Casts are reported as the average number per 10 low-power fields (lpfs).
RBCs and WBCs are reported as the average number per 10 high-power fields (hpfs).
Epithelial cells, crystals, and other elements are frequently reported in semiquantitative terms such as, rare, few, moderate, and many, or as 1+, 2+, 3+, and 4+.
Conversion of the average number of elements per lpf or hpf to the number per milliliter provide standardization among the various techniques in use.
Procedures should be completely documented and followed by all personnel.
Microscopic Elements | Physical | Chemical | Exceptions |
---|---|---|---|
RBCs | turbidity | + blood | number |
red color | hemolysis | ||
WBCs | turbidity | + protein | number |
+ nitrite | lysis | ||
+ leukocytes | |||
Epithelial Cells | turbidity | number | |
Casts | + protein | number | |
Bacteria | turbidity | pH | number and type |
+ nitrite | |||
+ leukocytes | |||
Crystals | turbidity | pH | number and type |
color |
Stain | Action | Function |
---|---|---|
Sternheimer-Malbin/Sedi-Stain/KOVA stain (crystal violet + safranin O) | delineates structure and contrasting colors of the nucleus and cytoplasm | identifies WBCs, epithelial cells, and casts |
0.5% toluidine blue | enhances nuclear detail | differentiates WBCs and renal tubular epithelial (RTE) cells |
2% acetic acid | lyses RBCs and enhances nuclei of WBCs | distinguishes RBCs from WBCs, yeast, oil droplets, and crystals; cannot be used for initial sediment analysis |
oil red O, Sudan III | stains triglycerides and neutral fats | identifies free fat droplets and lipid-containing cells and casts |
gram stain | differentiates gram-positive and gram-negative bacteria | identifies bacterial casts |
Hansel stain (methylene blue + eosin Y), Wright’s stain | stains eosinophilic granules | identifies urinary eosinophils |
Prussian blue stain | stains structures containing iron | identifies yellow-brown granules of hemosiderin in cells and casts |
Elements in Urinary Sediment | Usual Distinguishing Color of Stained Elements | Comments |
---|---|---|
RBCc | pink to purple (neutral pH), purple (alkaline pH) | |
WBCs | purple nucleus, purple granules in cytoplasm | |
glitter cells (Sternheimer-Malbin positive cells) | colorless or light blue nucleus, pale blue or gray cytoplasm | some may exhibit Brownian motion or erratic random movement |
renal tubular epithelial cells | dark blue-purple nucleus, light blue-purple cytoplasm | |
bladder tubular epithelial cells | blue--purple nucleus, light purple cytoplasm | |
squamous epithelial cells | dark orange-purple nucleus, light purple or blue cytoplasm | |
triglycerides, neutral fats | orange-red | |
cholesterol | not stained but polarized | |
hyaline casts | pale pink or pale purple | very uniform color; slightly darker than mucous threads |
coarse granular inclusion casts | dark purple granules in purple matrix | |
finely granular inclusion casts | fine dark purple granules in pale pink or pale purple matrix | |
waxy casts | pale pink or pale purple | darker than hyaline casts, but of a pale even color; distinct broken ends |
fat-inclusion casts | fat globules unstained in a pink matrix | rare; presence is confirmed if examination under polarized light indicates double refraction |
red cell inclusion casts | pink to orange-red | intact cells can be seen in matrix |
blood (hemoglobin) casts | orange-red | no intact cells |
bacteria | purple, but doesn’t stain if non-motile; blue for gram-positive, red for gram-negative | |
Trichomonas vaginalis | light blue-green | |
mucus | pale pink or pale blue | |
background | pale pink or pale purple |
Essentially all types of microscopes contain a lens system, illumination system, and a body consisting of a base, body tube and nosepiece.
Primary components of the lens system are the oculars, the objectives, and the coarse and fine adjustment knobs.
