Imaging for a Better Outcome for Adrenal Tumours

The addition of CT to the diagnostic imaging arsenal at the Southern Animal Emergency Centre has made the definitive diagnosis of adrenal tumours a straightforward process. Further, the scanning process has provided major advances in the identification of macroscopic spread of the disease in one simple scanning session.

Adrenal gland tumours are relatively common in dogs, comprising 1% of all canine tumours. Adrenal tumours can be further divided into adrenal cortical tumours and adrenal medullary tumours. Most cortical tumours secrete glucorticoids and varying amounts of mineralocorticoids and androgens. Cortical tumours secreting only androgens have been reported in both dogs and cats. Cortical tumours can be benign adenomas and marginally malignant adenocarcinomas. Adrenal medullary tumours, also called pheochromocytomas, secrete catecholamines (adrenalin and noradrenalin). They tend to be more malignant and are invasive in 40-50% of patients and metastasise in 15-30% of patients. The mean age for adrenal tumours is 11 years. Large breeds and females appear to be predisposed.

Clinical signs associated with an adrenal tumour depend on what it is secreting. Most adrenal cortical tumours have clinical signs consistent with hyperadrenocorticism and are characterised by polyuria, polydypsia, polyphagia, panting, and dermatological conditions. The diagnosis is based on appropriate clinical signs, elevation of liver enzymes, and appropriate endocrinological tests including endogenous ACTH, ACTH stimulation test, low-dose dexamethasone suppression test, high-dose dexamethasone suppression test and urine cortisol test. With pheochromocytomas, weight loss, anorexia, weakness, collapse, tachpnoea, tachycardia and mucous membrane pallor are the most common clinical signs. Diagnosis prior to surgery can be very difficult because of the nonspecific clinical signs and the lack of specific laboratory findings.

Abdominal ultrasound is very helpful in identifying an adrenal tumour. We have found computed tomography to be essential in the management of these patients. CT is definitive in making a diagnosis of an adrenal tumour as well as assessing the invasiveness and potential for a surgical cure. Evaluation of the liver and lungs is possible to assess for the presence of macroscopic metastasis.

Treatment of adrenal tumours is generrally surgical. This depends on a thorough evaluation of general health status, invasiveness of the tumour, and the lack of gross systemic metastasis. Surgical mortality is reported to be 20%. Dr. Charles Kuntz, the surgical specialist at the Southern Animal Referral Centre, has operated on 78 adrenal tumours to date. The surgical mortality for tumours not invading the vena cava is 3%. Surgical mortality for tumours having invaded the vena cava is reported to be 50%. Charles has operated on 11 patients with vena cava invasion with a surgical mortality of 27%. In patients where surgical removal of adrenal tumours is not possible, the use of o,p’-DDD is possible, with relapses occurring in 50% of patients. It is also possible to pretreat patients prior to intended surgical resection.

Prognosis for adrenocortical tumours is generally good. Dr. Charles Kuntz coauthored a study of 23 dogs with adrenal cortical tumours. 11 had benign tumours, 11 had malignant tumours and one had a benign tumour on one side and a malignant tumour on the other side. In our study, all dogs who survived to be discharged from the hospital lived to the end of the study period, regardless of the malignancy of the tumour. Note that the malignant tumours were more invasive. Since the completion of this study, Charles has seen two dogs who have developed liver metastasis following removal of adrenal cortical tumours. Regarding pheochromocytomas, as stated previously, they are more invasive and 15-30% will have metastasised at the time of diagnosis.

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