Diagnosis Of Cushing’s Disease In Dogs
There are many diagnostic procedures that are used to obtain a positive veterinary diagnosis of a dog for Cushing’s disease. Since the symptoms of Cushing’s disease are relatively generic, and can also be symptoms of many other medical conditions, more than one of these diagnostic procedures may be done by a veterinarian.
CBC, Urinalysis, Blood Chemistry Panel
All of these three tests are usually recommended by a veterinarian. A CBC (complete blood count), urinalysis, and blood chemistry panel can all help detect certain abnormalities in your dog’s body. Though not providing a definitive diagnosis, this may help your veterinarian to be able to form a positive diagnosis for Cushing’s disease. The most common abnormalities detected in dogs with Cushing’s disease are increased cholesterol, decreased kidney function, increased alkaline phosphate levels, and increased liver enzymes (more specifically, ALT).
This is another diagnostic procedure commonly used by a veterinarian when attempting to form a positive diagnosis for Cushing’s disease. By using an ultrasound machine, a veterinary technician is able to study the size and shape of your dog’s internal organs. Also, this ultrasound can be specifically used to examine the state of the adrenal glands.
Depending on which of the three types of Cushing’s disease your dog has, the Adrenal glands may appear slightly different. If there is a tumor in the adrenal glands, one adrenal gland will typically appear abnormally shaped, or much larger than the other adrenal gland. If your dog has pituitary dependent hyperadrenocorticism, the adrenal glands will usually appear of normal size and shape during the ultrasound procedure.
Low Dose Dexamethasone Suppression Test
This is another very common diagnostic procedure that is used to positively diagnose a dog with Cushing’s disease. In this procedure, the dog suspected of being afflicted with Cushing’s disease is given several low doses of dexamethasone. After roughly an 8-hour period, the dog is tested for blood cortisol levels. Most healthy dogs that are not being affected by Cushing’s disease will show an obvious decrease in blood cortisol levels when tested at this time.
However, if a dog has Cushing’s disease, there will be no change in the blood cortisol levels even after being given the dexamethasone. This is a relatively accurate method for diagnosing Cushing’s disease, since over 90% of dogs with Cushing’s disease will have no response to the dexamethasone.
Urine Cortisol:Creatinine Ratio
This test involves the participation of a dog’s owner, in order to be executed successfully. A dog’s owner will collect a sample of their dog’s urine at home. This is done outside the veterinary office, since the stress of being at the vet can cause fluctuations in the test results. Once the sample is collected, it is returned to the veterinary office, where it is then sent out to a special laboratory that will test the cortisol to creatinine ratio of the dog’s urine.
If a dog is being affected by Cushing’s disease, most of the time, the result will be abnormal. However, this is not a definitive diagnosis for Cushing’s disease, because an abnormal cortisol to creatinine ratio can also be caused by several other medical conditions.
Treatment For Cushing’s Disease In Dogs
Depending on the cause of hyperadrenocorticism (Cushing’s disease) in your dog, several different treatment options are available. Treatment for Cushing’s disease is also heavily dependent on how well your dog would be able to handle surgery, or other procedures that will put significant stress on your dog’s system. Some treatment options involve chemotherapy, which may not be feasible for older or very ill dogs.
Withdrawal Of Glucocorticoids
If your dog has iatrogenic hyperadrenocorticism, treatment is fairly simple. Since this type of Cushing’s disease is caused by over-administration of glucocorticoids due to treatment of a chronic condition, treatment simply involves the gradual withdrawal of the glucocorticoids. With the subsequent decrease of corticosteroids in your dog’s system, the adrenal glands will eventually begin to function normally once again.
This is a treatment that is usually used for adrenal-based hyperadrenocorticism. In this treatment procedure, the dog undergoes an operation to remove the adrenal gland tumor, as well as the affected adrenal gland. In most cases, this is able to “cure” adrenal-based hyperadrenocorticism, since the tumor (if benign) usually doesn’t manifest in the remaining adrenal gland.
However, since one of the symptoms of Cushing’s disease is slow healing of wounds, this procedure must be done with extreme care. Prior to surgery, some dogs are given ketoconazole which sometimes helps to minimize symptoms of Cushing’s disease.
Since roughly half of adrenal gland tumors are malignant, however, it’s possible that the tumor has metastasized to other organs such as the lungs or liver. Most adrenal tumors aren’t discovered in time to perform surgery, mostly due to the lengthy diagnosis required by most cases of Cushing’s disease. Also, some older dogs may not survive this procedure, so many dog owners choose an alternate form of treatment.
In the roughly 80-85% of cases of Cushing’s disease where it is pituitary-dependent, Lysodren is the most popular, and most effective treatment.
To treat Cushing’s disease, Lysodren targets the outer layer of the adrenal glands, also called the “cortex”. With regular administration of Lysodren, the cortex tissue of the adrenal gland is gradually destroyed, usually in about a week of daily Lysodren treatments. The damaged adrenals are not able to respond as effectively to the over-secretion of ACTH by the pituitary gland, so blood cortisol levels subsequently drop.
After a dog’s blood cortisol levels are within a normal level, they must be given Lysodren for the rest of their lives to maintain their condition. The danger with Lysodren is that the adrenals may incur too much damage, which would result in below-normal blood cortisol levels, also known as Addison’s disease.
Ketaconazole is usually used in dogs that don’t respond to Lysodren treatment. It can be used to treat both adrenal-based and pituitary-dependent hyperadrenocorticism. Ketaconazole is an anti-fungal medication that also suppresses hormone production. Though safer to use than Lysodren, approximately 25% of dogs do not respond to this method of treatment.
This treatment method has been approved for treatment of Cushing’s disease in dogs, though it’s effectiveness is highly debated. Anipryl decreases the production of ACTH by increasing levels of dopamine. The decreased ACTH levels will cause a drop in cortisol levels in pituitary-dependent cases of hyperadrenocorticism. Though clinically approved for use as a treatment for Cushing’s disease, many veterinarians claim that it is only 15-40% effective.