Urine sediment evaluation Flashcards
Why look for urine sediment
A microscopic examination is performed on a centrifuged sample
The sediment exam is used to look for cells, casts, bacteria crystals, etc
Microscopic examination complements the urine test strip
Sediment exam is the best method for performing a preliminary screen for the presence of bacteria
It is used to confirm the presence of RBCs and WBCs
It is hugely limited by the users technical abilities
What type of collection would you use for urine sedimentation
A freecatch sample is the best option for assessing the lower urogenital tract
First morning sample preferred
Cystocentesis is the best option to asses for the presence of bacteria in the bladder or kidneys
What should you do with urine after collected and why
The sample should be assessed right away
The sample should be stored in the fridge if it will not be evaluated within one hour of collection
Storage at room temp may result in bacterial overgrowth
Storage in the fridge may cause crystal artifacts
Casts may dissolve in alkaline urine
How much urine should you collect
Collect 3-10mL of urine and place it in a labelled centrifuge tube
The text recommends using 10mL of urine→ we often only acquire 3-5mL from SA patients; either volume is acceptable, but be consistent
Remember: always set aside small “sterile” sample (0.5cc at least) in the event that a urine culture is required
What to do to look at urine sedimentation
Centrifuge the sample
Make sure sample is balanced in the centrifuge
Centrifuge at 100-2000 RPM for 3-6 minutes
Use “urine setting” if available
Allow centrifuge to stop on its own
You may see a small pellet at the bottom of the tube
Decant supernatant leaving 0.5-1mL of urine in the tube
Pur the decant into a separate container if the chemical analysis has not yet been performed
Re-suspended sediment by flicking the tube or by gently drawing the sample up and down with a pipette
Place on drop of urine on a slide and add the cover slip
Optional- stain can also be added to the slide at thai time
Let slide sit for 30-60 sec
Scan with the entire slide on 10x objective to look for large formed elements like casts and clusters of cells
Move to high dry (40x objective)
What should you look for on high dry for urine
Identify the following with unstained urine (presence may be confirmed in stained urine)
RBC
WBC
Fat droplets
Bacteria
Crystals
Epithelial cells
Transitional cells
Debris/other
Look at a minimum of 10 fields of view under high power and record your results
What should you record on a urine sediment evaluation
Record the average number of casts and crystals per low power field (lpf)
Record the average number of all other cellular elements per high power field (hpf)
Bacteria
Sperm and mucus are only reported as being present
How to record cellular elements in urine
The number of RBCs, WBCs and epithelial cells present can be reported as an average number per 10 hpfs OR as a range of the number present in the fields examined
How to quantify bacteria in urine
Few: <5% of the filed os occupied
Moderate: 5-25% of the field is occupied
Many: 25-75% of the field is occupied
TNTC: >75% of the field os occupied
How to describe bacteria and crystals in urine
Bacteria may be reported as few, moderate, or many OR by the number range that is present/hpf (can also be reported as TNTC)
Bacteria and crystals may also be reported on the 1+ to 4+ scale
Give morphological description of any bacteria that are noted (cocci, rods, single, diploid, chains, clumps)
What stain is comonly used on urine
Sedi-stain
Advantages of sedi-stain
Highlights cells so that it is easier to identify the cell type
Fat droplets do not stain
Disadvantages of sedi-stain
Often contaminated so may result in falsely elevated bacterial counts
Stain sediment can be easily confused with crystals
Can remove stain sediment by filtering stain weekly
Quantification of elements MUST be done on the unstained slide as the stain will dilute the sample
Never add the stain directly to the collection tube
How to use sedi-stain on urine
Never add the stain directly to the collection tube
To stain
Add 1 drop urine+1 drop stian to slide, then coverslip
OR
Add one drop stain to edge of coverslip after viewing the unstained urine
Normal sediment in cat and dog urine is
Normal cat/dog urine has very little to no sediment
May have small numbers of sperm, epithelial cells, RBCs and WBCs depending on the method of collection and neuter status
May have fat droplets, mucus threads, hyaline casts and struvite/amorphous crystals
Normal sediment in equine and rabbit urine
Normal equine and rabbit urine can have a significant amount of sediment
This is due to large numbers of calcium carbonate crystals in healthy animals
Types of cells found inurine
Squamous epithelial cells
Transitional epithelial cells
Renal epithelial cells
RBCs
WBCs
Influenced by the collection method used
Common cells in free catch urine
squamous epithelial
sometimes WBC
common cells in catheter samples
