Microscopic Examination of Urine Sediment
Crystal composition: colorless "envelope" form
calcium oxalate
Abnormal Crystal of Iatrogenic Origin: Medications: Indinavir: pH?
can be observed in acid urine but are more often observed in neutral and alkaline urines
Crystals of normal urine: Calcium oxalate: pH?
can form in urine at any pH
positive LE test despite few or no WBCs present microscopically
can occur because of WBC lysis and disintegration different populations of WBCs have varying quantities of cytoplasmic granules and therefore differing amounts of leukocyte esterase; in fact, lymphocytes have no leukocyte esterase
Urinary stasis: Occurs? What does it promote?
can occur because of obstruction from disease processes or congenital abnormalities promotes the accumulation and concentration of ultrafiltrate components, hence cast formation
Crystals in normal urine: Triple phosphate: comments/clinical significance?
common little clinical significance but have been associated with UTIs characterized by an alkaline pH and have been implicated in the formation of renal calculi normal urine solute = can be found in healthy individuals NH4MgPO4 = ammonium magnesium phosphate
Crystals in normal urine solutes: acid urates (Na, K, NH4): comments/clinical significance?
common in old urine, but frequently not observed in fresh urine may be misidentified as leucine crystals no clinical significance reported as "urate crystals"
Crystals of normal urine solutes: amorphous urates: comments/clinical significance?
common; macroscopic appearance--orange-pink precipitate ("brick dust")--urinary pigment uroerythrin deposits on surfaces of urate crystals indicate urine is acidic no clinical significance distinguished from amorphous phosphates on the basis of urine pH, their macroscopic appearance, and solubility characteristics
Crystals in normal urine: amorphous phosphate: comments/clinical significance?
common; macroscopic appearance--white to beige precipitate
Crystals of normal urine: Calcium oxalate: comments/clinical significance?
common; often accompanies ethylene glycol ingestion; often observed during severe chronic renal disease calcium and oxalate are solutes normally present in urine of healthy people; approx. 50% of the oxalate typically present in urine is derived from ascorbic acid (Vitamin C), an oxalate precursor or from oxalic acid as urine forms in the renal tubules, oxalate ions associate with calcium ions to become calcium oxalate foodstuffs high in oxalic acid or ascorbic acid include vegetables and citrus fruits; beverages high in oxalic acid include tea, cocoa, coffee, and chocolate
How are casts classified microscopically?
composition of matrix and types of substances/cells enmeshed within them
Sperm in female urine samples
considered a vaginal contaminant
For women, what does the presence of yeast in urine indicate?
contamination of the urine with vaginal secretions
What type of contamination will make it seem like nephrotic syndrome is present?
contamination of urine by men with prostatitis = prostatic fluid (contains WBCs, macrophages, oval-fat bodies, fat globules)
How are IV radiopaque contrast media (x-ray dye) such as meglumine diatrizoate and diatrizoate sodium differentiated from cholesterol crystals?
correlate microscopic findings with chemical examination results; x-ray dyes have high specific gravity and are not associated with proteinuria or lipiduria; cholesterol crystals are seen in urine with normal specific gravity and must be accompanied by proteinuria and lipiduria
Benefits of commercial slides (acrylic)
cost competitive easy to adapt to necessary to ensure reproducible and accurate results
Casts vs fibers
cotton threads or diaper fibers can resemble waxy casts fibers tend to be flatter in the middle and thicker at their margins, whereas casts are cylindrical and thicker in the center fibers are more refractile than casts and polarize light under polarizing microscopy, whereas casts do not fibers may contaminate the urine at any time, whereas casts, must be accompanied by proteinuria
Casts vs crystals
crystals such as amorphous urates and phosphates can aggregate together or along a mucous thread to simulate a cast with polarizing microscopy, their birefringence identifies them as crystalline entities, and the lack of a distinct matrix differentiates them from a true cast
Other Inclusion Casts: crystal casts: microscopic features?
crystals within matrix not common; those encountered are usually composed of calcium oxalate or sulfonamide crystals
Crystal in normal urine: ammonium biurate: color?
dark yellow-brown
What are the primary functions of monocytes/macrophages?
defend against microorganisms removed dead or dying cells and cellular debris interact immunologically with lymphoid cells
What can cause increased urine solute saturation?
dehydration, urinary excess, medications
Cellular Casts: Red blood cell casts: correlations?
diagnostic of intrinsic renal disease RBCs are most often of glomerular origin but can result from tubular damage varying degrees of proteinuria are also present associated with glomerular disease (e.g., glomerulonephritis, nephritis) a rare cast may be observed following contact sports (i.e., athletic pseudonephritis)--return to normal after 24-48 hours can monitor patients response to treatment by monitoring RBC cast presence
Crystals in normal urine: calcium phosphate: microscopic appearance?
dibasic calcium phosphate: thin prisms in rosette or stellar form; prisms have one tapered end; rarely, as long, thin needles, weak birefringence; sometimes called stellar phosphates monobasic calcium phosphate: irregular, granular-appearing sheets or flat plates; can resemble large degenerating squamous epithelial cells
Crystals of normal urine: Calcium oxalate: microscopic appearance?
dihydrate; octahedral or envelope form; weak to moderate birefringence monohydrate; ovoid or dumbbell form; strong birefringence (how to distinguish from RBCs)
Where are urinary casts formed?
distal and collecting tubules with a core matrix of uromodulin (formerly known as Tamm-Horsfall protein)
Which epithelial cell type is "oval to round; small nucleus"?
distal tubular cell
Renal: Convoluted Tubular Cells: Relative Size and Diameter?
distal tubular cells: 14-25 um proximal tubular cells: 20-60 um
RBCs vs small bubbles or droplets of oil contaminating the urine sediment
distinguished from RBCs by their variation in size, uniformity in appearance, and high refractility
Interference contrast microscopy
enhances imaging of formed elements by producing three-dimensional images of high contrast and resolution 2 types: differential interference contrast (Nomarski) and modulation contrast (Hoffman) suited ideally for formed elements
Phase-contrast microscopy
enhances the imaging of translucent or low-refractile formed elements and living cells allows identification of traditionally difficult to view formed elements: hyaline casts and mucous threads
Which leukocyte predominates in urine during acute interstitial nephritis caused by drug hypersensitivity?
eosinophils
RBCs in hypotonic urine--"ghost" cells
erythrocytes swell and release their hemoglobin to become "ghost" cells, which are cells with intact cell membranes but no hemoglobin difficult to see using brightfield microscopy; readily visible with phase-contrast or interference contrast microscopy
How is Schistosoma haematobium acquired?
exposure to water where infected snails live
Trichomonas vaginalis: undulating membrane
extends halfway down the body of the organism rotates flagella
Fatty Casts: microscopic features?
fat globules or oval fat bodies (OFBs) within matrix--hyaline or granular highly refractile fat globules have yellowish to green sheen (brightfield microscopy) cholesterol granules form Maltese cross under polarizing microscopy--characteristic birefringement; triglycerides (neutral fat) stain orange or red using Sudan III or Oil Red O, respectively lipids do not take up Sternheimer-Malbin stain, but the protein matrix does
Squamous cells: where are they located?
females: line entire urethra males: distal portion of urethra only
How is the presence of bacteria reported?
few, moderate, many per hpf
Fibers vs urinary casts
fibers tend to be flat and thicker at their margins in contrast to casts, which are thicker in the middle fibers are anisotropic, and polarizing microscopy demonstrates their birefringence; casts are not anisotropic
Mucus
fibrillar protein common in urine sediment no clinical significance difficult to observe with brightfield microscopy = low refractive index delicate, ribbon-like strands and irregular or serrated ends = phase contrast or interference contrast microscopy distinct strands or clumped mass derived partly from renal tubules vaginal epithelium
Abnormal Crystals of Metabolic Origin: bilirubin: microscopic appearance?
fine needles or granules that form small clusters
How should dead Trichomonads present in urine be distinguished from WBCs and renal cells?
flagella can be seen with phase-contrast microscopy
Crystal in normal urine: magnesium phosphate: microscopic appearance?
flat, elongated rectangular or rhomboid plates; end or corner may be notched; edges can be irregular or eroded; weak birefringence
Abnormal Crystals of Metabolic Origin: cholesterol: microscopic appearance?
flat, rectangular plates with notched corners; weak birefringence
When does the presence of renal casts NOT indicate renal disease?
following strenuous exercise--such as marathon running some diuretic therapies
Abnormal Crystals of Iatrogenic Origin: medications: radiographic contrast media: microscopic appearance?
form varies with administration; strong birefringence: IV administration: flat, elongated rectangular plates Retrograde administration: long, slat-like prisms
Abnormal Crystals of Iatrogenic Origin: medication: sulfonamides: microscopic appearance?
form varies with drug; strong birefringence: Sulfamethoxazole sulfadiazine--brown rosettes or spheres with striations or dense globules Acetylsulfadiazine--yellow to brown as bundles of needles that resembles sheaves of wheat with eccentric binding; fan forms
What 3 forms are fats/lipids found in urine?
free-floating fat globules within oval fat bodies within a cast matrix
What is enhanced in an acidic environment that causes it to enhance cast formation?
gelation of protein and the precipitation of of solutes
What do oval fat bodies indicate? What are they accompanied by?
glomerular dysfunction and renal tubular cell death they are always accompanied by an increased amount of urine protein and cast formation
What is the presence of eosinophil casts diagnostic of?
good predictor of AIN associated with drug hypersensitivity, particularly hypersensitivity to penicillin and its derivatives
Classification of Urinary Casts: Other inclusions
granular fat globules--cholesterol, triglycerides hemosiderin granules crystals
Abnormal Crystals of Metabolic Origin: cystine: comments/clinical significance?
