Chemical Pathology – Metabolic and Intestinal

Metabolic and Intestinal Chemical Pathology

DIABETES MELLITUS mellitus (DM) is a common disease in and cats. Prevalence in the population appears to be increasing but this may be due to improved diagnostics and awareness in the client population. Two main mechanisms for the development of DM are deficiency or or interference. Altered protein and lipid metabolism also occurs with DM. Mobilisation of fatty acids as an alternative energy source leads to hepatic lipidosis and ketogenesis. Practically DM leads to tissue with weightloss despite polyphagia and hyperglycaemia at the tissue level. Without effective treatment, DM ultimately can lead to ketoacidosis and death.

Glucose determination is recommended in any case with a history of weakness, seizures, collapse, PU/PD; suspected or known hepatic, pancreatic and adrenal disease. It should also be monitored in cases with sepsis, neoplasia, monitoring treatment of DM and cases with glucosuria. It is important to document both persistent hyperglycaemia and glucosuria before diagnosing diabetes mellitus. Glucosuria occurs between 10 – 12 mmol/l (180-220 mg/dl) in dogs and cats; > 10 mmol/l (180 mg/dl) in horses and > 5.6 mmol/l (100 mg/dl) in cattle. Other causes of hyperglycaemia include:  Excess plasma glucocorticoid concentrations  Increased plasma catecholamine concentration  Increased growth  Increased progesterone production  Glucagon producing tumours   Hyperthyroidism  Pheochromocytoma  PPID in horses  Colic in horses  Proximal duodenal obstruction in cattle  Milk fever in cattle  Severe distress in sheep  Drugs including Megestrol acetate, Xylazine, Ketamine, Phenothiazine, Morphine * Type I diabetes is comparable to insulin-dependent diabetes mellitus (IDDM) in humans. It results in low basal insulin concentrations with impaired insulin secretion following a load. Treatment requires insulin injections. It is the most common form of . * Type II diabetes is similar to non-insulin dependent diabetes (NIDDM) in humans and is managed with dietary therapy and oral hypoglycaemic drugs. It causes normal to increased basal insulin concentrations with decreased secretion following a glucose load. Insulin may or may not be required for animals with Type II diabetes. * Type III diabetes is seen most commonly in hormonally induced diabetes in dogs and cats and is similar to impaired glucose tolerance (IGT) in humans. Diabetogenic (epinephrine, cortisol, glucagon and growth hormone) or medications interfere with insulin action and cause glucose intolerance, which can lead to diabetes.

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Blood glucose is elevated for 2-4 hours post-prandially in dogs and cats. Therefore fasted samples are indicated, preferably as long as 12 hours fast. Serum glucose concentrations can be misleading in stressed or excited animals. Excited cats can have glucose concentrations as high as 22.5 mmol/l (400 mg/dl) but it is transient. Protocol: Serum plasma should be separated from the erythrocytes within 30 minutes. Fluoride-oxalate tubes should be used if testing is not possible within 30 minutes. Heparin or EDTA plasma, separated from the red blood cells, can be used for point-of-care instruments or in-house analysers provided the test is run within 20 minutes of collection. Interpretation: Persistent fasted-glucose greater than values in this table, with glucosuria is consistent with DM. Species Canine Feline Equine Bovine Glucose Ref Range mmol/L 3.3-7.3 4.4-7.7 3.7-6.7 2.5-4.3 Diabetic mellitus * > 11 11 7 6 Danger Levels < 2.2 mmol/l – coma > 45 mmol/l CNS dysfunction *In horses insulin-resistance is a common phenomenon – see below.

