Abstract

Clinical pathology is a commonly used diagnostic tool in exotic pet medicine. In many cases, blood collection techniques are rarely as simple as they are for small animal medicine, and the interpretation of the results requires knowledge of species variation in haematologic and biochemical parameters in response to the patient’s clinical status. This presentation will discuss blood collection techniques in birds, reptiles and common small mammals. Interpretation of laboratory results will be explored, using case studies to illustrate species variation and response to disease.

Some Pearls to Help You Get the Best Possible Results

Interpretation of avian and biochemistry results is only part of the art of using haematology and biochemistry to assess your patients. To get the most out of a submitted sample it is important to provide your laboratory (external or in-house) with the best possible sample in the best possible condition. The following are some hints for doing that.

1.  Submit the largest size sample you can without compromising your patient’s wellbeing. Generally we can collect 5–10% of the patient’s blood volume (equal to 0.5–1% of its bodyweight), but the amount we collect in paediatric and anaemic patients is less. It is always worth speaking to your lab to find out what size sample they need, but negotiate with them if they want volumes larger than 0.5 ml of whole blood.

2.  Avoid haemolysis by using an appropriate size needle (23–27g) and using gentle negative pres- sure on the plunger to prevent turbulence during collection. Remove the needle before placing the sample into the collection bottles.

3.  Make several blood smears before placing the sample into anticoagulant. Rather than using another microscope slide to push the blood along the slide, use a cover slip to drag the sample along the slide.

4.  Use BD Microtainers® for your sample, but don’t under- or over-fill the tubes. Underfilling the tube mixes excessive anticoagulant with the blood; overfilling may result in a clotted tube.

5.  Use lithium heparin tubes (green top) for biochemistry and Na EDTA tubes (purple top) for haematology, unless your lab makes a different recommendation.

6.  Ensure the blood and anticoagulant are mixed immediately by rolling the tube along the palm of your hand or gently inverting the tube 10 times. Do not shake the sample, as this may result in haemolysis.

7.  If sample processing is likely to be delayed more than a few hours, centrifuge the lithium sample and separate the plasma from the red cells. Decant the plasma and place in another lithium heparin bottle. This prevents artefacts associated by prolonged contact time with the erythrocytes.

8.  Avoid over-interpretation of results. Look for significant elevations or decreases, not changes that could be within the range of error or normal variations for the machine or patient. Be aware of artefactual changes affecting some parameters (e.g., hyperkalaemia due to haemolysis).

9.  Always treat your patient, not your test results!

Blood Collection and Handling

Birds

Blood can be collected from the right jugular vein (the left jugular vein is accessible, but is much smaller), the basilic vein (on the medial aspect of the elbow) or the medial tibiotarsal vein (in large birds). The right jugular vein is usually preferred in companion birds because of the relatively easy access; it lies under an apteryla and, with practice, a sole operator can both restrain the bird and perform the venepuncture. It must be remembered that avian veins have thin walls and tear easily. Coagulation in birds usually relies on extrinsic clotting pathways requiring tissue thromboplastin, rather than the intrinsic clotting pathways utilized by mammals. Care must therefore be taken to prevent accidentally tearing the vein wall, which can lead to a rapidly fatal haemorrhage. It is advisable to apply digital pressure to the venepuncture site for 30–60 seconds to minimize haematoma formation. Using a 25–29-gauge needle minimizes the iatrogenic trauma to the vein, but the smaller the needle bore the more likely haemolysis is to occur during collection. Once the needle has entered the vein, avoid using excessive pressure to draw back; this will prevent both collapsing the vein and haemolysing the sample. It is sometimes advantageous to use a heparinised syringe for blood collection.

Reptiles

Blood can be collected from most reptiles with varying degrees of difficulty.

1.  Snakes – collect from the ventral tail vein or, if unsuccessful, from the heart.

2.  Lizards – collect from the ventral tail vein. Be careful of autonomy in skinks and geckos.

3.  Turtles – collect from the jugular vein or the dorsal subcarapacial venous sinus.

Small Mammals

There are a number of venepuncture sites that can be used in small mammals.

The Reasons Why Blood Results May Vary From Reference Intervals

Haematologic or biochemical parameters in the blood can be influenced by either physiological or pathological processes. Physiological variations can be due to age, sex, body fat to muscle ratio, nutritional status, reproductive status and species. However, pathological processes, including cellular damage or abnormal function of an organ system (or systems), often produce significant changes in parameters.