squamous and transitional epithelial
RBC
Common cells found in cysto urine
sometimes Squamous and transitional epithelial
sometimes RBCs
Hematuria is
present of blood in urine
RBC in urine can indicate
Usually indicates haemorrhage of the urogenital tract
Causes of hematuria
Inflammation, infection, trauma, calculi, strenuous exercise, neoplasia, estrus, clotting/breeding disorder, severe renal disease
What can cause contamination hematuria
Can be contaminated due to cystocentesis, manual expression, or rough catheterization
What are common signs of hematuria
Usually corresponds with increase protein level on the dipstick
Cells appear as pale reddish brown to yellow colour with paler centre
Is fresh sample they will be uniform in size and shape (round and smooth)
Often crenated in concentrated urine or a sample that has sat for a period of time
Can be confused with fat globules or yeast
Fat globules have significant variation in size, sit on a different plane, refract light, and do not take up stain
Whit blood cells in urine is caused by
Indicates inflammation, infection, trauma, or peripheral blood contamination
May be present in small numbers in free catch samples due to contamination from the lower urogenital tract
When is WBCs in urine abnormal
> 2-3/hpf is abnormal- blood contaminations needs to be taken into consideration
What do WBCs in urine look like
WBC are uniformly round cells, slightly larger than RBCs but smaller than renal epithelial cells
Can have a slight grey to greenish-yellow colour
They often have granules in the cytoplasm and will have a lobulated nucleus
Most WBC present in urine are neutrophils
Cellular features are heightened with stain
May be found alone or in clumps
Pyuria is and can indicate
Increased numbers of WBCs in the urine are called pyuria
Pyuria can indicate a bacterial UTI even if bacteria are not visible on the sediment exam
Indication to culture
Are epithelial cells in urine normal and what will their presence increase
A few are normal in a urine sample
The acceptable number depends on the method of collection used
A marked increase in number usually indicates inflammation
Their presence will increase the protein level reading on the urine test strip
What are the 2 types of epithelial cells that can be present in urine
Squamous epithelial cells
Transitional epithelial cells
Renal epithelial cells
Squamous epithelial cells located where and look like
Located in the distal urethra, vagina, vulva and prepuce
Most commonly observed in free catch samples
Seldom present if a cystocentesis is performed
Very large, flat, thin, irregularly shaped
Easily fold over on themselves
Small centrally placed nuclei
Abundant cytoplasm
Transitional epithelial cells look like and located where
Line the bladder, ureters, renal pelvis and proximal urethra
2-4 times larger than WBC
They are round to pear-shaped and have abundant granular cytoplasm
They will have a small nucleus that is centrally located
May be found in clumps
0-1/hpf are normal in health
May be increased in samples collected by catheterization
Increased numbers may indicate cystitis or pyelonephritis
Renal epithelial cells are and look like
The smallest epithelial cells in urine
Only slightly larger than WBCs
Often confused with WBCs
Originate in the renal tubules
They are round with a central, large, round nucleus
The cytoplasm may be agranular or may contain fine granules
If >1/hpf are present, there is likely disease of the renal parenchymal tissue
Neoplastic cells are
Any cells that contain more than one nucleoli, have multiple nuclei/cell, mitotic figure, variations in cell size, variations in the size of the nuclei, have inclusions, or appear in large clumps should be brought to the vets attention
Samples are often sent to a pathologist for identification
May request follow up testing such as ultrasound or traumatic catheterization
Urine casts look like and are composed of
Cylindrically shaped structures with parallel sides
Ends may be tapered, irregular or round
Composed of mucoprotein
May also contain trapped cells and other debris
Formed within the renal tubules
How do urine casts diffenrtiate
Casts differentiated based on their composition and appearance
Hyaline
Granular
Epithelial
Cellular (contains RBC, WBC, or both)
Waxy
Fatty
Mixed
When do urine casts dissolve
Casts dissolve in alkaline urine
Urine should be examined promptly to prevent false negative results
How to look at urine casts
View with 10X objective to start: move to 40X objective to determine type
0-1 hyaline or granular casts/lpf in concentrated urine may be reported in normal animals
Higher numbers indicate renal tubular injury
Any type of cast can be stained with bilirubin (yellow-brown colour) when there is excess amounts of bilirubin in the urine
Casts may also contain various crystal types
Hyaline casts are
One of the most common types of casts
Clear, colourless and somewhat transparent
Do not contain inclusions
Cylindrical with parallel sides and rounded ends
Made of protein
