Urinalysis Flashcards
what is urinalysis?
analysis of urine by physical, chemical or microscopic means to aid in the diagnosis and management of underlying disease
what are the 5 key reasons to perform urinalysis?
rapid
cheap
basic equipment required
can be a critical diagnostic technique
supportive for renal, bladder and prostate pathologies
can allow more accurate interpretation of other tests
what pathologies is urinalysis supportive for?
renal, bladder and prostate
what are the 3 parts of urinalysis?
physical exam
chemical analysis
sediment analysis
what 4th part of urinalysis is sometimes included?
uroculture
what are the equipment requirements for urinalysis?
microscope with 100x and 400x magnification capacity
centrifuge capable of approx 1500rpm
conical centrifuge tube (capped)
sediment stain
standard graticule grid (or slides and slide covers)
+/- cytological stain
why should the centrifuge tube be capped?
some infectious bacteria that can be passed in urine is zoonotic
what effect can method of collection have on the urine sample?
can cause massive variation in results particularly sediment and culture
why does collection method affect results?
depending on where in the urinary tract the sample has been gained from there will be different types of bacteria
more invasive sampling can result in blood in the sample
what are the 6 main methods of urine collection?
off floor clean container free catch bladder squeeze catheterisation cystocentesis
what is cystocentesis?
removal of urine from bladder through the abdominal wall via a needle
what are the advantages of free catch collection?
easy to collect
can be collected at home
what are the disadvantages of free catch collection?
may not be sterile so not as good for culture
may contain cells from distal urinary/reproductive tract
what are the advantages of catheter collection?
should be sterile
what are the disadvantages of catheter collection?
difficult in females
may be traumatic leading to blood and increased epithelial cells in urine
requires sedation
what are the advantages of cystocentesis collection?
sterile - best for culture
what are the disadvantages of cystocentesis collection?
more invasive
may cause blood to be present
may require sedation
how much urine should be collected?
at least 5ml
what should urine be collected into?
sterile universal container to ensure no bacterial contamination
what can be done when using a free catch sample for culture?
use of a boric acid tube
what is the role of boric acid in storage of free catch for culture?
stops the growth of contaminant bacteria so levels should remain the same as they were when sampled
what must happen when using boric acid tubes?
must fill to the line to ensure that sample is not altered by acid
what tubes should be used for cytology?
EDTA
where should urine be stored if sampling is delayed more than 30 mins?
in the fridge
what effect can leaving urine in direct sunlight have?
degradation of bilirubin leading to a false negative
within what time frame is urinalysis best performed?
ASAP - within an hour of collection
what is the effect of refrigeration on urine samples?
preserves physical and chemical properties of urine, slows bacterial overgrowth and maintains cellular elements
if a sample has been refrigerated what must happen before proceeding with analysis?
allow sample to return to room temperature
what effect can storage have on urine samples?
formation of urate crystals
how should samples for uroculture be stored?
sterile or boric acid
should boric acid be used in cysto samples?
no
what must be remembered if cytology is required on urine?
collect some into EDTA and make fresh sediment smears
before the test what must be considered?
pre-analytical factors
what are the main pre-analytical factors during urinalysis?
collection methods
medication that may influence results (antibiotics/steroids)
diet/time post meal
what is the effect of a meal on urine pH?
makes it more alkaline
what 3 elements of urine appearance should be recorded?
turbidity
colour
any odour
does normal appearance of urine vary between species?
yes
what is the usual colour range of urine?
pale yellow to amber depending on urochrome pigments
in what species can urine be turbid?
horses and rabbits
what colour may urine be in rabbits?
tinged red/brown
what effect will time after sampling have on urine colour?
will make it darker
what is altered urine colour at sampling usually due to?
haematuria
haemoglobinuria
myoglobinuria
bilirubinuria
what colour will urine with haematuria or haemoglobinuria be?
red
what colour will urine with myoglobinuria be?
brown/black
what colour will urine with bilirubinuria be?
orange
what is myoglobinuria due to?
muscle damage
what part of urinalysis is specific gravity part of?
physical exam
what is specific gravity measured with?
refractometer
what is a method for quality control of refractometers?
measuring specific gravity of distilled water
what is the specific gravity of distilled water?
0.0
at what temperature should specific gravity be measured?
room temp
should specific gravity be measured with a dipstick?
no
why may specific gravity vary normally?
hydration levels
what is hypersthenuria?
concentrated urine of normal healthy animals
what is the specific gravity of hypersthenuria (normal urine)?
