Clinical Pathology Intro

Transcription

1 Detect, Describe, Deduce Consider - impact of species/breed/age/sex Organs/tissues affected? Time course? Pathological processes? -Inflammation and repair -Circulatory disturbances -Disorders of growth -Degeneration and necrosis -Pigments and deposits Cause? -Living agents of disease -Physical agents -Chemical agents -Heritable diseases -Immune-based disease Clinical Pathology Intro Interpreting Data: Reference range covers 95% of the NORMAL population therefore not always correct False positives = healthy animals with values outside ref range False negatives = sick animals with values inside ref range ** be sceptical of values just inside or just outside ref range** Blood Biochemistry Serum = fluid component from clotted blood Plasma = fluid component from whole blood + anticoagulant - still has clotting factors (eg fibrinogen) Anticoagulants heparin for biochemistry - EDTA for haematology Blood Characteristics affecting results Haemolysis cause - poor handling of blood post-collection - delayed time between collection and analysis - solution take needle off syringe (don t forcefully squirt through needle) - analyse blood samples ASAP - centrifuge and pipette off plasma/serum if delay in unavoidable - effects on results - MCHC - alter conc. of biochemical constituents (things we re measuring) eg - conc if serum conc>intracellular conc - conc if serum conc< intracellular conc - decrease accuracy of biochemical test (free Hb interferes) Gross Lipaemia cause incidental - post prandiol - pathological diabetes mellitus - hypera or iatrogenic corticosteroids - hypothyroidism - acute pancreatitis - hepatic disease - chronic renal failure - starvation in ponies and donkeys - Lipids triglycerides = main form of lipid storage - causes post prandiol lipaemia - transported in chylomicrons and VLDL - cholesterol = precursor for steroid hormones, bile acids, vit D - doesn t cause post-prandiol lipaemia - transported in LDL and HDL ** circulating cholesterol = circulating triglycerides** - gross appearance milky serum/plasma diffuse or plug of white stuff

2 - effect interferes w/ measurement of pathological hyperlipidaemia - causes haemolysis ( RBC fragility) - causes increases/decreases in the things we re trying to measure - solution fast for 8 hours before collecting blood (only for monogastrics) Hyperglycaemia incidental post prandiol (only in monogastrics) - pathological - glucocorticoids (stress/hypera/iatrogenic) - diabetes mellitus - acute pancreatitis (insulin stops being secreted) - Iatrogenic drugs frusemide - xylazine - ketamine - morphine - saffan - solution fast for 12 hours - use oxalate floride tube (prevents glycolysis by blood cells) Can combine enzymes to detect disease process eg CK = drops w/in 2-4 days of muscle damage - AST = drops w/in 1 week of muscle damage Hepatic Disease Definitions acute phase reactants increase in specific proteins in the blood globulin - fibrinogen - haptoglobin - C-reactive protein - rise due to acute necrosis/inflammation Main Use Active hepatocytes damage Cholestasis Cholestasis/cell damage Functional Hepatic Mass Biochemical Test ALT, OCT, GD, ARG, LD, AST, ID, ICD species differences leak from damaged cells ALP, GGT Bilirubin analysis Bile Acids, BSP test, Blood ammonia/urea, serum proteins Hepatocellular Damage (damage/necrosis) Serum enzyme elevation = ACTIVE damaging process to LOTS of hepatocytes (acute/sub-acute dz) - enzyme levels in reversible damage and necrosis (enzyme conc Px) Enzymes ALT - specific for hepatocellular damage in the dog and cat - ALT + ARG can use ALT in combo w/ arginase to detect progressive damage - arginase = liver specific and have a shorter t ½ (returns to normal quicker) eg dogs ALT T ½ = hrs, ARG T ½ = < 12 hours - caution! - may in some muscle diseases/trauma, combine w/ CK if unsure! - can leak out of hepatocytes if cell permeability increases ( ALT death) - ALT increases more dramatically in sublethal cell damage - can be induced by anticonvulsants or corticosteroids ID - Iditol dehydrogenase - liver specific in ruminants and horses - short T ½ - returns to normal rapidly (if hepatocellular damage non-progressive) OCT - Liver specific, used for pigs GD - liver specific, used for horses and ruminants LD, AST, ICD not liver specific - used to detect cell damage if other organ diseases can be excluded (esp muscle) - only used if more specific enzymes not available