FRUCTOSAMINE CONCENTRATION is a general term that refers to glycated protein. Glucose binds irreversibly to the amine groups of albumin and other proteins forming stable compounds known as fructosamine. In dogs, albumin has the greatest affinity for glucose; while in cats globulins do. Low levels of are present in normal animals but in hyperglycaemia increased serum concentrations occur. The fructosamine concentration at any given point is an indicator of the hyperglycaemic condition of the previous 10-21 days (half-life of serum albumin 8 – 10 days). This assay provides more information regarding the duration of hyperglycaemia whereas a random glucose concentration is only related to the previous 1-2 hours. . Albumin is the most frequently involved protein in dogs and therefore in hypoalbuminaemic dogs, fructosamine assays must be interpreted with caution. . Fructosamine is the most reliable method of differentiating stress hyperglycaemia (which is transient) from true persistent hyperglycaemia in cats. Protocol: Different laboratories prefer different samples but most commonly plasma from EDTA or heparin is used. Some laboratories do use serum from clotted blood but gel- separation tubes must not be used. Slight haemolysis will cause false elevations in the assay but lipaemia does not interfere. Interpretation: Normal ranges vary between laboratories. SPECIES Normal Fructosamine Excess Fructosamine 230 – 375 umol/l > 450 umol/l CAT 175 – 400 umol/l > 450 umol/l

. When monitoring patients on insulin therapy the aim is to maintain fructosamine concentrations between 350-450 umol/l.

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. Values greater than 450 need to be monitored carefully because once it rises above 500 umol/l the dog/cat will be suffering from hyperglycaemic episodes. . Values below 250 umol/l in the dog, and 200 umol/l in the cat, may be indicative that the insulin dose is excessive and might need downward adjustment.

Glycated haemoglobin (GH) is not recommended in animals. GH occurs normally but is increased in hyperglycaemic conditions. The GH concentration is reflective of a longer period than fructosamine, usually the previous 3-4 months. Even when normoglycaemia follows hyperglycaemia, GH concentrations may remain elevated. Such decreases in GH may be delayed for several weeks. Therefore fructosamine is preferred as a diagnostic tool because it can identify DM sooner and when monitoring animals the fructosamine decline will occur sooner than with GH.

SERUM INSULIN ASSAY A useful assay when serum glucose is abnormal, it is used to evaluate the cause of both hypoglycaemia and hyperglycaemia. The insulin assay must be run in conjunction with a glucose assay. The most common indication is suspicion of an insulinoma in intermittent hypoglycaemia or incidental hypoglycaemic cases. It is important to note that many other causes of hypoglycaemia occur, including extra- panreatic tumours, hepatic insufficiency, sepsis, idiopathic hypoglycaemia, hypoadrenocorticism and iatrogenic hypoglycaemia. Protocol: Serum for insulin assay should be harvested from the clotted blood within 30 minutes and then measured or frozen. Do not use gel-separator tubes. Insulin units often reported in uU/ml = mU/l and multiplied by 7.18 = pmol/l.

Interpretation: Insulin Concentration (pmol/l) SIGNIFICANCE 30 – 120 Normal in cats and dogs (normoglycaemic) 36 – 72 Low/normal insulin, insulinoma possible if glucose very low 72 - 145 High/normal insulin, insulinoma likely if glucose low > 145 High insulin, insulinoma very likely if glucose low . Insulinomas and other causes of fasted hypoglycaemia may have insulin levels that fall within the low normal range (eg. 30-60 pmol/l) and a repeat assay is recommended for such patients. . A subnormal (< 30 pmol/l) insulin level in the face of hypoglycaemia is not compatible with a diagnosis of insulinoma.

EQUINE INSULIN RESISTANCE SYNDROME Equine insulin resistance (IR) can affect horses of any age. It is common in older horses suffering from Pituitary Pars Intermedia Dysfunction and should always be screened for in horses diagnosed with PPID (see endocrine section). However it also occurs in younger horses and in horses without PPID. Equine metabolic syndrome has been coined to describe a phenotype of equid that suffers from IR. This phenotype includes obesity, regional adiposity, increased risk of laminitis, IR, hypertriglyceridaemia, hyperleptinaemia, hypertension and lean horses predisposed to laminitis. Horses suffering from IR are at increased risk of developing laminitis. If mild laminitis develops in a young horse, especially when on sugar-rich pastures, IR should be suspected. However other clinical signs include colic (from abdominal pedunculated lipomas), hyperlipaemia and abnormal reproductive cycling in mares.

