CONDITION

Phaeochromocytoma

A phaeochromocytoma is a tumour that arises from specialised cells in the adrenal gland—a small organ that sits near the kidney and produces hormones involved in stress response and blood pressure regulation. When these cells become tumorous, they often release excessive amounts of adrenaline and related hormones into the bloodstream, which can affect how the body responds to everyday activity or stress. Owners often arrive on this page because their dog has shown episodes of collapse, restlessness, increased panting, or unexpectedly high heart rate, or because a mass near the kidney has been found during imaging for something else. The signs tend to be episodic rather than constant, and in many cases the tumour is discovered incidentally when investigating another concern. Historically no consistent breed predisposition was recognised, though a 2025 UK-wide VetCompass study found Soft-Coated Wheaten Terriers, German Pointers, and Miniature Schnauzers to be significantly more likely to be diagnosed than crossbred dogs; the same study found a male predominance, with neutered males at higher risk than intact males or females. Most affected dogs are middle-aged or older. This page explores what an owner may observe, the mechanisms that produce those signs, how the condition is investigated through imaging and hormone measurement, and the surgical and medical approaches that exist. It also outlines what is understood about behaviour over time, both with and without intervention.

Why this matters now

Phaeochromocytomas tend to appear in middle-aged to older dogs, most often between nine and twelve years of age (median around 10.6 years), with risk continuing to rise up to about fifteen years, though younger animals can occasionally be affected. Neutered male dogs, and certain breeds including Soft-Coated Wheaten Terriers, German Pointers, and Miniature Schnauzers, are at significantly higher risk, per a 2025 UK-wide VetCompass study. The tumour typically develops without any identifiable trigger, and many are discovered incidentally during imaging performed for another reason.

The tumour may grow slowly over months or years, and the clinical picture often evolves in a stepwise fashion rather than following a smooth trajectory. Some dogs show intermittent signs that appear during periods of stress or activity, then resolve, while others develop more persistent patterns as the tumour enlarges and hormone release becomes less regulated. The pace and character of progression can vary considerably between individuals, and in some cases the tumour remains clinically silent for an extended period.

Signals & patterns

Early signals

Episodes of panting or restlessness

An owner may notice periods where the dog pants heavily without obvious exertion, or seems unable to settle, often in the evening or after mild activity. These episodes can last minutes to hours and may occur sporadically.

Increased thirst and urination

The water bowl may need refilling more often, and the dog may ask to go outside more frequently or have accidents indoors. This pattern can develop gradually and may be mistaken for age-related change or a urinary issue.

Unexplained anxiety or agitation

The dog may appear nervous, pace without clear cause, or seek the owner's company more insistently than usual. This behaviour can come and go, and owners sometimes describe it as the dog seeming 'on edge' without an obvious stressor.

Intermittent weakness or lethargy

Some dogs show brief periods of reduced energy or reluctance to move, which may alternate with normal activity levels. These episodes can be subtle and are often noticed in retrospect once a pattern emerges.

Later signals

Persistent rapid heart rate

An owner resting a hand on the dog's chest may feel the heart beating noticeably faster than usual, even when the dog is calm. This can be present consistently rather than only during episodes.

Weight loss despite normal appetite

The dog may continue to eat well but lose body condition over weeks to months. Muscle mass may diminish, and the ribs or spine may become more prominent.

Abdominal distension or discomfort

As the tumour enlarges, the abdomen may appear fuller, or the dog may show reluctance to be touched in that area. Some dogs adopt a hunched posture or become less willing to lie on one side.

Click to read about the biological mechanisms

How this is usually investigated

The investigation of a suspected phaeochromocytoma typically begins with a detailed history and physical examination, followed by blood and urine tests to assess overall organ function and look for metabolic effects of excess catecholamine release. Imaging is then used to locate and characterise any adrenal mass, and in some cases specialised hormone measurements help to confirm the diagnosis. The sequence and selection of tests often depends on what initial findings suggest and on the practical constraints of the individual case.

