Page 862 - Small Animal Internal Medicine, 6th Edition

834 PART VI Endocrine Disorders

diabetic remission because of the suppressive effects of the diabetic cat is avoidance of symptomatic hypoglycemia,
glucose toxicity on circulating insulin concentrations. An especially in the home environment. Considerable overlap in
VetBooks.ir insulin assay validated for the cat should be used when mea- the insulin dosage range that causes hypoglycemia, estab-
lishes control of glycemia, and does not establish control of
suring serum insulin concentrations in cats.
A thorough evaluation of the cat’s overall health is recom-
effective dosage of any insulin product that does not cause
mended once the diagnosis of diabetes mellitus has been glycemia exists with all insulin preparations. Predicting an
established. The minimal laboratory evaluation in any dia- hypoglycemia in some diabetic cats is difficult, in part
betic cat should include a CBC, a serum biochemical panel, because of variability between cats in their response to
a serum thyroxine concentration, and urinalysis with bacte- insulin. For this reason, our starting insulin dosage is always
rial culture. If available, abdominal ultrasound should also on the low end of the range, typically 0.25 U/kg per injection
be a routine part of the diagnostic evaluation to assess the ( 1 2 to 2 U/injection), and we prefer to start with twice-a-day
liver, kidneys, adrenal glands, and especially the pancreas for insulin administration because the overwhelming major-
chronic pancreatitis. Measurement of baseline serum insulin ity of diabetic cats require insulin glargine and PZI twice a
concentration or performance of an insulin secretory day. The most common problem with insulin glargine and
response test is not routinely done in cats because of prob- PZI is a prolonged duration of effect (>12 hours). This can
lems encountered with glucose toxicity. Additional tests may create problems with hypoglycemia when these insulin prep-
be warranted after the history is obtained, the physical exam- arations are administered twice a day, problems that can be
ination is performed, or ketoacidosis is identified. See Box minimized by starting with an insulin dose at the lower end
49.4 for a list of potential clinical pathologic abnormalities. of the effective range.

Treatment DIET
The significant incidence of type 2 diabetes in cats raises The general principles for dietary therapy are listed in Box
interesting questions regarding the need for insulin treat- 49.6. Obesity, feeding practices, and content of the diet
ment. Glycemic control can be maintained in some diabetic warrant discussion in diabetic cats. Obesity is common in
cats with dietary changes, correction of obesity, control of diabetic cats and results from excessive caloric intake typi-
concurrent diseases, discontinuation of insulin-antagonistic cally caused by free-choice feeding of dry cat food. Obesity
drugs, or a combination of these. The ultimate differentiation causes reversible insulin resistance that resolves as obesity is
between insulin-dependent and non–insulin-dependent dia- corrected. Control of glycemia often improves, and some
betes is usually made retrospectively, after the clinician has diabetic cats experience diabetic remission after weight
had several weeks to assess the response of the cat to therapy reduction. Correction of obesity is difficult in cats because it
and to determine the cat’s need for insulin. The initial treat- requires restriction of daily caloric intake without a corre-
ment strategy is based on the severity of clinical signs and sponding increase in caloric expenditure (i.e., exercise).
physical abnormalities, the presence or absence of ketonuria Typical weight-reducing diets recommended for obese dia-
and ketoacidosis, the general health of the cat, and client betic cats include diets with increased protein and decreased
wishes. For most newly diagnosed diabetic cats, treatment carbohydrate content, and low-calorie-dense diets with
includes insulin, adjustments in diet, and correction or decreased fat and increased fiber content. The reader is
control of concurrent insulin resistance. referred to Chapter 51 for more information on correction
of obesity in cats.
INITIAL INSULIN RECOMMENDATIONS The eating habits of cats vary considerably, from eating
FOR DIABETIC CATS everything at the time food is offered to grazing throughout
Diabetic cats are notoriously unpredictable in their response the day and night. The primary goal of dietary therapy is to
to exogenous insulin, and all insulin preparations have the minimize the impact of a meal on postprandial blood glucose
potential for short duration of effect in cats. No insulin prep- concentrations. Consuming the same number of calories in
aration is consistently effective in maintaining control of multiple small amounts throughout a 12-hour period should
glycemia, even with twice-daily administration. Insulin have less impact than consuming the calories at a single large
preparations used for the long-term management of diabetic meal. Half of the cat’s total daily caloric intake should be
cats include porcine lente insulin, recombinant human PZI, offered at the time of each insulin injection and should
insulin glargine, and insulin detemir (see p. 812 and Fig. remain available to the cat to consume when it wishes.
49.11). Because short duration of insulin effect is common Attempts to force a grazing cat to eat the entire meal at one
in cats, we prefer to start insulin therapy using insulin time usually fail and are not warranted as long as the cat has
glargine (Lantus) or recombinant human PZI (ProZinc). access to the food during the ensuing 12 hours.
Both insulin preparations are effective in controlling glyce- Cats are carnivores and, as such, have higher dietary
mia and inducing diabetic remission in diabetic cats. Studies protein requirements than omnivores such as humans and
to date suggest that the median dosage of insulin glargine dogs. Hepatic glucokinase and hexokinase activity is lower
and PZI required to attain glucose control in most diabetic in cats, compared with that in carnivores with omnivorous
cats is approximately 0.5 U/kg/injection, with a range of 0.2 eating habits. This suggests that diabetic cats may be pre-
to 0.8 U/kg. One important goal in the initial regulation of disposed to developing higher postprandial blood glucose