism of calcium and phosphorus)
- Puerperal tetany (Clinical neurological syndrome characterized by muscular twitching and cramps and seizures; associated with calcium deficiency [hypoparathyroidism] or vitamin D deficiency or alkalosis)
- Phosphate-containing enemas used in patients with severe constipation
- Citrate toxicity in patients with multiple blood transfusions were conducted for some other health problem
There are occasions where a laboratory error reflects hypocalcemia when in fact your cat is just fine. To verify, it is important you give a detailed history of your cat’s health, onset and nature of symptoms, and possible incidence that might have precipitated the condition. Your veterinarian will also perform a thorough physical exam to evaluate all body systems to evaluate overall health of your cat. Routine tests including complete blood count, biochemistry profile, and urinalysis will provide valuable information about the blood calcium levels and information about the possible inciting cause(s) of hypocalcemia in your cat.
If kidney failure is the precipitating cause of hypocalcemia, complete blood count may show anemia in cats with chronic kidney failure. Anemia may also be present in patients with nutrition related secondary hyperparathyroidism or poor intestinal absorption of calcium in the gut.
In case of infection or inflammation (like pancreatitis), the number of white blood cells may have found to be abnormally high. In cats patients with pancreatitis, amylase and lipase enzymes are also found to be elevated. In cats with low levels of albumin (hypoalbuminemia), the biochemistry profile will show levels of albumin and disturbances in calcium levels. Meanwhile, if alkalosis is a cause of hypocalcemia, the blood gas analysis will reveal abnormally high levels of carbon dioxide in the blood of your cat.
Cats with with kidney failure, ethylene glycol toxicity, or oxalate toxicity may present abnormally high levels of Blood Urea Nitrogen (BUN) and creatinine. Phosphorous derangements are also common in conditions leading to low calcium levels and in patients with kidney problems, ethylene glycol toxicity, oxalate toxicity, and hypoparathyroidism, biochemistry profile may show abnormally high levels of phosphorous. High phosphorous levels and hypocalcemia may also be found in the blood if enemas containing phosphorous are used in patients requiring enema; in constipation, for example. Urinalysis may reveal abnormally low concentrated urine and presence of glucose in patients with kidney problems or ethylene or oxalate toxicity.
To determine if the low level of calcium is responsible for the symptoms present, your veterinarian may order further testing to find the concentration of ionized fractions of calcium, which is the active form of calcium in the blood. In case of ethylene glycol toxicity, the ethylene glycol test will be performed to confirm the toxicity. Your veterinarian will draw a blood sample from a vein of your cat and will send it to the laboratory to determine the levels of ethylene glycol in the blood. Normally, the level of ethylene glycol in the blood should be zero. If hypoparathyroidism is suspected, more detailed tests to evaluate the functions of the parathyroid gland will be conducted.
Radiography of the abdomen may reveal smaller than normal sized kidneys in cats with chronic kidney failure and large-sized kidney in animals with ethylene glycol toxicity, oxalate toxicity, or acute kidney failure. Cats with nutrition related secondary hypoparathyroidism, meanwhile, may display low bone density on bone X-rays.