> 1.012-1.015
what is isosthenuria?
urine is neither concentrated or dilute and equal to plasma filtrate
what is the specific gravity of isosthenuria (normal urine)?
1.007 - 1.012
what does isosthenuria suggest?
fluid has moved through kidney and remained exactly the same
what is hyposthenuria?
urine more dilute than plasma
what is the specific gravity of hyposthenuria?
<1.007
what does persistent isosthenuria and hyposthenuria warrant?
further investigation
when should urea be concentrated?
in a dehydrated animal
what are specific gravity readings for dehydrated cats and dogs?
Dogs - 1.025 - 1.030
Cats - 1.030 - 1.035
what are the 3 main benefits of urine dipstick analysis?
simple
cheap
quick
what is crucial about reading results from a urine strip chart?
readings are taken at the correct time after test begins
what are the reliable readings on a urine dipstick in animals?
pH protein glucose ketones bilirubin blood
what is measured by a urine dipstick looking at blood?
anything containing haem
what are the unreliable readings on a urine dipstick in animals?
urine specific gravity
urobilinogen
nitrate
leukocytes
what is the issue with urine dipstick tests of nitrites?
more specific than sensitive, many non-nitrate producing UTI’s exist
what would positive nitrates on a dipstick suggest?
UTI
what would negative nitrates on a dipstick suggest?
may still be a UTI from bacteria that don’t produce nitrates!
what is pH of a sample rapidly affected by?
storage of the sample
what is the normal urine pH in herbivores?
alkaline >7
what is the normal urine pH in carnivores?
acidic 5.5-7.5
what forms at different pH levels?
different urine stones
what protein is most often measured on dipstick tests?
albumin
when may dipsticks give false negatives for protein?
in alkaline urine or in presence of detergents
what must the amount of protein be considered in relation to?
urine concentration
what is normal in highly concentrated samples?
trace or 1+ proteinuria
what should proteinuria in dilute samples or >1+ in concentrated samples be checked with?
urine protein to creatinine ratio (UPC)
what is the role of the protein:creatinine ratio?
removes the influence of concentration of urine on assessment of the amount of protein
what can influence UPC?
haematuria
what UPC in non-azotemic animals is considered normal?
<0.5
what UPC in non-azotemic animals should be rechecked?
0.5-1
what UPC in non-azotemic animals suggests glomerular disease?
> 2
how does azotemia affect proteinuria significance?
smaller limits - >0.4 is considered proteinuric
what causes pre renal proteinuria?
hyperproteinaemia hyperthermia intense exercise seizures venous congestion secondary to cardiac disease
what causes renal proteinuria?
glomerular
tubular
what causes post renal proteinuria?
inflammation
hematuria from after renal pelvis or extra-urinary sources (genital tract)
can a urine dipstick differentiate between intact RBC, haemoglobin and myoglobin?
no - microscopy required
is the glucose test on a dipstick accurate for animals?
yes
is glucose normally found in the urine of healthy animals?
no
what causes glycosuria?
persistent hyperglycaemia
transient hyperglycaemia
renal tubular disorders (glucose leaking from blood)
false positives
what causes persistent hyperglycaemia?
diabetes mellitus
what causes transient hyperglycaemia?
stress in cats
drugs
IV fluids containing glucose
convulsion
what causes false positive for glucose?
bleach
hydrogen peroxide
sample collection pot!
is the ketone test on a dipstick accurate for animals?
yes
what does ketone test on a dipstick not detect?
beta-hydroxybutiric acid which is one of the first ketones to rise
are ketones normally found in the urine of healthy animals?
no (traces in rabbits)
what are the causes of ketonuria?
diabetes mellitus in diabetic ketoacidosis
starvation
ketosis
what level of bilirubin is normal in dogs if urine is concentrated?
trace to +
is there any bilirubin present in the urine of healthy animals apart from dogs?
no
what are the causes of bilirubinaemia?
liver/biliary disease
haemolytic anaemia
what are the normal findings on a urine strip?
majority negative
pH varies between species (carnivore/herbivore)
dogs can have 1+ for bilirubin if urine is concentrated
cats can have 1+ for protein if urine is concentrated
what should be done to the urine sample immediately before centrifugation for analysis?
sample should be mixed well
once urine has been mixed where should it be transferred to?
conical tipped, capped centrifuge tube
how much urine should be transferred the centrifuge tube?
standard volume (usually 5ml but doesn’t matter as long as it is always the same)
what rpm should the centrifuge be set on and for how long?