3 Bilirubin Analysis Bile Acid Analysis Cholestasis Enzymes - Enzyme elevation detectable before hyperbilirubinemia or bilirubinuria. - cholestasis doesn t always cause hyperbilirubinemia, enzymes may be high and bilirubin normal Puppies and kittens serum ALP/GGT high due to ingested colostrums - can t measure ALT/GGT until 2 weeks old ALP use cholestasis in dogs and cats - production liver - osteoblasts - intestinal epithelium - renal epithelium - placenta - ALP Dogs and cats - cholestasis - Bone growth and disease - 2-3X increases in blood levels - GIT disease short T ½! little effect on blood levels - dogs - hyperadrenocorticism/iatrogenic glucocorticoids (hepatic isoenzyme induced) - ALP a few days after drug admin - anticonvulsants - volatile anaesthetics - barbiturates ** ALP w/ no other signs of liver disease = not significant** - cats no hepatic isoenzyme for steroids - cholestasis - ALP increases less dramatic than dogs w/ equivalent disease Cause lower ALP levels in hepatocytes & biliary epithelium - shorter T ½ ** ANY rise in ALP in cats is significant! INVESTIGATE!!** GGT use blood GGT = cholestasis in horses and ruminants (and dogs) - urine GGT = renal tubular damage (released by renal epithelium when damaged) Use in dogs not affected by barbiturates or anticonvulsants - induced by corticosteroids Bilirubin Analysis Serum bilirubin levels - visual assessment - icterus index (II) = visually assess serum/plasma colour - Van den Bergh's test = total serum bilirubin - can determine unconjugated:conjugated Urine bilirubin levels indicate blood levels of conjugated bilirubin as only conjugated bilirubin is passed by the kidney (combine w/ van den bergh to determine unconjugated) Interpreting canine bilirubinuria - Dogs have low renal threshold for conjugated bilirubin - Male dog's - kidneys can break down Hb & conjugate bilirubin ** + or ++ may be insignificant in a male or in concentrated urine ( USG) Urine urobilinogen levels not really used urobilinogen haemolysis - certain liver diseases urobilinogen - disturbed enterohepatic circulation - incidental finding Faecal Bile Pigments not really used anymore Hyperbilirubinaemia - 3 types

4 Retention hyperbilirubinemia (prehepatic) - Form in blood = unconjugated bilirubin - Bilirubinuria variably present - unconjugated bilirubin + protein too big for glomerulus - cause large scale haemolysis - internal haemorrhage - anorexia esp horses and ruminants! (jaundice usually doesn t develop) - congenital/acquired conjugation defects - mechanism too much bilirubin!liver overwhelmed! bilirubin backs up ~ most common cause of hyperbilirubinaemia in horses and ruminants Combined hyperbilirubinemia (hepatic) - Form in blood = conjugated and unconjugated bilirubin - bilirubinuria usually present - Cause acute/chronic hepatic disease ~ most common cause of hyperbilirubinemia in dogs and cats Regurgitation hyperbilirubinemia (post hepatic) - form in blood - conjugated bilirubin - Bilirubinuria usually present - cause cholestasis - intrahepatic or extraheptic obstruction to bile flow ** horses unconjugated bilirubin always predominates. % of conjugated bilirubin in cholestatic disease **Ruminants hyperbilirubinaemia less consistent test in combo w/ GGT Bile Acid Analysis Cholesterol analysis Reduced Functional Hepatic Mass Tests - only useful for chronic dz (serum bile acids, ammonia & proteins take a long time to change) - Bile acids hepatocytes synthesise from cholesterol (detects hepatocellular damage, cholestasis & functional mass) conjugated and excretion in bile concentrated in the gall bladder CCK release following gastric emptying gall bladder contraction and bile released into the duodenum. Assimilate fat in the small intestine 90% reabsorbed and returned to the liver via the portal vein - interpreting results - the liver has reserve capacity to produce bile acids -liver will produce bile acids while other enzyme levels in hepatic dz - failure to synthesise bile acids is rare - causes - serum bile acids = failure of enterohepatic circulation of bile acids - hepatocellular damage - cholestasis - functional hepatic mass - portosystemic shunts - serum bile acids - end stage liver disease (> 90% of functional mass gone) Determining vascular shunting and cirrhosis ( functional mass) -Compare bile acid levels after fasting and post-prandiol