How to look at hyaline casts and when are they elevated
Easily missed; adjust your condenser and fine focus
Easier to identify in strained than unstrained samples
They do nor necessarily indicate kidney disease
Low numbers (0-1/lpf) may be normal
Elevated numbers will be seen with mild renal irritation, fever, decreased renal perfusion, GA or strenuous exercise
Granular casts are and look like
The most common type of casts seen in animals
They are hyaline casts that contain granules
The granules are tubular epithelial cells, RBC, or WBC that become incorporated into the casts and then degenerate
Casts can be classified as course or fine granular casts
What does large number of urine granular casts indicate
Large numbers indicate more severe kidney damage than if just hyaline casts are observed
Acute nephritis
As the course granular casts ages, it becomes a fine granular cast
Urine epithelial casts are
A hyaline cast that has entrapped renal epithelial cells within its matrix
Seen with degenerative renal tubular diseases and acute nephritis which results in epithelial cell sloughing
Cellular- leukocyte casts in urine are and look like
These casts contain WBCs- mostly neutrophils
Indicates inflammation of the renal tubules
Cellular- erythrocyte casts in urine look like and indicate
RBC casts will have a yellow to orange colour
RBC membranes may or may not be visible
Indicates renal haemorrhage
Trauma disorders or inflammation
Waxy casts in urine look like and indicate
Resemble hyaline casts
Usually wider, with square ends, instead of rounded ones
Are gray to colourless and have a dull waxy appearance
They are usually highly refractile
Indicate severe and chronic renal tubular degeneration
Waxy casts are easily missed unless you have your condenser low and adjust the fine focus of your microscope
Fatty casts in urine look like and indicate
Contain many small droplets of fat
They have small refractile bodies in the cast
Common in dogs with renal disease, and dogs with diabetes mellitus
Large numbers will be seen with renal tubular degeneration
Crystals in urine is called and where is it found
Crystalluria- the presence of crystals in the urine
Found in both normal and abnormal urine
Different types of crystals have different chemical make-ups
Crystal type depends on and how to ID
The pH of the urine
Genetics
Identification is based on the shape of the crystal
Factors that increase crystal formation
Certain diets
Urine concentration (higher USG → more crystals)
Temp (cold→ more crystals)
Alkaline urine
Urinary tract infection in dogs
Stuvite crystals are
AKA triple phosphate crystals
AKA magnesium ammonium phosphate (MAP) crystals
Increased formation in alkaline urine (pH 7.0 and up)
Often associated with urease producing bacterial UTIs
Small numbers can be normal in dogs and cats
Are clinically significant when they are in large numbers and are accompanied by clinical signs
Struvite crystals look like and are dissolved by
Prism of coffin-lid shape and will have the “Y” formation
Can form if urine left to sit for long periods
Struvite crystals can be dissolved with diet
Can be small to very large
Calcium oxalate crystals in urine two forms
2 forms
Clinically important to specify which type is present
Calcium oxalate dihydrate
Square with “x”
Calcium oxalate monohydrate
Various shapes
Ethylene glycol toxicity
Calcium oxalate dihydrate crystals in urine look like
Appear as small boxes with “X” across the crystal
Looks like the back of an envelope
Can vary in size though tend to be smaller than struvite crystals
Calcium oxalate dihydrate are found where in urine
Found in urine with an acidic or neutral pH
Small numbers are normal in horses, cattle and other herbivores
In dogs
May be an incidental finding if present in small numbers
Clinically significant if large numbers are present
Risk factors: a diet high in calcium and/or oxalate: genetics
Calcium oxalate monohydrate look like
Usually small, bumb-bell shaped crystals
Less commonly round disks, or enlarged and pointed like a picket fence
Most commonly seen with ethylene glycol toxicity
Urate crystals look like and are common in
Uric acid crystals
Usually diamond or rhomboid shaped crystals
Yellow to yellow-brown in colour
Commonly found in Dalmations
Otherwise rare in dogs and cats
Amorphous crystals in urine are found in and look like
Amorphous phosphate crystals are found in alkaline urine
Amorphous urates look very similar to amorphous phosphate crystals but are found in acidic urine
Are colourless, granular precipitate
Can be artefact from cooling the urine
Calcium carbonate crystals are and look like
Common in horses and rabbits
Have a variety of forms
Dumb-bell shaped
Striated spheres
Clover leaf shape
Found in neutral to alkaline urine
Very rare in dogs and cats
No clinical significance
Ammonium biurate crystals are found in and look like
Found in slightly acidic, neutral or alkaline urine
Brown in colour
They crystals have a round shape with long irregular spicules
Have been called “thorn apple crystals”
