Adrenal glands are small, peanut-shaped glands that sit close to each kidney. These glands produce around 30 different hormones that maintain vital functions in the body.
Unfortunately, the excellent blood supply to the adrenal glands means that aggressive cancers spread quickly to the liver, lungs, kidney or spleen.
Adrenal gland cancers are uncommon in dogs, and extremely rare in cats. The symptoms shown depend on the type of cancer present and which part of the gland is affected.
The 3 most common tumors of the adrenal gland are:
- Adrenocortical adenomas — small, well-demarcated tumors that spread slowly
- Adrenocortical carcinomas — large and invasive, and readily spread
- Pheochromocytoma — may be benign (cause a local problem) or malignant (spread to other parts of the body)
A tumor in the adrenal gland causes increased secretion of hormones. The signs of illness depend on which hormone is produced in excess. Often the tumor secretes hormones intermittently, so symptoms come and go.
Common symptoms include:
- Drinking a lot and urinating more
- A pot belly
- Excessive trembling
- Episodes of collapse
Dogs or cats with adrenal gland cancer may have high blood pressure and racing heart rates.
Unusual presentations include swelling of the back legs (because of pressure by the tumor on the major blood vessels to the rear end), and in some unfortunate cases, internal hemorrhage from a tumor that ruptures.
What Causes Adrenal Gland Cancer?
The short answer is that no one really knows. In humans, it is thought to be a genetic predisposition, but this has not been proven for cats or dogs.
A normal adrenal gland is a small structure not visible on radiographs; it requires a skilled ultrasonographer to identify them on a scan.
If your vet suspects adrenal gland cancer, she may want to perform screening imaging, such as X-rays or an ultrasound scan, to rule out other reasons for the pet’s ill health and to check for any spread of cancer.
A firm diagnosis is best made by an MRI, or CT scan, or an ultrasound scan performed by an expert. Even then, this tells the clinician only that the gland is abnormal and that a biopsy is necessary to put a name to the type of cancer.
The symptoms associated with adrenal gland cancer, such as high blood pressure, can be dangerous. Thus the first issue is to treat these conditions using beta blockers to slow a racing heart, and amlodipine to control high blood pressure.
There is no effective chemotherapy for adrenal gland cancer, and surgical removal of the diseased gland may be the best option. Unfortunately, the operation carries a risk of hemorrhage.
Also, handling the diseased gland during surgery causes release of adrenal hormones, which make the patient a high-risk anesthetic. All in all, this is a difficult operation that should only be undertaken at a clinic with intensive care facilities.
Unfortunately, nothing can prevent a pet from developing cancer of the adrenal glands, but fortunately, the condition is rare.
- Clinical Medicine in the Dog and Cat. Michael Schaer. Publ: Manson Publishing.
This pet health content was written by a veterinarian.