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RESTING BLOOD GLUCOSE AND INSULIN Glucose and insulin should be determined simultaneously. Protocol: The horse should be starved for 6 hours, kept off pasture and stressed as little as possible. Serum for insulin assay should be harvested from the clotted blood within 30 minutes and then measured or frozen. Do not use gel-separator tubes. Insulin units often reported in uU/ml = mU/l and multiplied by 7.18 = pmol/l. Glucose requires a fluoro-oxalate tube or serum can be used provided the sample is centrifuged immediately and serum separated from blood within 20 minutes. Interpretation: Normal glucose is between 3.3 – 6.7 mmol/l; normal insulin < 140 pmol/l. GLUCOSE INSULIN (mmol/l) CONCENTRATION SIGNIFICANCE (pmol/l) < 5.6 < 140 No evidence IR. Address obesity if required. Normoglycaemia but hyperinsulinaemia. Compensated < 5.6 > 140 IR – strict diet, exercise. Laminitis risk!! Normoglycaemia, marked hyperinsulinaemia. Severe < 5.6 > 700 compensated IR. Very high laminitis risk!! Hyperglycaemia and hyperinsulinaemia. Pancreatic > 5.6 > 140 exhaustion. Transitioning from severe compensated to uncompensated IR. High laminitis risk!! Hyperglycaemia and normal to low insulin. Unregulated > 6.7 < 140 glucose and pancreatic insufficiency. Uncompensated IR. DM II – check for glucosuria and PPID. If hay has been fed, cut-off for hyperinsulinaemia is 210 pmol/l

For horses that have normal insulin and glucose values but clinical signs of IR, the combined glucose-insulin-test is recommended. This is a dynamic test assessing the ’ response to a sugar load. Contact the laboratory for the method.

CALCIUM METABOLISM Total calcium in the blood is composed of three fractions. About 40% is protein- bound calcium (pCa), which is bound mainly to albumin. The fraction that is used best to assess calcium balance is the ionized calcium (iCa), because it is the free biologically active form, constituting 50% of total calcium. The third fraction is complexed calcium (cCa), which is usually about 10% bound to phosphate, lactate, sulfate, bicarbonate, and citrate molecules in the blood. Total calcium is insensitive because it is influenced by many factors and may appear abnormal while iCa is normal. Both total calcium and iCa are influenced by pH and therefore acid-base status must be taken into account. Acidosis increases concentrations of both, while alkalosis lowers their concentrations. Calcium should always be assessed in conjunction with phosphate. Phosphate and iCa are in concentrations high enough to cause precipitation if inhibitors were not present but when the product of total calcium and phosphate in mg/dl exceeds 70, mineralisation in soft tissues is possible.

Units and conversions – mg/dl x 0.2495 = mmol/l. Total calcium is measured on serum samples and is relatively stable in serum samples. Converting total calcium results to an adjusted value as an estimate of iCa has been shown to be unreliable. These formulas can be used as a rough guide but abnormal values must be checked with a proper iCa measurement. Adjustment formulas do not work in cats. The

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Chemical Pathology – Metabolic and Intestinal formula using serum albumin concentration is the most reliable in dogs. Many in- house analysers offer ionized calcium as routine measurement which is very useful. Submitting samples to a commercial laboratory for iCa requires stringent sample handling, transport and processing – contact your laboratory.

IONISED CALCIUM Protocol: Different laboratories and analysers use different samples but most commonly plasma from heparin or serum is used. Others analysers use whole blood. Gel-separation tubes must not be used. Slight lipaemia will cause false elevations in the assay and icterus will cause false decreases. Minimum 0.5ml required. Interpretation: Normal ranges vary between laboratories. Unit Canine Feline Equine Bovine Total Calcium mmol/l 2.30-2.80 2.22-2.78 2.75-3.25 2.10-2.80 Ionised Calcium mmol/l 1.12 – 1.42 1.12 – 1.4 . Serum TCa and iCa in dogs younger than 1 year may be 0.1 mmol/l higher. . TCa does not fluctuate with age in cats but iCa will be higher by 0.1 mmol/l in cats younger than 2 years.

