Urinalysis Flashcards
Complete Urinalysis involves what 3 components
- Gross visual assessment of urine & USG
- Chemical evaluation
- Microscopic examination of sediment
Urinalysis in General…
- timing
- temp
- Ideal > within 30 min of collection
> Refrigerate
> Low USG can lead to cellular lysis
<><><> - Refrigerate 12 h in sterile, opaque, airtight container > light breaks stuff in it down
> Warm to room T for 20 min
> Gently swish to remix
Gross visual assessment of urine & USG includes…
a. Physical properties
i. Colour – blood
ii. Turbidity – crystals, cells, bacteria, mucus, casts
iii. Odour – ketones, ammonia, UTI
b. USG–soluteconcentration
USG includes…
- temp? why?
Dissolved ions & molecules
* 3+-> 4+ glucose
* 4+ protein
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Room temperature urine only
* Cold fluids are more dense > FALSELY increased USG
USG - what makes things turbid
Turbid urine?
* Cells, casts & crystals are not dissolved > do not contribute to USG
* Light refraction makes line fuzzy
* Use supernatant
USG
- should be interpreted with what?
- values for common species
- isosthenuria?
- cats?
- Interpret with hydration status
- Dehydrated dog and cat should be at least 1.030 and 1.035, respectively
- Horse and bovine 1.025
- Isosthenuria 1.008-1.012
- Cats maintain some concentrating ability in kidney disease
USG
- hyposthenuria
> what does this mean?
- USG <1.008 – hyposthenuria
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Active dilution, kidneys working… but… - Rarely see in kidney disease when electrolyte concentrations are decreased
- Central / nephrogenic diabetes insipidus
- Primary polydipsia
- Insensitivity to ADH
ignore what dipstick values?
- Leukocytes
- USG
- Nitrite
Record what dipstick values?
- Glucose
- Bilirubin
- Ketones
- Blood
- pH
- Protein
> timing of when you record each matters!
> don’t let things leak onto other ones!
dipstick glucose
- when to read?
- when is it present?
- threshold for common species
- read at 30s (yes, it matters)
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Not present in healthy individuals except in certain situations - puppies up to 8 weeks of age – immature tubules
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Kidney glucose threshold (mmol/L) [mg/dL]: - 6 cattle [100]
- 10 dog [180]
- 10 horse [180]
- 15 cat [280]
- 33 birds [594]
Conjugated bilirubin
- when measured on dipstick?
- species with low threshold?
> what will we see in them?
- what about other species?
- Measure at 30s
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Dog: - Low renal threshold
- Expect bilirubinuria before bilirubinemia
- Canine PCT can conjugate Hb & excrete bilirubin
- More than 20% normal dogs > 1+ bilirubinuria
<><> - Any other spp > bilirubinuria is ABNORMAL
DDx bilirubinuria:
- Liver disease
- Bile duct obstruction
- Starvation
- Hemolysis
- Pyrexia
- Horses off feed
- 20% of cats with DM or hyperthyroidism
ketones on the dipstick
- when do we measure?
- what do they tell us? Ddx?
- what exactly does the dipstick detect?
- measure at 40s
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Excessive / defective lipid or carbohydrate metabolism - Ketonuria before ketonemia
- DDx:
> NEB
> DKA
> Insulinoma
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Dipstick detects: - Acetoacetic acid & acetone – NOT β-OHB
- β-OHB is predominant form in ruminants
- Expect β-OHB in bovine ketosis & pregnancy toxemia in ewes
dipstick blood - what is the test detecting?
- pad reacts to ‘iron’
- Iron – peroxidase activity
- RBCs lyse & release Hb
hematuria vs. Hemoglobinuria vs. Myoglobinuria
- how do we tell
Hematuria:
- PCV: WRI
- Plasma colour: colourless / straw
- Pre-spin urine colour: pink to red
- urine blood rxn: +
- RBCs in sediment: +
- AST & CK: WRI
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Myoglobinuria
- PCV: WRI
- Plasma colour: colourless / straw
- Pre-spin urine colour: red/brown
- urine blood rxn: +
- RBCs in sediment:
- AST & CK: Increased
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Hemoglobinuria
- PCV: Decreased
- Plasma colour: pink to red
- Pre-spin urine colour: pink to red
- urine blood rxn: +
- RBCs in sediment:
- AST & CK: WRI
dipstick ph
- what is normal
- what can mess this reading up?
Normal urine pH:
* Dog, cat, herbivore on milk: 5.5 – 7.5
* Herbivores: 7.0 – 8.5
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* Protein pad leakage onto pH pad > false decreased pH
* Pigmenturia > stains pad
* Old sample > loss of CO2, urea converts to ammonia = increased pH
Dipstick Alkaline pH
Caused by:
- UTI (e.g., Proteus and Staph)
- Low protein diets
- Respiratory alkalosis
- Metabolic alkalosis
- Alkalinizing drugs
Dipstick Acidic pH
- when we see this?
Carnivores, herbivores on milk, certain drugs
* increased Protein catabolism (diet, hyperthyroid, pyrexia, steroids, neoplasia)
* Furosemide
* Renal tubular acidosis
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* Metabolic acidoses
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Hypochloremic metabolic alkalosis
* Cow with displaced abomasum / other species upper GIT foreign body or intestinal ileus
> Low chloride and paradoxical aciduria
dipstick protein
- primarily detects what?
- not as good for what? another test?
- SSA
- relation to USG
Primarily detects albumin – negative charge
* Insensitive to Bence-Jones proteins & globulins
* Confirm with sulfosalicylic acid turbidometric test
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SSA – FP
* X-ray contrast media, penicillin, cephalosporins
* Cats
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* 1,000 mg/dL protein increases USG ~0.003
protein false positive
- how common, species
False positives – common:
* Random FP in cats > dogs
dipstick protein false negatives
- Low degree of albuminuria
- Bence Jones proteinuria
what can we do with the urine dipstick for protein to further investigate?
- Measure directly on the biochemical analyzer
> Urine protein:Urine creatinine ratio - Urine protein-electrophoresis
Urobilinogen on the dipstick:
- what does it tell us? use?
- Unobstructed biliary system
- Fresh urine
- Ignore
Urine Sediment Preparation
- Spin down urine
- Pipette supernatant leaving 10% of starting
volume and sediment
ßFlick to resuspend
ßOr gently pipette up and down
Doing it this way makes it more standardized each time you look at a patient’s urine!
Urine Sediment Examination
- what do we evaluate at 10x? 40x?
- how do we prep the slide?
- Casts / LPF (10x)
- WBC, RBC, epithelial cells, crystals, & bacteria / HPF (40x)
<><> - Use Sedistain
- Make thick air-dried prep and then stain with Diff-Quik or Wright’s
RBC & WBC in Urine Sediment
- normal values? interpretation?
Normal <5 RBC and <5 WBC / HPF in well-concentrated urine
* Number should vary directly with amount of urine being produced
* Dilute and alkaline urine may lyse
casts in urine sediment - what is normal? interpretation
- <2 fine granular or hyaline casts / 10x field in well-concentrated urine
- Absence of casts does not rule out kidney disease
microscopic hematuria is associated with what on urine sediment exam?
- Cystocentesis – microscopic hematuria
> Especially cats & animals with bladder wall inflammation
> Trace to 1+ on dipstick
