12c. Urinalysis: Sediment Examination Flashcards
How is urine sediment examined?
a microscopic exam performed on a centrifuged sample
sediment exam is used to look for cells, casts, bacteria, crystals, etc
Microscopic examination complements the urine test strip
sediment exam is best method for performing a preliminary screen for the presence of bacteria
used to confirm the presence of RBC’s and WBCs
it is hugely limited by user’s technical abilities
What is the best option for assessing the lower urogenital tract?
free-catch, first morning sample
What is the best option to assess for the presence of bacteria in the bladder or kidney
cystosentesis
How should samples be stored?
stored in frige if not evaled within 1hr
store at room temp may result in bacterial overgrowth
store in fridge may cause crystal artifacts
casts may dissolve alkaline urine
How should a urine sample be collected for a sediment exam?
collect 30-10mL of urine and place it in a labelled centrifuge tube
text recommends using 10mL of urine, often only require 3-5mL from small animal patients; either volume is acceptable but be consistent
What should we remember to set aside in the event that a urine culture is required?
a small “sterile” sample (0.5cc at least)
How should a urine sample be centrifuged for urine sediment
make sure sample is balanced in the centrifuge
centrifuge @ 1000-2000RPM for 3-6 minutes
allow centrifuge to stop on its own
decant supernatant leaving 0.5-1.0mL of urine in the tube (pour decant into a separate container if the chemical analysis has not been performed)
Once a sediment sample has been centrifuged, what should we do in the preparation process?
re-suspend sediment by flicking tube or by drawing sample up/down w/ a pipette
place 1 drop of urine on slide and add cover slip
let slide sit for 30-60 seconds
scan with the entire slide on 10x objective to look for large formed elements like casts and cluster of cells
Once we’ve examined the slide on 10x objective, what do we do?
move to high dry 40x objective
ID following unstained urine (presence may be confirmed in stained urine)
WBCs, RBC, fat droplets, bacteria, crystals, transitional and epithelia cells, debris/other
look at min. 10 fields and record result
Ex. WBC 5-10/hpf OR WBC 8/hpf
How is bacteria recorded when recording results?
bact may be reported as few, mod, or mny OR by # range that is present/hpf (can be reported as TNTC)
bact crystals may also be reported on 1+ to 4+ scale
Give morphological description of any bacteria that are noted (cocci, rods, single, diploid, chains, clumps)
What do you record when bacteria is few, mod, many or TNTC in %?
Few: <5% of the field is occupied
Moderate: 5-25%
Many: 25-75%
TNTC: >75%
What do you record if you see sperm and mucus?
Present
What is the advantage of staining with sedi-stain?
highlights cells so that it is easier to identify the cell type
fat droplets do not stain
What is the disadvantage of staining with 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 same unstained slide as the stain will dilute the sample
How do we stain a sample?
NEVER add stain directly to collection tube
Add 1 drop urine + 1 drop stain to slide then cover slip OR add one drop stain to ege of coverslip after viewing the unstained urine
In terms of sediment, what is the normal for cat/dog? What might you see instead?
Very little to no sediment
May have sm #’s of sperm, epithelia 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
In terms of sediment, what might you find in an equine/rabbit. What might you find instead?
can have significant amount - bc of lg #s of calcium carbonate crystals in healthy animals
What are the types of cells you might find in urine?
Squamous and transitional epithelial cells, renal epithelial cells, RBCs, WBCs, influenced by collection method used
Cysto +/- squamous, transitional epithelial +/-, RBC +/-, WBC X
Catheter: + squamous, ++ transitional, ++ RBC, WBC X
Free catch: + squamous, X transitional, X RBC, +/- WBC
Why might we find RBCs in the urine? What is the presence of it called
Hematuria. Usually indicates hemorrhage of urogenital tract
Can be caused by inflam, infection, trauma, calculi, strenuous exercise, neoplasia, estrus, clotting/bleeding disorder, severe renal dz
Can be contam due to cystocentesis, manual expression or rough catheterization
usually corresponds with increased protein lvl on dipstick
What do RBCs look like in the urine?
cells appear pale reddish brown to yellow color with a paler center
In fresh sample, uniform in size/shap (round and smooth)
often created in concentrated urine or sample that has sat for a period of time
can be confused w/ fat globules or yeast
What do fat globules look like in urine?
significant variation in size, sit of diff plane, refract light, and do not take up stain
What could WBCs in the urine indicate?
inflam, infection, trauma, or peripheral blood contamination - may be present in sm #’s in free catch samples due to contamination from the lower urogenital tract
>2-3/hpf is abnormal - blood contamination needs to be taken into consideration
What do WBCs look like in urine?