HYPERCALCAEMIA HYPOCALCAEMIA Hyperalbuminaemia () Hypoalbuminaemia Hypercalcaemia of malignancy (lymphosarcoma) Malabsorption Primary hyperparathyroidism Parturient paresis Excessive vitamin D or Ca Eclampsia Young, growing animals Pancreatic necrosis Hypoadrenocorticism Massive myopathy, rhabdomyolysis Chronic and Acute Renal failure Renal secondary hyperparathyroidism Lipaemia (artifact) Artifact - EDTA anticoagulant, haemolysis

PARATHYROID HORMONE ASSAY Serum PTH concentrations should be evaluated relative to the total or, preferably, ionised calcium concentration. Assays validated for use in dogs and cats are so-called ‘two-site’ radio-immunoassays that measure 2 amino acid sequences of the PTH molecule. Protocol: Serum or EDTA plasma can be used, but since PTH is relatively labile it should be appropriately handled to prevent erroneously low results. Serum or plasma must be separated from blood cells and frozen for transport.

Interpretation: Azotaemia makes interpretation difficult. Low levels are caused by non-parathyroid causes of hypercalcaemia, except hypercalcaemia of CRF. Low levels in the presence of hypocalcaemia strongly suggest primary hypoparathyroidism. Raised concentrations occur in primary hyperparathyroidism, renal secondary hyperparathyroidism, nutritional secondary hyperparathyroidism and non-parathyroid causes of hypocalcaemia. Mid-normal to mildly elevated PTH in the presence of hypercalcaemia with normal renal function, strongly suggests primary hyperparathyroidism.

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NORMAL RANGES UNITS Parathyroid hormone 2 – 13 pmol/l Parathormone-related protein < 0.2 pmol/l Vitamin D or Calcitriol 80 – 285 nmol/l

DISORDER T-Ca I-Ca PHOS PTH PTHrP VIT D Malignancy ↑ ↑ ±↓ ↓ ↑ ↓ Primary Hyperparathyroidism ↑ ↑ ±↓ ↑ ↓ ↑ Renal failure ↑ ±↓ ↑ ↑ ↑ ↓ Vitamin D toxicity ↑ ↑ ↑ ↓ ↓ ↑ Hypoadrenocorticism ↑ ↑ ↑ Nutritional 2ndry Hyperparathyroidism ↓ ↓ ↑ ↑

SERUM PHOSPHATE and MAGNESIUM Protocol: Serum samples are adequate for both phosphate (inorganic phosphate) and magnesium measurement. Ionised Mg is more accurate but not always available.

Interpretation: Unit Canine Feline Equine Bovine

Phosphate mmol/L 0.90 - 1.85 0.80 - 2.29 0.73 - 1.71 1.47 - 2.63 Magnesium mmol/l 0.70 - 1.10 0.80 - 1.10 0.6 - 1.00 0.82 - 1.30

HYPERPHOSPHATAEMIA HYPOPHOSPHATAEMIA Young, growing animals Inadequate diet (P, vit D, Ca) Decreased renal clearance - azotaemia Malabsorption, Steatorrhoea, diarrhoea Anorexia, , dehydration, Parturient paresis (cattle) Excessive vitamin D or P Hyperparathyroidism, primary or secondary Chronic and Acute Renal failure Excessive antacid/bicarbonate dosing Tissue trauma, necrosis, neoplasia Hyperinsulinism, adenoma or administration Acidosis Hypercalcaemia of malignancy Haemolysis, Lipaemia (artifact) Diabetes mellitus (ketoacidosis)

HYPERMAGNESAEMIA HYPOMAGNESAEMIA Renal failure Hypoalbuminaemia, protein Diabetes mellitus (coma) Malabsorption, chronic diarrhoea Adrenocortical insufficiency Renal magnesium wasting – DM (dka), Excessive Mg administration Hyperthyroidism Hibernation Pancreatic necrosis Excessive parenteral fluids or nutrition Primary hyperparathyroidism Primary hyperaldosteronism

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Laboratory Investigation of Intestinal Conditions Chronic intestinal diseases classically present with chronic intermittent or persistent diarrhoea, but other signs may include vomiting (sometimes the main sign in cats with intestinal disease), weight loss or failure to gain weight, and polyphagia or anorexia. These cases are some of the most common complaints practitioners receive and it can be a very frustrating diagnostic challenge.

