Clinical pathology Flashcards
what are the four things that can be tested in regards to the liver?
hepatocellular injury
cholestasis
hepatocellular function
hepatic portal circulation
what is used to test for hepatocellular injury?
enzyme leakage
what can be used to test for cholestasis?
enzyme release due to retained bile
how do the tests for liver enzymes work?
testing the activity of the enzyme in question rather than the direct amount
what are the enzymes associated with liver damage?
ALT, AST, LDH, SDH, GLDH
what enzyme is specific to the liver in small animals?
ALT
where is AST and LDH found?
both liver and muscle (not liver specific)
what is the most common enzyme used to determine liver damage?
AST (aspirate aminotransferase)
what does the magnitude of AST increase correlate to?
the degree of liver damage (not the reversibility, prognosis or function)
what is a possible artifactual reason that ALT can be increased?
haemolysis (not liver disease)
what are the enzymes used to measure for cholestasis?
ALP and GGT
is the sensitivity of testing for ALP better for dogs or cats?
better sensitivity for dogs
what components of bile can be tested for?
bilirubin, bile acids, cholesterol
where is ALP found normally?
on the membrane of cells (when pressed on due to cholestasis they fall off)
other than cholestasis what can cause increase in ALP?
drugs - corticosteroids and phenobarbital (also diseases that increase corticosteroids)
what bile components may increase in cholestasis cases?
bilirubin, bile acids, cholesterol
what are the two isoenzymes of ALP?
intestinal and non-tissue specific
what are the three types of hyperbilirubinaemia?
pre-hepatic
hepatic
post-hepatic
what is pre-hepatic hyperbilirubinaemia?
secondary to haemolysis so too much bilirubin is being produced (check for anaemia)
what is hepatic hyperbilirubinaemia?
decreased bilirubin uptake, excretion and conjugation - disfunctional/diseased liver
what is post-hepatic hyperbilirubinaemia?
occurs secondary to an obstructed bile duct
what are the ways bilirubin can be measured?
total bilirubin
conjugated bilirubin (direct)
what is the main clinical signs of hyperbilirubinaemia?
jaundice (icterus)
when will jaundice be seen without a bilirubinaemia?
if jaundice is due to delta-bilirubin (bilirubin bound to albumin) - cause of jaundice is resolved but jaundice persists for a little while
what are some of the functions of the liver?
store glycogen, iron, copper, vitamins
detoxification
synthesis of cholesterol and bile acids
synthesis of plasma proteins
RBC breakdown
produce clotting factor
metabolisation
what ways can hepatocellular function be tested?
uptake/excretion of bilirubin and bile acids
conversion of ammonia to urea
synthesis of metabolites (albumin, cholesterol…)
synthesis of coagulation proteins
immunologic function
how can decreases in hepatic blood supply be tested for?
increased bile acids (decreased uptake)
increased ammonia (decreased conversion)
decreased antigens (immune function) - infection
how is ammonia metabolised?
uptake by hepatocytes and synthesised to urea, amino acids and proteins then diffuse into sinusoidal blood or bile canaliculi
what happens to the majority of bile acids secreted into the intestine?
reabsorbed from the oleum and enter the portal vein to return to the liver (small amount lost in faeces)
what can cause an increase in bile acids in blood?
reduced uptake/excretion by hepatocytes
disruption to enterohepatic circulation - portosystemic shunts, cholestasis…
do bile acids need taking if bilirubin is already raised?
no - bilirubin a much more sensitive test
what value of fasting bile acids would be a cause for concern?
> 25-30 mmol/L
how can you stimulate bile acid release?
give food (post prandial serum bile acids)
how is a post prandial serum bile acid test carried out?
take resting sample and then feed a fatty meal
measure bile acids 2 hours after feeding
what are possible abnormalities that can be seen on haematology of animals with liver disease?
microcytosis (altered iron transport/metabolism)
ovalcytes (cats with hepatic lipidosis)
acanthocytes
what can be seen on urinalysis of liver disease?
often unremarkable
isosthenuria or low USG
bilirubinuria
uroliths
what are the three functions of the pancreas?
