Cholesterol in cats and dogs

What it shows

Cholesterol travels in the blood inside lipoproteins. It comes from food and from the liver, and the liver also gets rid of it through bile. So cholesterol tends to rise when bile cannot flow, when hormones disturb fat metabolism or when the kidneys lose protein, and to fall when the liver cannot make enough or the gut cannot absorb or loses too much.

Unlike triglycerides, cholesterol changes little after a meal: eClinPath explains that chylomicrons, the fat particles from food, carry very little cholesterol. eClinPath still recommends fasting dogs and cats for around 12 hours before the sample.

Higher than reference — what it may be a sign of

• Hormonal diseases: hypothyroidism in dogs (mild to marked rises), hyperadrenocorticism (Cushing’s syndrome) and diabetes mellitus.
• Bile not flowing (cholestasis): obstruction of the bile duct outside the liver raises cholesterol in dogs and cats.
• Protein loss through the kidneys: protein-losing nephropathy and nephrotic syndrome, which combines oedema, low albumin, high cholesterol and protein in the urine.
• Pancreatitis: high triglycerides are more typical, but cholesterol may rise at the same time.
• Inherited lipid disorders: familial hypercholesterolemia is reported in Briards, Rottweilers, Shetland Sheepdogs and Dobermans; Miniature Schnauzers have their own breed hyperlipidemia.

Merck also lists fatty meals and liver disease among causes of a higher cholesterol.

Lower than reference

eClinPath names protein-losing enteropathy (protein loss through the gut) in dogs and cancer in dogs and cats as the most common causes of low cholesterol. Other causes are chronic liver disease or liver failure, portosystemic shunts (blood bypassing the liver), maldigestion and malabsorption including exocrine pancreatic insufficiency, and Addison’s disease in dogs. Merck adds that it occasionally decreases in hyperthyroidism. Low albumin, low globulins and low cholesterol together are a classic pattern of protein-losing enteropathy (Merck).

Look at together with

• Triglycerides — in dogs, common causes of high cholesterol without high triglycerides are nephrotic syndrome, hypothyroidism and cholestasis; both high fit diabetes and other metabolic conditions.
• ALP, GGT, bilirubin — markers of bile flow.
• Albumin and UPC — low albumin with protein in the urine and high cholesterol suggests the kidneys; low albumin with low cholesterol, the gut.
• Glucose and thyroid tests in dogs — for diabetes and hypothyroidism.

Units and conversion

European labs usually report cholesterol in mmol/L, North American labs in mg/dL. 1 mg/dL equals 0.0259 mmol/L, so 200 mg/dL is about 5.2 mmol/L. In the app each row keeps the unit printed on the form; the chart converts to one unit so forms from different labs line up.

Reference range

The reference range is on your lab’s form. It depends on the lab and method, and a value is read against the interval printed next to it. Fasting matters less for cholesterol than for triglycerides, but results are easiest to compare when samples were taken in the same conditions. eClinPath mentions that in hypothyroid dogs a cholesterol above 750 mg/dL (about 19 mmol/L) is associated with a risk of atherosclerosis — a rare situation, and a risk marker rather than a reference value.

Cats and dogs

Sources

1. eClinPath (Cornell University College of Veterinary Medicine) — Cholesterol
2. eClinPath (Cornell University College of Veterinary Medicine) — Lipid overview
3. Whitbread TJ. Clinical Biochemistry. Merck Veterinary Manual
4. VCA Animal Hospitals — Hyperlipidemia
5. Miscellaneous Serum Biochemical Measures in Hepatic Disease in Small Animals. Merck Veterinary Manual