Pheochromocytoma in Dogs: Adrenal Tumor Signs and Care

Pheochromocytoma is an uncommon tumor of the adrenal gland in dogs, and it can be one of the more puzzling conditions for owners to recognize. The tumor releases bursts of stress hormones, so a dog may seem completely normal for days and then suddenly pant hard, pace, tremble, or show a racing heartbeat for no obvious reason. Some dogs show no signs, and the mass is found by chance on ultrasound. This guide covers how the tumor works, the signs that warrant a veterinary exam, diagnosis, surgical care, and home support.

Important: This article shares general educational information for pet owners and is not a substitute for an in-person veterinary examination, diagnosis, or treatment. For any medical concern or emergency, contact your veterinarian promptly.

What Is Pheochromocytoma?

Dogs have two small adrenal glands, one sitting near each kidney. Each gland has two layers. The outer layer, called the cortex, makes hormones such as cortisol. The inner layer, called the medulla, makes catecholamines, the hormones epinephrine (adrenaline) and norepinephrine.

A pheochromocytoma is a tumor that grows from the cells of the adrenal medulla. Because those cells are built to produce catecholamines, the tumor often keeps making and releasing them on its own schedule, without the normal signals that tell the body when a stress response is needed.

Most pheochromocytomas in dogs are considered malignant, meaning they can invade nearby tissue and, in some dogs, spread to other organs. A key concern is that the tumor can grow into the large vein that runs alongside the adrenal gland and carries blood back to the heart. This is one reason careful imaging matters before surgery.

Why the Signs Come and Go

Epinephrine and norepinephrine prepare the body for sudden action. They speed up the heart, tighten blood vessels, raise blood pressure, and make breathing faster. In a healthy dog, these effects switch on briefly during excitement or fear and then settle.

A pheochromocytoma may release these hormones in unpredictable surges. During a surge, a dog can look as though it is under intense stress even while resting quietly at home. When the surge passes, the dog may return to normal, which is why many owners describe the problem as "episodes" or "spells."

Between episodes, some dogs have ongoing high blood pressure, while others have normal readings. Over time, sustained or repeated high blood pressure can strain the heart, kidneys, eyes, and brain. Our guide to high blood pressure in dogs explains why these organs are especially sensitive.

Signs That Warrant a Veterinary Exam

Signs vary widely, may be mild, and often appear in episodes. Many of them overlap with other common conditions, so they point toward the need for an exam rather than toward any single cause.

Episodic signs

• Heavy panting at rest: panting that is out of proportion to temperature, activity, or excitement. Our guide to panting in dogs explains what is normal.
• Restlessness and pacing: a dog that cannot settle, wanders, or seems anxious for no clear reason.
• Rapid or pounding heartbeat: you may feel the heart racing when you place a hand on the chest.
• Trembling or shaking: episodes of shivering that are not related to cold.
• Weakness: wobbly legs or reluctance to move during or after an episode.

Ongoing or gradual signs

• Decreased appetite or weight loss
• Increased thirst and urination
• Lethargy or seeming less interested in walks and play
• A swollen-looking belly in some dogs
• Intermittent vomiting or diarrhea

Because episodes may be brief, try to record one on your phone and note the time, what your dog was doing, and how long it lasted. This information can be very helpful to your veterinarian. If panting turns into labored breathing or your dog collapses, contact your veterinarian or an emergency clinic right away.

Signs That Need Help Right Away

A surge of catecholamines or a complication of the tumor can become an emergency. Contact your veterinarian or an emergency clinic right away if your dog shows any of the following:

• Collapse or fainting
• Breathing trouble, such as labored or struggling breathing, or heavy panting that does not ease and comes with weakness, collapse, or pale gums
• Pale, gray, or white gums
• Sudden blindness, bumping into objects, or dilated pupils that do not respond to light
• A severe nosebleed or bleeding that does not let up
• Seizures
• Severe weakness or inability to stand
• A suddenly swollen belly with weakness, which can signal internal bleeding

Sudden blindness and nosebleeds can be linked to very high blood pressure, while pale gums with collapse can suggest bleeding from the tumor. These are not wait-and-see signs.

How Veterinarians Diagnose Pheochromocytoma

There is no single simple test. Your veterinarian puts together several pieces of information, and the process often takes more than one visit.

1. History and physical exam: your description of the episodes, plus a check of heart rate, heart rhythm, gum color, the eyes, and the abdomen.
2. Blood pressure measurement: repeated readings help show whether blood pressure is high all the time or only now and then.
3. Bloodwork and urinalysis: these give an overall picture of organ function and help rule out other conditions with similar signs.
4. Abdominal ultrasound: imaging can show an adrenal mass and whether it appears to involve nearby blood vessels.
5. Metanephrine testing: metanephrines are breakdown products of catecholamines. Measuring them in urine or blood is one of the more useful tests for supporting a diagnosis of pheochromocytoma.
6. Advanced imaging: a CT scan is often recommended before surgery to map the tumor, check whether it has grown into the large vein nearby, and look for spread to the lungs or other organs.

