Definitive Tests for Feline Cushing's Disease

Feline Cushing's disease, or hyperadrenocorticism, is caused by a tumor on the pituitary or adrenal glands which results in an overproduction of the hormone cortisol. Symptoms include increased urination, water drinking or appetite, weight fluctuations, bloated bellies, thinning hair or skin and a dull coat. Since there are no definitive tests for the disease, veterinarians perform a variety of tests which help them to make a diagnosis of Cushing's disease, according to Washington State University.

  1. Blood Tests

    • A complete blood count will be taken, and the vet will look for an increase in red blood cells. The CBC measures the levels of every different type of cell in the blood. A stress leukogram is taken to check the proportions of different types of white blood cells. There is a typical pattern produced by cortisol as the body responds to stress. If this pattern is seen in a patient that does not seem stressed, there is a possibility that an excess of cortisol is present. This can indicate Cushing's disease.

    Urinalysis

    • Cushing's disease causes immunosuppression, so evidence of bacterial infections may be present. The urine may be obtained by catching a sample during normal urination, passing a catheter into the bladder or inserting a needle through the body into the bladder for a sample. Many animals with Cushing's disease carry bladder infections without any symptoms, such as straining to urinate.

    X-rays and Ultrasound

    • X-rays can reveal calcium near the adrenal glands, which suggests a tumor. They may also show an enlarged liver or enlarged adrenal glands. This test can help to make a diagnosis for Cushing's disease.

    Biomedical Profile

    • Testing may show that the cat has elevated glucose, elevated cholesterol, elevated alkaline phosphatase or low calcium levels.

    ACTH Stimulation Test

    • This test is performed after the blood has been injected with heparin, and then the cortisol levels are checked. In the normal cat, the level is expected to be up to 600 nmol/l, and levels higher than that lead the veterinarian to perform further tests for Cushing's disease. The cortisol levels are increased by the tumor located on the pituitary or adrenal glands.