CONDITION
Pheochromocytoma in Dogs
A pheochromocytoma is a tumour that develops in specialised tissue inside the adrenal gland—a small organ that sits near the kidney and produces hormones involved in stress response and blood pressure regulation. These tumours can release surges of adrenaline and related hormones into the bloodstream, sometimes unpredictably, which may create episodes of rapid heart rate, restlessness, heavy breathing, or collapse. In other cases, the release is steadier and signs develop more gradually. Owners often arrive at this possibility after observing intermittent episodes that seem out of character—panting without obvious cause, sudden weakness, or behaviour that suggests anxiety or discomfort—sometimes with normal periods in between. The episodes can vary in intensity and frequency, and in some dogs the condition is discovered incidentally during imaging or investigation for another concern. This page explores the signs that may prompt consideration of a pheochromocytoma, what is happening inside the adrenal gland and the wider body, how the condition is investigated through blood tests and imaging, and the approaches that exist for managing it, including surgery and medical options. The course and outcome depend on factors including the size and behaviour of the tumour, whether it has spread, and the individual dog's response to treatment.
Why this matters now
Pheochromocytomas tend to appear in middle-aged to older dogs, often between eight and eleven years of age, though younger animals can occasionally be affected. Earlier, smaller case series found no consistent breed or sex predisposition, but a larger 2025 UK population-based study has since identified significant breed predispositions—the Soft-Coated Wheaten Terrier, German Pointer, and Miniature Schnauzer are all at increased risk compared with crossbred dogs—along with higher odds in neutered males. The tumour develops without clear environmental or nutritional triggers; it arises from chromaffin cells that are present from birth and may undergo change over time.
The course can be quite variable. Some dogs experience intermittent episodes for weeks or months before the pattern becomes clear, whilst others develop signs more steadily as hormone release becomes sustained rather than episodic. The tumour may remain confined to the adrenal gland for a period, or it may begin to invade nearby blood vessels and tissues, and in some cases cells spread to the liver, lungs, or regional lymph nodes, which influences both the signs observed and the options available.
Signals & patterns
Early signals
Episodes of panting without exertion
A dog may begin panting heavily whilst resting or in cool conditions, often with no clear trigger. The episodes can last minutes to hours and may resolve completely, leaving the dog behaving normally in between.
Restlessness or pacing
Owners sometimes notice periods where the dog seems unable to settle, moving from room to room or shifting position frequently. This restlessness may coincide with panting or occur independently, and can be mistaken for anxiety or discomfort from another cause.
Intermittent weakness or wobbliness
Some dogs show brief episodes of unsteadiness in the hindlimbs, or they may sit or lie down suddenly during activity. The weakness typically passes, and the dog may appear entirely normal within minutes or hours.
Increased heart rate noticed at rest
An owner placing a hand on the chest may feel a noticeably fast or forceful heartbeat when the dog is calm or lying down. This can be episodic, corresponding to surges of hormone release, or it may become more persistent over time.
Later signals
Collapse or loss of consciousness
In some dogs, episodes progress to sudden collapse, with or without loss of awareness. The dog may recover spontaneously after seconds to minutes, but the events can recur and may become more frequent.
Visible abdominal swelling or discomfort
As the tumour enlarges or if bleeding occurs around it, the abdomen may appear distended or the dog may show signs of discomfort when the area is touched or when moving. This can reflect the physical mass or accumulation of fluid.
Persistent lethargy or reduced appetite
Dogs may become less interested in food or play, and rest more than usual. This shift can reflect the metabolic cost of sustained hormone excess, the presence of metastatic disease, or the effects of the tumour on surrounding structures.
Click to read about the biological mechanisms
How this is usually investigated
Investigation typically begins with a detailed history, particularly noting the pattern and timing of episodes, and a physical examination that may reveal an elevated heart rate or high blood pressure, though these can be intermittent. Blood and urine tests are used to look for biochemical changes and measure hormone breakdown products, whilst imaging helps locate a mass in the adrenal region and assess whether nearby structures are involved. The diagnosis often builds over several steps, as initial findings prompt more targeted tests and the picture becomes clearer.
Blood pressure measurement
Blood biochemistry and haematology
Urinary or plasma catecholamine metabolites
Abdominal ultrasound
Computed tomography or magnetic resonance imaging
Options & trade-offs
Management is often a combination of medical and surgical approaches, tailored to the tumour's size and behaviour, the presence or absence of spread, and the individual dog's cardiovascular stability and general health. Some owners and vets focus on controlling signs medically, whilst others pursue surgical removal when the tumour appears confined and the risks are judged acceptable. No single path suits every dog, and decisions tend to evolve as the condition declares itself more fully.