1500 rpm
5 mins
what should be done once the urine is removed from the centrifuge?
supernatant decanted with a pipette leaving a small amount for resuspension
how much supernatant should be left in the pipette for resuspension?
0.5ml
how much stain should be added to the sample if used?
equal volume to sediment
how can the sediment be resuspended?
flicking tube gently until well mixed
what are the main 2 methods for analysis of sediment?
using commercial graticule or single drop under a standard square coverslip
describe the process of sediment examination
sediment is remixed with a drop of supernatant and then pipetted onto a clean glass slide.
it is covered with a coverslip and then examined under low light
how do you examine under low light with a microscope?
lowering condenser and closing the aperture of the diaphragm
what is the benefit of viewing sediment crystals in low light?
makes the crystals easy to see
what can been seen during the low power (10x objective) view of sediment?
scanning overview and initial quantification of elements (casts, crystals, cells)
what objective is the low power lens?
10x
what objective is the high power lens?
40x
what can been seen during the high power (40x objective) view of sediment?
identification of morphology, bacteria and quantification of RBC and WBC
how may a sample be scored?
numerical scores per high power field subjective count (low, medium, high)
what sort of prep is used for sediment analysis?
wet prep
are sediment analysis slides usually stained?
no
what is the main aim of sediment analysis?
identifies categories of cells/objects present
what is mainly viewed in sediment analysis?
crystals and casts
what sort of prep is used for cytology slides?
dry prep - as with blood smear
are cytology slides stained?
yes - diff quick or Wrights
what is the main aim of cytology?
attempts to determine if cells are cancerous or not as well as presence of bacteria/infection
what is mainly viewed during cytology?
bacteria and cells
how many erythrocytes are usually seen per 400x field?
less than 5
what may affect levels of erythrocytes in specimen?
type of collection - free catch should have very little whereas cystocyntesis will produce more due to trauma
what can happen to erythrocytes in low specific gravity urine?
heamolysis
how will erythrocytes appear under the microscope?
biconcave disks - may be crenated or swollen
how will ruptured erythrocytes appear?
membrane only - ghost cells
what can the presence of erythrocytes in sediment analysis indicate?
trauma, oestrus, infection/inflammation
how many leucocytes are usually seen per 400x field?
less than 5
what does presence of leukocytes in sediment analysis suggest?
inflammatory process
what size are leucocytes compared to RBC?
1.5 to 2x larger
what do leucocytes look like under the microscope?
granular cytoplasm
lobed or segmented nuclei
what can be done to aid differentiation between leucocytes and epithelial cells?
air dried sample and Giemsa stain
visually what information about infection cannot be gained from viewing lecocytes in sediment analysis?
whether it is septic or sterile (eg. in response to uroliths)
why is using an air dried smear important when looking at leucocytes?
helps guide antimicrobial use and so aids stewardship
in what sort of collection method are squamous epithelial cells seen most often?
free catch
where do squamous epithelial cells originate from?
externally or distal urethra
how do squamous epithelial cells appear under the microscope?
large/flattened cell, usually anucleated
may be folded or rolled
what may be attached to squamous epithelial cells if the are external in origin?
bacteria
what sort of epithelial cells are often seen in urine samples?
transitional epithelial cells
how large are transitional epithelial cells?
up to 40 um
what must be done to diagnose transitional cell carcinoma?
nuclear staining - air dried cytology
what can changes in transitional epithelium morphology be caused by?
exposure to urine
what sort of sampling techniques most often delivers transitional epithelium in clusters?
traumatic (e.g. catheterisation)
what are the most common/important crystals found in urine?
struvite calcium oxalate (dihydrate and monohydrate) ammonium biurate bilirubin calcium carbonate (rabbits and horses)
what is formation of crystals influenced by?
urine pH
temperature
what are the 2 types of calcium oxalate crystals?
dihydrate and monohydrate
what are struvite crystals also known as?
magnesium ammonium phosphate
what do struvite crystals look like?
usually rectangular
‘roof tops or casket lids’
line through the centre is key feature
what pH are struvite crystals found at?
alkaline
in what animals are struvite crystals seen?
normal animals
those with uroliths of any type
urinary tract disease
UTI
what happens to struvite crystals if acidified?
dissolve
how can some struvite crystals be resolved?
feeding acidifying diets
what do calcium oxalate crystals look like?
squares with intersecting lines from each corner - a ‘tick box’
may occur singularly or conglomerate structures
can calcium oxalate dihydrate crystals be seen with or without calcium oxalate uroliths?
both with and without
why can calcium oxalate uroliths be seen on x-ray?
presence of calcium
what pH of urine are calcium oxalate crystals seen?
any
what do calcium oxalate monohydrate crystals look like?
