Urinalysis Flashcards
what can we test with a urine sample?
glucose
crystals
blood
infection
kidney function
what are the different types of urine collection?
what do we need for them?
free catch/manual expression
- kidney dish
- gloves
- sample pot and pipette
cystocentesis
- long needle and suitable syringe
- ultrasound for insertion
urinary catheter
- sterile gloves
- sterile lube
- catheter - rigid for temporary, foley for long term
- collection set
what is normal urine output?
1-2 ml/kg/hr
cats - 18-25mls/kg/day
dogs - 20-40mls/kg/day
what considerations need to be made when collecting a free catch sample?
if obtaining from dogs make sure you get midflow
- avoid skin cells, bacteria already in the tract
- not possible with cats as use katkor
try to get the first sample of the day
- more concentrated and likely to find abnormalities
always take samples before starting any treatment
- as can impact results
can be useful to collect along side other tests
- allow for comparable results
what are the advantages and disadvantages of free-catch sampling?
Advantages
- easy
- can be done by anyone - including owners
- can measure urine output throughout day
- least stressful
Disadvantages
- not a sterile sample so can’t culture
- contaminated with hair
- higher risk of urine contamination to person sampling
- cats dislike different litter
- dogs can be urine-shy
what are the advantages and disadvantages of manual expression sampling?
Advantages
- good for neurological patients - avoid UTIs and scolding
- can be done consciously
- non-invasive
- can measure urine output throughout the day
Disadvantages
- requires skill
- difficult in obese and very tense patients - high muscular tone/refusing can cause burst
- unsuitable if coagulopathic - bleeding risk
- can cause bladder rupture - especially if blocked
- non-sterile sample
what are the advantages and disadvantages of cystocentesis sampling?
Advantages
- sterile sample - can be cultured
- quick
- can be emergency help for blocked cats
Disadvantages
- only a veterinary surgeon can perform
- can cause trauma to other organs
- if diseased bladder - uroabdomen (bladder walls don’t contract down properly causing leaking into abdomen)
- may require a sedation - uncomfortable
what are the advantages and disadvantages of short term catheterisation sampling?
Advantages
- can completely empty bladder
- can obtain sterile sample
- can be done by a nurse or vet
- infection is less likekly
Disadvantages
- may require sedation
- difficult to place in bitches
- can cause urethral damage
- risk of introducing infection
what are the advantages and disadvantages of indwelling catheterisation sampling?
Advantages
- ideal for measuring urine output over a long period of time
- good for patients with infectious urine to contain it (eg lepto or cytotoxic drugs)
- can take a sterile sample
- allow to drain bladder if blocked
Disadvantages
- risk of introducing infection
- invasive
- may require sedation
- risk of patient interference - kink/twist or remove
how should you store urine samples?
plain urine tube
- all samples run within 24hours
boric acid tube
- all samples run after 24 hours
- prevents bacterial overgrowth
when using urine samples for diagnosis what do you need to consider?
patient history
- any clinical signs observed, changes in output and appearance
urinalysis
physical examination
- abdominal palpation - firm in bladder? stones?
definitive diagnosis
- ultrasonography urine tract
- radiography
- contrast radiography
what is involved in a crude assessment of urine?
what can different variations tell us?
colour
- light yellow = normal, low concentration - unless dehydrated as renal failure
- yellow = normal, normal concentration
- amber = normal, high concentration - can be bilirubinuria (caused by liver damage or breakdown of RBCs)
- red = haematuria or haemoglobinuria (acute breakdown of RBCs)
- brown = myoglobin (muscle damage), methaemoglobin or bilirubinuria (caused by liver damage or breakdown of RBCs)
smell
- noticeable bad smell
- highly concentrated
- bacterial infection
- toxins
amount
- 0.5-1ml/kg/hr = oliguria - not ideal but monitor
- <0.5ml/kg/hr = anuria - kidneys failed
- >2ml/kg/hr = polyuria - acute renal injury/start of renal disease
turbidity
- normal varies between species
- dogs = clear
- cats = slightly cloudy
- guinea pugs = cloudy
- abnormal = turbid
what are the advantages and disadvantages of dipsticks?
advantages
- rapid results
- non-invasive
- good early indicator
disadvantage
- no animal specific - some tests no useful for animals
- not reliable for SG
- timings can be hard to follow
what can pH on a dipstick tell us?
dogs and cats usually have slighly acidic urine
alkaluria can be caused by urease-producing bacteria
pH level also impact crystal production
- cystines = acidic
- struvite = alkaline
what can protein on a dipstick tell us?
detects albumin
a large amount has to be present to have a positive result
- large amounts of protein leaking from the kidneys
- late-stage kidney failure
what can glucose on a dipstick tell us?
