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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 elevat- ed with decreased water intake or dehydration through renal disease, vomiting or diarrhoea. Sodium may also be lost through the gastroin- testinal tract or the kidneys. Other causes of hy- ponatraemia include over-hydration, end-stage liver disease and congestive heart failure.
· Chloride is interpreted alongside sodium. It may be elevated with vomiting or regurgitation, al- though this is uncommon; low levels are usually
associated with regurgitation or vomiting, renal disease congestive heart failure and other con- ditions 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 multi- organ 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.
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