‘oval dingys’
very shiny
what conditions lead to calcium oxalate monohydrate crystals forming?
hypercalcaemia and excessive oxaluria
ethylene glycerol toxicity
what is ethylene glycerol toxicity?
anti-freeze poisoning
are calcium oxalate monohydrate crystals seen with calcium oxalate dihydrate crystals?
yes but can be seen alone as well
what do ammonium biurate crystals look like?
‘thorn apple’ - brownish with spikes
what conditions are indicated by ammonium biurate crystals?
liver function compromise particularly portosystemic shunt
what breeds have increased incidence of ammonium biurate crystals?
dalmatians and english bulldogs
what pH are ammonium biurate crystals seen at?
acidic and neutral
how do amorphus urates appear?
no defined shape - granular material
when are amorphus urates seen?
simular circumstances to ammonium biurate crystals
when may bilirubin crystals be normal?
concentrated urine in dogs
in what animal is any bilirubin abnormal?
cats
when are increased amounts of bilirubin crystals seen?
pre-hepatic, hepatic and post hepatic origin jaundice
what do bilirubin crystals look like?
golden yellow ‘winter trees’
what pH urine are calcium carbonate crystals seen in?
alkaline
what animals are calcium carbonate crystals common in?
horses and rabbits
what do calcium carbonate crystals look like?
brown/golden with concentric and radial striations
what do cystine crystals look like?
flat/hexagonal crystals
what do drug related crystals look like?
spiky with no colour
where are urinary casts formed?
nephron
what can form a hyaline (protein) cast?
Tamm-Horsfall mucoprotein secreted in loop of Henle, distal tubule and collecting duct
how are granular casts formed?
cells become snared on mucoprotein which then degenerate as it continues down tubule/duct
what are the 4 main types of cast?
hyaline
granular
waxy
cellular
which are the most common casts?
granular
what are the 3 types of cellular cast?
RBC
WBC
epithelial
what number and type of cast is normal in concentrated urine?
low level granular and hyaline
what do high numbers of casts suggest?
renal insult: hypoxia, ischemia
how are cast quantified for reporting?
number seen per low power field and classified by type
what is the appearance of granular casts?
textured - fine to course
what is the appearance of hyaline casts?
smooth
how are cellular casts formed?
with renal tubular injury epithelial cells slough into lumen of the renal tubules and are caught within hyaline cast (mucoprotein)
how are coarsely and finely granular casts formed?
degeneration of epithelial cells so they can no longer be recognised as cells within hyaline matrix. Coarsely granular are formed followed by finely granular
what is the final step in formation of casts?
waxy cast
what do waxy casts indicate?
chronic tubular disease
how can epithelial cell casts be differentiated from leukocyte casts?
cytology
what do epithelial cell casts imply?
renal damage by disease processes (e.g. ischemia or necrosis of tubular epithelial cells)
what may be seen alongside leukocyte cast?
lower UTI
what must leukocyte casts have to mold the cells into cylinders?
tubular molding through renal involvement
what colour are erythrocyte casts?
red
what does an erythrocyte cast denote?
renal bleeding - idiopathic renal haematuria or trauma
what is visible in the hyaline material of an erythrocyte cast?
individual erythrocytes
in what animals is lipid in urine normal?
cats
what is lipid presence in urine the result of ?
normal tubular degeneration
is there direct relationship between lipidaemia and lipiduria?
no
when may yeast or fungi in urine be pathological?
immunocompromised animals on chronic antibiotics
what should be suspected if presence of yeast/fungi with no inflammation (WBC)?
contamination and overgrowth
what are the common parasites seen in urine?
Capillaria plica or Capillaria felis cati - lemon shaped
Dioctophyme renale and Dirofiliria microfilaria
what other things may potentially be seen during sediment analysis?
spermatozoa
contaminants - particularly from free catch
what are 4 examples of common contaminants?
fungi
textile fibres
pollen
mites