digestive enzymes (exocrine)
regulate glucose (endocrine)
bicarbonate secretion
(main source of intrinsic factor in dog)
what are the three main diseases that involve the pancreas?
diabetes
pancreatitis
exocrine pancreatic insufficiency
what are the exocrine cells of the pancreas called?
acinar cells
what are the endocrine cells of the pancreas called?
islets of langerhan
what are the exocrine functions of the pancreas?
enzymes
bicarbonate secretion
B12 and zinc absorption
antibacterial
intestinal mucosal modulation
what tests is used to identify injury to the exocrine pancreas?
specific enzymes assays for amylase and lipase
what does amylase do?
catalyst for hydrolysis of complex starch
what does lipase do?
catalyst for hydrolysis of triglycerides
how long is the half life of amylase and lipase?
short (about 2 hours)
what species is amylase a more useful test for exocrine pancreas integrity?
dogs
what (relating to the kidney) can cause an increase in amylase and lipase?
decreased GFR (dehydration)
what enzyme test is a more specific test for pancreatitis?
DGGR lipase
how is pancreatitis diagnosed?
elevated DGGR lipase
clinical signs
ultrasound
what can often be seen on haematology in pancreatitis cases?
leucocytosis, neutrophilia and left shift (due to inflammation)
what abnormalities can possibly be seen on biochemistry in cases of pancreatitis?
hyperglycaemia (diabetes)
hyperlipidaemia
hypocalcaemia
what can cause hypocalcaemia in pancreatitis cases?
saponification of fat causes increased calcitonin release
what can be used to test for pancreatic function?
trypsin like immunoreactivity (TLI)
how useful is the TLI test?
very good for diagnosing exocrine pancreas function
what TLI cutoff is used to determine if a patient has exocrine pancreatic insufficiency?
<2.5 ug/L in dogs
what are the functions of the kidney?
excretion of waste
control of body fluid balance (volume and composition)
production of hormone
what hormones do the kidneys produce?
erythropoietin
calcitriol
renin
what does the nephron conserve?
water
amino acids/proteins
glucose
bicarbonate
sodium and chloride
magnesium and calcium
what does the nephron excrete?
urea
creatinine
potassium
hydrogen
phosphate
ketones/lactate
how is glomerular filtration rate measured?
using indirect markers - urea and creatinine
what produces creatinine?
muscle (constant steady rate)
is urea or creatinine a better marker of GFR?
creatinine (urea can be reabsorbed and isn’t produced at a steady rate)
what can cause an increase in urea in blood?
decreased GFR
upper GI haemorrhage
recent meal
catabolic state (fever, corticosteroids…)
what can cause a decreases blood urea concentration?
severe liver disease/portosystemic shunt
low protein diet
aggressive fluid therapy
PUPD
young animals
what can cause increased creatinine in blood?
decreased GFR
high muscle mass
high dietary protein
what can cause a decreased concentration of creatinine in blood?
reduced muscle mass
what is azotaemia?
increase in urea and creatinine in blood
what could cause post-renal azotaemia?
urethral obstruction
urinary tract rupture
how can you differentiate if an animal has pre-renal azotaemia?
evidence of dehydration/hypovolaemia
very concentrated urine (>1.030 in dogs and >1.035 in cats)
they respond to fluid therapy
how can you differentiate if an animal has renal azotaemia?
inadequately concentrated urine
how much kidney function has to be lost to see a change in creatinine?
75% of functioning nephrons
what is SDMA used for?
marker of GFR
what is SDMA?
symmetrical dimethyl arginine (GFR marker)
what does hyperphosphataemia in species with high dietary phosphorus suggest?
decreased GFR
what is the cut off for adequately concentrated urine in dogs/cats?
dogs - >1.030
cats - >1.035
is it normal to have a dehydrated patient with a USG of 1.020?
no - should be well concentrated if dehydrated (could be normal)
what does isosthenuric mean?
urine has the same specific gravity at plasma
what is the range on USG for isosthenuria?
1.008 - 1.012
what does hyposthenuria indicate about kidney function?
they are working because otherwise urine wouldn’t be this dilute (would be isosthenuric)
what figure can be used to quantify proteinuria?
urine protein to creatinine ration
what are some possible causes of pre-renal proteinuria?
fever
systemic inflammation
haemoglobinuria
myoglobinuria
what are some possible causes of a post-renal proteinuria?