There are three major causes of abnormal laboratory results:

• Normal variation between species and individuals
• Artefacts
• Pathology

Normal Variation Between Species and Individuals

We are dealing with three classes of exotic pets, with hundreds of species presented for veterinary care. There are major differences in anatomy, physiology, form and function. Some are carnivorous, some are herbivorous, and some are omnivorous. It is unrealistic to expect that they would all conform to a relatively narrow range of haematologic and biochemical values.

Other variations arise between individuals of the same species. These variations occur because of differences in age, sex, diet, husbandry, etc. For this reason some clinicians recommend establishing a set of normal values for individual animals during annual health examinations, and then using these values as a comparison, should the animal become ill.

Artefacts

When interpreting a blood result, care must be taken to distinguish between abnormal results due to disease and abnormal results due to other factors. These other factors, referred to as artefacts, can occur for a variety of reasons, including:

Physiological Changes

Stress due to transport and handling of the patient can lead to a release of endogenous corticosteroids, resulting in changes in the haemogram and in blood glucose.

Lipaemia, while occasionally seen in diseases of the liver and reproductive system, can also occur naturally in the reproductively active female. Regardless of the cause, lipaemia can cause false elevations in bile acids, protein, calcium, phosphorus and uric acid. It may also falsely decrease amylase.

Postprandial lipaemia is uncommon in pet birds and mammals, so fasting will not help; the clinician needs to check with the laboratory if the sample submitted was lipaemic before interpreting these biochemistries.

Previous Therapy

Before interpreting biochemistries, the clinician should consider if any treatment given prior to the sample collection could have had an effect on the results. Therapy given by another veterinarian or in an attempt to stabilize a crashing patient can have marked effects.

Parenteral fluids can dilute biochemistries; exogenous corticosteroids can markedly elevate aspartate aminotransferase (AST), creatine kinase (CK) and lactate dehydrogenase (LDH); intramuscular injections, particularly of irritant drugs, can do the same.

The Clinical Condition of the Patient

Trauma, starvation and dehydration can all have marked effects on biochemistries, and need to be considered when interpreting results. Trauma can cause elevations in AST and CK and possibly glucose; starvation can lower glucose and also elevate AST and CK if protein catabolism has begun; dehydration can elevate uric acid.

The Collection Method

Ideally, sample collection should be performed in such a manner that it has minimal impact on the patient while providing an artefact-free sample suitable for analysis. This usually requires venepuncture to be performed on a minimally stressed patient. Inexperienced clinicians may need to consider gaseous anaesthesia in order to collect a good sample without the bird struggling. Haemolysis can cause elevations in bile acids, LDH, CK, potassium and phosphorus.

Glucose and albumin may be decreased. Calcium may be elevated or decreased, according to the methodology used.

Storage and Transport of the Sample

Blood collected for biochemistry analysis should be placed immediately into a lithium heparin tube. Ideally, miniature tubes as used in medical paediatrics should be used.The sample should be gently rolled or rocked; clotting must be avoided, but haemolysis must be as well. If the analysis is to be performed in-house, it should be processed immediately. If a delay is likely, or if the sample is to be shipped to an outside laboratory, the sample should be centrifuged and the plasma harvested. Sending whole blood to an outside laboratory can result in decreased glucose (as cell metabolism continues) and haemolysis.

EDTA tubes are unsuitable for biochemistry analysis in most species, but can be used for haematology, lead analysis and fibrinogen determination

Haematology

The complete blood count (CBC) is an important test in determining many disease states. In most cases a CBC involves assessing:

• The erythrocytes, through the determination and assessment of:
• The haematocrit or packed cell volume (PCV)
• Erythrocyte morphology
• Reticulocytes
• The leucocytes, through the determination and assessment of:
• The total white cell count
• The leucocyte differential count
• The morphology of the leucocytes
• Thrombocyte numbers.

Erythrocytes

• The PCV of most birds lies between 0.4 l/l and 0.55 l/l. Non-flighted birds, such as chickens, usually have a lower PCV as they do not have the same oxygen demand that flight requires.
• The normal PCV in most reptiles is lower than mammals and birds, and values of 20– 35% are not unusual. Again, this may reflect their lower metabolic rate and subsequent lower oxygen requirement.
• Small mammals generally lie between these two extremes, with a PCV generally between 35–48%.

A low PCV can indicate blood loss, anaemia, shock or haemodilution following fluid therapy.