renal threshold is >18g/l in dogs and >24g/l in cats
if test is positive very likely to be diabetic
what can ketones on a dipstick tell us?
ketonuria is associated with diabetes mellitus in small animals
what can bilirubin on a dipstick tell us?
dogs can breakdown haemoglobin into bilirubin in the kidneys
bilirubinuria could mean either liver disease or haemolysis
what can blood on a dipstick tell us?
detects RBCs, haemoglobin and myoglobin
- so positive could mean haematuria, haemolysis or myoglobinuria
need to do further tests
- check plasma to determine haemoglobin or myoglobin
- check urine sediment
what is urine specific gravity?
what can it tell us?
the weight of a volume of liquid to the weight of an equal volume of distilled water
hypersthenia = >1.025 - 1.040
- high concentration
- ideal/normal
- kidneys retain the correct water amount so function fine
- may be slightly dehydrated
isothenuria = 1.010 - 1.025
- same concentration as blood
- not ideal but monitor
- may be overhydrated
- could be start of kidney failure
hyposthenuria = <1.001 - 1.005
- kidneys not concentrating urine at all
- pure water
- likely kidney failure
how do you prep a microscope slide for urinalysis?
spin urine sample in a centrifuge
- 2000 rpm for 5 mins
remove the supernatant and resuspend the sample
pipette sample onto slide and place cover slip
what would RBCs in a sediment tell us?
<5 RBCs per field is normal
can be iatrogenic
- consider sample
- cysto and expression likely to have some
> 5 RBCs per field = haematuria
- some damage within urinary tract
what would WBCs in a sediment tell us?
<5 WBCs per field is normal
- consider sample
- expressed or free catch likely to have few
> 5 WBCs per field = pyuria
- could mean inflammation, infection, trauma, neoplasia
- could also be due to contamination
what would epithelial cells in a sediment tell us?
transitional cells
- normal - wall of bladder/urethra
squamous cells
- normal in free-catch or expressed samples
neoplastic - carcinoma
what would casts in sediment tell us?
what are the different types?
Casts are a build-up of broken-down cells and/or material
some are normal with a few being fine but many suggest damage somewhere within the tract
types:
- myaline = few is normal
- epithelial = renal tubular disease
- granular = degenerated epithelial casts = few is normal
- waxy = degeneration of granular casts
- RBC = renal haemorrhage
- WBC = renal inflammation
- fatty = diabetes mellitus
what would bacteria cells in a sediment tell us?
depends on sample type taken
if present with a cysto sample then there is an infection
- if in free-catch/express could just be contamination
you would then confirm with gram stains and aerobic culture to find out type of bacteria and an effective antibiotic
what would yeast in a sediment tell us?
most likely due to contamination
but if seen in a cysto sample then suggest infection
- especially if on long term antibiotics and immunosuppressed
what would fungal hyphae in a sediment tell us?
most likely caused by contaminants overgrowth
but could be Aspergillus terreus
- systemic infection where colonisation can occur in the renal pelvis
what would parasitic ova in a sediment tell us?
Parasitic eggs present
could be parasites within the urinary bladder or kidney worms
if sample was free catch or expressed may be GI parasites contaminating sample (eg tapeworm eggs)
- so confirm with cysto sample
what would lipids in a sediment tell us?
renal dysfunction
common
- often mistaken for RBCs
- esp. in feline samples
what would sperm in a sediment tell us?
male or recently bred female
what would plant material in a sediment tell us?
debris
sample is contaminated
sample voided
what factors affect crystal formation?
Urine pH
Concentration of crystal-forming minerals
Urine temperature
Length of time between collection and examination
what are the characteristics of a struvite?
favours alkaline and lower-temp urine
there’s a risk of uroliths forming - especially cats - only if dogs get a UTI
dogs = normal
cats = abnormal
shaped as a coffin
what are the characteristics of cysteine?
favour acidic urine
no risk of uroliths forming
dogs = normal - especially male dogs and dachshunds, Newfoundlands, English bulldogs and Scottish terriers
cats = abnormal
caused by tubular defect in amino acid resorption
hexagon shaped
what are the characteristics of calcium oxalate (dihydrate)?
favours acidic and alkaline urine and lower temperatures
form due to storage
theres a risk of uroliths forming - especially in mini schnauzers
dogs = normal
cats =normal
enveloped shape
what are the characteristics of ammonium urate?
favours acidic urine
some risk of uroliths forming - more likely in Dalmatians
dogs = normal - especially with dalmations
cats = abnormal
sign of liver disease
irregular with spiky projections
what are the characteristics of bilirubin in urine?
favours acidic urine
no risk of uroliths forming
dogs = normal
cats = abnormal
caused by bilirubinurea
yellow/brown needle-like shape
what are the different types of uroliths?
struvite
calcium oxalate
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