Samples should be submitted for a full blood count and general biochemistry profile including , serum proteins, liver enzymes, renal function and some authors advocate amylase and lipase at this point. Unless there is significant azotaemia or liver enzyme elevation suggesting renal disease or a hepatopathy, these initial results are often non-specific and should be anticipated to be so. Routine haematology and biochemistry tests rarely afford a diagnosis of intestinal or pancreatic disease. However they are very useful in ruling out extra-intestinal or extra-pancreatic disease and there are some findings that might point to a gastrointestinal abnormality such as:  Hypoproteinaemia/hypoalbuminaemia – GI protein loss?  Hypocholesterolaemia – PLE or lymphangiectasia?  Azotaemia and hyperphosphataemia – pancreatitis?

Faecal samples should be submitted for parasitology and culture.

Tests that are No Longer Recommended (will not be performed by laboratory)  Microscopic evaluation of faeces for fat, starch and muscle fibers.*  Faecal proteolytic activity measured on substrates such as azocasien – wide daily variations and not widely available.Film or gelatin tests – far too subjective; many false positive and negatives.*  Oral fat absorption test- measured by observing turbidity of plasma/serum samples – many false negatives and false positives.  Quantitation of faecal fat- laborious and too time consuming! *These can be performed in-house if justification for pursuing the diagnosis of EPI is required.

The approach to investigating intestinal disorders can be broken down to: . Laboratory tests for maldigestion. . Laboratory tests for intestinal malabsorption. . Tests for protein-losing enteropathies. . Tests for antibiotic responsive enteropathies.

The most common cause of intestinal maldigestion is exocrine pancreatic insufficiency (EPI). Dogs and cats suffering from may eventually develop EPI. EPI should be excluded before investigating any other intestinal disease.

EXOCRINE PANCREATIC INSUFFICIENCY In dogs EPI is most commonly due to acinar atrophy, but occasionally due to pancreatic hypoplasia or acinar destruction following chronic bouts of pancreatitis. Pancreatic duct obstruction can also result in EPI. In cats chronic pancreatitis is the most common cause but acinar atrophy has been reported.

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TRYPSIN-LIKE IMMUNOREACTIVITY ASSAY Serum TLI is a species-specific immunoassay and represents the most sensitive and specific assay for EPI. The assay has been used for some years in dogs and a similar assay has been recently validated in cats. The test detects both trypsin and trypsinogen - the assay quantitates trypsinogen that normally leaks from the pancreas into the blood, and provides an indirect assessment of functional pancreatic tissue. Protocol: Serum samples are adequate preferably from a fasted animal. 1ml separated serum.

Interpretation: SPECIES NORMAL DEFICIENT INTERMEDIATE HIGH ^^ DOG 5.0-35.0 ug/l < 2.5 ug/l 2.5 – 5 ug/l * > 50 ug/l CAT 17-49 ug/l < 8 ug/l 9 – 17 ug/l * > 100 ug/l

*Borderline results must be repeated. ^^These levels can be consistent with pancreatitis; more specific in cats and should not be used a sole diagnosis in dogs.

o TLI levels are not affected by oral pancreatic enzyme supplementation, although it is recommended not to give any a week before the test. o TLI may be normal if there is pancreatic duct obstruction causing maldigestion. o Decreased GFR will elevate TLI and may mask EPI. o Some dogs, especially German Shepherds and Rough Coated , have persistently low (<5 ug/L) TLI values without clinical signs of EPI. It impossible to predict if or when these dogs might develop EPI. The faecal elastase test may be helpful in such cases.

