Page 245 - Problem-Based Feline Medicine

15 – THE CAT WITH POLYURIA AND POLYDIPSIA 237

Clinical signs If persistent hyperglycemia is present in a sick cat,
begin treatment with insulin, even if it is not clear if
Earliest signs are polyuria and polydipsia; nocturia
the hyperglycemia is illness-associated. Illness-
and urinary incontinence may occur.
associated stress hyperglycemia rarely results in
Weight loss occurs and is accompanied by increased blood glucose concentrations higher than 19
appetite. mmol/L (342 mg/dl).
● At the time of diagnosis, some cats are under- ● Plasma betahydroxybutyrate > 1 mmol/L (10
weight, some normal weight and others are obese. mg/dl) is indicative of diabetes mellitus. However,
some diabetic cats have normal plasma betahydrox-
At diagnosis, some cats have decreased appetite and
ybutyrate.
are depressed, others are polyphagic.
– A urine dipstick may be used in serum or
Lethargy or depression may be present. Other cats are heparinized plasma to detect ketonemia. A posi-
alert at presentation. tive test indicates ketonemia. It detects mainly
oxaloacetate rather than the predominant ketone
Muscle wasting and weakness are often present and
in cats, β-hydroxybutyrate.
may be evidenced as reluctance or inability to jump.
Dehydration is common in cats that are lethargic and
inappetent. Differential diagnoses
Vomiting occurs in one third of cats, but is usually Stress hyperglycemia from struggling or illness.
infrequent. Beware of misdiagnosis in cats with stress hyper-
glycemia from illness or struggling, which also have
Hepatomegaly from hepatic lipidosis, and occasionally
concomitant disease that produces similar signs to dia-
jaundice may be present.
betes mellitus, e.g. renal failure or hyperthyroidism.
Rear limb weakness or plantigrade posture (hocks ● In stress hyperglycemia associated with struggling,
touching the ground) occur occasionally secondary to blood glucose concentration is generally < 12
diabetic neuropathy. mmol/L (216 mg/dl) within 4 h if the cat is hospi-
talized and further struggling does not occur.
Acetone odor on breath may be evident on average 5
● Stress hyperglycemia associated with illness may
days before ketonuria is detected.
persist for several days and exceed 20 mmol/L (360
Poor unkempt scurfy hair coat. mg/dl). If in doubt, treat these cats with insulin and
closely monitor blood glucose.
Diagnosis Hyperthyroidism may produce similar signs, i.e. old
cat with weight loss, polyphagia and polyuria/polydip-
In most cats, blood glucose greater than 20 mmol/l
sia. Generally the polydipsia in hyperthyroidism is less
(360 mg/dl) is diagnostic of diabetes.
pronounced. Glucose may be elevated but less than 20
If blood glucose is 12–20 mmol/l (216–360 mg/dl), the mmol/L (360 mg/dl), from stress and insulin resistance.
presence of typical clinical signs (polyuria, polydipsia, Elevated thyroxine concentration is diagnostic.
polyphagia with weight loss), significant glycosuria,
and increased plasma fructosamine or betahydroxy- Treatment
butyrate or ketonuria must be used to differentiate dia-
betes from stress-induced hyperglycemia. General principles
● Plasma fructosamine > 406 umol/L is indicative of
diabetes mellitus. However, some diabetic cats have For initial management, most cats have better
a normal fructosamine concentration, and occasion- glycemic control using insulin rather than oral hypo-
ally, non-diabetic sick cats have mildly increased glycemic agents.
fructosamine concentrations. ● Insulin is more potent in decreasing blood glu-
● Persistent hyperglycemia over 24 h is highly sug- cose; this enables beta cells to overcome the effects
gestive of diabetes, but may also occur with illness. of glucose toxicity.