A high PCV indicates dehydration or polycythaemia (primary or secondary).

Morphological abnormalities seen in erythrocytes include:

• Excessive polychromasia. Polychromasia is an indicator of the patient’s erythrocyte regenerative abilities. Although some polychromasia (1–5%) is normal, excessive polychromasia indicates a regenerative response to blood loss or anaemia.
• Reticulocytosis, especially when combined with increased polychromasia, is seen as a regenerative response to blood loss or anaemia.
• Anisocytosis. Variation in the size of erythrocytes is occasionally seen in peripheral blood smears as a normal finding. However, the number increases in response to anaemia.
• Poikilocytosis, or variable cell shapes, may represent artefactual error, but is also seen when severe systemic infections affect the bone marrow. Erythrocytes may appear round, elongated or irregular. The nucleus may vary in appearance, location and number. Erythrocytes that appear round with oval nuclei are indicative of accelerated erythropoiesis. Binucleated erythrocytes may also indicate abnormal erythropoiesis in association with severe, chronic inflammatory processes and neoplasia. Poikilocytes are susceptible to damage, and therefore have a shorter life.
• Erythrocytic ballooning has been reported to be commonly associated with, although not pathognomonic for, lead toxicosis in birds. It is also seen with ‘conure bleeding syndrome.’There are bulges in the normal ellipsoid shape of the erythrocyte, often accompanied by areas of hypochromasia.
• Haemopararasites are occasionally seen in the erythrocyte cytoplasm of wild-caught birds and reptiles, or those exposed to biting insects.

Leucocytes

The white blood cell (WBC) count and differential are important tools in assessing a patient’s response to disease or injury. The WBC count in birds and reptiles can be determined using three testing methods:

• An automated count, which has recently become available in some laboratories.
• An estimated WBC count determined from a blood smear by counting all leucocytes in 10 high-power (40x) microscopic fields, dividing by the number of fields, and then multiplying this average by 2,000, giving a total WBC/µl.
• The Unopette method using phloxine B stain and a haemocytometer to count eosinophils and heterophils. This count is compared with the percentages of these cells in the differential and the WBC count is calculated using the formula: WBC=(Total Het + Eos)/(%Hets + %Eos) x 100. (Note: In late 2007 the Unopette system was discontinued by the manufacturer. An alternative test is the Avian Leuko-pet®, Vetlab).

Leucocytosis can be normal in young animalss, but it can also be due to:

• Stress
• Inflammation, often associated with bacterial and fungal infections

Leucopaenia can be due to:

• Chronic inflammation or disease, often with an acute decompensatory episode at the time of presentation
• Overwhelming bacterial and viral infections
• Artefacts resulting from poor sample handling (blood clotting) or technique

White cell differential counts are best obtained from fresh blood smears, as cellular morphology can be affected by anticoagulants in blood collection tubes. A differential count is typically obtained by examination of stained smears under high magnification. Both the type and morphology of the white cells seen are recorded. In many cases, the differential count and cellular morphology give more indication of a bird’s health status than the total white cell count.

Heterophils

The heterophil is the avian and reptile equivalent of the mammalian neutrophil. While it has a similar function to the neutrophil, morphologically it appears quite different. The nucleus contains coarsely clumped chromatin and usually has two to three lobes. The cytoplasm contains eosinophilic, spherical, oval or spindle-shaped granules. It is, in most species, the predominant white cell. Heterophils lack lysozyme, which is why birds form caseated, rather than liquid, pus. Abnormal changes seen with heterophils include:

• Heterophilia
• Heteropaenia
• Toxic heterophils (increased cytoplasmic basophilia, vacuolization, nuclear degeneration, degranulation or abnormal granules)
• Immature (band) heterophils

Eosinophils

The eosinophil is a round cell with a slightly basophilic cytoplasm (in contrast to the colourless cytoplasm of the heterophil). The granules are usually rounded, although shape and colour may vary greatly between species. The granules are distinctly eosinophilic and brighter in colour when compared with the heterophil granules. The function of eosinophils is still largely unknown; eosinophilia is rare, sometimes associated with parasitic infections but more commonly with marked tissue damage.

Lymphocytes

Lymphocytes are second only to the heterophil in frequency in most species. Size and shape vary, with small, medium and large cells that may be round or moulded around neighbouring cells being seen in the same smear. Occasional reactive lymphocytes are a normal finding, but large numbers indicate marked antigenic stimulation as seen in severe infections (e.g., severe viral infections, chlamydiosis, aspergillosis, salmonellosis and tuberculosis).

