Page 260 - Problem-Based Feline Medicine

252 PART 4 CAT WITH URINARY TRACT SIGNS

does not appear to be more advantageous than the Transsphenoid hypophysectomy may be available in
ACTH stimulation and dexamethasone suppression some referral centers.
tests evaluated separately.
Differentiation of pituitary-dependent from adrenal Prognosis
tumors is based on abdominal ultrasound (one
Prognosis is guarded to grave. Cats that have adreno-
enlarged adrenal if adrenal tumor) and ACTH concen-
cortical tumors surgically removed have the longest
tration. Normal to increased ACTH concentrations
survival.
support a diagnosis of pituitary-dependent disease.
Low concentrations support adrenal disease. This test
must only be used after hyperadrenocorticism is con-
HYPOADRENOCORTICISM
firmed, because normal cats often have low ACTH con-
centrations.
Classical signs
Differential diagnosis ● Very rare disease.
● Lethargy, depression, anorexia and weight
Other causes of poorly controlled diabetes need to be
loss.
considered, e.g. excessive insulin dose, too short a
● Dehydration, hypothermia, ± weakness or
duration of action of insulin, hyperthyroidism and
collapse.
acromegaly.
● ± Bradycardia.
Some cats appear to have poorly controlled diabetes ● ± Vomiting.
based on persistently high blood glucose concentra- ● ± Polyuria and polydipsia.
tions measured in hospital, but have good control of ● ± Waxing and waning illness, that responds
clinical signs (e.g. stable weight and water intake < 60 to fluids or glucocorticoids.
ml/kg). These cats have stress hyperglycemia associ-
ated with visits to the veterinarian. In contrast, cats
with undiagnosed hyperadrenocorticism and dia- Pathogenesis
betes usually have persisting clinical signs of dia-
Hypoadrenocorticism results from a deficiency of glu-
betes, despite insulin therapy.
cocorticoids and/or mineralocorticoids produced by
the adrenal gland.
Treatment
It can be classified as either primary or secondary
Medical therapy produces inconsistent results, but is adrenocortical insufficiency.
useful in improving the presurgical condition of the cat. ● Primary adrenocortical failure occurs rarely in
● Drugs which have produced improvement in some cats as a naturally occurring disease, and is pre-
cats are ketaconazole (15 mg/kg q 12 h) and sumed to result from immune-mediated destruc-
metyrapone (65 mg/kg q 12 h). tion of the adrenal cortices.
● Trilostane and L-depronyl have been used in dogs ● Secondary adrenocortical failure involves only a
successfully, but there is comparatively little infor- deficiency of glucocorticoid secretion as a result
mation available on their use in cats. Trilostane of reduced secretion of pituitary ACTH.
ameliorates clinical signs of hyper adrenocorticism ● Spontaneously occurring secondary hypoadreno-
in cats based on the studies published. corticism has not been reported in cats.
● Iatrogenic secondary hypoadrenocorticism can be
Surgical adrenalectomy (unilateral for adrenal
demonstrated with an ACTH stimulation test after
tumor and bilateral for pituitary-dependent hyper-
withdrawal of potent glucocorticoids or progestins,
adrenocorticism) provides the best response.
especially after long-term use. However, clinical
● Begin glucocorticoids, fluids and antibiotics just
signs are rarely seen.
before surgery.
● Fatal post-operative complications are relatively Glucocorticoid (cortisol) deficiency impairs the
common. body’s response to stressful situations.