Most microscopes are designed to be parfocal, indicating that they require only minimum adjustment when switching among objectives.
Objectives are adjusted to be near the specimen and perform the initial magnification of the object on the mechanical stage.
The image then passes to the oculars for further resolution.
The distance between the slide and the objective is controlled by the coarse and fine focusing knobs located on the body tube.
The illumination system contains the light source, condenser, and field and iris diaphragms.
Illumination for the modern microscope is provided by a light source located in the base of the microscope.
The light source is equipped with a rheostat to regulate the intensity of the light.
Filters may also be placed on the light source to vary the illumination and wavelengths of the emitted light.
A field diaphragm contained in the light source controls the diameter of the light beam reaching the slide and is adjusted for optimal illumination.
A condenser located below the stage then focuses the light on the specimen and controls the light for uniform illumination.
The normal position of the condenser is almost completely up with the front lens of the condenser near the slide but not touching it.
The condenser adjustment (focus) knob moves the condenser up and down to focus light on the object.
Two adjustments to the condenser—centering and Köhler illumination—provide optimal viewing of the illuminated field.
An aperture diaphragm in the condenser controls the amount of light and the angle of light rays that pass to the specimen and lens, which affects resolution, contrast, and depth of the field of image.
To center the condenser and obtain Köhler illumination, the following steps should be taken:
Place a slide on the stage and focus the object using the low-power objective with the condenser raised.
Close the field diaphragm and lower the condenser until the edges of the field diaphragm are sharply focused.
Center the image of the field diaphragm with the condenser centering screws.
Open the field diaphragm until its image is at the edge of the field.
Remove an eyepiece and look down through the eyepiece tube.
Adjust the aperture diaphragm until approximately 75% of the field is visible.
Replace the eyepiece.
Objects to be examined are placed on a platform, referred to as the mechanical stage.
Routine preventive maintenance procedures on the microscope ensure good optical performance.
Bright-Field Microscopy
Phase-Contrast Microscopy
It makes use of phase-contrast objective lens and a matching condenser that create variations of contrast in the specimen image due to the various refractive indexes in the object.
The principle is that the scattered light from the substance being examined slows down in comparison to the rays passing through air (media), thereby decreasing the intensity of the light and producing contrast.
This is called phase difference and is affected by the thickness of the object, refractive index, and other light-absorbance properties.
The best contrast is obtained when the light that does not pass through the specimen is shifted one quarter of a wavelength and compared with the phase difference of the specimen.
Two phase rings that appear as “targets” are placed in the condenser and the objective.
Phase-contrast microscopy is accomplished by adaptation of a bright-field microscope with a phase-contrast objective lens and a matching condenser..
Phase rings must match and be concentric, so it is important to check that the objective and condenser mode are the same.
The diameter of the rings varies with the magnification.
It is particularly advantageous for identifying low refractive hyaline casts or mixed cellular casts, mucous threads and Trichomonas without the need to stain.
The image has the best contrast when the background is darkest.
Polarizing Microscopy
It passes through a filter which selects a wave with the selected polarization or orientation.
It then passes through the specimen to be examined, and can either have positive birefringence or negative birefringence.
The refracted light then passes through another filter rotated 90° to the first filter.
Interference-Contrast Microscopy
Interference-contrast microscopy provides a three-dimensional image showing very fine structural detail by splitting the light ray so that the beams pass through different areas of the specimen.
The light interference produced by the varied depths of the specimen is compared, and a three-dimensional image is visualized.
Two types of interference-contrast microscopy are available: modulation contrast (Hoffman) and differential interference contrast (Nomarski).
In the modulation-contrast microscope, a split aperture is placed below the condenser, a polarizer is placed below the split aperture, and an amplitude filter is placed in back of each objective.
The differential interference-contrast microscope uses prisms.
