MICROSCOPIC EXAMINATION
OF URINE
CHAPTER 6
Copyright © 2014. F.A. Davis Company
Learning Objectives
Upon completing this chapter, the reader will be able to
1. List the physical and chemical parameters included in macroscopic urine
screening, and state their significance.
2. Discuss the advantages of commercial systems over the glass-slide method
for sediment examination.
3. Describe the recommended methods for standardizing specimen
preparation and volume; centrifugation; sediment preparation, volume,
and examination; and reporting results.
4. State the purpose of Sternheimer-Malbin, acetic acid, toluidine blue, Sudan
III, Gram, Hansel, and Prussian blue stains in the examination of urine
sediment.
5. Identify specimens that should be referred for cytodiagnostic testing.
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Learning Objectives (cont’d)
6. Describe the basic principles of bright-field, phase-contrast,
polarizing, dark-field, fluorescence, and interference-contrast
microscopy, and their relationship to sediment examination.
7. Differentiate between normal and abnormal sediment
constituents.
8. Discuss the significance of red blood cells (RBCs) in urine sediment.
9. Discuss the significance of white blood cells (WBCs) in urine
sediment.
10.Name, describe, and give the origin and significance of the three
types of epithelial cells found in urine sediment.
11.Discuss the significance of oval fat bodies.
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Learning Objectives (cont’d)
12. Describe the process of cast formation.
13. Describe and discuss the significance of hyaline, RBC, WBC,
bacterial, epithelial cell, granular, waxy, fatty, and broad casts.
14. List and identify the normal crystals found in acidic urine.
15. List and identify the normal crystals found in alkaline urine.
16. Describe and state the significance of cystine, cholesterol, leucine,
tyrosine, bilirubin, sulfonamide, radiographic dye, and ampicillin
crystals.
17. Differentiate between actual sediment constituents and artifacts.
18. Correlate physical and chemical urinalysis results with microscopic
observations and recognize discrepancies.
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Introduction
• Microscopic examination of the urinary sediment
• Identification of insoluble substances (formed elements)
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Red blood cells (RBCs)
White blood cells (WBCs)
Epithelial cells
Casts
Bacteria
Yeast
Parasites
Mucus
Spermatozoa
Crystals
Artifacts
• Least standardized, most time consuming
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Macroscopic Screening
• Microscopic is performed based on physical and
chemical results
• Color, clarity, blood, protein, nitrite, leukocyte
esterase, and possibly glucose
• Special populations: pregnant women; pediatric,
geriatric, diabetic, immunocompromised, and
renal patients
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Clinical and Laboratory Standards
Institute (CLSI)
• Requested by the physician
• Laboratory-specified population
• Any abnormal physical or chemical result
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Specimen Preparation
• Examine when fresh or preserved
– RBCs, WBCs, casts disintegrate in dilute, alkaline urine
• Refrigeration precipitates crystals
– Can obscure other elements
• Less contamination (epithelial cells) from a
midstream clean-catch specimen
• Thoroughly mix specimen before decanting to
the centrifuge tube
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Specimen Volume
• Centrifuge 10 to 15 mL urine (reagent strips fit
into 12 mL)
• Quantities <12 mL should be documented
• Too little volume = fewer formed elements
• Some laboratories correct for volume
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Centrifugation
• Standardize speed and time of centrifugation
• 5 min at relative centrifugal force (RCF) of 400 is
ideal
• RCF corrects for variations in the diameter of
centrifuge heads; revolutions per minute does not
• RCF = 1.118 × 10−5 × radius in centimeters × RPM2
• Do not brake the centrifuge
• Cap all specimens
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Sediment Standardization
• Preparation of sediment
• Volume of sediment examined
– 0.5 to 1.0 mL
• Methods of visualization
• Reporting of results