5 - if post-prandiol levels significantly increased = vascular shunting and cirrhosis ** exception Maltese dogs normally have bile acids way above reference intervals - Blood ammonia determination Ammonia (NH3) produced by GIT bacteria and converted to urea by the liver Abnormally NH3 end stage liver disease (significantly reduced functional hepatic mass) - normal after fasting if no shunting (acquired shunts from liver dz) - portosystemic shunts - highest after fasting - urea cycle enzyme deficiency - excessive vomiting - shock Ammonia tolerance test = test fasting levels, administer NH3 orally, test levels again (30 mins later) (ATT) *NH3 v. unstable collect, put on ice and test w/in 30 mins end stage liver disease marked increase in fasting blood NH3 (5 x) - portosystemic shunts moderate increase in fasting blood NH3 (2 2.5 x) - already pretty high after fasting ** should always compare ammonia and urea levels together (inverse relationship) Hepatic encephalopathy cause dogs and cats - portsystemic shunts - ruminants and horses portosystemic shunts - hepatic lipidoses - hepatic necrosis - chronic progressive hepatitis - lots of other liver diseases etc etc - investigation ATT + serum urea levels - liver biopsy - bile acid analysis (fasting & post-prandiol) - use with scepticism to detect shunting Serum protein estimation Use acute hepatic disease - acute phase reactants globulins, clotting proteins, haptoglobin, transferrin - Mild hypoalbuminemia in acute hepatic dz (busy making other proteins) - clotting factors (short T ½) - chronic hepatic disease w/ marked in functional hepatic mass - hypoproteinaemia - significant hypoalbuminemia - β and γ globulins (variable depends on the disease) - Fibrinogen (advanced hepatic insufficiency) - Clotting factors (acute and chronic liver disease) short T ½ - rarely enough to cause spontaneous hemorrhage - detect via modified clotting factor tests (OSPT, APTT) Tests routine biochemical profiles detects total serum protein, albumin and globulins (globulin value not actually measured, derived from TPP + albumin) - serum protein electrophoresis done if biochemistry shows abnormalities Use detects changes to albumin - separates globulins into various classes Detecting acute degenerative/inflammatory conditions via serum protein Positive acute phase reactants will increase - α and β globulins - Fibrinogen (especially in ruminants and horses) - C-reactive protein (especially in dogs and pigs)

6 - serum amyloid A (especially in dogs, horses, cattle and birds) - Haptoglobin - TNF-α (especially in cats) Negative acute phase reactants will decrease - pre-albumin and albumin - transferrin (may increase in acute liver disease) Interpreting results hyperproteinaemia dehydration - TPP (both albumin and globulins) - PCV - USG - true increase in globulins - cause acute inflamm (APR) - chronic inflamm (Ig) - chronic liver disease (Ig) - multiple myeloma (Ig) - neonates(colostrums=ig) - need TPP + albumin - ± serum protein electrophoresis - hypoproteinaemia young animals - < 9 months (lower protein than adult - Ig s) - hypoalbuminaemia (normal globulins) - protein intake - malabsortpion - starvation/bad diet - EPI (pancreas) - liver diseases - protein loss - 1 glomerulopathy - PLGE (GIT) - haemorrhage - results - total serum calcium (protein bound Ca) - be careful w/ highly protein bound drugs! o/d - oedema/effusions - hypoglobulinaemia neonates - colostrum deprivation - immunodeficiency diseases Other Laboratory Tests for hepatic disease Cholesterol production mainly hepatocytes - intestinal epithelium - Adrenal cortex - gonads - Used to synthesise bile acids - Hypercholesterolaemia causes post-prandiol (fast before blood sample!) - cholestasis (mainly excreted by bile) - nephrotic syndromes - acute pancreatitis - congenital hyperlipidemias - endocrinopathies diabetes mellitus - hyperadrenocorticism (cushings) - hypothyroidism - Hypocholesteroleamia causes portosystemic shunts - hepatic diseases ( production) - GIT problems - Exocrine Pancreatic Insufficiency - malabsorption - Protein Losing Gastroenteropathy Glucose - chronic liver disease - hypoglycemia after fasting - hyperglycemia post prandiol