WBC uniformly round cells, slightly lger than RBCs but smaller than renal epithelial cells
can have slight grey or greenish-yellow color
they often have granules in cytoplasm and will have lobulated nucleus (most WBC present in urine are neutrophils)
cellular features are highlighted w/ stain
What is one way to tell if WBCs in the urine is inflammation or blood contamination?
There will be equal or more WBCs than RBCs, which indicates inflam
What does increased numbers in the urine of WBCs called?
Pyuria (pus in the urine).
WBC may be found alone or in clumps
What could pyuria indicate?
A bact UTI, even if bact are not visible on sediment exam - indication to culture
What is an acceptable amount of epithelial cells in the urine?
acceptable # depends on the method of collection used
a marked increase in numbers usually indicates inflam
What are the 3 diff types of epithelial cells in the urine
Squamous, transitional, and renal
What value will increase on a urine test strip when epithelial cells are present?
protein lvl
What do squamous epithelia cells look like in the urine?
located in the distal uretrha, vagina, vulva and prepuce - common in fre catch samples, seldom present if a cystocentesis is performed
very lg, flat, thin, irregularly shaped
easily fold over on themselves
small centrally placed nuclei, abundant cytoplasm
Wha do transitional epithelial cells look like in the urine?
line the bladder, ureters, renal pelvis and proximal urethra
2-4 times lger than WBC
they are round to pear-shaped and have abundant granular cytoplasm
have small centrally nucleus
may be in clums
0-1/hpf normal, may be increased if collected by catheterization, but inc may also indicate cystitis or pyelonephritis
What do renal epithelial cells look like in the urine?
smlest epithelial cells in urine
only slightly larger than WBC
originate from renal tubules
round w/ central, large or round nucleus
cytoplasm may be granular to fine granules
If >1hpf are present, there is likely dz of the renal parenchymal tissue
If we see these cells, we need to call the vet. What cells are these?
Neoplastic cells, any cells that contain more than one nucleoli, have multiple nuclei/cell, mitotic figures, variations in cell size, variations in the size of the nuclei, have inclusions, or appear in lg clumps
May need follow up testing such as ultrasound or traumatic catheterization
What are urine casts?
cylindrically shaped structures w/ parallel sides
ends may be tapered, irregular or round\composed of mucoprotein
may be contained trapped cells and other debrie
Formed within the renal tubule
What type of urine casts are there?
A. Hyaline
B. Granular
C. Epithelial
D. Cellular (Contain RBCs, WBCs or both)
E. Waxy
F. Fatty
G. Mixed
How do we view urine casts?
Casts dissolve in alkaline urine
Urine should be examined promptly to prevent false negative results
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
What does a hyaline cast look like?
most common, clear, colorless and somewhat transparent, do not contain inclusions
cylindrical w/ parallel sides and ROUNDED ends
made of protein, easily missed bc of condenser and fine focus
Easier to identify in stained than unstained
samples
They do not 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
What do granular cast look like?
most common in animals
they are hyaline casts that contain granules - granules are tubular epithelia cells, RBCs, WBCS that become incorporated into cast and degenerate
can be classed as fine or course
lg #s = severe kidney damage or acute nephritis
as course granular cast ages, becomes fine granular cast
What do epithelia casts look like?
A hyaline cat that has entrapped renal epithelial cells within its matrix
seen w/ degenerative renal tubular dzs and acute nephritis which results in epithelia sloughing
What do cellular - leukocyte casts look like?
These contain WBCs - mostly neutrophils
indicats inflam of renal tubes
What do cellular - erythrocyte casts look like?
RBC casts will have yellow to orange color, RBC membranes may or may not be visible
indicates renale hemorrhage, trauma, bleeding disorders or inflam
What are waxy casts?
resemble hyaline, but are usually wider with SQUARE ends
gray to colorless and have dull waxy appearance
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
What are fatty casts?
contain many small droplets of fat
have small refractile bodies in the cast
common in cats w/ renal dz, and dogs w/ diabetes mellitus
lg #’s will be seen w/ renal tubular degeneration
What are urine cats?
any type of cast can be stained w/ bilirubin (yellow-brown color) when there is excess amounts of bilirubin in the urine
Casts may also contain various crystal types within them
What are urine crystals?
Crystalluria - presence of crystals in the urine
found in the both and abnormal urine
diff types of crystals have diff chemical make-ups
depends on pH of urine, genetics
identification is based on shape of crystal
What factors increase crystal formation?
certain diets, urine concentration (higher USD > more crystals), temperature (cold > more crystals)
Alkaline Urine
Urinary tract infections in dogs
same risks factors for crystal formation as for stone formation
What are struvite crystals?
AKA triple phosphate crystals/magnesium ammonium phosphate (MAP)
inc formation in alkaline urine (pH 7.0+) - also seen w/ urease prod bacteria (UTIs)
Sm #’s normal in D/C - clinically significant when in lg #’s and have clinical signs
What do struvite crystals look like?
prism or coffin-lid shape and will have Y formation
can form if urine left to sit for long periods
struvite can be dissolved w/ diet
can be small to very lg
What are calcium oxalate crystals?
