Urinalysis Flashcards
Indications for Urinalysis
- to eval clinical renal & lower UT abnormas (PU/PD, Dysuria, Haematuria)
- azotaemia
- assess hydration status
- assess metabolic & endocrine dzs
Components of Urinalysis
- physical eval
- biochemical testing
- urine sediment
- urine culture
Method of collection of urine
- free catch, midstream if possible
- catheterisation
- cystocentesis
What important factors must be taken into account when taking a free-catch sample?
- morning sample best
- contains cells + bacteria from urethra & vulva/prepuce
- midstream reduces qty of contaminants
What factors must be considered for catheterisation for urine collection?
- sterile polypropylene tubing
- Easiest in male dog
- female & some male anatomy is problematic
- blood contamination due to trauma of procedure
- bacteria & cells from terminal urethra may be collected
What factors must be considered for cystocentesis for urine collection?
- clip & Surgical prep
- good restraint essential (chemical or physical)
- samples have only bacteria & cells from bladder, may get small amt of blood contamination from needle
Physical exam of urine should include
- colour
- turbidity
- odour
- USG
Colour physical exam indicates…
- concentration & presence of pigmentation
Red urine
haematuria, haemaglobinuria
Brown to black urine
myoglobinuria
light to med yellow urine
assess depth of colour to assess kidney fxn
mild urine smell indicates
ammonia from bacterial urease
foul urine smell
cystitis, infection
sweet urine smell
acetone = diabetes, starvation
drug smell
Penicillin - yeast-like smell
diet smells of urine
high protein increases ammonia smell
lack of smell of urine
excretion of water, tubular dz
Turbidity reflects
increase in suspended substances (crystals or cells)
Definition of USG
Ratio of weight (density) of urine to that of an equal volume of water at the same temperature.
Values of USG depends on
- hydration status & water intake
- kidney’s concentrating ability
USG is a test of…
renal tubular fxn & w/ blood Ur/Cr discriminates btw dehydration & renal dz
Hypersthenuria
increased strength (aka concentrated)
Isosthenuria
1.008-1.012
Not dilute or concentrated
Hyposthenuria
below 1.008, dilute
Causes of Low USG
- PD (common)
- Iatrogenic
- endocrine
- diuretic therapy
- renal dz
Contraindications of a water deprivation test
- depressed, dehydrated, or azotaemic animals or if renal failure is suspected
Indications for Water Deprivation Test
Confirmation of the animal’s ability to concentrate urine when water is withheld
Protocol of water deprivation test
monitor USG q 2 hrs until 5% of body wt is lost or USG is >1.020
Interpretation of water deprivation test
- USG increases to 1.020: tubular fxn & ADH availability confirmed
- If USG remains <1.020: diabetes insipidus suspected
Important things to remember about urine dipsticks
- Ensure in-date or will give false +/-
- contamination of sample affects results
- requires cross check w/ history, signs
USG on dipstick
- inaccurate in animals
- ignore it
Dipstick protein values
- detect protein, esp albumin but may miss globulin-losing conditions
- trace or + protein may be normal in healthy animal, esp if high USG
- interpret w/ USG & serum albumin in mind
- increases w/ inflammation/infection, haemorrhage, protein-losing neuropathy
UPC Ratio
- used to assess clinical significance of proteinuria
- TP & creatinine conc. measured in single urine sample & expressed in same units
Interpretation of UPC
- <1.0: Proteinuria if present is not significant
- mild to mod increase (1-2): proteinuria from urogenital haemorrhage, urogenital inflammation, glomerular protein loss
- mod to marked increase (>2): glomerular protein loss
Dipstick glucose
- accurate for animals
- absent in healthy animals
Reasons why glucose may be present in urine
- Diabetes mellitus
- stress, cystitis in cats
- severe exertion, fits
- drugs - Rompun & ketamine
- Fanconi syndrome
What test should be done w/ a glucose dipstick?
