Page 926 - Small Animal Internal Medicine, 6th Edition

PART SEVEN Metabolic and Electrolyte Disorders
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PART VII Metabolic and Electrolyte Disorders
Jennifer A. Larsen and Ann-Marie Della Maggiore

VetBooks.ir CHAPTER 51

Weight Loss and Obesity

POLYPHAGIA WITH WEIGHT LOSS with gastrointestinal tract lymphoma, eosinophilic enteritis,
or histoplasmosis.
In some dogs and cats, polyphagia with concurrent weight In addition to routine medical history and status ques-
loss is the presenting complaint. The most common cause of tions posed to the client, the clinician should perform a
polyphagia with concurrent weight loss is inadequate caloric nutritional assessment including a diet history (types and
intake (Table 51.1). Although this seems obvious, some amounts of foods offered; total daily caloric intake from
owners are surprisingly unaware of appropriate feeding foods, treats, and supplements; feeding routines; and com-
amounts and unintentionally underfeed their pets. Daily petition for food from other dogs or cats). Daily caloric
caloric needs may not be met if inadequate quantities of food requirements in individual cats and dogs are quite variable
are being fed, if the diet is not complete and balanced, or if and depend on numerous factors, such as signalment,
the diet is of poor quality. Alternatively, the client may not climate, and the amount of daily physical activity. The average
recognize changes in nutritional needs (e.g., during late daily caloric requirement can be calculated using the equa-
pregnancy and lactation, and at times of strenuous exercise, tion for the resting energy requirement (RER): 70 × body
such as during hunting season) and may continue to feed the weight in kilograms 0.75 . Although most people have ready
animal at previously adequate caloric levels. Likewise, the access to computers and smart phones, this can also be cal-
owner may switch diets and continue to feed the same culated on a simple calculator with a square root button. To
volumes despite a lower energy density in the new food. determine RER, the current body weight in kilograms is
Endocrinopathies and gastrointestinal tract disorders multiplied by itself three times, and the square root of the
also cause polyphagia and weight loss in some dogs and cats result is taken twice before multiplying by 70. This value for
(see Table 51.1) as a result of an increase in basal metabolic RER has a unit of kcal per day and is multiplied by a factor
rate (hyperthyroidism), inadequate assimilation of dietary to derive the maintenance energy requirement (MER). The
nutrients (gastrointestinal tract disorders), or inappropriate factor for a neutered cat is 1.2, an intact cat’s factor is 1.4, a
use of nutrients (diabetes mellitus). Gastrointestinal tract neutered dog’s factor is 1.6, and an intact dog’s is 1.8. The
disorders include parasitism, pancreatic exocrine insuffi- daily caloric requirements in any individual dog or cat may
ciency, infiltrative bowel disorders, lymphangiectasia, and vary by as much as 50% more or less than this estimated
neoplasia (most notably gastrointestinal lymphoma). In value. Although this represents a large range for normal
most cases the history and physical findings usually provide caloric intake, the clinician may have a greater suspicion that
valuable clues to the diagnosis. For example, polyuria and an inadequate amount of calories is being fed if a confident
polydipsia are common signs of diabetes mellitus. A thyroid estimate of intake can be determined from the diet history,
nodule is usually palpable in dogs and cats with hyperthy- and if this amount is closer to 50% of MER. Similarly, con-
roidism. Fatty, voluminous stools are noted in animals with sumption of calories closer to 150% of MER may increase
pancreatic exocrine insufficiency. Diarrhea and vomiting the suspicion that adequate calories are being fed but that an
may occur in animals with various gastrointestinal tract dis- endocrinopathy and/or gastrointestinal tract disorder may
orders, and palpation of the abdomen may reveal abnormal be leading to polyphagia with concurrent weight loss. It is
loops of intestine and mesenteric lymphadenopathy. The last important to note that adjustment and monitoring is the
condition may be discernible in animals with any of the most valuable procedure for determining an individual’s true
infiltrative diseases, but it is especially noticeable in those calorie needs. If comparison of the actual caloric intake with

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