The advantage of interference-contrast microscopy is that an object appears bright against a dark background but without the diffraction halo associated with phase-contrast microscopy
These two types of microscopy provide layer-by-layer imaging of a specimen and enhanced detail for specimens with either a low or high refractive index.
However, it requires more extensive modifications to the bright-field microscope to perform this technique.
Dark-Field Microscopy
It makes use of an opaque disk that blocks the light from directly entering the objective, making the field of view black; however, as the light rays pass through the specimen, the light scatters, diffracts or reflects off the specimen and is captured by the objective lens.
The specimen appears light against the black background or dark-field.
It is used to enhance visualization of specimens that cannot be seen easily viewed with a bright-field microscope without staining.
In particular, it is used to identify the spirochete Treponema pallidum.
Fluorescence Microscopy
In this method, the specimen is illuminated with a light of a specific wavelength in the color spectrum that excites it’s fluorophores, which then emits a light of another wavelength that is is visualized with the use of special filters, called the excitation filter and the emission filter.
Powerful light sources are required and are usually either mercury or xenon arc lamps.
The excitation filter selects the excitation wavelength of light from a light source.
The emission filter selects a specific wavelength of emitted light from the specimen to become visible.
The filters are chosen to match the excitation and emission wavelengths of the fluorophore used to label the specimen.
A dichroic mirror reflects the excitation light to the specimen and transmits the emitted light to the emission filter, which is collected with the objective and imaged by the detector.
The fluorescent substance can be observed in the fluorescent microscope as a bright object against a dark background with high contrast when ultraviolet light source is used.
It is used to detect bacteria and viruses within cells and tissues through a technique called immunofluorescence.
They must be identified using high-power (40x) objective (x400 magnification) and reported as the average number per 10 high-power fields (hpfs)..
RBCs are the most difficult for students to recognize.
The morphology of RBCs can aid in determining the site of renal bleeding.
The number of cells present is indicative of the extent of damage to the glomerular membrane or vascular injury within the genitourinary tract.
WBCs are larger than RBCs, measuring an average of about 12 mm in diameter.
Characteristics and clinical implications differ depending on the type present.
Usually, fewer than five leukocytes per hpf are found in normal urine; however, higher numbers may be present in urine from females.
They represent normal sloughing of old cells from linings of the genitourinary system.
Three types of epithelial cells are seen in urine: squamous, transitional (urothelial), and renal tubular.
Squamous epithelial cells originate from the linings of the vagina and female urethra and the lower portion of the male urethra.
Squamous cells are the largest cells found in the urine sediment.
They may occasionally appear folded, and they contain abundant irregular cytoplasm and a prominent nucleus about the size of an RBC.
They are often the first structures observed when the sediment is examined under low-power magnification and can serve as a good reference for focusing of the microscope.
They are commonly reported in terms of rare, few, moderate, or many and in terms of low-power or high-power magnification based on laboratory protocol.
Difficulties with these cells include confusion with casts, disintegration in urine that’s not fresh and obstruction of RBCs and WBCs in examination.
They represent normal cellular sloughing and have no pathologic significance.
They are more frequently seen in urine from female patients.
Specimens collected using the midstream clean-catch technique contain less squamous cell contamination.
A variation of the squamous epithelial cell is the clue cell, which does have pathologic significance indicating vaginal infection by the bacterium Gardnerella vaginalis.
It is normally part of the vagina’s normal flora and small numbers of clue cells may be present in the urinary sediment, so routine testing is needed to monitor it’s number.
To be considered a clue cell, the bacteria should cover most of the cell surface and extend beyond the edges of the cell, giving a granular, irregular appearance.
Renal tubular epithelial (RTE) cells come from the renal tubules and have different characteristics depending on their area of origin.
RTE cells must be identified and enumerated using high-power magnification and reported as rare, few, moderate or many, or as the actual number per high-power field.
The presence of more than two RTE cells per high-power field indicates tubular injury, necrosis or glomerular disorder, and such specimens should be referred for cytologic urine testing.