Lymphocytosis is seen in:

• Chronic infectious or inflammatory conditions
• Lymphoid leukaemia
• Normal finding in Amazons and canaries

Lymphopaenia is seen in:

• Viral infections and diseases that cause bursal damage or bone marrow suppression
• Relative to a marked increase in heterophils.

Monocytes

Monocytes are the largest of the mononuclear leucocytes, but are rarely seen in peripheral blood smears. They spend only a short time in circulation before passing into tissues and becoming macrophages. The eccentric nuclei are either round, elongated or indented, and the cytoplasm typically stains a blue-grey colour with a reticular or finely granular appearance, with occasional vacuoles. Care must be taken not to confuse them with large lymphocytes.

Monocytosis is most commonly associated with chronic granulomatous infections.

Azurophils

Mature azurophils are similar in size to heterophils and vary in shape from round to monocytoid in appearance. The nuclei are usually eccentric and the cytoplasm is bluish grey with azurophilic granules. Azurophils occur at relatively low numbers in healthy reptiles, but are increased in bacterial infection and cellular necrosis.

Basophils

Basophils are uncommon in peripheral blood smears of birds. They appear as small cells with clear cytoplasm and spherical basophilic granules. The nucleus stains a light blue colour. Care must be taken not to confuse them with immature heterophils. Basophilia has been reported in respiratory disease (e.g., air sac mite in canaries), chlamydiosis and tissue trauma more than 48 hours old. In birds and reptiles, basophils appear to play an important role in early inflammatory and immediate hypersensitivity reactions, but differ from those in mammals by not contributing to delayed hypersensitivity.

Thrombocytes

Thrombocytes are small, oval, nucleated cells that can be differentiated from erythrocytes by their size (they are smaller than erythrocytes) and their nucleus, which is larger, more rounded and darkly basophilic-staining. The cytoplasm is colourless or a faint blue colour with one to two small basophilic inclusions at the poles. Total counts are difficult and not routinely performed as the thrombocytes tend to clump. However, there are typically 1–2 cells seen per high-power field. Their function is unclear; they contain little thromboplastin, so it is unlikely that they initiate clotting. With bacterial infections they tend to increase in numbers and become activated (pseudopodial formation and vacuolation) and tend to aggregate in clumps. They appear to have some phagocytic activity.

Thrombocytosis is rarely reported and may arise as in response to thrombocytopenia. Thrombocytopenia may occur due to bone marrow suppression or disease processes causing an excessive demand (e.g., viral diseases such as circovirus, reovirus or polyomavirus).

Clinical Biochemistry

Clinical biochemistry involves the measurement of specific groups of chemicals within the body and the interpretation of the results obtained. These chemicals include:

• Metabolites. Those chemicals that are produced as the end-products of various metabolic processes within the body.
• Tissue enzymes, which catalyse chemical reactions within the body without being altered themselves.
• Electrolytes, including sodium, potassium and chloride.
• Minerals, such as calcium, phosphorus and magnesium.
• Bile acids, produced in the liver from cholesterol and used in the emulsification of dietary fats.
• Lipids

Liver Enzymes

The detection of liver disease through biochemistry is complicated by the fact that there are no specific ‘liver enzymes’ that can be evaluated conclusively in each and every case. Liver disease can be broadly classified into three conditions: hepatocellular rupture, decreased hepatic function and cholestasis. These conditions can occur either separately or concurrently.

Hepatocellular Rupture

This releases intracellular enzymes, which then reach elevated levels in the blood. These so-called ‘leakage enzymes’ include:

• Aspartate aminotransferase. This cytosolic enzyme is found in many tissues in the body, but the highest concentrations are found in skeletal muscle and liver. Significant elevations usually represent either muscular or hepatocellular damage. AST, therefore, must be interpreted alongside CK (released from damaged muscle) to distinguish between the two. In general, an elevated AST with a normal CK indicates hepatocellular rupture. However, CK has a much shorter half-life than AST; a single-point muscle injury (e.g., an injection) 4–7 hours before sample collection could duplicate this biochemistry pattern. Although AST is considered to be the most useful liver enzyme, it cannot be considered in isolation as an indicator of liver disease.
• Glutamate dehydrogenase (GLDH), a mitochondrial enzyme, is the most specific enzyme for the detection of liver disease, but its sensitivity is low. Because it is bound to mitochondria, extensive and severe liver damage is required before elevations are detectable.
• Lactate dehydrogenase is not specific to any tissue; its main advantage lies with a half-life shorter than CK. Persistent elevation in the presence of normal CK is strongly suggestive of liver disease.
• Alanine aminotransferase (ALT) and alkaline phosphatase are not considered useful in detecting liver disease in birds, reptiles and rabbits. ALT in these species is very nonspecific for the liver, and normal levels have been shown in cases with severe liver damage.

