Page 700 - Problem-Based Feline Medicine

692 PART 9 CAT WITH SIGNS OF GASTROINTESTINAL TRACT DISEASE

Anemia, lymphocytosis and eosinophilia are rela- To differentiate pituitary or hypothalamic disease
tively uncommon (< 20%) findings in cats. from exogenous drug administration as the cause of
secondary hypoadrenocorticism, plasma ACTH con-
Serum biochemistries and urinalysis show hypona-
centration is measured.
tremia, azotemia (pre-renal or renal), and hyper-
phosphatemia in the majority of cats. Hyperkalemia
and hypochloridemia are also common, but not seen in INTUSSUSCEPTION
every case.
Classical signs
Other less common (< 30% cases reported) abnormali-
ties include metabolic acidosis, increased liver enzyme ● The classical sign is an acute onset of
activities, hypercalcemia and hyperbilirubinemia. frequent vomiting.
● Intermittent vomiting will occur in some
Slightly more than 50% of affected cats will have an cats.
unconcentrated urine sample (SG < 1.030), support-
ing renal azotemia.
See main reference on page 643 for details.
The definitive diagnostic test for hypoadrenocorticism
is an ACTH stimulation test, which will reveal a low Clinical signs
resting cortisol concentration, and no response (no
increase in cortisol levels) following administration of An acute onset of vomiting, abdominal pain or
ACTH (Cosyntropin 0.125 mg/cat, IM), at either the 30 anorexia is the most common sign. However, in some
or 60 min post-administration sampling times. cats with sliding, intermittent or incomplete intus-
Administration of steroids by any route (oral, parenteral susception, the signs may be intermittent. Weight loss
or topically) or progestins (e.g. megestrol acetate) will and vomiting will be more prevalent in these cats.
suppress cortisol response to ACTH. This suppression
may persist for weeks after the last time of administra- Diagnosis
tion, especially if administration was chronic.
A palpable abdominal mass may help direct the diag-
Radiographic changes include microcardia and
nostic approach if it is present.
hypoperfusion of the lungs due to hypovolemia. ECG
changes classically observed in dogs, such as peaked Contrast radiographs or ultrasound examination of
T waves, reduced or absent P waves, or atrial standstill the GI tract are the most definitive means of making the
are not seen in cats. diagnosis.
If serum electrolyte concentrations are normal, but a Intussusception rarely presents as a chronic prob-
subnormal response to ACTH administration is lem, so in these cases, abnormalities associated with
observed, the cat may have: (1) residual mineralocorti- chronic GI dysfunction (e.g. hypoproteinemia, hypoal-
coid secretion; (2) secondary hypoadrenocorticism buminemia) may be present.
from pituitary or hypothalamic disease causing only
glucocorticoid deficiency but this has not yet been LEAD POISONING
reported in cats; or (3) secondary hypoadrenocorti-
cism due to exogenous administration of glucocorti- Classical signs
coids or progestogens. Although this is the most
common cause of secondary hypoadrenocorticism and ● Gastrointestinal signs include anorexia,
suppressed adrenal response to ACTH, it rarely causes vomiting, diarrhea and abdominal pain.
sufficient lethargy for veterinary attention to be sought. ● Neurologic signs include aggression,
If clinical signs consistent with hypoadrenocorticism nervousness, tremors, seizures, blindness
are present in a cat with a suppressed ACTH stimula- and dementia.
tion test secondary to steroid administration, the signs
are most likely caused by another disease. See main reference on page 596 for details.