It can absorb other substances as they pass through during reabsorption.
In cases of liver damage, they absorb bilirubin and appear a deep yellow color.
After episodes of hemoglobinuria (transfusion reactions, paroxysmal nocturnal hemoglobinuria, etc.), RTE cells absorb hemoglobin and convert it to yellow-brown hemosiderin granules.
The granules may also be seen free-floating in the sediment.
Confirmation of the presence of hemosiderin is performed by staining the sediment with Prussian blue.
RTE cells absorb lipids that are present in the glomerular filtrate and become oval fat bodies.
They appear highly refractile and difficult to observe, so staining and polarizing microscopy is used.
They are reported as the average number per hpf.
The droplets are composed of triglycerides, neutral fats, and cholesterol.
They are usually seen in conjunction with free-floating fat droplets.
They may be confused with large fat-laden histiocytes and “bubble cells”.
The cells from the proximal convoluted tubule (PCT) are larger, have a rectangular convoluted shape resembling casts, and a coarsely granular cytoplasm.
The cells from the distal convoluted tubule (DCT) are round or oval and have an eccentrically placed round nucleus.
The cells from the collecting duct are cuboidal with at least one straight edge and never round, and they have an eccentrically placed nucleus that is not easily visible.
Transitional epithelial cells originate from the lining of the renal pelvis, calyces, ureters, and bladder, and from the upper portion of the male urethra.
Transitional epithelial cells are smaller than squamous cells, have distinct centrally-located nuclei, and appear in several forms, including spherical, polyhedral and caudate.
Transitional cells are identified and enumerated using high-power magnification.
They are usually reported as rare, few, moderate, or many following laboratory protocol.
They are usually present in small numbers in normal urine, representing normal cellular sloughing.
Increased numbers of transitional cells seen singly, in pairs, or in clumps (syncytia) are present following invasive urologic procedures such as catheterization and are of no clinical significance.
Bacteria may be present in the form of cocci (spherical) or bacilli (rods).
They must be observed using high-power magnification and reported as few, moderate, or many per high-power field.
To be considered significant for UTI, bacteria should be accompanied by WBCs.
The presence of bacteria can be indicative of either lower or upper UTI and are routinely followed up with a specimen for quantitative urine culture.
Yeast cells are reported as rare, few, moderate, or many per hpf.
Yeast cells, primarily Candida albicans, are seen in the urine of diabetic immunocompromised patients and women with vaginal moniliasis.
The most frequent parasite encountered in the urine is Trichomonas vaginalis.
The ova of the bladder parasite, Schistosoma haematobium, will appear in the urine.
The presence of the ova from the pinworm Enterobius vermicularis indicates fecal contamination.
They are characterized by oval slightly tapered heads, long flagella-like tails and no motility.
Spermatozoa are occasionally found in the urine of both men and women following sexual intercourse, masturbation, or nocturnal emission.
They are rarely of clinical significance except in cases of male infertility or retrograde ejaculation in which sperm is expelled into the bladder instead of the urethra.
A positive reagent strip test for protein may be seen when increased amounts of semen are present.
Reporting protocols vary due to varied degrees of clinical significance and possible legal consequences.
Mucus is a protein material produced by the glands and epithelial cells of the lower genitourinary tract and the RTE cells.
It is characterized by thread-like structures with a low refractive index.
Mucous threads are reported as rare, few, moderate, or many per lpf.
Mucus is more frequently present in female urine specimens.
It has no clinical significance when present in either female or male urine.
They are formed within the lumens of the distal convoluted tubules and collecting ducts and are unique to the kidney.
The major constituent of casts is Tamm-Horsfall protein, a glycoprotein excreted by the RTE cells of the distal convoluted tubules and upper collecting ducts.
Under normal conditions, Tamm-Horsfall protein is excreted at a relatively constant rate but can increase from stress, exercise, dehydration and heat exposure.