rare; congenital cystinosis or cystinuria; confirm with nitroprusside test tend to deposit within the tubules as calculi, resulting in renal damage thin, hexagonal uric acid crystals can be confused with cystine crystals; therefore a confirmatory test should be performed before cystine is reported = cyanide-prusside reaction
Abnormal Crystals of Metabolic Origin: tyrosine and leucine: microscopic appearance?
leucine: spheres with concentric circles or radial striations; strong birefringence but light pattern produced is not a true Maltese pattern tyrosine: fine, delicate needles in clusters or sheets but may also appear singly or in small groups
WBCs: correlation with physical and chemical examinations
leukocyte esterase reaction--can be negative despite increased WBCs owing to excess hydration or when the WBCs are lymphocytes negative nitrite reaction: suggestive of inflammation or nonbacterial infection positive nitrite reaction: suggests bacterial infections
During a UTI, what is bacteriuria usually accompanied by?
leukocytes
Where are transitional epithelial cells found?
lining the bladder, ureters, renal pelves, and male urethra (except the distal portion); NOT FOUND IN FEMALE URETHRA
nephrotic syndrome
lipiduria and proteinuria
Abnormal Crystal of Iatrogenic Origin: Medications: Ampicillin: microscopic appearance?
long, thin needles or prisms; strong birefringence; small groups or large clusters
Squamous cells: hpf or lpf?
lpf
Which leukocyte predominates in urine during a renal allograft rejection?
lymphocytes
Collecting duct cell look-alikes?
macrophages/monocytes
Starch vs cholesterol
maltese pattern under polar microscopy similar to cholesterol; however the edges of the maltese pattern of starch are less defined visual differences in brightfield microscopy
Cast with Inclusions: Granular Casts: coarsely granular casts: correlations?
not associated with any specific disease, just any intrinsic renal disease degeneration of cellular casts accompany other pathologic casts in urine sediment, such as cellular casts degeneration of granular casts into waxy casts can occur during urine stasis
Reference Intervals: Casts
number = 0 to 2 hyaline (or finely granular) magnification = per lpf
Reference Intervals: RBCs
number = 0 to 3 magnification = per hpf
Reference Intervals: WBCs
number = 0-8 magnification = per hpf
Reference Intervals: Epithelial cells--Renal
number = few magnification = per hpf
Reference Intervals: Epithelial cells--Transitional
number = few magnification = per hpf
Reference Intervals: Epithelial cells--Squamous
number = few magnification = per lpf
Reference Intervals: Bacteria and yeast
number = negative magnification = per hpf
Reference Intervals: Abnormal crystals
number = none magnification = per lpf
Qualitative Terms and Descriptions for Fields of View (FOVs)
rare--1+--present, but hard to find few--1+--one (or more) present in almost every field of view moderate--2+--easy to find; number present in FOV varies; "more than few, less than many" many--3+--prominent; large number present in all FOVs packed--4+--FOV is crowded by or overwhelmed with the elements
Abnormal Crystals of Iatrogenic Origin: medication: sulfonamides: comments/clinical significance?
rare: accompany antibiotic therapy; confirm with diazo reaction test; some forms resemble acid urates and ammonium biurate
What are characteristics of neutrophils found in urine sediment?
they are approx. 10-14 um in diameter they shrink in hypertonic urine but do not crenate as they are disintegrating, vacuoles and blebs form and their nuclei fuse
How are other components (RBCs, WBCs, casts) assessed?
they are enumerated as a range of formed elements present (e.g., 0 to 2, 2 to 5, 5 to 10)
When are lymphocytes usually present in urine?
they are normally present in urine in small amounts but are present in increasing #s during inflammatory conditions such as acute pyelonephritis lymphocytes predominant over neutrophils from patients experiencing renal transplant rejection will NOT provide a positive LE test because they do NOT contain leukocyte esterases
What happens to uric acid crystals if urine pH is adjusted to an alkaline pH?
they dissolve and become urate salt crystals
Why are glass microscope slides and coverslips not recommended for viewing urine sediment?
they do not yield standardized, reproducible results
At times, clusters or sheets of transitional epithelium are observed following urinary catheterization or other types of instrumental procedures. What is indicated when sheets of cells appear without these procedures?
they indicate a pathologic process that requires further investigation, such as transitional cell carcinoma
Crystal in normal urine: calcium carbonate: microscopic appearance?
tiny granular spheres; often in pairs (dumbbells) or tetrads; strong birefringence also be found as aggregate masses that are difficult to distinguish from amorphous material
Why is well-mixed urine centrifuged at a certain speed?
to allow for optimal sediment concentration without damaging fragile formed elements such as cellular casts
Abnormal Crystals of Metabolic Origin: cholesterol: comments/clinical significance?
rare; crystals induced by storage at 2*C to 8*C; indicates lipiduria; found with proteinuria and other forms of urinary fat; seen with nephrotic syndrome and in conditions resulting from chyluria: the rupture of lymphatic vessels into the renal tubules as a result of tumors, filariasis, etc.
How is crystal formation enhanced?
slow urine flow through the renal tubules = allows time for maximum concentration of solutes in the ultrafiltrate; at the same time, the tubules are effecting pH changes in the ultrafiltrate; when the pH becomes optimal for supersaturated solute, crystals form
Renal: Collecting Duct Cells: Relative Size and Diameter?
small ducts: 12-20um large ducts: 6-10 um
Cast with Inclusions: Granular Casts: finely granular casts: microscopic features?
small granules dispersed throughout matrix, giving it a sandpaper appearance granules from renal cell metabolic by-products
Crystals in normal urine solutes: acid urates (Na, K, NH4): solubility characteristics?
soluble (dissolve) at approx. 60*C; convert to uric acid with glacial acetic acid
Crystals in normal urine: Triple phosphate: solubility characteristics?
soluble in acetic acid; fern-like form can be induced by addition of ammonia
Crystal in normal urine: magnesium phosphate: solubility characteristics?
soluble in acetic acid; insoluble in potassium hydroxide
Abnormal Crystals of Metabolic Origin: cystine: solubility characteristics?
soluble in alkali; present in urine with a pka less than 8.3, solubility increases with pH
Abnormal Crystals of Metabolic Origin: bilirubin: solubility characteristics?
soluble in alkali; soluble in strong acid
Crystals of normal urine: Calcium oxalate: solubility characteristics?
soluble in dilute HCl
Crystals in normal urine: calcium phosphate: solubility characteristics?
soluble in dilute acid
Crystal in normal urine: ammonium biurate: solubility characteristics?
soluble with acetic acid; soluble at approx. 60*C; convert to uric acid crystals with concentrated HCl or acetic acid
Crystals in normal urine: amorphous phosphate: solubility characteristics?
soluble with acid; insoluble at approx. 60*C
Crystals of normal urine: uric acid: solubility characteristics?
soluble with alkali
Crystals of normal urine solutes: amorphous urates: solubility characteristics?
soluble with alkali; dissolution when heated to approx. 60*C; convert to uric acid with concentrated HCl
Crystals in normal urine solutes: monosodium urate: solubility characteristics?
soluble with alkali; soluble at approx. 60*C
Crystal in normal urine: ammonium biurate: microscopic appearance?
spheres with striations or spicules (irregular projections); "thorny apple"; strong birefringence
WBCs: Neutrophils: Microscopic features
spherical cells, 12-14 um in diameter granular cytoplasm lobed nuclei glitter cells--dilute urine (low SG)
WBCs: Monocytes and Macrophages: Microscopic features
spherical cells, 20-25 um in diameter granular cytoplasm mononuclear--round to oval cytoplasm often vacuolated with ingested debris azurophilic granules
WBCs: Lymphocytes: Microscopic features
spherical cells, 6-9 um in diameter mononuclear--single round to slightly oval nucleus and scant clear cytoplasm that usually extends out from one side of the cell
What epithelial cell type is "large and flagstone; can be anucleated"?
squamous epithelial cell centered or slightly eccentric
Casts vs. squamous epithelial cells
squamous epithelial cells folded into a tubular shape may be misidentified as casts
Clue cells
squamous epithelial cells from the vaginal mucosa with large numbers of bacteria adhering to them; they can be present in urine specimens contaminated with vaginal secretions they are indicative of bacterial vaginosis, a synergistic infection most often involving Gardnerella vaginalis and an anaerobe, usually Mobiluncus spp. (e.g., Mobiluncus curtisii)
What are the 3 types of epithelial cells observed in urine sediment?
squamous--most common one encountered transitional (urothelial) renal tubular epithelial cells
Fat stains: Sudan III, Oil Red O
stains triglyceride (neutral fat) globules a characteristic orange (Sudan III) or red (Oil Red O) color used to confirm the presence of fat in urine
Fat vs starch granules
starch granules form a similar Maltese pattern with polarizing microscopy; however, they are easily distinguished from fat globules with the use of brightfield microscopy; starch granules are highly refractile, tend to have a central dimple, and are not spherical
Crystal composition: yellow-brown sheaves of wheat
sulfonamides
How is sediment concentrated?
supernatant urine is removed by decanting or using a disposable pipette until 1 ml of urine is retained. Then, a pipette is used to gently resuspend the sediment. Too vigorous agitation of sediment can cause fragile and brittle formed elements, sch as RBC casts and waxy casts, to break into pieces
Where does uric acid originate from?
the catabolism of purine nucleosides (adenosine and guanine from RNA and DNA)
What part of the nephron are urinary casts formed?
the distal and collecting tubules
When a microscopic examination is performed, what is the volume of sediment in each microscopic FOV determined by?
the optical lenses of the microscope and the standardized slide system used FOV = ocular field number and objective lens; the larger the FOV, the greater is the number of components that may be visible
What do crystals result from?
the precipitation of urine solutes out of solution; form as urine cools to room or refrigerator temperature (depending on storage)
What is uromodulin (a glycoprotein) secreted by?