• Commercial systems: KOVA
– Calibrated centrifuge tubes, special slides to control
volume, decanting pipettes, grids for better
quantitation
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Postcentrifuge Sediment
• 0.5 to 1.0 mL after decantation
• Concentration factor: volume of urine
centrifuged/sediment volume
– Probability of detecting low quantities of formed
elements
• Aspirate rather than pour off urine (pipettes
available for this)
• Mix sediment gently, not vigorously
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Volume of Sediment Examined
• Be consistent
• Commercial systems control this
• Glass slide method
– 20 μL
– 22 × 22 glass cover slip
– Do not overflow cover slip
• Heavier elements (casts) flow outside
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Commercial Systems
• Chambers capable of containing a standardized
– Chamber volume
– Size of the viewing area
– Approximate number of low-power and high-power viewing
areas
• Based on the area of the field of view using a standard
microscope
• CLSI recommends these systems together with
standardization of all phases of the methodology
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Commercial Systems (cont’d)
• Capped, calibrated centrifuge tubes
• Decanting pipettes to control sediment volume
• Slides that
– Control the amount of sediment examined
– Produce a consistent monolayer of sediment for
examination
– Provide calibrated grids for more consistent
quantitation
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Examination of Sediment
• Be consistent
• Minimum 10 low (10×) and 10 high (40×) fields
• Low power: casts, general composition
– Scan edges for casts with glass slide method
• High power: identification of type
• Initial focusing: low power, reduced light
– Focus on epithelial cell, not artifacts that are in a
different plane
• Use fine adjustment continuously for best view
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Reporting the Microscopic
Examination
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Consistent within laboratory
Casts: average per lpf
RBCs, WBCs: average per hpf
Epithelial cells, crystals, etc., in semiquantitative terms
– Few, moderate, many
– 1+, 2+, 3+, 4+
– Follwed by /lpf or /hpf
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Reporting the Microscopic
Examination (cont'd)
Converting the average number of elements per lpf or hpf to
elements per mL
1. Calculating the area of an lpf or hpf for the microscope in use using the
manufacturer-supplied field of view diameter and the formula πr2 = area
Diameter of hpf = 0.35 mm
3.14 × 0.1752 = 0.096 mm2
2. Calculating the maximum number of lpfs or hpfs in the viewing area;
area under a 22 mm × 22 mm cover slip = 484 mm2
484 = 5040 hpfs
.096
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Reporting the Microscopic
Examination (cont'd)
3. Calculating the number of hpfs per milliliter of urine tested using the
concentration factor and the volume of sediment examined
5040____ =
5040
0.02 mL x 12 .24
= 21,000 hpf/mL of urine
4. Calculating the number of formed elements per milliliter of urine by multiplying
the number of hpfs per milliliter by the average number of formed elements
per field
4 WBC/hpf × 21,000 = 84,000 WBC/mL
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Correlating Results
Microscopic
Elements
RBCs
WBCs
Physical
Chemical
Exceptions
Turbidity
Red color
Turbidity
+ Blood
+ Protein
+ Protein
+ Nitrite
+ LE
Number
Hemolysis
Number
Lysis
Epithelial cells
Casts
Bacteria
Turbidity
Crystals
Turbidity
+ Protein
pH
+ Nitrite
+ Leukocytes
pH
Color
+ Bilirubin
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Turbidity
Number
Number
Number and type
Number and type
Sediment Examination
Techniques
• Sediment appearance
– Cells and casts in various stages of development and
degeneration
– Distortion of cells and crystals by the chemical content of the
specimen
– The presence of inclusions in cells and casts
– Contamination by artifacts
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Sediment Stains
• Low refractive index elements are often difficult to see
under bright-field microscopy
• Sternheimer-Malbin stain: crystal violet /Safranin O
– Increases refractive index
– Stains nuclei, cytoplasm, inclusions
– Sedi-Stain, KOVA stain, etc.
