Urinalysis Flashcards
What should be checked before performing a urinalysis?
Dipstick:
Expiry date, starting colours of pads, any damage.
Refractometer:
Calibrate and check if clean.
Sample:
Label, ask how fresh it is if no information. If older than 12 hours, it isn’t a good sample to use.
What value should the specific gravity read when calibrating the refractometer?
1
What are the normal specific gravity ranges for cats?
1.035 -1.060
What are the normal specific gravity ranges for dogs?
1.015-1.045
What is the healthy urine pH range for dogs and cats?
6.5 to 7.0
What does turbidity in urine mean?
Whether it’s clear or cloudy.
What are the normal daily water input and urine output for dogs and cats?
1-2ml per kg per day for water input, urine output should match this (1-2ml per kg per day).
What are the urine collection methods?
free catch, bladder expression, cystocentesis, catheterization
What time has the best urine sample?
Morning samples as these are after a few hours of water deprivation to allow kidneys to concentrate the urine.
When should urine samples be analysed?
Within 30 minutes.
What things can urine tell us?
- Renal function
- UTI vs FLUTD vs Inappropriate Urinations vs Incontinence
- Diabetes Mellitus vs Diabetes Insipidus
- Jaundice
- Acid/Base disturbances
- Cancer of the Urogenital system (kidney, bladder, prostate etc)
How should a urine sample be analysed?
Physical Properties:
Colour, Clarity, Odour, USG
Chemical Properties:
pH, Protein, Glucose,
Ketones, Blood, Bilirubin
Urine Sediment:
Crystals, Casts, RBCs, WBCs, Epithelial Cells, Bacteria, Sperm
What do different urine colours/properties indicate?
Light yellow/clear-dark yellow = hydration
Turbid red colour = bleeding
Clear red = Haemolysis
Greenish-yellow = bulirubin
Clear red/brown= Myoglobin from muscle damage
Cloudiness = can be caused by pus, crystals, or lipids
What do different urine colours indicate?
Pale Yellow: Normal urochromes and Urobilin
Deep Yellow: Highly concentrated, lots of Riboflavin (Vit B2 – converts carbs into glucose and metabolise fats/proteins)
Blue: Methylene blue, Pseudomonas
Green (Blue + Yellow): Biliverdin, bile pigment
Orange-Yellow: Highly concentrated, excess urobilin, bilirubin
Red, Pink, Red-Brown, Red-Orange, Orange: Haematuria, haemoglobinuria, Myoglobinuria
Brownish: Methaemoglobin, melanin, sulphonamides
Yellow-Brown, Green-Brown: Bile pigments
Brown to Black: Melanin, Methaemoglobin, myoglobin, bile
Colourless: Very dilute
Milky White: Chyle, pus, crystals, lipids
What is important to remember about urine clarity?
- Remember that clear and colourless are not the same
- Turbid urine is cloudy or opaque or thick with suspended matter
- Red urine due to frank blood will be cloudy
- Red urine due to lysed RBCs will be clear
- RBCs will spin down, pigments will not
What is important to remember about urine smell?
Concentrated urine often smells normal but stronger. But a change in smell could be a sign of UTI, tumours, Diabetes etc
With UTIs it depends on the bacteria but 40% of UTIs in dogs and cats will be E.coli which is a urea splitter causing a urine that smells like ammonia and rotting fish
What needs to be remembered about albumin on a urine dipstick?
It’s in tiny amounts in normal patients
What needs to be remembered about protein on a urine dipstick?
can be caused by:
Fever, strenuous exercise, seizures, kidney disease, inflammation, infection
Trace amounts of protein more significant in dilute urine than concentrated urine
What needs to be remembered about pH on a urine dipstick?
Typically acidic (pH<7.0)
E. coli bacteria produce an alkaline urine usually (pH>7.0)
What needs to be remembered about glucose on a urine dipstick?
Glucosuria will occur when the blood glucose levels exceed the renal threshold for reabsorption (10 mmol/L for dogs; 12 mmol/L for cats).