UTI
nephrolithiasis
urinary tract tumour
if the UPCR is above 2 where is the problem probably localised to?
glomerular
what figures aren’t accurate and should be disregarded on a dipstick test?
nitrites
leucocytes
where do casts come from in urine?
kidney tubules (inside of the kidney tubule)
where can disease be localised to if you see casts in the urine?
kidney
what are struvite crystals made of?
magnesium ammonium phosphate
what pH urine do struvite crystals form in?
alkaline
what pH urine do urate crystals form in?
acidic
what urianry crystals are seen with ethylene glycol poisoning?
calcium oxalate monohydrate (picket fence appearance)
what electrolytes are mainly found within cells?
potassium
magnesium
phosphorous
sulfure
what electrolytes are mainly found outside cells?
sodium
chloride
what anions are responsible for balancing sodium?
chloride and bicarbonate
what systems regulate sodium in the body?
RAAS
ADH
what is the rough outline of the RAAS system?
decrease BP/perfusion to kidney causes renin release, which acts on angiotensinogen to form angiotensin 1, this is converted to angiotensin 2 by ACE. This then causes vasoconstriction and aldosterone release from adrenal gland
what dies ADH act on?
collecting duct
what is the function of ADH?
prevent water excretion from kidney
what are some possible causes of hyponatraemia?
sodium loss - GI, kidney, drugs, Addisons
water gain - CHF, iatrogenic
what are some possible causes of hypernatraemia?
hypotonic fluid loss - GI, kidney, post-obstructive diuresis
free water loss - heat stroke, pyrexia, no water access, adipsia
gain salt - excessive intake, iatrogenic
what controls potassium concentration in plasma?
aldosterone (and insulin)
how does aldosterone control potassium levels in plasma?
causes excretion if too high
what are clinical signs of hypokalaemia?
muscle weakness
PUPD
anorexia
ileus/constipation
what are some possible causes of hypokalaemia?
decreased intake - anorexia, low potassium fluid therapy
translocation (from ECF to ICF) - insulin, catecholamines
potassium loss - GI, renal, excess aldosterone, drugs
what are some clinical signs of hyperkalaemia?
muscle weakness
cardiac abnormalities
bradycardia (can be tachy)
what are some possible causes of hyperkalaemia?
artefactual - EDTA contamination, aged samples
decreased urinary excretion - obstruction, bladder rupture, Addisons, drugs
translocation (ICF to ECF) - tumour lysis syndrome, repercussion injuries
increased intake - excessive supplement, iatrogenic
what is a potassium sparing diuretic?
spironolactone (aldosterone antagonist)
how is hyperkalaemia managed?
IVFT - saline/hartmans
calcium gluconate
what hormone is most important for controlling plasma osmolarity?
ADH
what are the three forms of calcium?
protein bound
complexed (bound to other anions)
ionised
what is most of protein bound calcium bound to?
albumin
what is ionised calcium regulated by?
PTH and vitamin D
what are the possible causes of hypercalcaemia?
malignancy (lymphoma…)
renal failure
primary hyperparathyroidism
Addisons
what is the main clinical sign of hypercalcaemia?
extreme PUPD
what are the clinical signs of hypocalcaemia?
muscle tremors, twitch, cramps
seizures
restless, behavioural change
what should be checked first if the animal has hypocalcaemia?
if they have hypoalbuminaemia - this could be the cause of low calcium
what are some possible causes of hypocalcaemia?
eclampsia
renal disease
hypoparathyroidism
nutritional
ethylene glycol
what is the main regulator of phosphate?
parathyroid hormone
what effect does parathyroid hormone have on phosphate?
causes excretion
what are some possible causes of hyperphosphataemia?
failure of excretion (decreased GFR, obstruction)
release from bones (young animals)
increased intake
hypoparathyroidism
tumour lysis
what are some possible causes of hypophosphataemia?
(rare)
anorexic cats
how will EDTA effect calcium levels?
cause an artifactual decrease
