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