Associated with liver disease (portosystemic shunts)
Crystals: sulphonamide look like and are common in
Patients being treated with sulfonamides will often have these types of crystals present in their urine
Check the patient history
Individual crystals radiating out from the center
Dark in appearance
Crystals: bilirubin look like and indicates
Pigmented, golden-brown feather-like appearance
Found in acidic urine
Represents an increased urinary concentration of bilirubin
May indicate cholestatic liver disease or hemolytic anemia
Crystals: cystine look like and are associated with
Appear to be flat or thin
6 sided (hexagonal)
Colourless
Associated with renal tubular dysfunction or cystine urolithiasis
Microorganisms are common in urine when
Bacteria, fungi, and protozoa may be found in urine
Organisms are not found in healthy urine when collected by catheterization or cystocentesis
May be found in free catch samples as contaminants from the genital tract and surrounding skin/fur
Will replicate if left at room temp
Refrigerate sample if analysis will not occur in the first 60 min
How to look at bacteria in urine and report it
Identify 40x objective
Report morphology: cocci, rods
Give arrangement: single, diploid, short chains, occasionally tetrad
Look for motility
Differentiate from Brownian movement
Give number: few, moderate, many, TNTC; when possible, give average #/hpf or range/hpf
Bacteria in urine can indicate
The presence of bacteria alone DOES NOT indicate a urinary tract infection with free catch samples
Normally there will be increase in WBCs and some RBCs when there is a UTI, pyelonephritis, prostatitis or a pyometra
Bacteria are most significant when they are found within WBCs
A cystocentesis sample is the preferred collection method when a UTI is suspected or a urine culture is required
Yeast in urine looks like and is an indicator of
Often confused with RBCs or fat droplets
Will have characteristic budding and double refractile walls
They are usually a contaminant
Can be from a dermal yeast infection if it is a free catch sample
Fungi in urine is caused by
Rarely found in urine, but when they are, it can be very serious
Can be contaminant from the environment when collected as a free catch sample
They are filamentous and usually branching
Parasites in urine are caused by
Can be from faecal contamination or parasites of the urinary tract
The following parasites can all be found in urine
Pearsonema plica- bladder worm (dogs and cats)
Dirofilaria immitis
Dioctophyma renale- kidney worm (dogs)
Mucus threads in urine look like
Can be confused with casts
Edges are not as well defined as in casts
Resembles a twisted ribbon
Prevalent in equine urine
In other animals it indicates urethral irritation or contamination from genital secretions
Spermatozoa in urine is caused by
Seen in the urine of intact males or recently bred females
No clinical significance
May cause an increase in protein levels in the urine test strip
Fat droplets in urine are caused by and look like
Very common
Highly refractile, spherical bodies that vary in size
If you let your slide sit for 1 minute, the fat droplets will rise to the top of the drop of urine and not be in the same field of view as the other elements
Not clinically significant
Artefacts in urine can look like
These are of little significance and are commonly found in urine collected from dusty environments or in tall dry grasses
Includes
Air bubbles
Hair
Fecal material
Plant spores, pollen or other plant material
Fibres
Dust
Starch granules - from gloves
Glass fragments from the coverslips or slides
Normal urine results
0-3 RBC/hpf – largely dependent on collection method
0-3 WBC/hpf
Few epithelial cells/hpf (more in samples collected by catheterization)
0-1 hyaline or granular casts/lpf in concentrated urine
Fat droplets are common in dog/cat urine
Spermatozoa in intact males or recently bred females
Bacteria in small numbers when urine collected by free-catch or with poor catheterization technique
Small numbers of crystals (struvite and/or calcium oxalate dihydrate) in cats and dogs
Calcium carbonate and calcium oxalate dihydrate crystals in horses
Mucus strands in equine urine
Environmental contaminants/artifacts
Abnormal urine results
> 3 RBC/hpf
3 WBC/hpf
Casts
->0-1/lpf –hyaline or granular casts
-The presence of any cast other than hyalin or granular
Large numbers of crystals or the appearance of unexpected crystal types
Parasite ova and microfilaria
Bacteria in cystocentesis samples
Phagocytosed bacteria
Large numbers of yeast or hyphae (watch for contamination)
Increased numbers of epithelial cells or abnormal epithelial cells
Line preparation for urine is
Place a drop of urine sediment on a slide, take another slide and prepare a smear like you would for hematology
BUt, half-way through, lift the spreader slide off the bottom slide
Creates a line of concentrated cellular elements on the slide
Air dry completely
Strain as you would for a blood smear
Examine under oil immersion lens
Best for identifying cells and bacteria