Decreased Liver Function

Decreased liver function can occur with any number of liver diseases, not all of which involve hepatocellular rupture. Chronic cirrhosis, amyloidosis and hepatic lipidosis can all have an adverse effect on liver function without causing any cellular damage. In these cases a ‘liver function test’ is necessary to detect the problem. Bile acids serve this purpose well. Produced in the liver, they are excreted in bile into the small intestine where they act to emulsify fat. Most of the bile acids are then resorbed in the small intestine, enter the portal system and are taken up by the liver to be recycled. Elevated levels occur when there is impairment of the liver’s ability to remove bile acids from the portal circulation. A two- to fourfold increase in bile acids indicates a significant decrease in liver function. It needs to be noted though that a severely dysfunctional liver (e.g., end-stage cirrhosis) may not be able to produce normal levels of bile acids, leading to low-to-normal results. Total protein, especially albumin, may also be decreased with decreased liver function.

Cholestasis

Cholestasis occurs when the biliary system is partially or totally obstructed. This can be seen with biliary neoplasia, pancreatic disease or diffuse swelling of the entire liver. Gamma glutamyl transferase (GGT) is an enzyme found in the cell membranes of the bile ducts. Elevations can be seen in cholestatic disease (e.g., bile duct carcinoma), but it is considered to be a relatively insensitive test for liver disease in parrots.

Bilirubin is not produced in birds and reptiles; they utilize biliverdin instead. There are no commercial assays for biliverdin. Bilirubin is useful for evaluating cholestasis in small mammals.

Kidney Function

Birds

The end-product of protein metabolism in birds is uric acid. It is produced in the liver, enters the circulation and is then secreted by renal tubules (>90%) or filtered in the glomerulus (<10%). Significant loss of renal tubules will therefore result in elevations of uric acid. Dehydration is less likely to cause hyperuricaemia because glomerular filtration is relatively unimportant.

At first glance, it would appear that uric acid offers a sensitive and specific test for renal disease. There are, however, several confounding factors. Firstly, species differences: carnivorous birds have higher normal uric acid levels than granivorous birds. Secondly, age: juvenile birds may have lower levels than adults. Thirdly, although significant elevations usually indicate renal disease, normal levels do not mean the kidneys are normal: mild increases could indicate early renal disease or dehydration (or both). There must be severe renal damage before uric acid levels begin to rise.

Because of this relative insensitivity of uric acid in detecting renal disease, levels are best interpreted alongside a determination of the bird’s water intake and loss and a physical examination. To distinguish renal disease from dehydration, the patient’s haematocrit, total protein and blood urea nitrogen (BUN) should be evaluated concurrently. Dehydration can lead to decreased glomerular filtration rates (GFRs), in turn leading to elevated levels of BUN; this same decrease in GFR can lead to elevations of uric acid without primary renal disease being present. It is therefore prudent, in cases of an elevated uric acid level, to rehydrate the patient over 2–3 days before definitively diagnosing renal disease. Persistent hyperuricaemia after fluid therapy, and with haematocrit, total protein and BUN returning to normal, confirms a diagnosis of renal disease.

Creatinine is generally accepted as being of little or no value in evaluating renal function in birds. Phosphorus elevations are usually not seen in birds with renal disease.

Reptiles

Hyperuricaemia in reptiles is commonly associated with high-protein diets, a recent meal, dehydration, and gout. It is not commonly observed in reptiles with renal disease. This is because it is excreted in the proximal tubules and so it is usually widespread renal disease that affects blood concentrations.

Elevations in urea nitrogen may be associated with pre-renal, renal, or post-renal disease. Hypocalcaemia and hyperphosphataemia are common in reptiles with renal disease, with a Ca:P ratio less than 1.0 been strongly suggestive of renal dysfunction.

