Hyperlipidemic states in the dog and cat (Proceedings)
In 1985, the National Institutes of Health established the National Cholesterol Education Program (NCEP) with the goal of reducing the prevalence of high blood cholesterol in the United States. The program, which is still in effect today, is aimed at increasing the general public's awareness of the fact that there is an undisputed risk of coronary heart disease associated with elevated cholesterol levels, particularly low-density lipoprotein (LDL) cholesterol. The NCEP has also stressed the importance of every adult's knowing his or her cholesterol level. With over 5.4 million Americans having symptomatic coronary heart disease and a large number of others with undiagnosed coronary heart disease, it is estimated that one in four American adults has a cholesterol level high enough to increase individual risk of coronary heart disease. [Consensus Conference, 1985].
Elevations in blood lipid levels are certainly recognized in dogs and cats; however the relationship between hyperlipidemia and clinical disease is not well understood. Despite the paucity of literature addressing the clinical significance of hyper- lipidemia, at least three facts are clear: 1) hyperlipidemia in the fasted (> 12 hours) dog or cat is abnormal, 2) there appears to be significant morbidity, and occasional mortality, associated with hyperlipidemia in dogs and cats, and 3) specific dietary and/or drug intervention can eliminate or at least diminish the morbidity associated with hyperlipidemia.
Hyperlipidemia DefinedThe term hyperlipidemia applies to those patients with concentrations of blood cholesterol and/or triglyceride. Although standardized values for these analytes have not been strictly defined in veterinary medicine, most laboratories report the normal serum total cholesterol to be in the range of 120 to 270 mg/dL for the dog and 70 to 200 mg/dL for the cat. It must be assumed that these values apply only to adult dogs and cats in the fasted state; lipid values in dogs and cats less than 6 months of age have not been reported. Those animals with values exceeding the upper range of normal are considered hyperlipidemic. However, it is important to note that abnormal elevations of blood lipids do not necessarily reflect a significant health risk for the affected dog or cat, hyperlipidemia may represent an early signal for underlying disorders affecting lipid and lipoprotein metabolism, e.g. diabetes mellitus, hyperadreocorticism (canine Cushings), hypothyroidism.
Visual Inspection. Lipemia is the term used to describe samples of whole blood, serum, or plasma in which lipid is grossly visible (appearing white to cloudy...in whole blood, lipemic samples may appear pink-ish). Lipemic serum is caused by excessive concentrations of triglyceride, as opposed to cholesterol, and is the type of hyperlipidemia most commonly recognized in companion animal medicine. Lactescence refers to serum or plasma that contains elevations of triglyceride sufficient to cause the sample to be milk-like in appearance and opaque. Patients with lactescent serum typically have extreme elevations of triglyceride-rich chylomicrons. Measured triglyceride levels typically exceed 1000 mg/dL. Regardless of the underlying cause, patients with lactescent serum, especially if fasted, must be regarded as being at risk of developing acute pancreatitis and signs of gastrointestinal distress (dogs) and eruptive cutaneous xanthomata (cats).