Physical examination

Purpose: A general assessment may reveal an elevated heart rate, heart murmur, or irregular rhythm, along with signs such as pale mucous membranes or muscle wasting that suggest sustained metabolic stress.
Considerations: Many dogs appear outwardly normal between episodes, and the examination findings can be subtle or absent if hormone release is intermittent at the time of the visit.

Blood pressure measurement

Purpose: Repeated measurements over a short period can identify persistently elevated blood pressure or marked fluctuations that are consistent with surges of catecholamine release.
Considerations: Blood pressure can be transiently raised by stress or excitement in the consulting room, and some dogs with a phaeochromocytoma have normal readings if measured between episodes or if the tumour releases hormones in a different pattern.

Chemistry panel

Purpose: Assesses kidney and liver function, electrolyte balance, and glucose concentration, any of which may be affected by prolonged catecholamine excess or by secondary effects on organ perfusion.
Considerations: Results are often within reference ranges, or show only mild, non-specific changes; an unremarkable panel does not exclude the diagnosis.

Abdominal ultrasound

Purpose: Visualises the adrenal glands and can identify a mass, assess its size and internal structure, and look for invasion into nearby blood vessels or spread to other organs such as the liver.
Considerations: Small tumours may be difficult to distinguish from normal adrenal tissue, and some masses are found incidentally during scans performed for other reasons, requiring further tests to determine whether they are hormonally active.

Computed tomography (CT)

Purpose: Provides detailed cross-sectional images of the adrenal region and surrounding structures, helping to define the extent of the tumour, its relationship to major blood vessels, and the presence of distant metastases.
Considerations: CT requires general anaesthesia and is usually reserved for cases where surgical planning is being considered or where ultrasound findings are inconclusive; it does not confirm hormone secretion on its own.

Options & trade-offs

Management of a phaeochromocytoma is usually built around the individual animal's clinical picture, the size and behaviour of the tumour, and what the owner finds workable over time. Some approaches focus on controlling the effects of excess hormone release, others on removing the source, and many cases involve a combination of medical preparation followed by a decision about whether or when to pursue surgery. Different combinations suit different circumstances, and the balance of benefit and burden shifts as the disease evolves.

Surgical removal of the tumour

Adrenalectomy involves removing the affected adrenal gland and, if present, any portion of tumour that has extended into nearby blood vessels. The procedure is typically preceded by several weeks of medication to block the effects of circulating catecholamines and stabilise blood pressure and heart rate. Surgery offers the possibility of prolonged disease-free intervals if the tumour has not spread widely, though the operation itself carries significant anaesthetic and haemorrhage risk because of the gland's blood supply and the potential for sudden hormone surges during manipulation.

Trade-offs: Perioperative complications can include severe blood pressure swings, cardiac arrhythmias, and bleeding; postoperative monitoring is intensive, and recovery can be prolonged. Not all tumours are amenable to complete removal, and metastatic disease may only become apparent after surgery.

Medical management with alpha- and beta-adrenergic blockade

Medications that block the action of catecholamines at their receptors can reduce heart rate, lower blood pressure, and diminish the episodic signs that many dogs experience. Alpha-blockers are usually introduced first to prevent unopposed vasoconstriction, followed by beta-blockers if heart rate or rhythm disturbances persist. This approach does not shrink the tumour or alter its growth, but it can improve quality of life and is sometimes continued long-term in dogs who are not candidates for surgery.

Trade-offs: Dose adjustments are often needed over weeks to balance control of signs against side effects such as lethargy or weakness, and the medications do not address the underlying tumour or prevent progression or metastasis.

Monitoring without immediate intervention

Some phaeochromocytomas are discovered incidentally in dogs with minimal or no clinical signs, and in these cases observation with periodic reassessment of blood pressure, imaging, and clinical status may be appropriate. This approach avoids the risks of surgery or the side effects of medication while the tumour remains small and quiescent, though it requires a commitment to regular follow-up and a willingness to move to active treatment if signs emerge or imaging shows progression.

