Page 262 - Problem-Based Feline Medicine

254 PART 4 CAT WITH URINARY TRACT SIGNS

Chronic glucocorticoid or megestrol acetate admin- nisone (0.25–1 mg/cat PO q 12 h) or methylpred-
istration may result in a similar ACTH stimulation test nisolone (10 mg IM q 1 month).
result. The cortisol increase is suppressed in the ACTH
Stressful events may warrant an increase in medication
stimulation test. However, ACTH concentration is also
dose.
suppressed, and electrolytes are normal.
An Addisonian crisis needs to be differentiated from
Prognosis
other critical conditions such as diabetic ketoacidosis,
necrotizing pancreatitis and septic shock. Prognosis is good with appropriate treatment, provided
the hyperkalemia and electrolyte imbalance is cor-
Mild hypoadrenocorticism displays signs that are rela-
rected in time. Cats with adrenal insufficiency will have
tively non-specific, and are often seen in other gas-
a normal life expectancy provided they are treated
trointestinal and renal diseases.
appropriately.
Treatment Prevention
An acute Addisonian crisis is a medical emergency. Secondary adrenocorticism caused by rapid withdrawal
of chronic corticosteroid therapy can be prevented via
Immediate correction of hypotension, hypov-
staged withdrawal of steroids and progestins, which
olemia, electrolyte imbalances and metabolic acido-
allows adrenal gland function to recover from chronic
sis via fluid administration is essential. Use isotonic
suppression.
fluids (0.9% NaCl) at 40 ml/kg/h IV initially for the
first 1–4 hours. Once dehydration is corrected, reduce
the fluid rate to 60–90 ml/kg/day, using the higher
ACROMEGALY (HYPERSOMATOTROPISM;
fluid rate if the cat is not eating.
GROWTH HORMONE-PRODUCING TUMOR)
● Potassium supplementation in fluids is contraindi-
cated, but if the only fluids available immediately
Classical signs
have potassium, use them.
● Poorly controlled, insulin-resistant
Provide an immediate source of glucocorticoids.
diabetes mellitus requiring high doses of
● Prednisolone sodium succinate (4–20 mg/kg, IV) or
insulin.
dexamethasome (0.1–2.0 mg/kg, IV or IM).
● Polyuria, polydipsia, polyphagia.
● Mineralocorticoids should be replaced using oral flu-
● Weight gain despite poorly controlled
drocortisone acetate (0.05–0.1 mg/cat PO q 12 h) or
diabetes.
DOCP (deoxycorticosterone pivalate, 2.2 mg/kg, IM
● Large, blocky or coarse body and head.
q 25 days). In Australia, the long-acting form in oil for
● Enlarged tongue, widely spaced teeth,
intramuscular injection is an acetate product (DOCA).
thickened soft palate.
● If the cat is in shock, higher doses of glucocorti-
● Cardiomegaly.
coids may be warranted.
Despite appropriate therapy, lethargy, anorexia and See main reference on page 322 for details (The Cat
weakness may persist for 3–5 days, unlike the rapid With Weight Loss and a Good Appetite).
response in dogs.
Pathogenesis
In the long term, glucocorticoid and mineralocorti-
coid replacement is required lifelong. Use either flu- Very rare disease.
drocortisone acetate (0.05–0.1 mg/cat PO q 12 h) or
Caused by a functional adenoma of the pars distalis
DOCA (2.2 mg/kg, IM q 25 days) for mineralocorti-
which produces excess growth hormone.
coid replacement long term. Some cats require addi-
tional glucocorticoid replacement long term or at times Excess growth hormone results in soft tissue and bone
of stress, which can be provided using prednisolone/pred- overgrowth from the chronic hypertrophic actions of