the renal tubular cells of the thick ascending limb of the loop of Henle (i.e., straight portion of distal tubules) and by the distal convoluted tubules
What should a technologist do if the urine sediment is positive for bacteria but no leukocytes are present?
the specimen collection and handling should be investigated
In urine sediments, what is the most prevalent form of transitional epithelial cells found?
the superficial type: round or pear-shaped, with a dense oval to round nucleus and abundant cytoplasm
Why are renal casts present following strenuous exercise?
these casts are linked to the increased albuminuria resulting from exercise-induced glomerular permeability changes
Fatty Casts: chemical examination correlation?
protein positive blood +/-
Other Inclusion Casts: crystal casts: chemical examination correlation?
protein positive blood +/-
Cellular Casts: WBC casts: chemical examination correlation?
protein positive leukocyte esterase (LE) positive blood +/- nitrite +/-
Trichomonas vaginalis: size, shape?
protozoan flagellates that appear as turnip-shaped flagellates whose cellular bodies average 15 um in length although organisms as small as 5 um and as large as 30 um are possible
Which epithelial cell type is "oblong or cigar shaped; small eccentric nucleus"?
proximal tubular cell
How are some components (e.g., mucus, crystals, bacteria) assessed?
qualitatively assessed per field of view (FOV)
Abnormal Crystals of Iatrogenic Origin: medications: radiographic contrast media: comments/clinical significance?
radiographic procedures; causes high specific gravity (>1.040); can resemble cholesterol crystals can cause a false-positive sulfosalicyclic acid precipitation test for protein
Crystal in normal urine: calcium carbonate: comments/clinical significance?
rare no clinical significance
Crystal in normal urine: ammonium biurate: comments/clinical significance?
rare in fresh urine; iatrogenic alkalinization can induce; common in old urine; can resemble sulfonamides occur most frequently in urine specimens that have undergone prolonged storage when they precipitate out of solution in fresh urine (e.g., following iatrogenically induced alkalinization), they are clinically significant, because in vivo precipitation can cause renal tubular damage presence most often indicates inadequate hydration of the patient
Crystals in normal urine solutes: monosodium urate: microscopic appearance?
slender, pencil-like prisms with blunt ends; often in small clusters of 2-3 crystals or single ends are not pointed
Which of the following when found in urine sediment from a female patient is not considered a vaginal contaminant? a. fat b. clue cells c. spermatozoa d. trichomonads
a. fat
Why do lipids enter the urine?
adverse changes in glomerular filtration barriers, which allow plasma lipids to pass
What factors influence crystal formation?
(1) concentration of solute in urine (2) urine pH--how it affects solubility of urine solutes (3) flow of urine through the tubules
Where can the lipids (triglyceride/neutral fat) be found after staining?
(1) free floating as droplets or globules (2) within renal cells or macrophages, aptly termed oval fat bodies (3) within the matrix of casts as globules or oval fat bodies
How do fecal materials contaminate urine?
(1) improper collection technique (2) abnormal connection or fistula between urinary tract and bowel
To achieve consistency, several commercial urinalysis systems are available. What does each system seek to consistently do?
(1) produce the same concentration of urine or sediment volume (2) present the same volume of sediment for microscopic examination (3) control microscopic variables such as the volume of sediment viewed and the optical properties of the slides
How are IV administration radiographic contrast media crystals differentiated from cholesterol crystals?
(1) the large number of crystals usually present (2) the high urine specific gravity (greater than 1.040) (3) the lack of significant proteinuria and lipiduria
Casts vs scratched on coverslip
...
Hyaline Casts: normal concentration?
0 to 2 per low-power field
How do you convert the number of formed elements observed per low- or high-power field to the number present per mL of urine tested?
1. calculate the areas of the low-power and high-power fields of view for your microscope using the formula: Area = (pie)(r)^2 2. calculate the maximum number of low-power and high-power fields possible using your microscope and the standardized microscope slides in use: (total coverslip area for viewing) / (area per high power field (or low-power field)) = # of view fields possible 3. calculate the field conversion factor, which is the number of microscope fields per milliliter or urine tested: (# of view fields possible) / [(volume of sediment viewed (ml) x (concentration factor)] = (number of view fields) / (1 ml of urine tested) 4. convert the number of formed elements observed per high-power field (or low-power field) to the number present per milliliter of urine by multiplying the number observed per view field by the appropriate field conversion factor
Which urinary sediment component(s) when observed microscopically can resemble red blood cells?
1. yeasts 2. air bubbles 3. oil droplets 4. calcium oxalate crystals
What volume of urine is recommended for urinalysis? Pediatric patients?
12 ml, but volumes ranging from 10 ml to 15 ml can be used for pediatric patients, or other patients, where you may not be able to get 12 ml, the volume of urine can be reduced to 6 ml, and all the numeric counts from the sediment examination must be doubled
When are hemosiderin granules found in urine sediment?
2-3 days after a severe hemolytic episode (e.g., transfusion reaction, paroxysmal nocturnal hemoglobinuria) plasma haptoglobin is saturated with hemoglobin, and any remaining free hemoglobin is able to pass through the glomerular filtration barrier to be absorbed by the renal tubular epithelium the tubular cells metabolize the hemoglobin to ferritin and denature it to form hemosiderin; hemoglobin is toxic to cells, and as these cells degenerate, hemosiderin granules are found in the urine
Transitional cells: relative size and diameter?
20-40 um
When protein excretion is ____________ or greater, the urine sediment should be specifically screened for _________ with the use of polarizing microscopy or fat stains such as Sudan III or Oil Red O.
300 mg/dL fat
Squamous cells: relative size and diameter?
40-60 um
After well-mixed urine is poured into a centrifuge tube, how long and at what speed is it centrifuged?
400 to 450 g for 5 min
How is cytocentrifugation performed?
Because a monolayer of sediment components is desired, an initial microscopic examination is required to determine the amount or volume of urine sediment to use when preparing the slide. The appropriate amount of concentrated urine sediment is added to a specially designed cartridge fitted with a microscopic slide that is placed in a cytocentrifuge. After cytocentrifugation, a dry circular monolayer of sediment components is fixed permanently using an appropriate fixative and is stained (Papanicolaou's stain or Wright's stain) The end result is a monolayer of the urine sediment components with their structural details greatly enhanced by staining; this enables the quantitation and differentiation of WBCs and epithelial cells in the urine sediment
Candida albicans vs C. glabrata
C. albicans--characteristic budding, formation of pseudohyphae C. glabrata--do not form pseudohyphae; may be found phagocytized within WBCs
What is the most commonly encountered yeast in urine sediment?
Candida albicans
During microscopic examination of a urine sediment, cystine crystals are found. The laboratorian should perform which of the following before reporting the presence of these crystals? 1. perform confirmatory chemical test 2. ensure the urine specimen has an acid pH 3. assess the number of crystals per high-power field 4. check the current medications that the patient is taking a. 1, 2, and 3 are correct b. 1 and 3 are correct c. 4 is correct d. all are correct
a. 1, 2, and 3 are correct
All of the following enhance urinary cast formation EXCEPT a. an alkaline pH b. urinary stasis c. an increase in the solute concentration of the ultrafiltrate d. an increase in the quantity of plasma proteins in the ultrafiltrate
a. an alkaline pH
Hemosiderin staining
Prussian blue color
The microscopic identification of hemosiderin is enhanced when urine sediment is stained with _____________.
Prussian blue stain
Glomerular disease: Nephrotic syndrome
RBC = + RTE = + RTE cell cast = +/- Coarsely granular cast = + waxy cast = + Fat casts = +++
Glomerular disease: Chronic glomerulonephritis
RBC = + WBC = + RTE = + RBC cast = +/- RTE cell cast = ++ Coarsely granular cast = ++ Waxy cast = ++ Broad casts present
Infection/inflammation: Upper UTI: Acute pyelonephritis (bacterial)
RBC = + WBC = +++ RTE = + WBC casts = ++ RTE cast = + coarsely granular cast = ++ Waxy cast = +/- bacteria = +/- macrophages = with severe infection
Tubular Disease: Acute tubular necrosis (ATN)
RBC = ++ WBC = ++ RTE = +++ WBC casts = +/- RTE cell cast = ++ Coarsely granular casts = ++ Waxy casts = ++ Fat casts = (+/-) proximal RTE cells with toxic ATN collecting duct RTE cells with ischemic ATN epithelial fragments present
Infection/inflammation: Acute interstitial nephritis (drug-induced)
RBC = ++ WBC = +++ RTE = ++ WBC cast = + RTE cast = ++ Coarsely granular cast = ++ waxy cast = +/- eosinophils = predominate
Infection/inflammation: Lower UTI: Cystitis/urethritis (bacterial)
RBC = ++ WBC = +++ TE = ++ Bacteria = +
Glomerular disease: Acute glomerulonephritis (AGN)
RBC = +++ WBC = + RTE = + RBC cast = +++ WBC cast = + RTE cell cast = + Coarsely granular cast = ++ dysmorphic RBCs
What do yeast cells resemble? How are they differentiated?
RBCs yeast are more refractile than RBCs yeast do NOT dissolve in acid do not stain with supravital stains
RBCs in hypertonic urine--crenated forms
RBCs become smaller as intracellular water is lost from the cell by osmosis, which causes them to become crenated = appear rough microscopically compared with normal erythrocytes
positive chemical test for blood but microscopic exam reveals not RBCs
RBCs readily lyse and disintegrate in hypotonic or alkaline urine; such lysis can also occur within the urinary tract before urine collection; as a result, urine specimens can be encountered that contain only hemoglobin from RBCs that are no longer intact or microscopically visible other substances, such as myoblobin, microbial peroxidases, and strong oxidizing agents can cause a positive blood chemical test false-positives because RBCs or blood is not present
How do you calculate what RPM (revolutions per minute) is needed to generate a certain RCF,g (centrifugal force)
RCF (g) = 1.118 x 10^-5 x radius (cm) x RPM^2
Cellular: Renal Tubular Cell casts: microscopic features?
