Why Is My Dog Or Cat's Blood Serum Turbid Or Cloudy?












Ron Hines DVM PhD

To see what normal blood and urine values are, go here

For an explanation of causes of most abnormal blood and urine tests, go here

To see how tests are grouped, go here

Turbidity = Cloudiness In Your Pet's Blood Serum Sample

Some clinical chemists and diagnostic laboratories do not differentiate between the cloudiness of blood serum samples that contain large amounts of tiny fat droplets (lipemic samples) and those that contain tiny grains of other materials that make it appear cloudy (turbid). I was taught that the two are not always the same. If you consider them to be the same, read the source and causes of lipemia in blood samples here and add them to this explanation and list of causes of turbidity.

When your pet's blood sample is taken the elements that compose it stratify. The lower, heavier portion consisting of red and white blood cells is removed. The upper liquid portion (the serum) should be pale yellow and clear. If it is not, your pet most likely ate too recently and the serum portion is milky with fat droplets (lipemic). The other possibility is that the sample is turgid or cloudy due to fine granules of protein and other constituents that have come out of solution.

Turbidity and lipemia are both important because they can alter many of your pet’s blood chemistry test values. (ref) Many of the machines used to record blood chemistry values depend upon the amount of light that passes through your pet's serum sample after chemicals have been added (absorbence readings). Particles that form turbidity or the tiny globules of fat in lipemic serum scatter and prevent the normal passage of that light through the sample. Since the effect of turbidity occurs across all wavelengths of light, many blood test values can be altered when turbidity is present. Some result values will go up and some will go down.

Other tests that identify specific blood constituents by there speed of movement through a matrix (electrophoresis) can also be affected when serum samples are cloudy.



Some Reasons Why Your Pet’s Blood Sample Might Be Turbid :

Blood serum samples that have gone through major temperature changes are the ones most likely to become turbid. Freezing and thawing or prolonged storage in hot environments can cause proteins within the sample to fall out of solution (cryoprecipitate) – like fine snow (eg a calcium phosphate precipitate). The problem is worse with blood plasma than it is with blood serum because plasma still has large amounts of additional fibrinogen protein dissolved in it.

Blood samples that were not allowed to fully clot before the upper serum portion was removed also have a tendency to be turbid.

Less commonly, tumors of antibody-producing cells of the immune system (plasma cells, a type of leukemia) will cause extremely high levels of a single antibody protein to be in the blood stream. That problem, also called a monoclonal gammopathy, has been known to cause turbid blood samples.

Bacterial contamination of samples that were not refrigerated properly or soon enough can also cause turbid serum.

Persistent cloudy serum due to fat droplets (lipemic serum) can also be the result of inherited genetic mutations that result in excess fats (lipids) to be present in the pet's blood.