ENDOCRINOLOGY
Dealing With Incidental
Adrenal Tumours
Dr Frank Kettner BVSc MMedVet(Med), DipECVIM(CA),
Tygerberg Animal Hospital – Bellville, Cape Town
[email protected], Tel (021) 919 1191
An adrenal “incidentaloma” is an adrenal mass, found as an incidental finding during ultrasound or CT examination of the abdomen, where adrenal pathology is not initially suspected
In humans the incidence varies from <1% to 7%, and increases with the age of the population
In canine and feline veterinary patients, most incidentally discovered adrenal masses, in otherwise healthy
patients, are non-functional benign tumours or nonneoplastic lesions. Most functional adrenal masses are
either cortisol secreting tumours or pheochromocytomas. In veterinary medicine there is no consensus
on the best approach to an incidentaloma. Deciding
upon an appropriate treatment plan requires classification of the incidentaloma as malignant or benign
and functional or non-functional.
Normal adrenal gland anatomy and physiology
The adrenal gland consists of an outer cortex and an
inner medulla. The latter is the site of catecholamine
production. The cortex has 3 zones: from the outside to the inside these are the zona glomerulosa, the
zona fasciculata and the zona reticularis. The zona
glomerulosa is responsible for the production of mineralocorticoids (aldosterone). Glucocorticoids (cortisol) and androgens are synthesized in both the zona
fasciculata and reticularis.
In human medicine the causes for adrenal masses include:
a. Functional masses (up to 15%): adenoma (aldosterone or cortisol); carcinoma (any adrenal hormone); pheochromocytoma; congenital adrenal
hyperplasia; massive macro nodular adrenal disease; nodular variant of Cushing’s disease
b. Non-functional masses: adenoma; myelolipoma;
neuroblastoma; ganglioneuroma; haemangioma;
carcinoma; metastasis; cyst; haemorrhage; granuloma; amyloidosis; infiltrative disease
Hormones that are released from functional masses
include: cortisol or one of the precursors (Cushing’s
disease); aldosterone (Conn’s syndrome); sex hormones and adrenalin (pheochromocytoma).
The canine patient may be completely asymptomatic,
as would be expected in a non-functional, small benign adrenal adenoma. Patients with functional adrenal masses may present with signs of the underlying
hormone excess. Animals with malignant tumours
(functional or non-functional), may show non-specific
signs such as decreased appetite, weight loss, lethargy and nausea. Should metastasis be present, clinical
signs will further depend on the organ/s which have
been affected.
Surgical removed of functional or malignant adrenal
masses would be ideal. However, not every mass
needs to be removed and surgery holds significant
risks to the patient, either due to age related anaesthetic issues, co-existing morbidity or due to surgical
complications. On the other hand, surgically removing a pre-metastatic adrenal malignancy may be lifesaving.
General guidelines for surgical removal include
masses that are larger than 3cm, show signs of malignancy, are functional or show invasion of the surrounding blood vessels. It may not