Page 2608 - Cote clinical veterinary advisor dogs and cats 4th

1324 Cholesterol

Next Diagnostic Steps to Consider • False increase: halides (bromide, iodide) are free water and differentials for hyponatremia
if Levels are Low + • Sample handling: Cl increases if free water or hypernatremia are investigated. Corrected
−
measured as Cl if using potentiometry.
−
• Evaluate in relation to [Na ], acid-base
VetBooks.ir • Calculate corrected serum [Cl ] to determine Specimen Collection and Handling an acid-base disturbance and should be
chloride outside reference interval suggests
loss from improperly stoppered tube.
balance.
−
−
interpreted with HCO 3 and anion gap.
if proportional change.
subject to electrolyte exclusion effect artifacts.
Serum (red top tube) preferred; heparinized • Most reference laboratory methods are
Drug Effects plasma (green top tube) may be used. Portable point-of-care analyzer methods
• Decreased: thiazide or loop diuretics, usually not affected.
−
NaHCO 3 , glucocorticoids Relative Cost: Individual test, electrolyte
• Increased: NH 4Cl, KCl, hypertonic saline, panel or other partial panels: $; included in AUTHOR: Mary Leissinger, DVM, MS, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
acetazolamide, spironolactone. Halides cause full chemistry panel: $$
artifactual increase.
Pearls
Lab Artifacts • If corrected chloride is within reference inter-
• Marked hyperlipidemia or hyperglobulinemia val, changes in chloride are due to changes in
−
may decrease measured [Cl ] by electrolyte
exclusion effect (if using indirect potenti-
ometry). Serum osmolality is normal.
Cholesterol

Definition Briard dogs, Doberman pinschers, and Drug Effects
• Lipid found only in animal tissues. rottweilers; familial hyperchylomicronemia • Increase: exogenous corticosteroids, phe-
Test measures circulating blood (serum) of cats nytoin, methimazole
concentration. • Secondary hyperlipidemia: postprandial • Decrease: lipid-lowering diets, bile acid
• Hyperlipidemia signifies hypercholesterolemia (most common), hypothyroidism, diabetes sequestrants, hepatic hydroxymethylglutaryl
and/or hypertriglyceridemia. mellitus, liver disease, cholestasis, hyper- coenzyme A reductase inhibitors (statins),
adrenocorticism, pancreatitis, nephrotic and dirlotapide lower serum cholesterol levels
Physiology syndrome
Synthesized by the liver or absorbed from diet • See pp. 496 and 1236. Lab Artifacts
in the intestines, cholesterol is essential to life Increase: hemolysis
as a major component of cell membranes and Next Diagnostic Steps to Consider
precursor for synthesis of steroid hormones if Levels are High Specimen Collection and Handling
and bile acids. The liver is the major site of • Ensure that blood sample was drawn after • 10- to 12-hour fast is required, but postpran-
cholesterol synthesis, excretion, and catabolism. ≥ 12-hour fast. dial hypercholesterolemia is mild (usually
Cholesterol and other lipids are insoluble in • Assess for causes of secondary hyperlipid- < 2 times the reference interval).
water. They are transported in blood attached emia (endocrine or metabolic disease). If • Serum (red top tube), heparinized plasma
to apoproteins. Lipid–apoprotein complexes no cause is identified, consider primary (green top tube), or EDTA plasma (lavender
are called lipoproteins. They contain variable hyperlipidemia. top tube). Stable for 1 week at 2°C-8°C and
proportions of triglycerides, cholesterol, cho- 4 weeks at −20°C
lesterol esters, and phospholipid. In laboratory Causes of Abnormally Low Levels
analysis, lipoproteins can be separated by ultra- Chronic liver disease, hypoadrenocorticism, Relative Cost: Single test $; included in a
centrifugation into chylomicra, high-density intestinal lymphangiectasia, starvation variety of panels $-$$
lipoproteins (HDL), intermediate-density
lipoproteins, low-density lipoproteins (LDL), Next Diagnostic Steps to Consider Pearls
and very-low-density lipoproteins (VLDL), but if Levels are Low • The most common cause for hypercho-
the clinical importance of lipoprotein profiling Clinical evaluation for disorders listed above. lesterolemia and no other CBC/serum
in small animal medicine is minimal compared biochemistry abnormalities in an adult,
to human medicine. Important Interspecies Differences fasted dog is hypothyroidism.
Dogs and cats are resistant to atherosclerosis, • In icteric dogs, increased cholesterol sup-
Reference Interval partly owing to the low concentration of very- ports cholestasis while decreased cholesterol
Dogs: 112-328 mg/dL. Cats: 82-218 mg/dL. low-density lipoproteins in these species. High- supports liver failure.
Unit conversion: 38.7 mg/dL = 1 mmol/L. density lipoproteins are the major lipoproteins
in dogs and cats. AUTHOR: Ruanna E. Gossett, DVM, PhD, DACVP
Causes of Abnormally High Levels EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
• Primary hyperlipidemia: idiopathic in
schnauzer dogs; hypercholesterolemia of

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