Diabetes mellitus is a common cause of glucosuria
Stress in some animals (particularly cats) can cause a transient hyperglycaemia
Glucosuria associated with normal blood glucose concentrations is indicative of renal tubular dysfunction. This can be an inherited condition
Approximately 20% of cats with chronic renal failure will have glucosuria
What needs to be remembered about ketones on a urine dipstick?
Ketones are formed during fat metabolism. They are freely filtered in the glomerulus and excreted in the urine.
This test often underestimates the amount the ketones present.
Ketonuria indicates an excessive shift from carbohydrate metabolism to fat metabolism, and ketones are found in the urine before blood ketone levels increase.
Ketonuria is most commonly associated with ketoacidosis secondary to diabetes mellitus, but may be seen secondary to starvation
What needs to be remembered about bilirubin on a urine dipstick?
Bilirubin is a breakdown by-product of haemoglobin.
Unconjugated (indirect) bilirubin is bound to albumin in the blood and cannot pass through the glomerulus.
Conjugated (direct) bilirubin is water soluble and can travel in the blood without being bound to plasma proteins and can pass through the glomerulus and be excreted in the urine.
In dogs, some conjugated bilirubin is formed by the renal tubular epithelial cells from absorbed haemoglobin.
Increased urine bilirubin should prompt evaluation of the serum bilirubin concentration (and liver enzymes) = liver disease or haemolysis.
Bilirubinuria, like hyperbilirubinemia, can occur in: haemolytic disease (prehepatic), hepatic insufficiency (hepatic), and obstruction of bile flow (post-hepatic).
What needs to be remembered about occult blood on a urine dipstick?
The occult blood test pad measures myoglobin and haemoglobin.
Haemoglobin may be either free haemoglobin (haemoglobinuria) or intact erythrocytes (haematuria) since red cells will invariably lyse.
Positive occult blood reactions should be interpreted with the urine sediment findings.
The presence of red cells in the sediment indicates haematuria as the cause of the occult blood.
True haemoglobinuria may occur after episodes of intravascular haemolysis
What parts of the dipstick should be ignored?
urobilinogen, nitrates, leukocytes, and urine specific gravity.
What’s important to remember about Struvite Crystals?
- appear typically as “coffin-lids” or “prisms“ but they may also have no clear shape
- Found in less acidic urine
- can form in stored, uncovered urine.
- are commonly seen in canine and feline urine.
- Struvite crystalluria in dogs is not a problem unless there is a concurrent bacterial urinary tract infection (UTI)
- Without an infection, struvite crystals in dogs are not associated with struvite urolith formation.
- However, some animals (e.g., cats) do form struvite crystals without a bacterial urinary tract infection.
What’s important to remember about Calcium oxalate dihydrate Crystals?
- Appear as squares with an “X” in the middle, or “envelope-shaped.”
- These crystals are found in neutral to acidic urine.
- Calcium oxalate crystalluria occurs less commonly in dogs and cats.
- If persistent, it may indicate an increased risk of calcium oxalate urolith formation.
What’s important to remember about Ammonium biurate crystals?
- Occur in acidic urine and are yellow-brown spheres with irregular, spiny projections; but may also have no defined shape.
- Ammonium acid urate crystals suggest liver disease (portosystemic shunt).
- Certain breeds of dogs (Dalmatians and English Bulldogs) can normally have ammonium acid urate crystalluria.
- Ammonium acid urate crystals are never a normal finding in cats.
What’s important to remember about Cystine Crystals?
- Clear, smooth, six-sided, variably sized crystals.
- They are seen in acidic urine.
- Presence of cystine crystals represents a proximal tubular defect in amino acid reabsorption.
- Cystinuria has been reported in many breeds of dogs and rarely in cats.
- Dachshunds, Newfoundlands, English Bulldogs, and Scottish Terriers have a high incidence of cystine urolithiasis.
What’s important to remember about Bilirubin Crystals?
- Occur with bilirubinuria; however, they may be normal in small numbers in dogs.
- They are never a normal finding in cats and are suggestive of liver disease.
What’s important to remember about Calcium oxalate monohydrate Crystals?
- Calcium oxalate monohydrate crystals are “dumbbell” shaped or may be small, flat, and colourless and shaped like “picket fence posts.”
- Calcium oxalate monohydrate crystals may be seen in association with ethylene glycol toxicity.