RTE cells within matrix high refractive index may appear aligned as fragments of tubular lining = indicated portion of the nephron has been severely damaged, with tubular basement membrane stripped of its epithelium can be misidentified as WBC casts
Which of the following crystals, when found in the urine sediment, most likely indicates an abnormal metabolic condition? a. bilirubin b. sulfonamides c. triple phosphate d. uric acid
a. bilirubin
What does the presence of bacteria in urine sediment mean?
UTI or urine contamination, fistula
Upper urinary tract infections
WBC casts in the urine cellular casts (i.e., cell identity cannot be determined) granular casts (result from cell degradation) positive protein reagent strip
RBCs vs yeast and calcium oxalate crystals
a Sternheimer-Malbin stain characteristically colors RBCs, whereas neither yeast nor calcium oxalate crystals stain polar microscopy can identify calcium oxalate crystals 2% acetic acid can be added, which lyses RBCs but does not eliminate yeast or calcium oxalate crystals yeast varies in size and tends to be spherical or ovoid rather than biconcave, and often exhibits budding
Prussian blue reaction
a concentrated urine sediment is examined for the presence of coarse yellow-brown hemosiderin granules, free floating or within casts or tubular epithelial cells; the urine sediment is suspended in a freshly prepared solution of potassium ferricyanide-HCl and is allowed to stand at room temperature for 10 minutes; after centrifugation and discarding of the supernatant, the sediment is reexamined for the presence of coarse blue granules; in this preparation, hemosiderin iron causes the granules to stain Prussian blue; because the action can be delayed, negative sediments are examined a second time after 30 minutes
How do you perform a gram stain?
a dry preparation of the urine sediment is made on a microscope slide by smearing and air drying or by cytocentrifugation; the slide is heat-fixed and stained
What might you find in healthy urine? What should NOT be present in urine?
a few epithelial cells, a rare RBC and few WBCs; a few hyaline casts or an occasional finely granular cast bacteria/yeast because urine is sterile
Hemosiderin
a form of iron that results from ferritin denaturation
What do most urine sediment findings indicate?
a process (e.g., infection, inflammation) or functional change (e.g., glomerular changes, tubular dysfunction, obstruction) that is occurring in the kidneys or urinary tract
Sternheimer-Malbin
a supravital stain that characteristically stains cellular structures and other formed elements enables detailed viewing an differentiation of cells, cast inclusions, and low refractile elements (e.g., hyaline casts, mucus) most commonly used stain enhances formed element identification by enabling more detailed viewing of internal structures, particularly WBCs, epithelial cells, and casts
Cytocentrifugation
a technique used to produce permanent microscopic slides of urine sediment and body fluids
Abnormal Crystal of Iatrogenic Origin: Medications: Indinavir: color?
colorless; gray to brown when aggregated
Which of the following statements regarding the microscopic examination of urine sediment is FALSE? a. if large numbers of leukocytes are present microscopically, then bacteria are present b. if urinary fat is present microscopically, then the chemical test for protein should be positive c. if large numbers of casts are present microscopically, then the chemical test for protein should be positive d. if large numbers of red blood cells are present microscopically, then the chemical test for blood should be positive
a. if large numbers of leukocytes are present microscopically, then bacteria are present
Which of the following is NOT a distinguishing characteristic of yeast in the urine sediment? a. motility b. budding forms c. hyphae formation d. colorless ovoid forms
a. motility
The following are initial results obtained during a routine analysis. Which results should be investigated further? a. negative protein; 2 to 5 waxy casts b. cloudy, brown urine; 2 to 5 red blood cells c. urine pH 7.5; ammonium biurate crystals d. clear, colorless urine; specific gravity 1.010
a. negative protein; 2 to 5 waxy casts
Which of the following does NOT contribute to the size, shape, or length of a urinary cast? a. the concentration of protein in the core matrix of the cast b. the configuration of the tubular lumen in which the cast is formed c. the diameter of the tubular lumen in which the cast is formed d. the duration of time the cast is allowed to form in the tubule
a. the concentration of protein in the core matrix of the cast
A urine sediment could have which of the following formed elements and still be considered "normal"? a. two or fewer hyaline casts b. five to 10 red blood cells c. a few bacteria d. a few yeast cells
a. two or fewer hyaline casts
2% acetic acid
accentuates the nuclei of leukocytes (WBCs) and epithelial cells lyses RBCs
Cast with Inclusions: Granular Casts: finely granular casts: correlations?
accompany strenuous exercise, stress, dehydration, fever by-products of protein metabolism, in part lysosomal, that are excreted by renal tubular epithelial cells--this accounts for the appearance in normal healthy people
What urine pH facilitates crystalline formation of cholesterol?
acid
What urine pH facilitates crystalline formation of radiographic contrast media?
acid
What urine pH facilitates crystalline formation of sulfonamides?
acid
What urine pH facilitates crystalline formation of tyrosine?
acid
What urine pH facilitates crystalline formation of uric acid?
acid
What urine pH facilitates crystalline formation of cystine?
acid (and alkaline, neutral)
What urine pH facilitates crystalline formation of amorphous sulfates?
acid (and neutral)
Abnormal Crystals of Metabolic Origin: bilirubin: pH?
acid urine only
What urine pH facilitates crystalline formation of calcium oxalate?
acid, neutral, and alkaline
Abnormal Crystal of Iatrogenic Origin: Medications: Ampicillin: pH?
acidic urine
Abnormal Crystals of Iatrogenic Origin: medication: sulfonamides: pH?
acidic urine
Abnormal Crystals of Iatrogenic Origin: medications: radiographic contrast media: pH?
acidic urine
Abnormal Crystals of Metabolic Origin: cholesterol: pH?
acidic urine
Abnormal Crystals of Metabolic Origin: cystine: pH?
acidic urine
Abnormal Crystals of Metabolic Origin: tyrosine and leucine: pH?
acidic urine
Why type of urine are most clinically significant crystals found?
acidic urine
eosinophiluria
acute interstitial nephritis (AIN) occasionally, chronic urinary tract infections (UTIs)
Hansel stain
aids in the identification of eosinophils Wright's stain or Giemsa stain also distinguishes eosinophils, but Hansel stain is preferred Patients with acute interstitial nephritis caused by hypersensitivity to a medication such as a penicillin derivative can have increased numbers of eosinophils in the urine sediment. Identification of this renal disease is important because it is one of the few renal diseases for which quick and effective treatment is available: cessation of drug administration
Crystals in normal urine: Triple phosphate: pH?
akaline and neutral urine
What urine pH facilitates crystalline formation of ammonium biurate?
alkaline
What urine pH facilitates crystalline formation of amorphous phosphates?
alkaline (and neutral)
What urine pH facilitates crystalline formation of triple phosphate?
alkaline (and neutral)
Crystals in normal urine: amorphous phosphate: pH?
alkaline and neutral urine
Crystal in normal urine: ammonium biurate: pH?
alkaline or neutral urine
Crystal in normal urine: calcium carbonate: pH?
alkaline urine
RBCs in alkaline urine
alkaline urine promotes red blood cell lysis and disintegration, resulting in ghost cells and erythrocyte remnants
Lipiduria
always clinically significant; presence doesn't pinpoint a specific diagnosis; renal diseases, crush injuries; also accompanied by some degree of proteinuria characteristic feature of nephrotic syndrome; diabetes mellitus; preeclampsia; extreme physical exercise identifying and monitoring presence of lipids aids in determination whether disease process is progressing or improving
Crystal composition: yellow-brown "thorny apple" form
ammonium biurate
Which crystals are found in alkaline urine?
amorphous phosphate triple phosphate calcium phosphate magnesium phosphate ammonium biurate calcium carbonate
Which crystals are found in acidic urine?
amorphous urates acid urates monosodium urate uric acid calcium oxalate
Crystals in normal urine: amorphous phosphate: microscopic appearance?
amorphous, granular noncrystalline form resembles fine, colorless, grains of sand
Crystals of normal urine solutes: amorphous urates: microscopic appearance?
amorphous, granular; strong birefringence
What factors enhance cast formation?
an acid pH, increased solute concentration, urine stasis, increased plasma proteins (particularly albumin)
How much hemoglobin must be present in urine to be detected by routine protein reagent test strips?
an amount exceeding 10 mg/dl
0.5% toluidine blue
another supravital stain a metachromatic stain that enhances the nuclear detail of cells aids in differentiating WBCs and renal tubular epithelial cells stains various cell components differently, hence the differentiation between the nucleus and cytoplasm becomes more apparent aids in distinguishing cells of similar size, such as leukocytes from renal collecting duct cells
Abnormal Crystal of Iatrogenic Origin: Medications: Indinavir: comments/clinical significance?
antiretroviral therapy
Clue cells--microscopic appearance?
appear soft and finely granular with indistinct cell borders caused by numerous bacteria adhering to them = often described as having shaggy edges nucleus may or may not be visible
Pigmented Casts: Hemoglobin
appear yellow to brown accompanied by hematuria
Neutrophils: Microscopic appearance
approx. 14 um in diameter, but range from 10 to 20 um, depending on the tonicity of the urine larger than erythrocytes similar in size to epithelial cells characteristic cytoplasmic granules and lobed or segmented nuclei unstained = grayish hue and appear grainy may occur singly or aggregated in clumps; clumping, which often occurs in acute inflammatory conditions, makes their enumeration difficult fresh urine specimens = features readily apparent by brightfield microscopy
Eosinophils vs neutrophils
are slightly larger than neutrophils and have bilobed nuceli when specifically requested, eosinophils should be centrifuged and stained using Hansel stain
What makes neutrophils hard to distinguish from renal tubular cells?
as neutrophils age they begin to disintegrate, their lobed nuclei fuse, and they can resemble a mononuclear cells; these changes make it difficult to distinguish them from renal tubular collecting duct cells
How are observed Trichomonads reported?