2 forms, Ca-Ox dihydrate, a square with an X
Ca-Ox monohydrate, various shapes and seen w/ theylene glycol toxicity
What do Ca-Ox dihydrate crystals look like?
Small box w/ X across
various sizess but smaller than struvite
Found in urine w/ acidic or neutral pH
sm #s normal in Eq, cattle and other herbs
In dogs: may be incidental finding if present in low #s, clinically significant if lg #s, risk factors: diet high in Ca and/or oxalate: genetics
What do Ca-Ox monohydrate crystals look like?
usually sm, dumb-bell shaped crystals
less commonly round disks, or elongated and pointed like a picket fence
most commonly seen w/ ethylene glycol toxicity
What do urate crystals look like?
uric acid crystals
usually diamond or rhomboid shaped crystals, yellow to yellow-brown in color
common in dalmations but otherwise rare in C/D
What are amorphous crystals?
amorphous phosphate crystals found in alkaline urine
amorphous urates similar to ^^ but found in ACIDIC acid
colorless, granular precipitate
can be artefact from cooling urine
What do calcium carbonate crystals look like?
common in horses/rabbits
variety of forms - dumbbell shape, striated spheres, cloverleaf shape
found in neutral to alkaline urine
very rare in D/C, no clinical significance
What do ammonium biurate look like?
found in slightly acidic, neutral or alkaline urine
brown in color
crystals have round shape with long irregular spicules
have been called thorn apple crystals
associated w/ liver dz (portosystemic shunts)
What are sulphonamine crystals?
patients being treated w/ sulfonamides often have them in the urine so check patient hx
individual crystals radiating out from the center
dark in appearance
What do bilirubin crystals look like
pigmented, golden-brown feather like appearance (frost on a window)
Found in acidic urine
represents an increased urinary concentration of bilirubin
may indicate cholestatis liver dz or hemolytic anemia
What are cystine crystals?
not common
appear to be flat or thin
6 sided (hexagonal)
colorless
associated w/ renal tubular dy
What microorganisms may be found in the urine? Why?
bact, fungi, protozoa
organisms not found in healthy urine when collected by catheterization or cystocentesis
may be found in free catch samples as contaminants from genital tract and surrounding skin/fur
will replicate if left at room temp - refrigerate sample if analysis will not occur in 1hr
How might you find bacteria in the urine?
identify under 40x objective
report morphology: cocci, rods
give arrangement: single, diploid, short chains, occasionally tetrad
look for motility: differentiate from brownian movement
give #: few, moderate, many, TNTC; when possible, give average #/hpf or range/hpf
What does bacteria in the urine indicate?
bact alone DOES NOT indicate a UTI w/ free catch samples - normally an inc in WBCs and some RBCs w/ UTI, pyelonephritic, prostatitis or a pyometra
bact most significant when found within WBCs
a cysto sample preferred collection with UTI suspected or a urine culture required
What does yeast look like in urine?
often confused with RBCs or fat droplets
will have characteristic budding and double refractile walls
usually a contaminant
can be from dermal year infection if it is a free catch sample
What do fungi look like in the urine?
rarely found in urine, can be serious if they are found
can also be contaminat from enviro with free catch
can be filamentous and usually branching
What do parasites look like in urine?
can be from fecal contam or parasties in urinary tract
pearsonema plica - bladder worm
dirofilaria immitis - heart worm
dioctophyma renale - kidney worm (dogs)
What are mucus threads in urine?
can be confused w/ casts - edges not as well defined as casts
resembles twisted ribbon
prevalent in equine urine
in other anims indicates urethral irritation or contam from genital secretions
What does spermatoza look like in the urine
seen in the urine of intact males and recently bred females
no clinical significance
may cause inc in protein lvls in the urine test strip
What are fat droplets in the urine?
very common, highly refractile, spherical bodies that vary in size, may have slight green tinge
if you let slide sit for 1 min, droplets will rise to top of drop of urine and not be in the same field of view as other elements
not clinically significant
What are some common artifacts that we might see in urine?
little signifiance, common when collected from dusty environments or in tall dry grasses
Air bubbles, hair, fecal material, plant spores, pollen or other plant material, fibers, dust, starch granules - from gloves, glass fragments from coverslips or slides
What are some normal urine results, if these things were to show up
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 c`ommon 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
What are some abnormal urine constituents?
>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
What is line preparation?
Prepare a urine sample as you would a blood smear, BUT half-way through, lift spreader slide off the bottom slide to form a rectangle shaped sample
creates a line of concentrated cellular elements on slide, air dry completely, stain as you would for blood smear
examine under oil
best for id’ing cells and bact