- UPC
Dipstick ketones
- accurate in animals
- detects ONLY acetoacetate, not beta-hydroxybutyrate
- not common in urine normally, EXCEPT in rabbit
Reasons for ketonuria
- DM in small animals
- pregnancy toxaemia
- ketosis & fatty liver in cattle
- secondary to anorexia, starvation, other conditions
Blood on dipsticks
- reliable
- detects haem found in RBCs & Hb/Myoglobin
- check RBCs in sediment exam
- catehterisation & cystocentesis give positive blood results
Common illnesses that lead to blood in the urine
- oestrus, trauma, coagulopathy, urogenital inflammation, neoplasia
- most common from catheterisation
- FUS, IMHA
- Hburia - acute HA, baciliary
- Hburia - Cu toxicity
Bilirubin on dipstick
- reliable in animals
- normal dogs have 0 or + bilirubin
- no bilirubin in cat expected
- soluble: i.e. conjugated bilirubin detected
Diseases that cause increased bilirubin on dipstick
- increased in icteric animals - hepatic & post-hepatic
- haemolytic anaemia
Urobilinogen on dipstick
- unreliable in animals
- presence confirms patency of bile duct & bile is entering intestine
Unreliable dipstick measurements
- Nitrite
- WBC
- USG
Urea is measured in…
- serum or plasma
Urea is a
nitrogenous waste product excreted by kidneys & is non-toxic
Why would urea increase?
- pre-renal, renal, or post-renal causes
azotaemia
increased urea
BUN
Blood urea nitrogen
= concentration of nitrogen component of urea in blood
BUN value is lower than
urea value
BUN is often interchangeable with…
urea
BUN: urea ratio is approximately
1:2
Ammonia can be…
neurotoxic
Ammonia is detoxed in the
liver –> passses into urea cycle –> excreted by kidney after being in blood stream
Reasons urea is increased…
- due to renal dz (>75% fxnl mass lost)
- uraemia clinical syndrome due to reduced renal excretion of toxic substances - urea is increased w/ uraemia
Uraemia
clinical syndrome due to reduced renal excretion of toxic substances
Urea is increased w/ what clinical syndrome?
uraemia
Reasons for decreased urea
- usually anorexia, protein deficient diet or malabsorption
- markedly decreased liver fxn (PSS, hepatic insufficiency)
- overhydration
- young animals w/ hepatic metabolic system not fully fxning
Creatine breaks down to
creatinine
creatinine is from
spontaneous degradation of creatine in muscle
Rate of fomraiton of creatine is constant reflecting
muscle mass
Decreased creatinine may occur with…
loss of muscle mass (body weight)
Creatinine is filtered by glomeruli and…
not absorbed by tubules
Fxn of Creatine, Creatinine, cK
PCr works w/ CK to buffer atp & shuttle energy from mitochondria to cytoplasma & w/ ATPase as an energy transducer in muscle, heart, brain
Deficiency of fxn of creatinine, creatine, CK
- mitochondrial dysfxn, cell energy def, myopathy, marked intellectual disability
- May be dietary or AGAT, GAMT, CK, CrT mutation
Supplementation of Creatine
- treats deficiency
- increase muscle mass, strength, high-intensity exercise performance in humans/dogs
Ruminants & horses do not have a mechanism for absorption, so is useless in these animals
Reasons creatinine would increase
- 80-90% of nephrons must be lost for creatinine to rise significantly
- better marker of severe renal dz in ruminants & horses due to excretion of urea into digestive tract in species
Pre-renal azotaemia is due to
- decreased renal perfusion
- haemoconcentration, endotoxaemia or reduced CO, shock –> decreased perfusion of the kidney
- high protein diet or GI haemorrhage
Serum creatinine is a biomarker of
muscle mass
Creatinine is especially useful
in muscle wasting such as renal dz, anorexia
Creatinine is proportional to
muscle mass
serum creatinine is lower in
females over males
juveniles over adults
Adults over geriatrics
sedentary vs athletic mammals
Vegetarians
Cr dependence on muscle mass weakens its use as…
a GFR biomarker
Cr is a more effective muscle biomarker if corrected for…
renal fxn & dietary meat intake
Serum creatinine, creatinine, urinary creatinine excretion, endogenous creatinine clearance all
increase w/ body weight
Severe renal dz will cause what changes to creatinine or urea?