• 0.5% solution of toluidine blue enhancement of nuclear
detail
• Acetic acid will enhance WBC nuclei
– RBCs are lysed by this
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Sediment Stains (cont’d)
• Lipid stains
– Oil Red O and Sudan III for triglycerides and neutral fats;
cholesterol polarizes
• Gram stain
– Identification of bacterial casts
• Hansel stain
– Urinary eosinophils
– Methylene blue and eosin Y: better than Wright stain
• Prussian blue stain
– Hemosiderin granules seen with hemoglobinuria
Copyright © 2014. F.A. Davis Company
Cytodiagnostic Urine Testing
• Cytodiagnostic urine testing is frequently performed to
detect and monitor renal disease/malignancies
• Preparation of permanent slides using
cytocentrifugation
• Papanicolaou stain
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Transplant rejection
Viral, fungal, and parasitic infections
Cellular inclusions
Pathologic casts
Inflammatory conditions
Copyright © 2014. F.A. Davis Company
Microscopy
• Bright field most common in urinalysis
– Reduced light is essential
– Magnification is 10× and 40×
– Par focal means minimal adjustment when changing objectives
(use fine adjustment)
– Lower light using the rheostat
– Condenser can be raised up and down
– Do not use the aperture diaphragm
• Others include phase contrast, polarizing, dark field,
fluorescence, and interference contrast
Copyright © 2014. F.A. Davis Company
Microscopy (cont’d)
• Phase-contrast microscopy
– Increases refractive index
• Polarizing microscopy
– Crystals and lipids
– Ability to split light into two beams
– Crystals are multicolored
– Cholesterol produces Maltese cross formations
• Interference-contrast microscopy
– Three-dimensional images
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The Microscope
• Compound bright-field microscope
• Two-lens system
– In the oculars, the objectives
– The coarse- and fine-adjustment knobs
• Illumination system
– Light source, condenser, and field and iris diaphragms
• Body consisting of
– Base
– Body tube
– Nosepiece
• Mechanical stage
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The Microscope (cont’d)
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The Microscope (cont’d)
• Binocular 10×
– Adjusts for interpupillary distance
• Field of view is determined by the eyepiece and is the
diameter of the circle of view when looking through the
oculars
• Objectives: near specimen
– UA sediment magnifications of 10× (low power, dry), 40× (high
power, dry)
• Final magnification of an object is the product of the
objective magnification times the ocular magnification
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The Microscope (cont’d)
• Objective characteristics
– Type of objective, magnification, numerical aperture,
microscope tube length, and cover-slip thickness to be used
– Length of the objectives attached to the nosepiece varies with
magnification
– Changing the distance between the lens and the slide when
they are rotated
• Parfocal
– Only minimum adjustment when switching among objectives
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The Microscope (cont’d)
• The distance between the slide and the objective is
controlled by the coarse and fine focusing knobs
– Coarse focus: initial focusing
– Fine focus: sharpen image, focusing after changing
magnification
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The Microscope (cont’d)
• Illumination
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Base
Equipped with rheostat
Regulates intensity
Filters vary illumination and wavelength
Diaphragm contained in the light source controls the diameter
of the light beam
– Condenser located below the stage to focus the light
– All have adjustments for optimal lighting
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The Microscope (cont’d)
• Köhler illumination: provide optimal viewing of the
illuminated field
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Care of the Microscope
1. Carry microscope with two hands, supporting the base with one
hand.
2. Always hold the microscope in a vertical position.
3. Only clean optical surfaces with a good quality lens tissue and
commercial lens cleaner.
4. Do not use the 10× and 40× objectives with oil.
5. Clean the oil immersion lens after use.
6. Always remove slides with the low-power objective raised.
7. Store the microscope with the low-power objective in position
and the stage centered.