as present or not
How are urinary casts formed?
as the contents of the tubular lumen become concentrated, uromodulin forms fibrils that attach it to the lumen cells, holding it temporarily in place while it enmeshes into its matrix many substances that are present; any urinary component, whether chemical or a formed element, can be found incorporated into a cast; eventually the formed cast detaches from the tubular epithelial cells and is flushed through the remaining portions of the nephron with the lumen fluid
RBCs present microscopically but a chemical screen for blood is negative
ascorbic acid interference should be suspected if ascorbic acid is ruled out, it is possible that the formed elements observed are not RBCs but a "look-alike" component such as yeast or monohydrate calcium oxalate crystals; in this case the identity should be confirmed by an alternative technique such as staining or using polarizing microscopy
Bacterial Casts: correlations?
associated with bacterial pyelonephritis
Cellular Casts: WBC casts: correlations?
associated with infectious disease (e.g., bacterial or viral pyelonephritis) and inflammatory disorders (e.g., interstitial nephritis, lupus erythematosus, glomerulonephritis) if glomerular origin = red blood cell casts will be present too and in greater numbers than the WBCs if tubular origin = bacteriuria, varying degrees of proteinuria and hematuria accompany WBC casts
Fatty Casts: correlations?
associated with nephrotic syndrome, diabetic nephropathy (acute tubular necrosis and crush injuries) may be present with acute tubular necrosis and crush injuries with disruption of body fat oval fat bodies often indicate renal tubular cell death accompanied by significant proteinuria
Other Inclusion Casts: crystal casts: correlations?
associated with renal calculi (kidney stones) formation or drug precipitation due to insufficient hydration indicates crystal precipitation within the tubules, which can damage tubular epithelium as well as cause tubular obstruction = varying amounts of hematuria usually accompany crystalline casts in the urine sediment
When the laboratorian performs the microscopic examination of urine sediment, which of the following are enumerated using low-power magnification? a. bacteria b. casts c. red blood cells d. renal tubular cells
b. casts
Mucous threads can be difficult to differentiate from a. fibers b. hyaline casts c. pigmented casts d. waxy casts
b. hyaline casts
Which of the following urinary tract structures are NOT lined with transitional epithelium? a. bladder b. nephrons c. renal pelves d. ureters
b. nephrons
Which of the following does NOT affect the formation of urinary crystals within nephrons? a. the pH of the ultrafiltrate b. the diameter of the tubular lumen c. the flow of urine through the tubules d. the concentration of solutes in the ultrafiltrate
b. the diameter of the tubular lumen
Which of the following statements regarding the characteristics of urinary fat is true? a. cholesterol droplets stain with Sudan III stain b. triglyceride or neutral fat stains with Oil Red O stain c. cholesterol droplets do not form a Maltese cross pattern under polarized light d. triglycerides and neutral fat are anisotropic and form a Maltese cross pattern under polarized light
b. triglyceride or neutral fat stains with Oil Red O stain
Bacterial Casts: microscopic features?
bacteria within matrix usually include leukocytes (so are actually mixed casts)
Crystals in normal urine solutes: acid urates (Na, K, NH4): microscopic appearance?
balls or spheres; resemble biurates; strong birefringence
Why are the distal and collecting tubules the site of most cast formation?
because acidification and concentration of urine occur in these tubules
Why is it important to report the presence of sperm in urine from females?
because it could potentially identify sexual abuse in underage and other vulnerable females; this information enables the health care provider to appropriately intervene, if necessary
Abnormal Crystals of Metabolic Origin: cholesterol: solubility characteristics?
because of their organic composition they are soluble in chloroform and ether
What do convoluted renal tubular cells look like when phase-contrast microscopy is used?
because the cytoplasm is coarsely granular, their nuclei are not readily visible when phase-contrast is used, and these cells can resemble granular casts
Pigmented Casts: Bilirubin
colors all urine sediment yellow- or golden-brown
Why can visualization of urine sediment components be difficult when brightfield microscopy is used? How is this remedied?
because the refractive index of urine and some sediment components are similar, lacking sufficient contrast for optimal viewing staining changes the refractive index of formed elements and increases their visibility another approach is to change they type of microscopy, which can also facilitate visualization of low-refractibility components or can be used to confirm the identity of suspected substances such as fat
Why are waxy casts often referred to as renal failure casts?
because they are most frequently found in patients with chronic renal failure
Why is it important to identify and report medication crystals if they are occurring in vivo? How are adverse effects be prevented?
because they can cause kidney damage treatments such as increased hydration or the infusion of pH-adjusting agents
Why must the centrifuge brake not be used?
because this will cause the sediment to resuspend, resulting in erroneously decreased numbers of formed elements in the concentrated sediment
neutrophils in hypertonic urine
become small as water is lost osmotically from the cells, but they do not crenate
Which crystals are from a metabolic origin?
bilirubin cystine tyrosine and leucine cholesterol
Classification of Urinary Casts: Pigmented
bilirubin hemoglobin myoglobin
Transitional cells: where are they located?
bladder ureters renal pelves renal calyces males = majority of urethra (except distal portion)
Cellular Casts: Red blood cell casts: chemical examination correlation?
blood positive protein positive
Contaminants: Starch
body powders, protective gloves
Classification of Urinary Casts: Size
broad
How do increased numbers of leukocytes usually get into urine?
by active ameboid movement through tissues and epithelium
How are bilirubin crystals confirmed?
by correlation with the chemical examination--crystals can only be present if the chemical screen for bilirubin is positive
How do you identify the species of yeast?
by fungal culture
How is semiquantitation performed during microscopic examination of leukocytes?
by observing 10 representative high-power fields and determining the average number of WBCs present in each field normal = 0 to 8 WBCs per high-power field or approx. 10 WBCs per microliter of urine sediment
How is hemosiderin identified in the urine sediment and in tissues?
by the Prussian blue reaction, also called Rous test
How are monocytes/macrophages identified more easily?
by using supravital stains or by making a cytocentrifuged preparation followed by Wright's or Papanicolaou's stain they can be detected by the chemical screening test for leukocyte esterase if present in sufficient numbers because they contain azurophilic granules
Which of the following statements about red blood cells in urine is true? a. red blood cells crenate in hypotonic urine b. red blood cell remnants are called "ghost cells" c. alkaline and hypotonic urine promotes red blood cell disintegration d. dysmorphic red blood cells often are associated with renal tubular disease
c. alkaline and hypotonic urine promotes red blood cell disintegration
The following are initial results obtained during a routine analysis. Which results should be investigated further? a. negative protein; 0 to 2 hyaline casts b. urine pH 6.0; calcium oxalate crystals c. cloudy, yellow urine; specific gravity 1.050 d. amber urine with yellow foam; negative bilirubin by reagent strip; positive Icotest
c. cloudy, yellow urine; specific gravity 1.050
cytodiagnostic urinalysis
can play an important role in early detection of renal allograft rejection and in the differential diagnosis of renal disease involves making a 10:1 concentration of first morning urine specimen, followed by cytocentrifugation of the urine sediment and Papanlaou's staining uniquely valuable in identification of blood cell types, cellular fragments, epithelial cells (atypical and neoplastic), cellular inclusions (viral and nonviral), and cellular casts
Which urine components are viewed using low power?
casts squamous epithelial cells abnormal crystals
What are cylindroids? What do they result from?
casts that are well formed at one end but are tapered or have a tail at the other end result from (1) incomplete cast formation, (2) formation of a cast in a tubule where the lumen width differs (naturally or from disease), or (3) cast disintegration
Mixed Cell Casts
casts with multiple cell types within the matrix often enumerated and reported as cellular casts, with their composition provided in the report
neutrophils in hypotonic urine--"glitter cells"
causes them to swell and become spherical balls that lyse as rapidly as 50% in 2 to 3 hours at room temperature in these large swollen cells, brownian movement of the refractile cytoplasmic granules is often evident = "glitter cells"
What is the purpose of staining?
changes the refractive index of formed elements and increases their visibility
Microscopic Organism in Urine: Bacteria
characteristic features: Bacilli (rods) or cocci (spheres); single organisms, in chains, or in groups (e.g., diplococci, tetrads) UA correlations: WBCs increased; WBC clumps and macrophages with severe infection; LE +/- and nitrite +/-
Microorganisms in urine: parasites: Schistosoma haematobium
characteristic features: football shaped or ovoid eggs with a spike at one end; thick, transparent cell wall; larva visible inside UA correlations: blood positive; RBCs increased, hematuria
Microorganisms in urine: parasites: Enterobius vermicularis (pinworm)
characteristic features: football-shaped or ovoid eggs; 50-60 um long by 20-30 um wide; transparent cell wall, larva visible inside UA correlations: none; fecal contaminant
Microorganisms in urine: parasites: Giardia lamblia
characteristic features: ovoid eggs, 8-12 um long; smooth, well-defined cell wall UA correlations: none; fecal contaminant most often acquired by drinking contaminated water
Microorganisms in urine: Yeast
characteristic features: ovoid, colorless, refractile cells; no nucleus; characteristic budding forms; pseudohyphae may be present UA correlations: WBCs increased; LE +/-
Microorganisms in urine: Trichomonads
characteristic features: pear-shaped; average length = 15 um; 4 anterior flagella, 1 posterior axostyle, undulating membrane; identify based on characteristic flitting or jerky motion UA correlations: WBCs increased, WBC clumps present; LE +/-
Crystal composition: colorless rectangular plates with notched corners
cholesterol
WBCs: physical findings
cloudy = WBCs in increased amounts strong, foul odor = extent of infection is great macroscopic exam of sediment button = large amount of gray-white material = the concentrated leukocytes
Hemosiderin unstained
coarse yellow-brown granules; difficult to distinguish from amorphous crystalline material
Leukocytes with cytoplasmic granulation vs collecting duct cells
collecting duct cells = large, dense nuclei and polygonal shape staining with Sternheimer-Malbin stain or toluidine blue
Renal Tubular Cells: Location?
