What is idiopathic hypercalcaemia of cats (IHC)?
IHC is the most common cause of high blood calcium in cats. The cause IHC is unclear, but in most situations it can be effectively controlled.
High blood calcium (hypercalcaemia) can be caused by many diseases in cats including cancer, hormonal problems and vitamin D excess. Idiopathic hypercalcaemia (IHC) is likely the most common cause of high blood calcium in cats, however the cause of the disease is currently unknown and research is ongoing in this area.
What are the signs of hypercalcaemia in cats?
IHC can be detected as an incidental finding (where the cat has no specific symptoms of the high calcium), but when high blood calcium is causing signs, these can include:
- Reduced appetite
- Weight loss
Unlike dogs, cats rarely become thirsty when they have high blood calcium. High blood calcium will lead to increased levels of calcium in the urine, which can cause stones to form in the kidneys or bladder. Kidney stones can cause blockages of the ureters (the pipes which transport urine from the kidneys to the bladder), which results in kidney damage. Bladder stones can cause bladder irritation which tends to manifest as small, frequent urination, bloody urine, or peeing in strange places in the house.
How is idiopathic hypercalcaemia of cats diagnosed?
High blood calcium is documented on a blood test. The most basic test of blood calcium is a measure called total calcium; unfortunately total calcium assessment does not always represent the true calcium level and often an additional blood test called ionised calcium, which measures the true level of active calcium, is required to diagnose high blood calcium.
There is no specific test for IHC, and it is important to exclude the other causes of high calcium (including cancer, hormonal problems and vitamin D excess)- as these problems would be treated in other ways.
How is IHC treated?
There are several treatments which can prove effective in the control of this condition. Specific diets have been shown to be helpful in reducing the calcium levels. Medications called bisphosphonates, which reduce calcium release from the bones can often be used to control the problem. Steroids such as prednisolone can often help too. Sometimes a combination of treatments is required to normalise the blood calcium.
What is the long term outlook (prognosis)?
It can take a few weeks or months to determine the best treatment regime for a patient with IHC, but in the vast majority of cats the condition can be well controlled. Monitoring will be required to ensure that the blood calcium levels remain normal.
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