Copyright © 2014. F.A. Davis Company
Urine Sediment Constituents
• Small amounts of constituents can be normal
or pathogenic based on the clinical picture
• Many urines have just a rare epithelial cell
• Some constituents are easily distorted
– Concentrations, pH, and presence of metabolites
• Normals are not clearly defined
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RBCs
• Identification difficulties
– Yeast: look for buds
– Oil droplets: refractility
– Air bubbles: refractility
and possibly in a different
plane
– Starch: refractile,
polarizes
– Reagent strip correlation
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RBCs (cont’d)
• Smooth, nonnucleated,
biconcave disks ~7 µm
• Crenated in
hypersthenuric urine
• Ghost cells in
hyposthenuric urine
• Identify using high
power
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RBCs (cont’d)
Air Bubble
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Oil Droplets
RBCs (cont’d)
• Dysmorphic RBCs
– Glomerular bleeding
– Strenuous exercise
– Acanthocytic, blebs
– Fragmented, hypochromic
– Aid in diagnosis
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Clinical Significance
• Normal value: 0–3 to 5/hpf
• Damage to glomerular membrane or vascular
injury to the genitourinary tract
• Number of cells = extent of damage
• Macroscopic versus microscopic hematuria
– Cloudy, red urine, advanced disease, trauma, acute
infection, coagulation disorders
– Clear urine, early glomerular disease, malignancy,
strenuous exercise, renal calculi confirmation
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WBCs
• 12 µm
• Neutrophil is
predominant
• Identify under high power
• Glitter cells
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Hypotonic urine
Brownian movement
Swell; granules sparkle
Pale blue if stained
Nonpathologic
WBCs (cont’d)
• Glitter cell
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WBCs (cont’d)
• Eosinophils
– Drug-induced interstitial
nephritis
– Renal transplant rejection
• Hansel stain
– Percent per 100 to 500 cells
– >1% significant
– Concentrate sediment,
centrifuge, or cytocentrifuge
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WBCs (cont’d)
• Mononuclear cells
– Lymphocytes, monocytes,
macrophages, histiocytes are
rare
– Differentiate from renal
tubular epithelial (RTE) cells
• Staining
– Lymphocytes may resemble
RBCs; seen in early transplant
rejection
– May need to refer to
cytodiagnostic testing
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Clinical Significance
• Normal = <5 per hpf, more in females
• May enter through glomerulus or trauma but also by
amoeboid migration
• Increased WBCs = pyuria
• Infections: cystitis, pyelonephritis, prostatitis,
urethritis
• Glomerulonephritis, lupus erythematosus,
interstitial nephritis, tumors
• Report presence of bacteria
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Epithelial Cells
• Three types
1. Squamous
2. Transitional (urothelial)
3. RTE
• Classification
– Squamous: vagina, male and
female urethra
– First structures observed
– Transitional: bladder, renal
pelvis, calyces, ureters,
upper male urethra
– RTE: renal tubules
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Squamous Epithelial Cells
• Largest cell in urine
• Good for focusing
microscope
• Rare, few, moderate,
many
• lpf or hpf per laboratory
• Normal sloughing
• Contamination if not
midstream clean-catch
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Squamous Epithelial Cells (cont’d)
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Clue Cells
• Squamous cell with pathologic significance
• Gardnerella vaginalis: vaginal infection
• Coccobacillus sp. covers most of the cell and
extends over the edges
• Seen in urine but more common in vaginal wet
preparation
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Transitional Epithelial
(Urothelial) Cells
• Three forms
1. Spherical: absorb water in bladder and become large and
round
2. Caudate: appear to have a tail
3. Polyhedral: multiple sides
• Differentiate from RTE
– Centrally located nucleus
• Syncytia = clumps
– Catheterization
– Malignancy
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Transitional Epithelial
(Urothelial) Cells (cont'd)
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Renal Tubular Epithelial Cells
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Size and shape vary with renal tubular area
Columnar = proximal convoluted tubule (PCT)
Round, oval = distal convoluted tubule (DCT)
Cuboidal = collecting duct
Three or more cuboidal cells = renal fragment
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PCT Cells
• Larger than other RTEs