collecting duct cells and convoluted tubular cells
Which epithelial cell type is "polygonal; large nucleus"?
collecting tubular cell
Which epithelial cells can be found in urine sediment as an intact fragment or sheet of cells?
collecting tubular epithelium and transitional epithelium
Abnormal Crystal of Iatrogenic Origin: Medications: Ampicillin: color?
colorless
Abnormal Crystals of Iatrogenic Origin: medications: radiographic contrast media: color?
colorless
Abnormal Crystals of Metabolic Origin: cholesterol: color?
colorless
Abnormal Crystals of Metabolic Origin: cystine: color?
colorless
Crystal in normal urine: calcium carbonate: color?
colorless
Crystal in normal urine: magnesium phosphate: color?
colorless
Crystals in normal urine: Triple phosphate: color?
colorless
Crystals in normal urine: calcium phosphate: color?
colorless
Crystals of normal urine: Calcium oxalate: color?
colorless
Crystals in normal urine: amorphous phosphate: color?
colorless large quantities = appear cloudy
Crystals in normal urine solutes: monosodium urate: color?
colorless to light yellow
Crystals of normal urine: uric acid: color?
colorless to yellow to golden brown
Crystals of normal urine solutes: amorphous urates: color?
colorless to yellow-brown
Hyaline Cast: microscopic features?
colorless, fibrillar matrix--homogenous uromodulin protein matrix low refractile index--difficult to see using brightfield microscopy--appear colorless in unstained sediment with rounded ends and in various shapes and sizes phase-contrast or interference contrast--their fibrillar protein matrix is more apparent and often includes some fine granulation
Casts: morphology?
cylindrical microscopically appear thicker in the middle than along their edges parallel sides with ends that can be rounded or straight shape and size vary greatly depending on the diameter and shape of the tubule in which they form; the narrower the tubule lumen, the narrower is the resulting cast
Hyaline casts vs mucus
cylindrical composition of casts and their rounded ends
Crystal composition: colorless hexagonal plates
cystine
What type of microscopy/staining technique can be used to specifically identify convoluted tubular cells?
cytocentrifugation followed by Papanicolaou's staining of the urine sediment then viewed using Brightfield microscopy
What should a technologist do if they find it difficult to identify bacteria in a certain urine sediment?
cytospin preparation followed by Gram staining
When urine sediment is viewed, what are stains and various microscopic techniques are used to 1. enhance the observation of fine detail 2. confirm the identity of suspected components 3. differentiate formed elements that look alike 4. facilitate the visualization of low-refractile components a. 1, 2, and 3 are correct b. 1 and 3 are correct c. 4 is correct d. all are correct
d. all are correct
Hemoglobin is a protein that will a. not react in the protein reagent strip test b. interfere with the protein reagent strip test, producing erroneous results c. always contribute to the protein reagent strip results, regardless of the amount of hemoglobin present d. contribute to the protein reagent strip result only when large concentrations of hemoglobin are present
d. contribute to the protein reagent strip result only when large concentrations of hemoglobin are present
Which of the following are NOT standardized when commercial systems are used for the processing and microscopic examination of urine sediment? a. microscopic variables, such as the number of focal planes b. the concentration and volume of the urine sediment prepared c. the volume of the urine sediment dispensed for microscopic viewing d. identification and enumeration of formed elements in the urine sediment
d. identification and enumeration of formed elements in the urine sediment
Which statement regarding lymphocytes found in urine sediment is correct? a. they are not normally present in the urine b. they produce a positive leukocyte esterase test c. their number is increased in patients with drug hypersensitivity d. their number is increased in patients experiencing kidney transplant rejection
d. their number is increased in patients experiencing kidney transplant rejection
Fat can be found in the urine sediment in all of the following forms EXCEPT a. within casts b. within cells c. as free-floating globules d. within hemosiderin granules
d. within hemosiderin granules
Waxy Casts: Microscopic features?
ground glass appearance high refractive index (easy to see using brightfield) homogenous matrix cracks or fissures from margins or along length of cast often present often broad indicating their formation in dilated tubules or collecting ducts unstained = colorless, gray, or yellow Sternheimer-Malbin stain = darker pink than hyaline casts and have a diffuse, ground-glass appearance
Contaminants: Fibers
hair, cotton, other fabric threads can be large with distinct edges and are often moderately to highly refractile
How can you confirm the presence of a fistula?
have the patient ingest charcoal particles; after ingestion, the patient's urine is collected for 24 hours or longer, and the entire collection is concentrated by centrifugation; the resultant urine sediment is thoroughly screened microscopically for the presence of charcoal particles; if charcoal particles are found, they confirm the diagnosis of a fistula between the bowel and the urinary tract
What do the presence of cystine crystals indicate?
hereditary diseases of cystinuria or cystinosis
Abnormal Crystals of Metabolic Origin: cystine: microscopic appearance?
hexagonal plates, often layered; weak to moderate birefringence that varies with thickness; tend to clump
What is the distinguishing feature of lipids in urine sediment?
high refractility
Abnormal Crystals of Iatrogenic Origin: medications: radiographic contrast media: solubility characteristics?
highly soluble in water = readily excreted in urine
Macrophages are derived from monocytes. what are they often called when they reside in interstitial tissues?
histiocytes
transitional and renal epithelial cells: hpf or lpf?
hpf
Classification of Urinary Casts: Homogenous matrix composition
hyaline casts waxy casts
Which elements of urine are hard to see using brightfield microscopy?
hyaline casts, mucous threads, bacteria
Pigmented Casts: microscopic features?
hyaline matrix distinct coloration characterized by incorporation of the pigment within the casts hemoglobin, myoglobin, bilirubin (bile) casts
What promotes the disintegration of casts in urine sediment?
hypotonic (i.e. diluted) and alkaline urine
Gram stain
identifies and classifies bacteria as gram-negative or gram-positive aids in the identification of bacterial and fungal casts gram-positive = pink gram-negative = dark purple
Prussian blue reaction stain
identifies hemosiderin, which can be free-floating, in epithelial cells, or in casts stains the iron of hemosiderin granules a characteristic blue
Why must you check all centrifuge settings before use?
if other lab personnel use the centrifuge for other tests besides urinalysis, the settings will be different and the resultant urine sediments can show dramatic variations in their formed elements because of processing differences in speed, time, or braking
Granular casts: shape, size, color?
in brightfield microscopy (they have a high refractive index) they often appear colorless to shades of yellow; all shapes and sizes
Maltese cross pattern
in polarizing microscopy, cholesterol droplets appear as orbs against a black background divided into four quadrants by a bright Maltese-style cross starch granules also do this, but they can be distinguished from cholesterol by using brightfield microscopy
What is one disadvantage of the use of the Sternheimer-Malbin stain?
in strongly alkaline urines, this stain can precipitate, which obstructs the visualization of sediment components
blood casts/muddy brown casts
in sufficient urine stasis, RBC casts degenerate into pigmented, granular casts contain no distinct RBCs in their matrix because of cell lysis and degeneration can also occur in vitro if the urine specimen is old and improperly stored can also occur by overly vigorous resuspension of the urine sediment = casts break into pieces
Renal bleeding: below the kidney or due to contamination
increased # of RBCs without casts or proteinuria
Lower urinary tract infections (below kidney)
increased WBCs but without cellular casts; if protein is present, it is usually at a low level
Crystals of normal urine: uric acid: comments/clinical significance?
increased excretion following chemotherapy and gout
Renal: collecting duct cells: small ducts AND large ducts: clinical significance?
increased number with ischemic events: shock, anoxia, sepsis trauma fragments of undisrupted tubular epithelium (at least 3 cells sloughed together with a bordering edge intact); in addition to these renal cell fragments, pathologic casts (e.g., granular, waxy, renal tubular cell) and increased #s of blood cells are usually present renal diseases, including nephritis, acute tubular necrosis, kidney transplant rejection, and salicylate poisoning
Renal bleeding: either glomerular or tubular
increased numbers of RBCs along with red blood cell casts
Casts: Correlation with physical and chemical examinations
increased numbers of casts or abnormal casts must be accompanied by proteinuria, although degree of proteinuria can vary (in contrast, proteinuria can occur without cast formation) if RBC casts are identified, the chemical test for blood should be positive, or its negativity accounted for before these casts are reported leukocyte casts may or may not be associated with a positive leukocyte esterase test, depending on the types and numbers of leukocytes present leukocyte casts are often accompanied by bacteriuria, the most common causative agent of UTI; in these cases nitrite may also be positive bile-pigmented casts should be accompanied by a positive chemical test for bilirubin; similarly, hemoglobin-or myoglobin-pigmented casts should be accompanied by a positive chemical test for blood
Transitional cells: clinical significance?
increased numbers with infection or inflammation of bladder, ureters, renal pelves, or male urethra cell clusters or sheets can occur after catheterization or instrumentation of urinary tract (e.g., cytoscopy)
Renal: convoluted tubular cells: distal tubular cells AND proximal tubular cells: clinical significance?
increased numbers with toxic events: heavy metals, hemoglobinuria, myoglobinuria; poisons; drugs found in urine as a result of acute ischemic or toxic renal tubular disease (e.g., acute tubular necrosis) from heavy metals or drug (aminoglycosides) toxicity
Cast look-alikes: Mucous threads: correlations?
increased with infection or inflammation of urinary tract
Size casts: Broad
indicate cast formation in dilated tubules or in the large collecting ducts because several nephrons empty into a single collecting duct, cast formation here indicates significant urinary stasis due to obstruction or disease poor prognosis = presence of many broad casts may be of any type; however, when a significant amount of urinary stasis is involved, they principally present as granular or waxy casts in chronic renal diseases in which nephrons have sustained previous damage, broad hyaline casts may be encountered
Waxy casts: correlations?