FAECAL PANCREATIC ELASTASE 1 This test is the most-used test for EPI in man. Pancreatic elastase is a zymogen produced exclusively by pancreatic acinar cells and excreted in the faeces. It is stable and resistant to proteolytic degradation in the gut. If samples cannot be processed reasonably soon, they can be frozen. Low levels (preliminary studies suggest <10 ug/g) indicate EPI. However, daily fluctuations do occur and some authors recommend sampling 3 separate bowel movements. A canine-specific ELISA assay is now commercially available but not in South Africa. As yet a feline assay has not been developed.

The easiest and often most useful tests for intestinal malabsorption are serum folate and cobalamin.

SERUM FOLATE and COBALAMIN Assays of serum folate and cobalamin provide useful information that can make a significant contribution to the diagnosis of small intestinal disease in dogs and cats. While normal results cannot exclude intestinal disease, abnormal results can assist in the detection and ever provide clues as to the possible cause of small intestinal pathology. Normal absorption of dietary folate occurs predominantly in the proximal small intestine. In marked contrast, normal absorption of dietary cobalamin occurs specifically in the distal small intestine. Serum folate and cobalamin concentrations are meaningful only if pancreatic function is normal. Both cobalamin and folate are

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Chemical Pathology – Metabolic and Intestinal readily available in commercial diets so that dietary deficiency is unlikely unless anorexia is prolonged. Protocol: Serum samples are adequate preferably from a fasted animal. 1ml separated serum. Specimens for cobalamin and folate assay must be protected from exposure to sunlight. Samples must be kept at4°C and processed within 48 hours. Haemolysis of the sample will falsely increase the results because erythrocytes have greater folate concentrations than serum. Interpretation: Normal ranges differ between laboratories depending on the assay method used. RANGES COBALAMIN FOLATE Dog 251 - 908 ng/l or 185 – 670 pmol/l 7.7 - 24.4 µg/l or 17.5 – 55.5 nmol/l Cat 290 - 1,500 ng/l or 210 – 1100 pmol/l 9.7 - 21.6 µg/l or 22 – 49 nmol/l

INCREASE DECREASE Dietary deficiency EPI High dietary content ARE/SIBO COBALAMIN Parenteral supplementation Ileal disease Immunoproliferative disease Intestinal villous atrophy Hereditary cobalamin malabsorption High dietary content Parenteral supplementation Dietary deficiency FOLATE ARE/SIBO (due to bacterial synthesis of folate) Proximal small intestinal disease EPI Drugs (sulphasalazine, phenytoin) Low intestinal pH Cobalamin and folate levels are often normal in many of the above conditions.  Decreased serum concentrations of both folate and cobalamin suggest severe, long- standing disease affecting the entire small intestine.  Decreased folate concentration with normal cobalamin is consistent with upper small intestinal dysfunction.  Decreased cobalamin concentration with normal folate and normal pancreatic function suggests lower small intestinal dysfunction.  Decreased cobalamin and increased folate in dogs with normal pancreatic exocrine function is highly suggestive of bacterial overgrowth.  Decreased cobalamin with or without an increase in folate is also consistent with EPI. If this pattern is seen, TLI is indicated if not already done.  In some breeds (Giant , Border Collies) there may be specific inherited defects in cobalamin absorption.

Tests for protein loss through the intestinal tract are not readily available. Alpha1- proteinase inhibitor has a molecular mass similar to that of albumin. Thus, when gastrointestinal disease is severe enough to result in albumin loss, α1-PI is lost as well. In contrast to albumin, α1-PI is not hydrolyzed by digestive and bacterial proteinases in the gastrointestinal tract. Therefore, α1-PI can be measured by use of a species-specific immunoassay in faeces. Currently, assays for both canine and feline α1-PI are only available through the Gastrointestinal Laboratory at Texas A&M University. Faecal samples from 3 bowel movements are required to be submitted in special tubes provided by the above laboratory.

Tests of intestinal permeability, motility, small-intestinal bacterial overgrowth and hydrogen breath tests are beyond the scope of this manual.