• Columnar, convoluted,
rectangular
• May resemble casts
• Coarsely granular
cytoplasm
• Notice presence of
nucleus
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DCT Cells
• Round or oval shaped,
smaller
• May resemble WBCs or
spherical transitional
cells
• Observe the eccentrically
placed nucleus to
differentiate from
spherical transitional
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Collecting Duct RTEs
• Cuboidal, never round
– At least one straight
edge
– Eccentric nucleus
• Three or more cells in
clump is renal fragment;
often large sheets
• PCT and DCT not seen in
clumps
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Clinical Significance
• RTE cells are the most clinically significant urine
epithelial cells; indicate tubular necrosis;
fragments indicate severe destruction
– Heavy metals, drug toxicity, hemoglobin, myoglobin,
viral infections, pyelonephritis, transplant rejection,
salicylate poisoning
• Single cuboidal cells = salicylate poisoning
• Absorb: bilirubin, hemoglobin, lipids
• Hemosiderin stains with Prussian blue
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RTE cells
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Oval Fat Bodies
• RTE cells that have
absorbed lipid in the
filtrate
• Also free-floating
refractile droplets
• Maltese cross formation
with polarized light
• If negative check with
Sudan III or oil red O stain
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Oval Fat Bodies (cont’d)
• Stain polarizing negative
structures
• Cholesterol polarizes
• Triglycerides and neutral
fats stain
• Lipiduria: nephrotic
syndrome, acute tubular
necrosis, diabetes, crush
syndromes
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Bacteria
• Urine is usually sterile,
contaminated on the way out;
contaminants multiply fast
• WBCs should accompany
bacteria in UTI
• Report few, moderate, many
per hpf
• Rods and cocci may be seen;
rods most common
• Nitrite helps to confirm rods,
not cocci
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Yeast
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Single, refractile, budding structures
Mycelial forms may be present
Report: few, moderate, many
Diabetic urine: ↑ glucose and acid ideal for yeast
growth
• Immunocompromised, vaginal moniliasis
• Nitrite negative, WBCs present
• Confuse with RBCs
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Yeast (cont’d)
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Parasites
• Most common: Trichomonas vaginalis
– Pear-shaped flagellate
– Swims across field rapidly
• Report few, moderate, many
• If not moving, may resemble WBC, transitional,
or RTE cells
• Also Schistosoma haematobium and Enterobius
vermicularis
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Parasites (cont’d)
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Spermatozoa
• Oval, tapered heads and long tail
• Urine is toxic to sperm, so they
are immobile
• Rarely significant, infertility:
sperm expelled into bladder
instead of urethra
• May cause positive protein
• Reporting varies with
laboratories
• Lack of clinical significance, legal
consequences
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Mucus
• Protein from RTE,
glands, squamous cells
• Threadlike, low
refractive index
• Confuse with casts
– Irregular, composed of
uromodulin protein
• Female specimens, no
clinical significance
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Casts
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Elements unique to the kidney
Formed in DCT and collecting duct
Parallel sides, rounded ends, inclusions
Detect under low power, ID high power
Scan edges of glass cover slip
Low light is essential
Report number per lpf
Many pathologic and nonpathologic causes
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Composition and Formation
• Uromodulin protein secreted by RTE of DCT and
collecting duct
• Consistent excretion normally
– ↑ stress and exercise
• Formation of protein fibrils into matrix
– Urine stasis, acid pH, Na, and Ca
• Uromodulin protein not detected by reagent strips
• ↑ protein is from renal disease
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Composition and Formation (cont’d)
• Formation
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Aggregated uromodulin fibrils attached to RTEs
Interweaving to loose network, traps elements
More interweaving to form solid matrix
Attachment of elements to matrix
Detachment of fibrils from RTEs
Excretion of cast
• Cylindroids
– Tapered ends, one or both
– Same significance as cast
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Hyaline Casts
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Low refractive index
