Page 947 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

922 CHAPTER 6

VetBooks.ir Prognosis Diagnosis
Phaeochromocytoma can be suspected based on
Once the horse has been stabilised, clinical signs
usually resolve and the prognosis is quite good. In
most instances, corticosteroid therapy can be gradu- clinical signs and hyperglycaemia but diagnosis
is achieved by demonstration of increased blood
ally decreased and eventually stopped as horses and/or urinary adrenaline (epinephrine). Adrenal
regain normal adrenal function. tumours may be palpable p/r if they are large
enough and on the left side. Ultrasonography may
ADRENAL TUMOURS reveal a mass in the area of the right or left kid-
ney and may provide guidance for biopsy. Most
Definition/overview tumours of the adrenal glands, however, are diag-
Tumours of the adrenal gland are uncommon, usu- nosed at necropsy.
ally non-functional and generally found as incidental
findings at necropsy. Tumours of the adrenal cortex Management
include adenoma and carcinoma. The most common Surgical removal of an adrenal tumour is possible if
tumour of the adrenal medulla is phaeochromocy- the tumour is unilateral, diagnosed early and small.
toma. The pathophysiology of functional tumours Many of such cases are, however, subclinical or inci-
relates to oversecretion of hormones by a particular dental, while clinical cases are often too large to be
part of the adrenal gland. considered surgical candidates.

Clinical presentation Prognosis
Tumours of the adrenal cortex of the horse have been The prognosis for horses exhibiting clinical signs of
associated with lethargy, colic, weight loss, limb phaeochromocytoma is poor.
oedema and seizures. Hyponatraemia has also been
reported in tumours involving the zona glomerulosa. FURTHER READING
Clinical signs of phaeochromocytoma, if present, Bertin FR, de Laat MA (2017) The diagnosis of equine
include hyperhidrosis, muscle fasciculations, tachycar- insulin dysregulation. Equine Vet J 49:570–576.
dia, tachypnoea, polyuria and polydipsia. Horses may Breuhaus BA (2011) Disorders of the equine thyroid
appear to be apprehensive and have mydriasis. Recurrent gland. Vet Clin North Am Equine Pract 27:115–128.
episodes of colic may be encountered. Typically, there Durham AE (2016) Endocrine disease in aged horses.
is a disconnection between the high heart rate and the Vet Clin North Am Equine Pract 32:301–315.
apparent low degree of abdominal pain. Durham AE (2017) Therapeutics for equine endocrine
disorders. Vet Clin North Am Equine Pract 33:127–139.
Differential diagnosis Ireland JL, McGowan CM (2018) Epidemiology of
pituitary pars intermedia dysfunction: a systematic
Differential diagnoses for horses exhibiting clinical literature review of clinical presentation, disease
signs of phaeochromocytoma may include systemic prevalence and risk factors. Vet J 235:22–33.
inflammatory response syndrome, colic, electrolyte Toribio RE (2011) Disorders of calcium and phosphate
abnormalities, myositis, tetanus and equine motor metabolism in horses. Vet Clin North Am Equine Pract
neuron disease. 27:129–147.