3396. Interpreting rabbit blood values. A Shih Tzu has a painful neck abscess

INTERPRETING LAB TEST RESULTS ON RABBITS

by Lucile Moore

Understanding those emailed or printed results we get after our rabbit’s lab test can be difficult. I hope that the following explanations of two commonly‐ordered tests will help readers interpret their rabbit’s test results.

Printed results of the tests may be presented in graphical or numerical form. They usually include the test name and/or abbreviation, results, and the low and high ends of the normal range for that test.

Results that fall outside the normal range may be noted in some way. It is important to compare the results to the range provided by the laboratory rather than ranges published in texts or online as different methodologies used for the test will result in slightly different ranges.

Rarely, errors in taking, handling or analyzing the sample will cause erroneous results, particularly if the sample is not stored correctly or is not analyzed soon enough after taking it. If you have concerns about the validity of a test result discuss it with your vet. In some cases a new test may be warranted.

Haematology.
In a CBC, or complete blood cell count, the amounts of the different kinds of blood cells present are tested.

Red blood cell (RBC or erythrocyte) count: Male rabbits and older rabbits tend to have higher counts than female and younger rabbits. Dehydration and stress from cold temperatures can cause high RBC counts. High counts of nucleated RBCs can be a sign of a bacterial infection; a very high count of nucleated RBCs can be a sign of a bad flea infestation or internal bleeding.

Slightly elevated counts of nucleated RBCs are not an abnormal finding in rabbits. The HCT (Hct, haematocrit) is a test in which the percent of red blood cells is calculated. A low value may be a sign of anemia. Hb, or hemoglobin concentration, can be used to help diagnose anaemia (low Hb) and its origin. Female rabbits tend to have much lower HB and Hct than males. Rabbits that get a lot of exercise may have elevated RBC, HB, and Hct values.

Platelets: High counts may be associated with iron‐deficiency anaemia and chronic bleeding. Cold stress can also cause elevated platelet values, as may drugs such as glucocorticoids and epinephrine. 

Low levels may be a sign of a severe allergic reaction, massive bleeding, aplastic anaemia, and systemic bacterial or fungal infections. Low values can also be caused by storing the sample for too long before it is analyzed.

White blood cells (WBC, leukocytes): White blood cell counts vary depending upon the age,  sex, breed and season of the year. 

WBC counts may include counts for specific types, such as monocytes, lymphocytes, neutrophils/heterophils and basophils. 

In rabbits it is often the proportion of the differing kinds rather than the total WBC count that helps determine the presence of an infectious disease. The proportion of neutrophils to lymphocytes should be 1:1; in a rabbit with an acute infection the proportion will often be nearer 2:1. 

A high value for monocytes can be a sign of chronic infection and a high value for eosinophils and/or basophils can be a sign of a parasitical infection.

Serum/blood chemistry. The focus on these tests is on parameters of blood other than cell counts.

Serum glucose: Although high glucose can be a sign of kidney disease, it is often caused by stress, including the stress of the trip to the vet and having blood drawn. High glucose values can also occur in rabbits with acute intestinal obstruction, hepatic lipidosis, hyperthermia, and shock. 

Some drugs can also cause elevated glucose levels, as can diabetes, but diabetes is extremely rare in rabbits. Low glucose levels can be caused by anorexia, digestive tract problems, liver disease, and septicaemia.

BUN (blood urea nitrogen): A key test used to assess kidney function. Urea levels depend upon a wide variety of factors, including the time of day, the amount of protein in the diet and how hydrated the rabbit is. Slightly high values are not uncommon in healthy rabbits. 

High values may indicate there is some kind of kidney disease. Elevated values can also be a sign of encephalitozoonosis (EC). Low levels may be caused by anabolic steroids or liver damage.

Rabbits on corticosteroids, tetracycline, or aminoglycosides may have elevated levels; rabbits on chloramphenicol can have either low or high levels.

Creatinine: High values are often a sign of severe kidney or muscle damage. This test is less influenced by external factors than the BUN. However, levels may be high in rabbits that have gone a few hours without drinking water. A disadvantage of this test is that it does not show high levels until there has been substantial loss of kidney function (excepting temporarily high levels caused by dehydration, which do not involve such loss of function).

 Cholesterol and triglycerides: To obtain accurate values for cholesterol the animal must be fasting. Since it is unsafe to fast rabbits for more than a couple of hours, not to mention that it is essentially impossible to fast most rabbits because of consumption of cecotrophs, results from this test should be considered only in conjunction with other tests. 