Colorless when unstained
Uromodulin protein
Use low light or phase
Normal parallel sides or
convoluted, wrinkled,
cylindroid, occasional
adhering cell or granule
Clinical Significance
• Most frequently seen
• 0 to 2 is normal
• Nonpathologic: stress,
exercise, fever, heat
exposure, dehydration
• Pathologic:
glomerulonephritis,
pyelonephritis, chronic
renal disease, congestive
heart failure
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Clinical Significance (cont’d)
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RBC Casts
• Orange-red color
• Embedded and
adhering cells
• May be fragmented
• Confirm seeing free
RBCs and positive
reagent strip for blood
• Look for cast matrix to
avoid mistaking a RBC
clump for a cast
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Clinical Significance
• Bleeding within the nephron, casts are more
specific than free RBCs in urine
• Glomerular damage or nephron capillary damage
• Glomerular damage: dysmorphic RBCs and
elevated protein
• May be seen following strenuous exercise
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Clinical Significance (cont’d)
• Cells begin to disintegrate
with more stasis of urine
flow
• Hemoglobin and myoglobin
damage tubules
• Hemoglobin degraded to
methemoglobin = dirty
brown casts
• Look for RTE cells to confirm
tubular necrosis
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WBC Casts
• Mostly neutrophils and
lobed nucleus and
granules are seen
• Staining helps
differentiate from RTE
cells
• May be tightly packed;
look for cast matrix to
distinguish from WBC
clump
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WBC Casts (cont’d)
• WBC casts are seen with
infection and inflammation
of the tubules
• Pyelonephritis: WBC casts,
bacteria
• Acute interstitial nephtitis:
WBC casts, no bacteria
• May accompany RBC casts
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Bacterial Casts
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May be pure bacteria or mixed with WBCs
Resemble granular casts
Look for free WBCs and bacteria
Confirm with Gram stain
Seen in pyelonephritis
Mixed cellular casts
– Glomerular nephritis: RBCs and WBCs
• Look for predominant type of cell
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Epithelial (RTE) Casts
• Formed in DCT = small,
round cells
• Fibrils forming cast pull
cells from damaged
tubules
• Majority of cells are on
the cast matrix
• Differentiate from WBCs:
stain to show single
nucleus
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Clinical Significance
• Tubular damage, heavy
metals, viral infections,
drug toxicity, graft
rejection, pyelonephritis
• Cells may appear bilirubin
stained
• Look for matrix to
distinguish fragments
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Fatty Casts
• Seen with oval fat bodies
(OFBs) and fat droplets
• Highly refractile, OFBs
may attach to matrix
• Polarized microscopy and
lipid stains
• Nephrotic syndrome,
diabetes, crush trauma,
tubular necrosis
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Mixed Cellular Casts
• RBC and WBC casts in glomerulonephritis
• WBC and RTE cell casts, or WBC and bacterial
casts in pyelonephritis
• Identification difficult
– Staining or phase microscopy aids in the
identification
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Granular Casts
• Coarse and finely granular
• Granule origin
– RTE lysosomes, excreted
in normal metabolism,
more after exercise and
activity
– Disintegration of cellular
casts and free cells
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Granular Casts (cont’d)
• Detect with low power, ID
with high power
• Granules disintegrate to
form waxy casts
• Differentiate granular
casts from clumps of
debris and crystals; look
for matrix
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Waxy Casts
• Brittle, highly refractile
• Often fragmented with
jagged ends and notches
• Well visualized with stain
• Degenerated hyaline and
granular casts
• Extreme urine stasis
• Renal failure
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Broad Casts
• Renal failure casts
• Destruction and widening of
the DCTs
• Formation in the upper
collecting duct
• All types of casts may be
broad
• Most common are granular
and waxy
• Bilirubin stained from viral
hepatitis
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Urinary Crystals
• Most are not clinically significant but are reported
• True geometrically formed structures or as amorphous
material
• Must differentiate from the few abnormal crystals
indicating liver disease, inborn errors of metabolism,
and damage to tubules
