A pheochromocytoma is a tumor of the adrenal gland, which causes the glands to over produce certain types of hormones. This usually causes an increase in the heart rate, blood pressure, and breathing rate. These symptoms are intermittent (not present all of the time) because the hormones that cause them are not made all of the time or are made in low amounts.
Pheochromocytomas are rare in dogs. They usually occur in dogs that are older than seven years but can occasionally occur in younger dogs as well. Because this tumor affects an endocrine gland that functions to spread hormones, pheochromocytomas commonly spread to organs that are near them and can rapidly metastasize to other areas of the body.
This form of cancer can have many different types of symptoms. These include:
- Lack of appetite (anorexia)
- Lack of energy (lethargy)
- No interest in usual activities (depression)
- Rapid breathing (tachypnea)
- Increased urination (polyuria)
- Increased thirst (polydipsia)
- Weight loss
- Bloated abdomen
- Symptoms may seem to come and go
- Occasionally no symptoms
Pheochromocytoma is labeled idiopathic, since there is no known cause for this condition. Research is still ongoing with this form of cancer.
Your veterinarian will need a thorough medical history of your dog's behavior, health and onset of symptoms. A rapid heart rate (tachycardia) is sometimes found during the physical examination. Your veterinarian will palpate your dog's belly to see if a mass can be felt or if there is extra fluid present. Sometimes, there will not be anything that appears to be abnormal during the examination. Standard blood work, including a complete blood count, biochemical profile and urinalysis will be ordered. These will indicate how well your dog's internal organs are working and whether there are any infections present in the body. Your veterinarian may also order a special blood test which tells whether the adrenal gland is functioning normally. Your dog's blood pressure will be taken, and in some cases, the blood pressure will be very high, indicating hypertension.
If your dog's heart rate is very high, or its heart seems to have an abnormal rhythm, your veterinarian may order an electrocardiogram (ECG) to check the electrical capability of the heart. Your veterinarian will also order x-rays and/or ultrasound images of your dog's abdomen and thorax (chest). If there are abnormalities of the internal organs, they may show up on an x-ray or ultrasound image. Further diagnostic tests may include a computed tomography (CT) scan or magnetic resonance image (MRI). These imaging tools are higher sensitivity tests, which can give a more detailed picture of your dog's internal organs. To confirm a final diagnosis, your veterinarian will need to take a biopsy of the adrenal gland for laboratory analysis. It is common for dogs with a pheochromocytoma to have more than one medical problem diagnosed and treatment will be approached according to which condition is most critical.
Surgery is the chosen treatment for a pheochromocytoma. If your dog has high blood pressure or a very high heart rate, these conditions will be treated with medication and your pet stabilized before surgery can be performed. If its blood pressure or heart rate are dangerously high, your dog may need to be in intensive care before surgery can be performed. Some dogs need to be on medication to control blood pressure and heart rate for several weeks before surgery can be performed.
During surgery, the affected adrenal gland will be removed. Because the adrenal gland is near some very large blood vessels, surgery can be difficult. If, during surgery, it is found that other organs are being affected by the tumor, they will need to be removed as well, either in part or in their entirety, depending on the organ. After surgery, your dog will be kept in the hospital intensive care unit until it is stable. Problems during and after surgery are common. Your veterinarian will monitor for bleeding, high or low blood pressure, abnormal heart rhythm, difficulty breathing, or post-operative infections. Some dogs do not make it through recovery because of these problems, especially if they have other medical problems. Your veterinarian will help you to decide the best course of action based on the diagnosis and expectations for recovery.
Living and Management
Once your dog's tumor has been removed and it is able to return home with you, it will take a little time for your dog to return to a normal life with normal activity. Dogs may live three or more years after surgery if they have no other medical problems.