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PANCREATITIS In dogs is a common disorder which may result in death if not diagnosed in a timely fashion. It is often difficult to diagnose because the clinical signs, physical examination findings, and clinicopathologic changes are often non- specific. Cats have even fewer signs than dogs that point towards pancreatitis, and often only have lethargy and anorexia. In dogs pancreatitis can be acute or chronic, and the severity of both varies from case to case. In cats, chronic pancreatitis appears more common but acute disease is probably more common than previously thought. Results of the complete blood count (CBC), serum biochemistry profile, and urinalysis are non-specific in both species.

SERUM AMYLASE and LIPASE Serum amylase levels in health are largely of extra-pancreatic origin, probably from the duodenal mucosa. Destruction of pancreatic acinar tissue results in the escape of pancreatic enzymes into the pancreas and peritoneal cavity. The enzymes enter the blood by way of lymphatics or capillaries with subsequent elevation of serum levels.

Hyperamylasaemia occurs in most dogs (more than 80%) with pancreatitis, but increases occur with decreased glomerular filtration (pre-, renal and post-renal azotaemia) and intestinal disease. Azotaemia usually provokes only mild increases (eg. less than 2-3 x normal) whereas higher levels strengthen suspicion of pancreatic origin. Mild increases can also occur in gastrointestinal and hepatobiliary disease so the enzyme should not be regarded as an organ-specific one. Although regarded as a relatively sensitive assay for pancreatic injury, serum amylase can occasionally be misleadingly normal in dogs with pancreatitis. Serum lipase should always be run in conjunction with amylase as there are fewer false negative results with lipase in pancreatitis. After onset of pancreatic necrosis in dogs, amylase levels rise rapidly, peak by 12-48 hours, remain elevated for approximately 1 week and usually return to normal by 8-14 days after a single insult.

There are several forms of lipase: pancreatic lipase, colipase and lipoprotein lipase stemming from the pancreas and the gastric mucosa. Serum lipase is a slightly more sensitive indicator of pancreatic injury than amylase in both the dog and cat but false negative results occur, especially in cats. Increases of at least 2 x normal are seen in pancreatitis. In dogs, lipase increases within 24 hours and peaks (at a higher level than amylase) at 2-5 days. Increases of 3x normal support a diagnosis of pancreatitis more strongly than more moderate increases, which may be accounted for by non- pancreatic causes. Lipase may be normal in up to 28% of dogs with pancreatitis. In the cat, lipase is not consistently elevated in pancreatitis. Increases 5 x normal levels are documented in the absence of pancreatic injury with corticosteroid use. Mild increases are reported with gastric and proximal intestinal pathology. Protocol: Serum samples are adequate preferably from a fasted animal. 1ml separated serum. Lipaemia can cause false decreases in serum amylase and haemolysis can cause false increases. Haemolysis, bilirubin and lipaemia may interfere with lipase assays.

Interpretation: Normal values vary due to many different assay methodologies. See above text for interpretation.

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PANCREATIC LIPASE IMMUNOREACTIVITY (PLI) Test for both canine and feline specific PLI’s are commercially available in South Africa. Quantitative snap tests are also available for dogs (see below). These assays are far more specific for pancreatic necrosis. However the PLI can also be elevated in azotaemia. Protocol: Serum samples are adequate preferably from a fasted animal. 0.5ml separated serum. Haemolysis can cause false increases.

Interpretation: SPECIES NORMAL INTERMEDIATE PANCREATITIS CANINE 0 – 200 ug/l 201 – 399 ug/l * > 400 ug/l FELINE 0 – 3.5 ug/l 3.6 – 5.3 ug/l ** > 5.4 ug/l *The dog may have pancreatitis and serum PLI should be re-evaluated in 2-3 weeks. Also, other differential diagnoses should be investigated. **The cat may have pancreatitis and PLI should be re-evaluated in two weeks if clinical signs persist. Investigate other differentials.

SNAP-CPL® in-house test kits are available for use in screening for suspected . These tests are qualitative, providing a result of normal or abnormal concentrations of CPLI, dependant on colour changes. An abnormal result correlates with values of 200 ug/l or greater and therefore will be abnormal including the intermediate range according to the above table. Abnormal snap-CPL results should be checked with a spec-CPL™ quantitative assay. A feline equivalent is not commercially available.

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