High cholesterol values can be caused by obesity, a diet high in fats, pancreatitis and chronic kidney failure. Values also be high if the rabbit is not eating enough, but this is a sign of advanced hepatic lipidosis and has a poor prognosis. High triglyceride levels may be a sign of chronic kidney failure.

Calcium and phosphorus: Calcium levels are primarily influenced by the calcium content of the diet. High blood calcium levels in conjunction with clear urine (showing it is not being excreted as it should) are a sign of kidney failure. 

Low calcium levels are rare but can occur in rabbits with poor nutrition. High phosphorus levels can be a sign of chronic kidney failure or soft tissue trauma.

Serum protein: Total protein levels may be high in rabbits that are dehydrated, whether from gastrointestinal hypomotility (stasis) or other reasons. Low levels can be caused by malnutrition or liver disease. Low levels of albumin (a specific protein) can be a sign of a heavy infestation of parasites, and high levels are a sign of advanced liver disease.

Bilirubin: High serum bilirubin levels in young rabbits are often caused by hepatic coccidiosis; in older rabbits they are more likely to be caused by an obstruction of the bile duct by neoplasia (cancer) or an abscess.

AP (ALP, alkaline phosphatase): The normal range for this test is wide and varies with age (young rabbits have higher levels) and breed. A high value may be a sign of diseases affecting liver function such as hepatic coccidiosis, liver abscesses, and neoplasia.

 ALT (alanine aminotransferase), also called GPT and SGPT: Another test that helps the vet assess whether there has been any liver damage. Mildly high levels may be found in rabbits that appear healthy and it is thought they may be caused by low concentrations of toxins such as aflatoxins in food or compounds in wood‐based litters. 

High levels may be a sign of hepatic lipidosis or liver damage from hepatic coccidiosis.

AST (aspartate aminotransferase), formerly called SGOT: High values in conjunction with high ALT, AP, or protein may be a sign of liver damage. High levels may also be caused by the rabbit struggling during collection of the sample.

Urinalysis
The urinalysis is another lab test that is ordered fairly frequently. More so than in blood work the normal value is often “negative,” or the absence of the tested‐for compound.

 Protein: The normal finding is negative to trace amounts. High amounts can be a result of kidney damage/disease. High levels can also be caused by dehydration, strenuous exercise or stress, and for this reason protein is best looked at in conjunction with the specific gravity and the ratio of protein to creatinine. Dilute urine with a high protein value is more likely to be a sign of kidney damage/disease than concentrated urine with a similar protein value. Low protein levels can be a sign of malnutrition.

SG (specific gravity): An SG level at the lower end of the normal range when combined with high creatinine and BUN is a sign of poor kidney function.

pH: Normal rabbit urine has a high pH (7.5‐9). Lower pH can be caused by high‐protein diets, severe
anorexia, and fever.

Glucose: The normal finding for glucose is negative, although trace amounts may be found in healthy rabbits. Higher amounts can be caused by stress, including pain or any experience which is frightening to the rabbit.

Ketones: The normal finding is negative. The presence of ketones indicates starvation or severe anorexia. Ketones may be seen in rabbits with severe dental disease that prevents them from eating or in rabbits on hay‐only diets that have severely impacted cecums. Rarely, ketones in the urine may be caused by diabetes mellitus.

Bilirubin: High levels of bilirubin in rabbit urine are unusual but elevated levels may be caused by poisoning from aflatoxins in contaminated food, hepatic coccidiosis, or neoplasia.

 Haematuria: Normally there is no blood present in rabbit urine. A positive result may be caused by inflammation and/or a urinary tract infection, crystals, or, less often, neoplasia.

Sediment: Calcium carbonate sediment is a normal finding in rabbit urine. Other crystals can be caused by drugs the rabbit is taking, and struvite crystals can be a sign of bacterial infection.

Urobilinogen: The finding for a healthy rabbit is negative. High levels may be caused by liver damage or drugs such as sulfonamides; low levels can be caused by long exposure to light.

Nitrate and nitrite: Urine normally contains nitrates, but some bacteria convert nitrate to nitrite. The normal result for nitrite is negative; a positive result is caused by bacteria in the urine. However, not all bacteria are able to convert nitrates to nitrite, so a negative result does not mean a UTI is not present.

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10 Dec 2010.

CHUBBY – DOG – Shih Tzu 9 Y/O Male. A very painful encapsulated neck abscess  

 CBC interpretation: Haematology Profile: Description: The CBC is commonly performed on an automated haematology analyzer using well mixed whole blood that is added to a chemical (EDTA – Ethylenediaminetetraacetic Acid) to prevent clotting.