Testing for cortisol-related conditions may also be done, because a mass from the adrenal cortex can cause different signs and needs a different plan. A final, definitive diagnosis usually comes from examining the tumor tissue after it has been removed.

Management and Surgery

The approach depends on the size of the tumor, whether it has invaded blood vessels or spread, and your dog's overall health. All medication should be given only as prescribed by your veterinarian.

Preparing for surgery with medication

Before surgery, dogs are commonly started on an alpha-blocker medication, as prescribed by your veterinarian. This class of medication relaxes blood vessels and is intended to keep blood pressure more stable, both day to day and during the hormone surges that can happen when the tumor is handled in surgery. Your veterinarian will decide how long your dog stays on it before the procedure. Some dogs also receive a beta-blocker medication to manage a rapid heart rate, but only once the alpha-blocker is in place and only as prescribed.

Adrenalectomy at a referral center

Surgical removal of the affected adrenal gland is called an adrenalectomy. It is a major operation, and it is usually performed by a board-certified surgeon at a referral or specialty hospital with an experienced anesthesia team and intensive care unit. Blood pressure and heart rhythm can change quickly during the procedure, so continuous monitoring is essential.

Dogs usually stay in the hospital for close observation after surgery. The first days are typically the most critical, and the surgical team will explain the specific risks for your dog.

When surgery is not an option

If the tumor cannot be removed safely, or if surgery is not right for your dog, your veterinarian may recommend ongoing medication to help manage blood pressure and heart rate, along with regular monitoring. Your veterinarian or a veterinary oncologist can discuss what this path involves for your dog's comfort and quality of life.

Supporting Your Dog at Home

Home care works alongside your veterinary team's plan and never replaces it.

After surgery, our guide to post-surgery recovery care at home offers practical tips for the weeks of rest that follow.

Common Mistakes and Myths

Myth: Panting always means a dog is just hot or excited.

Fact: panting at rest, especially in episodes with restlessness or a racing heart, deserves a veterinary exam.

Mistake: Waiting for the next episode before calling.

Fact: if episodes are recurring, schedule an exam now. If an episode includes collapse, breathing trouble, or pale gums, contact your veterinarian or an emergency clinic right away.

Myth: Every adrenal mass is cancer that needs surgery.

Fact: adrenal masses vary. Some are benign and cause no hormone changes. Testing and imaging help your veterinarian decide what kind of mass it is and what to do next.

Mistake: Giving leftover medication from a previous illness.

Fact: some medications can be dangerous for a dog with this tumor. Only give medication your veterinarian has prescribed for this condition.

When to Call Your Veterinarian

Schedule a veterinary exam soon if your dog shows milder or gradual changes, such as:

• Repeated bouts of panting or restlessness at rest that pass on their own
• Increased thirst or urination
• Decreased appetite, gradual weight loss, or lower energy
• Occasional trembling that is not related to cold or fear

Contact your veterinarian or an emergency clinic right away if your dog

• Collapses or faints
• Has breathing trouble
• Has pale, gray, or white gums
• Has sudden blindness or seizures
• Has a severe nosebleed
• Is severely weak or cannot stand
• Develops a suddenly swollen belly with weakness

If your dog has recently had an adrenalectomy, also call right away for any of these signs, or for vomiting, refusal to eat, or worsening redness, swelling, or discharge at the incision.

Frequently Asked Questions

Is pheochromocytoma painful for dogs?

The tumor itself is not usually described as painful, but hormone surges can make a dog feel distressed and unwell. A large tumor or bleeding can cause discomfort, so any sign of pain deserves an exam.

Can a dog live well after adrenalectomy?

Many dogs who recover from surgery go on to enjoy a good quality of life. The outlook depends on the size of the tumor, whether it has invaded blood vessels or spread, and how well the dog recovers.

Why does my dog need medication before surgery?

Handling the tumor during surgery can trigger large hormone surges. An alpha-blocker medication, as prescribed by your veterinarian, is intended to help keep blood pressure more stable before and during the procedure.

Is pheochromocytoma inherited?

It is not generally considered an inherited condition in dogs, and there is no known way for owners to predict it.

Key Takeaways

Pheochromocytoma is an uncommon tumor of the adrenal medulla that releases epinephrine and norepinephrine in unpredictable surges. Signs often come in episodes and can include heavy panting, restlessness, a racing heartbeat, trembling, and weakness, and some dogs have high blood pressure. Many tumors are found by chance on ultrasound. Diagnosis combines blood pressure checks, bloodwork, imaging, and urine or blood metanephrine testing, with a CT scan often used to plan surgery. Care usually involves an alpha-blocker medication before adrenalectomy at a referral center, all as prescribed by your veterinarian. Contact your veterinarian or an emergency clinic right away if your dog collapses, faints, has breathing trouble, pale gums, sudden blindness, seizures, or a severe nosebleed.