Surgical removal of the tumour
Adrenalectomy involves removing the affected adrenal gland and, when feasible, the entire tumour. The procedure requires careful anaesthetic management to minimise the risk of blood pressure surges during handling of the gland, and the surgery itself can be technically demanding if the tumour involves major blood vessels. When the tumour is confined and completely excised, hormone-related signs typically resolve.
Trade-offs: The perioperative period carries significant cardiovascular risk, particularly in dogs with unstable blood pressure or large, invasive tumours. Recovery can be prolonged, and in cases where the tumour has spread or cannot be fully removed, surgery may offer limited benefit. Access to experienced surgical and anaesthetic teams is often necessary.
Medical management with alpha- and beta-adrenergic blockers
Medications that block the effects of catecholamines on blood vessels and the heart can reduce blood pressure, slow heart rate, and lessen the intensity of episodes. Alpha-blockers are typically introduced first to allow blood vessels to relax, followed by beta-blockers to temper the heart's response. Doses are adjusted gradually based on the dog's signs and measured blood pressure.
Trade-offs: Medical management controls signs rather than removing the source, and some dogs continue to experience episodes, particularly if hormone release is erratic. Lifelong medication is required, and not all dogs tolerate the drugs equally well. This approach is often favoured when surgery carries high risk or when the tumour has spread.
Monitoring without immediate intervention
In some cases, particularly when signs are mild or intermittent and imaging suggests a small, stable tumour, observation with regular follow-up may be chosen. Blood pressure, clinical signs, and repeat imaging at intervals help track whether the condition is progressing or remaining quiescent.
Trade-offs: This approach avoids the risks and costs of early intervention but requires vigilance and acceptance that signs may worsen unpredictably. It is less suitable for dogs with frequent or severe episodes, and the window for surgery may narrow if the tumour grows or invades surrounding structures.
Chemotherapy for metastatic disease
When imaging confirms spread to distant sites, chemotherapy agents that target catecholamine-producing cells may be considered. These drugs are not widely available and are typically offered through specialist centres. The aim is to slow progression and reduce hormone production rather than to cure the disease.
Trade-offs: Response is variable, and the treatment can be expensive and require repeated visits. Side effects depend on the agent used, and the benefit in terms of quality of life and survival time is uncertain for many dogs.
Common misconceptions
"If blood pressure is normal during a veterinary visit, a pheochromocytoma can be ruled out."
Hormone release from a pheochromocytoma can be episodic, and blood pressure may be normal between episodes or when the dog is calm. A single measurement captures only that moment, and repeated assessments over time, along with other tests, are needed to build a fuller picture.
"Surgery always cures the condition and prevents future problems."
Surgery can be curative when the tumour is completely removed and has not spread, but the procedure carries significant perioperative risk, particularly related to blood pressure instability. In cases where the tumour has invaded nearby structures or metastasised, surgery may not prevent progression, and some dogs experience complications during or after the operation.
"Pheochromocytomas are always malignant and spread rapidly."
Whilst many pheochromocytomas do invade locally or metastasise, some remain confined to the adrenal gland for extended periods, and the behaviour of individual tumours varies. The presence of a tumour does not guarantee rapid progression, and some dogs live for months or years with appropriate management, whether surgical or medical.
Related conditions
Adrenal Tumours
Pheochromocytoma is one specific type of adrenal tumour, arising from the hormone-producing tissue in the inner part of the gland. Other adrenal tumours may develop from the outer layer and produce different hormones, creating a different pattern of signs.
Adrenocortical Carcinoma
Both conditions involve tumours of the adrenal gland, but adrenocortical carcinoma arises from the outer cortex and typically affects cortisol or sex hormone production, while pheochromocytoma develops in the inner medulla and releases adrenaline and related compounds. In some cases, imaging may be needed to distinguish between them.
Insulinoma
Both are hormone-secreting tumours that can cause episodic signs—pheochromocytoma through surges of adrenaline, and insulinoma through drops in blood glucose. The episodes may appear similar to an owner, though the underlying mechanisms and patterns differ.
Leptospirosis
Dogs with pheochromocytoma may show episodes of collapse, weakness, or rapid breathing that can resemble signs of acute illness such as leptospirosis. Blood tests and imaging help distinguish hormone-driven episodes from infectious or systemic disease.
Congestive Heart Failure in Dogs
The surges of adrenaline and related hormones released by a pheochromocytoma can raise blood pressure and increase the workload on the heart, and in some dogs this may contribute to the development or worsening of heart failure over time.
The wider context of adrenal function, how the body regulates stress hormones, and the interactions between the cardiovascular and metabolic systems can deepen understanding of what may be observed at home. Other conditions that affect blood pressure, heart rhythm, or exercise tolerance share some outward features, and exploring those connections may clarify what patterns are specific to this tumour and what may reflect overlapping processes. The conversation about individual risk, practical trade-offs between approaches, and how quality of life is weighed alongside measurable outcomes often unfolds over time and is shaped by what emerges during investigation and early management.