• Iatrogenic: caused by medications or treatments
• Report: rare few, moderate, many
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Crystal Formation
• Precipitation of urine solutes: salts, organic
compounds, and medications
• Formation based on temperature, solute
concentration, and pH
• Many crystals in refrigerated specimens
• High specific gravity needed in fresh specimens
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General Identification Techniques
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Most have characteristic shapes and colors
Most valuable ID is urine pH
Classification: normal acid, normal alkaline
All abnormal crystals are found in acid urine
Polarized microscopy characteristics are valuable
in ID
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Solubility Characteristics
• Temperature and pH contribute to formation and
solubility
• Amorphous urates form in refrigerated acid
urine; will dissolve with heat
• Amorphous phosphates form in refrigerated
alkaline urine; will dissolve in acetic acid; so will
RBCs
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Normal Crystals in Acid Urine
• Amorphous urates
– Yellow-brown granules
microscopically
– Urine sediment has pink
color due to the pigment
uroerythrin attaching on
surface of granules
– Often in clumps; may
resemble casts
– pH usually greater than
5.5
Copyright © 2014. F.A. Davis Company
Uric Acid Crystals
• Rhombic, whetstones,
wedges, rosettes
• Yellow-brown color
• May resemble cystine
crystals but always
polarize
• ↑ purines, nucleic acids
• Chemotherapy for
leukemia, gout
Copyright © 2014. F.A. Davis Company
Calcium Oxalate Crystals
• Acid and neutral pH
• Dihydrate is envelope or
two pyramid–shaped
– Most common
• Monohydrate is oval or
dumbbell shaped
– Antifreeze poisoning
• Calcium oxalate is a major
component of renal calculi
Copyright © 2014. F.A. Davis Company
Amorphous Phosphates
• May appear similar to
amorphous urates
• Differentiate
– Alkaline pH and heavy
white precipitate after
refrigeration
Copyright © 2014. F.A. Davis Company
Normal Crystals in Alkaline Urine
• Triple phosphate
• Colorless, prism, or coffinlid shaped
• Highly alkaline urine and
urinary tract infections
(UTIs)
• Polarize
• No clinical significance
Copyright © 2014. F.A. Davis Company
Calcium Phosphate and Carbonate
• Phosphate
– Flat rectangles and thin
prisms in rosettes
– No clinical significance
• Carbonate
– Small, dumbbell, and
spherical shapes
– Gas produced with
addition of acetic acid
– No clinical significance
Copyright © 2014. F.A. Davis Company
Ammonium Biurate Crystals
• Yellow-brown, spiculecovered spheres; “thorny
apples”
• Only urates in alkaline
urine
• Old specimens and with
urea-splitting bacteria
Copyright © 2014. F.A. Davis Company
Abnormal Crystals
• Cystine crystals
– Hexagonal, thin and thick
plates
– Similar to uric acid
– UA polarizes but only thick
cystine crystals polarize
– Seen in cystinuria: inability
to reabsorb cystine
– Confirm: cyanide
nitroprusside
Copyright © 2014. F.A. Davis Company
Cholesterol Crystals
• Refrigerated specimens
• Rectangular plates with
characteristic notched
corners
• Highly birefringent
• Nephrotic syndrome
accompanying fatty casts
and OFBs
Copyright © 2014. F.A. Davis Company
Radiographic Dye Crystals
• Radiographic dye
– Similar to cholesterol crystals, polarize
– Patient history
– Very high SG with refractometer
Copyright © 2014. F.A. Davis Company
Liver Disease Crystals
• Tyrosine crystals
– Fine yellow needles in
clumps or rosettes
– Seen with leucine
crystals
– Inherited amino acid
disorders
• Leucine crystals
– Yellow-brown spheres
with concentric circles
and radial striations
Copyright © 2014. F.A. Davis Company
Liver Disease Crystals (cont’d)
• Bilirubin crystals
– Clumped needles or
granules
– Characteristic yellow
color
– Viral hepatitis with
tubular damage
– Positive reagent strip for
bilirubin
Copyright © 2014. F.A. Davis Company
Sulfonamide Crystals
• Possibility of tubular
damage if crystals are
forming in the nephron
• Shapes most frequently
encountered include
needles, rhombics,
whetstones, sheaves of
wheat, and rosettes with
colors ranging from
colorless to yellow-brown
Copyright © 2014. F.A. Davis Company
Ampicillin Crystals
• Ampicillin crystals
appear as colorless
needles that tend to
form bundles following
refrigeration
Copyright © 2014. F.A. Davis Company
Urinary Sediment Artifacts
• Material fibers, meat
and vegetable fibers,
and hair
• Starch, oil droplets, air
bubbles, pollen grains,
vegetable fiber, hair,
diaper fiber
Copyright © 2014. F.A. Davis Company
Urinary Sediment Artifacts (cont’d)
Copyright © 2014. F.A. Davis Company