Rabbits

Renal disease will increase both BUN and creatinine concentrations. In chronic renal disease, an increase in the phosphorus concentration can be observed. Interpreting high calcium concentrations can be difficult as clinically normal rabbits can have high calcium concentrations. Rabbits appear to be more efficient than other mammals in absorbing calcium from their gastrointestinal tract. It is important to realize that high serum calcium concentrations in rabbits are not always associated with disease and may be an indication that the diet is too high in calcium.

Reproductive Activity

Birds

Clinical biochemistries can tell the clinician little about the male reproductive tract; they can, however, reveal something about the activity of the female reproductive tract. Oestrogen, produced by developing follicles, induces the production of calcium-binding protein and vitellogenesis in the liver. The net result of this activity is an increase in circulating total protein, calcium, triglycerides and cholesterol. The serum may appear lipaemic.

Radiographic evidence of hepatomegaly and increased long bone density can confirm reproductive activity. It should be noted, though, that normal calcium and protein do not reflect a lack of reproductive activity. Elevated triglyceride levels can be due to dietary factors, liver disease, ovarian activity, pancreatic disease, or causes not yet understood in parrots.

Reptiles

Elevated albumin concentrations in female reptiles during the breeding season are indicative of impending egg-laying; concurrent elevations in calcium and phosphorus are common in these individuals.

Gastrointestinal Tract

Gastrointestinal disease typically only gives nonspecific results with clinical biochemistry. Elevations of CK, AST and LDH are not uncommon, and are not specific to the intestinal tract. Electrolytes may give more information and should be evaluated with an understanding of the patient’s appetite and thirst, hydration status, previous or current therapy and pathologic processes (i.e., gastrointestinal or renal disease) which may alter electrolyte concentrations.

• Sodium must be interpreted with the knowledge of the patient’s hydration status. It may be elevated with decreased water intake or dehydration through renal disease, vomiting or diarrhoea. Sodium may also be lost through the gastrointestinal tract or the kidneys. Other causes of hyponatraemia include over-hydration, end-stage liver disease and congestive heart failure.
• Chloride is interpreted alongside sodium. It may be elevated with vomiting or regurgitation, although this is uncommon; low levels are usually associated with regurgitation or vomiting, renal disease, congestive heart failure and other conditions which cause water retention.
• Potassium may be decreased with vomiting/diarrhoea and elevated with dehydration, haemolysis, tissue damage, or poor sample handling.

There are many other possible causes of electrolyte disturbance, and our understanding of avian electrolyte balance is still in the very early stages.

Amylase and lipase have been proposed as useful parameters in the detection of pancreatic disease in birds. It is of little value in rabbits and its significance in reptiles is unknown. There is still considerable discussion of the incidence of pancreatic disease and the specificity of these enzymes. Significant elevations of these enzymes, when accompanied by clinical signs of gastrointestinal dysfunction (vomiting, ileus, diarrhoea, coelomic pain) should lead the clinician to consider pancreatic disease as a differential diagnosis. However, normal levels do not preclude a diagnosis of pancreatic disease, nor do abnormal levels confirm such a diagnosis.

Blood Glucose

Glucose is an essential energy source for nearly every cell in the body. Blood levels are governed by its intake, absorption, the interactions of hormones controlling carbohydrate metabolism (insulin, glucagon and somatostatin), the body’s metabolism, its ability to store glucose and its excretion. As disorders of glucose metabolism involve so many organ systems, it is treated here as a separate entity.

Hyperglycaemia may be a normal physiological process, (e.g., in juvenile birds). However, elevated levels are usually related to increased production or release (e.g., stress) or failure of tissues to take it up out of the blood (diabetes mellitus). Iatrogenic hyperglycaemia occurs when corticosteroids are administered or intravenous dextrose is given. Female reproductive disease may also elevate blood glucose, but this may be an indirect result due to inflammation affecting the endocrine pancreas.

Hypoglycaemia may result from poor handling of blood samples (i.e., artefactual rather than factual), or with decreased food intake (starvation, anorexia), increased glucose usage (septicaemias, neoplasia and multiorgan failure) or decreased production (liver disease). Reptiles normally have lower blood glucose levels than birds and mammals, reflecting their low metabolic rate. Glucose concentrations in reptiles are highly variable, but generally range between 2.0–10.0 mmol/L. Lower concentrations are more commonly noted in large snakes, while higher concentrations are common in animals under stress. Diabetes mellitus is rare in reptiles.