Trade-offs: The tumour may enlarge or begin to cause signs at any point, and delaying intervention can mean missing a window when surgery is still feasible; this approach is less suitable for dogs already showing frequent or severe episodes.

Palliative care focused on comfort

In cases where the tumour has spread widely, where other health conditions make anaesthesia or intensive treatment inadvisable, or where the owner's circumstances do not allow for complex management, the goal shifts to minimising distressing signs day to day. This may involve low doses of medications to ease panting or restlessness, adjustments to the home environment to reduce stress triggers, and close attention to changes that might signal a need for reassessment of the overall plan.

Trade-offs: This approach does not alter the disease course, and progression may eventually lead to signs that are difficult to control with simple measures alone.

Common misconceptions

Misconception:

"A phaeochromocytoma will always cause dramatic, easily recognised episodes of collapse or extreme agitation."

Reality:

Many dogs show subtle or intermittent signs that can be mistaken for anxiety, age-related slowing, or other common conditions. Some tumours produce hormones in patterns that do not result in obvious crises, and clinical signs can wax and wane over months, making the picture harder to interpret without targeted investigation.

Misconception:

"If the tumour is removed surgically, the condition is cured and no further monitoring is needed."

Reality:

Surgery can result in prolonged periods without clinical signs, but phaeochromocytomas can metastasise to distant sites, and some of these secondary tumours may not be visible at the time of the original operation. Follow-up imaging and clinical assessment remain important to detect recurrence or progression, and a proportion of dogs will eventually show signs related to tumour spread.

Misconception:

"Medical management alone will stop the tumour from growing or spreading."

Reality:

Medications that block the effects of catecholamines can improve signs and quality of life, but they do not shrink the tumour or prevent it from enlarging or metastasising. The underlying disease continues to progress, and the role of medication is to manage the consequences of hormone release rather than to alter the tumour's behaviour.

Related conditions

Adrenal Tumours

Phaeochromocytoma is one specific type of adrenal tumour, arising from the inner part of the gland rather than the outer cortex. Adrenal tumours more broadly can produce different hormones or none at all, so the distinction helps clarify which patterns of signs may appear.

Hyperaldosteronism in Cats

Both conditions involve tumours of the adrenal gland that release excessive hormones into the bloodstream, though phaeochromocytoma releases adrenaline-related compounds while hyperaldosteronism releases aldosterone. The location and hormone type differ, but the shared principle—a small gland producing large effects—can make the two worth considering side by side.

Cardiac Tamponade

Phaeochromocytomas can occasionally invade the large vessels near the heart or metastasise to the pericardium, and in rare cases bleeding from the tumour can lead to fluid accumulation around the heart. When this occurs, the combination of hormone-driven cardiovascular effects and mechanical compression can overlap in presentation.

Pulmonary Hypertension

The surges of adrenaline and related hormones released by a phaeochromocytoma can contribute to elevated blood pressure in the vessels of the lungs, either as a direct effect or through strain on the cardiovascular system. Pulmonary hypertension may develop alongside the tumour or be worsened by it.

Atrial Fibrillation

Excess circulating adrenaline from a phaeochromocytoma can place strain on the heart's electrical system, and in some cases this may trigger rhythm disturbances such as atrial fibrillation. The irregular rhythm may appear during episodes of hormone release or persist if the tumour has been active for some time.

Phaeochromocytomas sit within a broader group of endocrine tumours that can affect the adrenal glands and other hormone-producing tissues, and understanding the general principles of how these tumours behave and how the body responds to hormone excess can provide useful context. The metabolic health pillar explores the wider landscape of conditions that alter energy balance, fluid regulation, and stress responses, and many of the investigative and management principles overlap. Conversations about prognosis, the practicalities of long-term monitoring, and the signals that might prompt a change in approach are often iterative, evolving as the individual case unfolds.