Creatinine normal
urea increase
chronic renal dz will cause a chronic & progressive loss of
muscle mass, & thus creatinine
In CRD, there will be a lower relative
increase in Cr than in urea but not when compared to resting or post-dialysis values
If creatinine is not increased as much as urea in CRD, then there is likely
muscle wasting to the degree to which increases differ
In acute renal dz, the absence of other debilitating dz means changes in Cr & Ur will be…
similar
Urine sediment will look for…
- rbcs, wbcs, casts, epithelial cells, bacteria, crystals, sperm, fat droplets, yeasts, contaminants unless from cystocentesis
Haematuria in FUS has mainly blood in its
urine & struvite crystals
primary finding in FUS
haematuria
Increased s/p urea/creatinine & USG greater than the ideal numbers means you should consider
pre-renal causes
Increased s/p urea/creatinine & USG is less than the ideal numbers means you should consider
primary renal dz
Normal USGs of importance for horse, dog, cat
Horse: 1.025
Dog: 1.030
Cat: 1.035
increased epithelial cells in a urinary sediment exam occurs in what conditions?
inflammatory conditions
neoplasia
When should a sediment smear be stained?
increase in epithelial cells to look for evidence of malignancy
transitional cells shed in urine
- small to mod no.’s may be shed by healthy animals
- high no’s in inflammation & some neoplasias
squamous cells in urine
- small to mod no’s shed in healthy animals
- common in non-catheterised samples or indication of contamination sample from tract
Neoplastic cells in urine
inconsistent finding, but positive is diagnostic
Formation of casts
distal tubules & collecting ducts
Matrix of casts
Tamm-Horsfall glycoprotein
Different types of casts have
Different clinical meanings
With casts in urine and BG is high, what is the high differential?
Diabetes
What type of cast?
Hyaline cast
What type of cast?
epithelial cast
What type of cast?
RBC cast
What type of cast?
WBC cast
What kind of crystals are found in acidic urine?
Ca Oxalate dihydrate
What types of crystals are common in birds & reptiles?
urate crystals
What type of casts were present in alkaline urine?
phosphate/struvite crystals
Crystalluria definition
Too many crystals in urine (above normal limits)
Dihydrate crystals are always…
harmless
What crystals are common in liver dz?
cystine, tyrosine, leucine
What crystals are common in Dalmatians, E. bulldogs, liver dz & pss?
Ammonium biurate
Crystalluria depends on…
pH & temperature of the urine sample
What type of crystals?
What conditions?
Calcium oxalate dihydrate
(Maltese cross)
Conditions: normal in cows/horses/cats, hyperparathyroidism, genetic defect in Schnauzers
What crystal? Conditions?
Calcium oxalate monohydrate
Conditions: ethylene glycol poisoning - pathognomonic
What crystal? Conditions?
Calcium oxalate monohydrate
Conditions: chocolate poisoning in dogs
What is present here? Condition present?
Haemoglobin globules w/ bilirubin crystals
Condition: IMHA w/ intravascular haemolysis (or extravascular)
What type of crystal? Condition?
Calcium carbonate crystals
Condition: alkaline urine, little or no clinical significance
What types of crystals? When are they seen and in what animal?
Calcium carbonate & calcium oxalate dihydride crystals
Equine, winter
What crystals are common with liver dz? What conditions?
- leucine - liver dz
- cysteine - genetic liver dz
- tyrosine - liver dz
- ammonium biurate - PSS (congenital or acq’d)
Crystal type?
Ammonium biurate - thorn apple
Crystal type?
Cystine (hexagonal)
Crystal type?
leucine
Crystal type?
tyrosine
What crystal type? Normal in what species?
Urate crystals
normal in Dalmatians & E. bulldogs
Struvite crystals are known as…
triple phosphate (“coffin lids”)
struvite crystals are made of
Mg ammonium phosphate
What crystal is common in UTIs?
Struvite crystals
What crystals are pathognomonic for FUS if present in large no’s?
Struvite
What type of crystals?
Struvite crystals