7 Bromosulphthalein test (BSP test) Use detects hepatocellular damage, cholestasis and functional hepatic mass - research - in practice -rarely done, replaced by bile acid analysis - used to confirm diseases once simpler, cheaper tests done - used to detect conditions where other tests are insensitive (diseases w/ low levels of hepatocellular damage or cholestasis) BSP transported to liver bound to albumin conjugated by hepatocytes excreted in bile Interpretting BSP results - Also cleared by skeletal muscle and kidney interpret carefully (muscular/renal Dz) - Pathway same as bilrubin excretion = BSP useless during jaudice (pathway competition means test unreliable) Indocyanine Green advantage solely cleared by the liver (positive result more conclusive) - disadvantage very expensive Water, Electrolytes and Acid-Base Balance Hydration Status = Assessment of Total Body Water 1. Clinical assessment skin tenting - sunken eyes 2. Dehydration can derange lab results due to hypovolaemia - PCV - TPP - USG - urea and creatinine (pre-renal azotaemia - renal perfusion! GFR) 3. Measuring osmolality - osmolality = no. of solute particles per unit of weight of the solution - osmolarity = no. of solute particles per unit of volume of the solution ECF osmolarity=osmolality - process direct measurement use an osmometer on plasma or urine - indirect measurement - use a formula that considers factors affecting osmolality Eg 2[Na + K] if glucose and urea levels normal - 1.8[Na + K] + glucose + urea if glucose or urea levels raised osmolality indicates hydration status - only if pure water loss & no diseases affected electrolytes - Na+ and Cl- are main influences on osmolality - glucose - causes raise osmolality in diabetes mellitus - urea - doesn t have a physiological effect on osmolality but does affect our ability to measure osmolality - urea! hyper-osmolality - diseases altering Na+/Cl- levels will alter osmolality (no longer indicates hydration) Solution analyse osmolarity together w/ electrolyte levels - Osmolality of blood ~ mosmol/kg - Hypo-osmolality cause hyponatremia - can result in cerebral oedema & intravascular haemolysis if it develops quickly - mechanism rapid movement of fluid from ECF! ICF (ECF hypotonic) - hyper-osmolality cause hypernatremia - hyperglycaemia - blood urea

8 Electrolyte Status (Na, K, Cl) Sodium derangements 1. Hyponatremia + ECF water = hypotonic dehydration Osmolality -hypo-osmolality (excl DM) Na loss > water loss Causes diarrhoeas in horses - hypoadrenocorticism (due to aldosterone) - renal disease in cattle - Diabetes Mellitus osmolality may not be low as hyperglycaemia may override sodium loss 2. Hyponatremia + normal ECF water = normal hydration Causes - salt deficiency in cattle - excess saliva loss in horses - sustained exercise in dogs or horses - early hypoadrenocorticism ( aldosterone) 3. Normonatremia + ECF water = isotonic dehydration Osmolality = iso-osmolality Na loss = water loss Causes vomiting - diarrhoea in small animals - exudation - haemorrhage - gut fluid sequestration (fluid hides in the gut lumen) 4. Normonatremia + ECF water = oedema Osmolality iso-osmolality water and electrolytes are retained in the body and redistributed Causes - congestive heart failure - liver disease in dogs 5. Normonatremia + normal ECF water = healthy!! Hyponatremia, normonatremia and hypernatremia may occur with dehydration, normal hydration and overhydration Chloride derangements commonly copy sodium changes - exception vomiting - loss of gastric HCL! hypocholidemia w/out normonatraemia - metabolic acidosis = bicarbonate loss! hyperchloridemia w/ normonatremia Potassium Derangements - Serum potassium levels not a good indicator of total body K+ (intracellular ion) - Circulating levels indicate K+ available for the body to use (e.g. nerve function, muscle function etc) Alterations to serum K+ levels - internal shifts (ECF ICF) - external factors - / intake - / loss Hyperkalemia causes due to internal shift (K+ moves out of cells and into ECF) - metabolic acidosis - hyperosmolality - tissue degeneration/necrosis - insulin deficiency - haemolysis (depends on species & breeds) - horses & pigs RBC high in K+ - cattle & sheep RBC moderate to low in K+ - dogs and cats RBC low in K+ (doesn t K) - leukocytosis ( WBC) K+ leaks out - thrombocytosis K+ leaks out - diarrhoea (mainly calves) Hyperkalemia - causes due to external factors - anuria (acute renal failure or post-renal obstruction) - hypoadrenocorticism (due to aldosterone) - iatrogenic - e.g. high doses of crystalline penicillin