indicate prolonged stasis and tubular obstruction believed to represent an advanced stage of other casts that are transformed during urinary stasis, taking as long as 48 hours or more to form associated with neprhotic syndrome and chronic renal disease (glomerulonephritis, pyelonephritis), transplant rejection (renal allograft), and malignant hypertension
Cellular Casts: Red blood cell casts: microscopic features?
intact RBCs within matrix unstained = yellow or red-brown (red brown=RBC degeneration with hemoglobin oxidation) Sternheimer-Malbin stained = intact RBCs may appear colorless or lavender in a pink homogenous matrix
Cellular Casts: WBC casts: microscopic features?
intact WBCs within matrix highly refractile = brightfield microscopy is used use supravital stains or contrast microscopy when they are degenerative and hard to identify = help differentiate from renal tubular cells
What happens to cholesterol when you add stain to it?
it does not stain; they are identified by their birefringence--Maltese cross pattern
How are contaminating lipids, such as lubricants, ointments, creams, and lotions identified?
lack of associated abnormalities (proteinuria, fatty casts, oval fat bodies) and by (1) their presence only as free-floating globules, (2) homogeneity, (3) lack of structure, and (4) size (often droplets coalesce to become unusually large)
Cast with Inclusions: Granular Casts: coarsely granular casts: microscopic features?
large, coarse granules within matrix granules primarily from degenerating cells, trapped cellular debris, and metabolic by-products
Abnormal Crystals of Metabolic Origin: tyrosine and leucine: color?
leucine: dark yellow to brown tyrosine: colorless to yellow
Abnormal Crystals of Metabolic Origin: tyrosine and leucine: comments/clinical significance?
leucine: rare; liver disease, aminoaciduria; accompanies tyrosine; crystals induced by storage at 2*C to 8*C tyrosine: rare; liver disease, aminoaciduria; crystals induced by storage at 2-8*C present in the urine of patients with overflow aminoacidurias--rare inherited metabolic disorders; in these disorders, the concentrations of these amino acids in the blood are high (aminoacidemia), resulting in increased renal excretion although rare, these crystals have been observed in the urine of patients with severe liver disease confirmed before reported, by chromatographic methods require refrigeration to force them out of urine; rarely seen because of quick turnaround time for urinalyses; of the two, tyrosine is found more often because it is less soluble than leucine
Abnormal Crystals of Metabolic Origin: tyrosine and leucine: solubility characteristics?
leucine: soluble in alkali tyrosine: soluble in alkali
Which crystals are from an iatrogenic origin?
medications: ampicillin, indinavir, sulfonamides, radiographic contrast media
How are crystals identified?
microscopic appearance and pH at which they are present
WBC distribution in urine in healthy individuals
mirrors that of peripheral blood
Monocytes vs macrophages
monoctyes = 20-40 um, single large nucleus that is round to oval and often indented; abundant cytoplasm with azurophilic granules; large vacuoles containing debris macrophages = 30-40 um; derived from monocytes; they can be as small as 10 um or as large as 100 um; when they are small they are hard to distinguish from neutrophils due to their oval nuclei and azurophilic granules; usually have irregular kidney shaped nuclei and abundant cytoplasm
Red Blood Cells (Erythrocytes): Look-alike elements
monohydrate calcium oxalate crystals yeast cells
Hyaline Cast: correlations?
most commonly observed increased numbers with strenuous exercise, stress, dehydration, fever accompany other pathologic casts in urine sediment in renal disease and in cases of congestive heart failure
Cellular: Renal Tubular Cell casts: correlations?
most often associated with acute tubular necrosis but present in all types of renal disease often accompanied by proteinuria and granular casts nonspecific markers of tubular injury
negative LE test with increased #'s of WBCs present in urine
must ensure that the cells are granulocytic leukocytes, and that reagent strips are functioning properly although the LE screening test usually detects 10 to 25 WBCs per microliter, the amount of esterase present may be insufficient to produce a positive response owing to hydration, hypotonic urine could cause the leukocyte esterase to be diluted such that it is below the detection limit of the LE reaction
Triglycerides
neutral fat composed of glycerol backbone with three fatty acids esterified to it
Crystal in normal urine: magnesium phosphate: pH?
neutral or alkaline urine
Crystals in normal urine: calcium phosphate: pH?
neutral or slightly alkaline urine
What WBC is the one that predominates in urine and peripheral blood? When are the other WBCs the predominant ones found?
neutrophils with some renal conditions, other leukocytes predominate in urine; for example, in acute interstitial nephritis caused by drug hypersensitivity, the predominate leukocytes observed are eosinophils, whereas in renal allograft rejection, lymphocytes predominate
List the 5 types of WBCs that can be found in urine.
neutrophils basophils eosinophils lymphocytes monocytes (macrophages)
Are fats normally found in urine?
no it implicates renal disease because changes have occurred in the glomeruli such that triglycerides and cholesterol from the bloodstream are now passing the glomerular filtration barriers with the plasma ultrafiltrate
Crystals in normal urine: calcium phosphate: comments/clinical significance?
no clinical significance dibasic = common monobasic = rare
Hyaline casts with a single epithelial or blood cell in its matrix
no diagnostic significance
Squamous cells: clinical significance?
no diagnostic significance increased numbers are due to poor collection technique (i.e., not a clean catch)
Are urine contaminants reported?
no, only sperm in urine is reported
Sperm in male urine samples
nocturnal emissions from normal or retrograde ejaculation; simple reported as present
Hyaline Cast: chemical examination correlation?
none
RBC counts
normal = 0-3 per high-power field or 3-12 per microliter of urine sediment
RBCs--Clinical significance: Hematuria
numerous conditions can result in hematuria smoking as well as exercise can cause hematuria anticoagulant drugs and drugs that induce toxic reaction, such as sulfonamides, can also cause increase RBCs numbers in urine sediment any condition that results in inflammation or that compromises the integrity of the vascular system throughout the urinary tract can result in hematuria specimens contaminated with blood from vaginal secretions or hemorrhoidal blood can falsely imply hematuria
neutrophils--myelin forms (aging/disintegrating neutrophil)
numerous finger-like projections protruding from the cell surfaces result from breakdown of the cell membrane as these cells die, additional vacuolization, rupturing, or pseudopod formation may be observed
Dismorphic or distorted erythrocytes
occasionally present with normal erythrocytes in the urine of healthy individuals increased #'s of particularly acanthocytes are associated with glomerular disorders sickle cells = sickle cell disease
What do bacteria found in urine often reflect?
often reflects contamination from bacteria in the skin, vagina, and GI tract
KOH preparation
often used to detect yeast, hyphae, and other fungal cells in vaginal secretions
What types of fat stains? Which ones do not?
only neutral fats (e.g., triglycerides) stain cholesterol and cholesterol esters do not stain and must be confirmed by polarizing microscopy
Pigmented Casts: Urobilirubin
orange-brown color to urine, does not color the formed elements of the sediment
What are renal tubules called when they are engorged with absorbed fat from the tubular lumen or are degenerating their own intracellular lipids?
oval fat bodies
Sperm
oval heads approx. 3-5 um long and thin, threadlike tails about 40-60 um long; singly or in clumps of mucus
How are sulfonamides differentiated from ammonium biurate crystals?
pH, solubility, chemical confirmatory test; patient's current/past medications
What is Trichomonas vaginalis the most common cause of?
parasitic gynecologic infection in female patients represent infection of vagina and/or urethra; males = no symptoms
Hyaline casts stained with Sternheimer-Malbin stain
pink and edges are more clearly defined
Crystals of normal urine: uric acid: microscopic appearance?
pleomorphic; often flat, diamond, or rhombic; cubic and barrels forms; can layer or form rosettes; color varies with thickness; strong birefringence
What are broad granular casts considered to be an indicator of?
poor prognosis
What promotes the development of vaginal yeast infections?
pregnancy use of oral contraceptives diabetes mellitus
eosinophils and acute allograft rejection
presence of large #'s of eosinophils in a kidney biopsy specimen is considered a poor prognostic indicator
Crystals of normal urine solutes: amorphous urates: pH?
present in acidic or neutral conditions
Crystals in normal urine solutes: acid urates (Na, K, NH4 salts of uric acid): pH?
present in neutral to slightly acidic urine
Crystals of normal urine: uric acid: pH?
present only if urine pH is less than 5.7; at a pH higher than 5.7 uric acid is in its ionized form as urate and forms of urate salts (e.g., amorphous urates, sodium urate)
Crystals in normal urine solutes: monosodium urate: pH?
present when urine is acidic
Crystals in normal urine: Triple phosphate: microscopic appearance?
prism with 3 or 6 sides ("coffin lids") or less common flat, fern-like form (associated with rapid formation or prisms dissolving); moderate birefringence
Cast with Inclusions: Granular Casts: finely granular casts: chemical examination correlations?
protein +/- blood +/-
Waxy Casts: Chemical correlation?
protein positive blood +/-
Bacterial Casts: chemical examination correlation?
protein positive LE positive blood +/- nitrite +/-
Cast with Inclusions: Granular Casts: coarsely granular casts: chemical examination correlation?
protein positive blood +/-
Cellular: Renal Tubular Cell casts: chemical examination correlation?
protein positive blood +/-
Abnormal Crystals of Metabolic Origin: bilirubin: comments/clinical significance?
rare; crystals induced by storage at 2-8*C; bilirubinuria associated with liver disease or obstruction classified as abnormal because bilirubinuria indicates a metabolic disease process; however, because they from in the urine after excretion and cooling, they are not frequently observed and they are not usually reported
Abnormal Crystal of Iatrogenic Origin: Medications: Ampicillin: comments/clinical significance?