 A CBC is a group of tests used to quantify the number of RBCs, WBCs and platelets, provide information about their size and shape, measure the haemoglobin content of RBCs, determine the percentage and absolute number of the five white blood cell types, and identify early and abnormal blood cells.

These tests are performed simultaneously. Analysis (Haematology): Haematology Result Unit Ref. Range Haemoglobin 18.4 g/dL 12.0 – 18.0 Red Cell Count 7.7 X10^12 / L 5.5-8.5 Total White cell count 8.3 X10^9 / L 6.0 – 17.0 Differential Count % Absolute V. Unit Neutrophils 68.19 5.66 X10^9 / L Lymphocytes 21.08 1.75 X10^9 / L Monocytes 6.14 0.51 X10^9 / L 

 Eosinophils 3.49 0.29 X10^9 / L 

 Basophils 0.96 0.08 X10^9 / L PCV 0.48 0.37 – 0.55 MCV 63 fL 60 – 77 MCH 24 Pg 20 – 25 MCHC 38 g / dL 32 - 36 RDW 15.7 % Platelets 491 X10^9 / L 200 - 500 

 Haemoglobin: 18.4 g/dL • This value is lightly above reference range but it should not be of much significance as the red blood cell count, PCV, MCV, MCH, RDW are all within normal limits. 

• Haemoglobin concentration is normally used to diagnose anaemia, which can be caused by microcytic RBCs, which are smaller than usual in size and unable to carry sufficient Oxygen. Macrocytic anaemia usually occurs when the division of RBC precursor cells in the bone marrow is impaired. The most common cause of macrocytic anaemia are vitamin B12 deficiency, folate deficiency and liver disease. Normocytic anaemia may be caused by decreased production of RBCs (any cause of bone marrow failure), increased destruction of RBCs (haemolytic anaemia) or loss of blood. 

 Total White Cell Count: 8.3 x 10^9 / L (within normal limits) • 

Normal white cell count usually indicates that the animal is not in any threat of infectious diseases and foreign bodies. • An elevated white cell count usually occurs in infection, allergy, systemic illness, inflammation, tissue injury and leukemia.

 • A depressed white cell count may occur in some viral infections, immunodeficiency states and bone marrow failure.

 • The white blood cell differential count will reveal which WBCs are affected the most • Neutrophils are the most abundant granulocytic cells and are phagocytic cells that aid in the removal of bacteria and antibody-coated antigens • Lymphocytes are the 2nd most abundant monocytic WBCs and originate from the lymphoid tissues and are NOT phagocytic. They are responsible for initiating and regulating the immune response by the production of antibodies and cytokines.

 • Monocytes are the largest monocytic WBCs and are phagocytic cells that process and present antigens to lymphocytes, an event required for lymphocyte activation 

• Eosinophils are granulocytic WBCs that have cytoplasms filled with granules that contain peroxidise, hydrolases and basic proteins that aid in the destruction of phagocytised cells. They are increased in allergic and parasitic infections

 • Basophils are granulocytic WBCs that contain large amounts of histamine, heparin and acid mucopolysaccharides. They mediate the allergic response by releasing histamine.

 Platelets: 149 x 10^9 / L (Below reference range of 200-500) • Platelets are disc-shaped structures formed from the detachment of cytoplasm from megakaryocytes. They aid in the coagulation process by attaching or adhering to the walls of injured blood vessels, where they stick together to form the initial platelet plug. 

• A low platelet count may occur in patients with viral infections, lymphoma or animals taking certain drugs such as quinine and quinidine. • Decreased platelet production is also a cause of thrombocytopenia, and may be due to aplastic anaemia, leukemia, lymphoma or bone marrow fibrosis. • 

A low platelet count can occur due to increased destruction and can result in antibody production that is often drug-induced (heparin treatment being a prominent cause)

 • In relation to this case, Chubby’s decreased platelet count might be auto-immune, resulting in platelet destruction and decreasing his ability to clot blood and predisposing him to conditions such as TTP (Thrombotic thrombocytopenic purpura) and DIC (Disseminated intravascular coagulation). 

BIOCHEMISTRY RESULTS: BIOCHEMISTRY RESULT UNIT REF. RANGE Total Cholesterol 4.75 Mmol / L HDL Cholesterol 3.72 Mmol / L LDL Cholesterol 0.20 Mmol / L Cholesterol / HDL Ratio 1.28 Mmol / L Triglycerides 1.83 Mmol / L Glucose 4.1 Mmol / L 3.9 – 6.0 SGPT / ALT 59 U / L < 59 SGOT / AST 41 U / L < 81 Calcium 2.06 Mmol / L 1.50 – 3.60 Uric acid 0.01 Mmol / L