rarely observed with adequate hydration; high-dose antibiotic therapy
Crystal in normal urine: magnesium phosphate: comments/clinical significance?
rarely seen but present in normal urine
Motile sperm in urine
recent intercourse or ejaculation
Which type of urinary cast is diagnostic of glomerular or renal tubular damage?
red blood cell casts
Classification of Urinary Casts: Cellular inclusions
red blood cells leukocytes renal tubular epithelial cells mixed cells bacteria
Which urine components are viewed using high power?
red blood cells white blood cells transitional epithelial cells renal epithelial cells bacteria and yeast
Red urine
red blood cells present
WBCs: Look-alike elements
renal tubular epithelial cells (collecting ducts) dead trichomonads crenated red blood cells
What do casts reflect the status of?
renal tubules
Cast look-alikes: Mucous threads: microscopic features?
ribbon-like with twists and folds ends are serrated or regular low refractive index irregular can be misidentified as hyaline casts
What is the most commonly encountered bacteria in urine?
rod-shaped (bacilli) but coccoid forms also present
How is Trichomonas vaginalis transmitted?
sexually
Transitional cells: morphology?
shape varies with site: superficial cells--round or pear-shaped; large intermediate layer--smaller and rounder single basal layer--small, elongated (or columnar like) moderate amount of cytoplasm distinct cell borders that appear "firm" nucleus = approx. 8-14 um, round or oval, centrally located
Renal: collecting duct cells: large ducts: morphology?
shape: columnar nucleus: approx. 6-8 um, eccentric
Renal: convoluted tubular cells: proximal tubular cells: morphology?
shape: large, oblong, or cigar-shaped with indistinct cell membrane (note: resemble granular casts with single inclusion) cytoplasm: grainy nucleus: usually eccentric, can be multinucleated; dense chromatin pattern
Renal: convoluted tubular cells: distal tubular cells: morphology?
shape: oval to round cytoplasm: grainy nucleus: small, dense, round, central, or eccentric
Renal: collecting duct cells: small ducts: morphology?
shape: polygonal or cuboidal (look for a flat edge) nucleus: large, covers 60-70% of cell
Squamous cells: morphology?
shape: thin, flagstone-shaped with distinct cell membranes abundant cytoplasm; cytoplasmic granulation (keratohyalin granules) increases as cell ages nucleus: approx. 8-14 um, centrally located; can be anucleated or multinucleated
Pigmented Casts: Myoglobin
similar in appearance to hemoglobin casts = differentiation requires patient history with a possible diagnosis of rhabdomyolysis or confirmation that myoglobin is present
Trichomonas vaginalis vs leukocytes and renal tubular cells
similar in size differenitated based on motility
Bacteria--microscopic appearance?
single or in chains, depending on species present wet prep--their motility often distinguishes bacteria from amorphous substances that may be present
Why are calcium carbonate crystals sometimes mistaken for bacteria? How are they differentiated?
size and occasional rod shape strong birefringence under polarizing microscopy
What is the differentiation of proximal convoluted tubular cells and distal convoluted tubular cells based on?
size and shape
Abnormal Crystal of Iatrogenic Origin: Medications: Indinavir: microscopic appearance?
slender, feather-like crystals that aggregate into wing-like bundles which can also associate into a rosette-like or cross form; moderate to strong birefringence
Thomas Addis developed a procedure to quantitate formed elements in a 12-hour overnight urine collection. What was the purpose of this test, the Addis count? What indicated disease progression?
to follow the progress of renal disease, particularly acute glomerulonephritis increased numbers of erythrocytes, white blood cells, or casts in the urine disease indicated if the number of RBCs exceeded 500,000; the number of WBCs exceeded 2 million; or the number of casts exceeded 5000
Which epithelial cell type is "round, pear-shaped, or columnar with a small oval to round nucleus"?
transitional epithelial cell
All of the following can be found incorporated into a cast matrix EXCEPT a. bacteria b. crystals c. transitional epithelial cells d. white blood cells
transitional epithelial cells
Crystal composition: colorless "coffin-lid" form
triple phosphate
What happens to triglycerides when you add Sudan III or Oil Red O?
turns orange or red
Red Blood Cells (Erythrocytes): Microscopic Appearance
typical form--smooth, biconcave disks, 6-8 um in diameter; no nucleus crenated forms--in concentrated urine (high SG) ghost cells--in dilute urine (low SG) dysmorphic forms and cell fragments
Crystals in normal urine solutes: monosodium urate: comments/clinical significance?
uncommon no clinical significance and are often reported as "urate crystals"
How are leucine crystal distinguished from fat globules?
unlike fat, leucine crystals do NOT stain with fat stains
monocyte/macrophage look-alikes
unstained they can be misidentified as renal tubular cells; they are similar in size and both are mononucleated; however monocytes/macrophages are spherical in urine whereas renal tubular cells have dense nuclei and tend to be polygonal in shape with one or more flat edges when monocytes/macrophages have ingested lipoproteins or fat, these globular inclusions are distinctly refractile; call oval fat bodies, these cells are impossible to distinguish from renal tubular cells that can also absorb fat; you have to use polarizing microscopy or fat stains to confirm the identity of the lipid inclusions
Crystal composition: colorless to yellow; diamond-shaped or rhombic; can form layers
uric acid
What happens if urine with urate salt crystals is acidified?
uric acid crystals form
Red Blood Cells (Erythrocytes): Correlation with physical and chemical examinations
urine color--note that a normal appearing urine can still have increased RBCs present blood reaction--can be negative owing to ascorbic acid interference; degree of interference varies with reagent strip brand
How are ammonium biurate crystals differentiated from sulfonamide crystals?
urine pH, a sulfonamide confirmatory test, solubility characteristics of the crystals
How are amorphous phosphates differentiated from amorphous urates?
urine pH, solubility characteristics, macroscopic appearance large quantities appear cloudy; the precipitate is white or gray, in contrast to the pink-orange color of amorphous urates unlike urates, amorphous phosphates have no clinical significance and can make microscopic examination difficult when a large quantity is present = can be minimized by keeping specimens maintained at room temperature and analyzed within 2 hours
Factors that require standardization in the microscopic examination of urine
urine volume used (e.g., 10 ml, 12 ml, 15 ml) speed of centrifugation (400 or 450 x g) time of centrifugation (5 minutes) concentration of sediment prepared (e.g., 10:1, 12:1, 15:1, 30:1) volume of sediment examined--determined by commercial slides used and microscope optical properties (i.e., ocular field number) result reporting--format, terminology, reference intervals, magnification used for assessment
Urinary casts are formed with a core matrix of _________.
uromodulin
Leukocytes vs RBCs and renal tubular epithelial cells
use 2% acetic acid solution or a 0.5% toluidine blue stain to reveal the nuclear details present to determine proper cell identification
Lymphocytes are usually not recognized because of their small numbers. What should you do to make them more readily apparent and identifiable?
use a supravital stain or do a cytodiagnostic urinalysis using Wright's or Papanicolaou's stain
crenated RBCs vs WBCs
use acetic acid or toluidine blue stain = easier to see the nuclei of WBCs
Polarizing microscopy
used to confirm the presence of cholesterol globules by their characteristic Maltese cross pattern aids in identification of crystals assists in differentiating "look-alike" component: RBCs vs monohydrate calcium oxalate crystals--polarize light for monohydrate calcium oxalate crystal but NOT for RBCs Casts, mucus vs fibers (clothing, diapers), plastic fragments--do NOT polarize light for casts, mucus, but DO for the other Bacteria vs. amorphous crystals (urates: strongly; phosphates: very weakly)--do NOT polarize light for bacteria but DO for the other Cells, cellular debris (membrane phospholipids) vs cholesterol globules, starch granules--do NOT polarize light for cells, cellular debris but DO for the other
In a manual microscopic examination, how are urine components assessed or enumerated?
using at least 10 low-power (lpf) or 10 high-power fields (hpf)
How are oval fat bodies positively identified?
using polarizing microscopy or fat stains such as Sudan III or Oil Red O
neutrophils--formation of blebs (aging/disintegrating neutrophil)
vacuoles develop within the cell periphery or on their outer membranes; they appear to be empty or may contain a few small granules as these changes continue, the blebs or vacuoles can detach and become free floating in the urine; they may also develop and remain within the cell, pushing the cytoplasm to one side and giving rise to large pale areas intracellularly
Fat vs RBCs
variation in size of fat globules aids in differentiation; RBCs do not stain with fat dyes and are not birefringent; lipids stain yellow-green/gold when stained with Sternheimer-Malbin stain
Starch--identification
vary greatly in size usually have a centrally located dimple not perfectly round; they have scalloped or faceted edges maltese pattern under polar microscopy similar to cholesterol; however the edges of the maltese pattern of starch are less defined
When the laboratorian is using brightfield microscopy, a urinary cast that appears homogeneous with well-defined edges, blunt ends, and cracks is most likely a _____________.
waxy cast
What characteristic best differentiates waxy casts from fibers that may contaminate urine sediment?
waxy casts do not polarize light; fibers do
When is crystal formation clinically significant?
when crystals are present in freshly voided urine, indicating formation in vivo
Even though hemoglobin is a protein, in most cases of hematuria, it does not contribute to the protein result obtained by the chemical reagent test strip. What results are obtained if it is contributing?
when the chemical reagent strip test for blood reads less than large (3+), hemoglobin is NOT causing or contributing to the protein result; when blood result is greater than or equal to large (3+), hemoglobin may be contributing to the protein reagent strip test results
Crystal in normal urine: calcium carbonate: solubility characteristics?
with acetic acid produces CO2 gas (effervescence)
Abnormal Crystals of Iatrogenic Origin: medication: sulfonamides: color?
yellow-brown
Crystals in normal urine solutes: acid urates (Na, K, NH4): color?
yellow-brown
Abnormal Crystals of Metabolic Origin: bilirubin: color?
yellow-brown high pigmented