As the cast forms, urinary flow within the tubule decreases as the lumen becomes blocked.
The width of the cast depends on the size of the tubule in which it is formed.
The appearance of a cast is also influenced by the materials present in the filtrate at the time of its formation and the length of time it remains in the tubule.
Hyaline casts consist almost entirely of Tamm-Horsfall protein.
The morphology of hyaline casts is varied, consisting of normal parallel sides and rounded ends, cylindroid forms and wrinkled or convoluted shapes, occasional with an adhering cell or granules.
Hyaline casts appear colorless in unstained sediments and have a refractive index similar to that of urine.
They are the most common type, and the presence of zero to two hyaline casts per lpf is considered normal with the exception of increases from stress, exercise, dehydration and heat exposure.
Hyaline casts are increased in acute glomerulonephritis, pyelonephritis, chronic renal disease and congestive heart failure.
Granular casts represent the disintegration of cellular casts and tubule cells or protein aggregates filtered by the glomerulus.
They are easily visualized under low-power microscopy; however, final identification should be performed using high power to determine the presence of a cast matrix.
The origin of the granules in nonpathologic conditions appears to be from the lysosomes excreted by RTE cells during normal metabolism.
Waxy casts have a brittle, highly refractive cast matrix caused by degeneration of the hyaline cast matrix and any cellular elements or granules contained in the matrix.
Waxy casts are more easily visualized than hyaline casts because of their higher refractive index.
Waxy casts are representative of extreme urine stasis, indicating chronic renal failure.
Broad casts, also known as renal failure casts, are a a mold of the distal convoluted tubules or collecting duct.
They represent extreme urine stasis and indicate the destruction (widening) of the tubular walls or the compromise of the collecting duct.
Bile-stained broad, waxy casts are seen as the result of the tubular necrosis caused by viral hepatitis.
RBC casts are more fragile than other casts and may exist as fragments or have a more irregular shape as the result of tightly packed cells adhering to the protein matrix.
RBC casts are easily detected under low power by their orange-red color, but high-power magnification is used to observe the presence of a cast matrix, thereby differentiating the structure from a clump of RBCs.
It is highly improbable that RBC casts will be present in the absence of free-standing RBCs and a positive reagent strip test for blood.
They indicate bleeding within the nephron, specifically damage to the glomerulus (glomerulonephritis) and nephron capillary structure.
WBC casts are composed of neutrophils and may appear granular with multilobed nuclei and irregular borders.
WBC casts are visible under low-power magnification but must be positively identified using high power, along with supravital staining.
The appearance of WBC casts in the urine signifies infection or inflammation within the nephron such as pyelonephritis (upper UTI) or glomerulonephritis, or nonbacterial inflammations such as acute interstitial nephritis.
Bacterial casts resemble granular casts containing bacilli both within and bound to the protein matrix, and sometimes with WBCs.
Their presence should be considered when WBC casts and many free WBCs and bacteria are seen in the sediment, and it is confirmed by performing a Gram stain on the dried or cytocentrifuged sediment.
It is usually indicative of pyelonephritis.
Epithelial cell casts are similar to hyaline casts but have attached RTE cells that produce them.
Casts containing RTE cells represent the presence of advanced tubular destruction, producing urinary stasis along with disruption of the tubular linings.
Fatty casts are highly refractile with a cast matrix containing few or many fat droplets and intact oval fat bodies attached to the matrix.
Fatty casts are confirmed using polarized microscopy and Sudan III or Oil Red O fat stains.
Fatty casts are seen in conjunction with oval fat bodies and free fat droplets in disorders causing lipiduria.
They are most frequently associated with the nephrotic syndrome, but are also seen in toxic tubular necrosis, diabetes mellitus and crush injuries.
Mixed cellular casts containing multiple cell types are not uncommon.
Mixed cellular casts most frequently encountered include RBC and WBC casts in glomerulonephritis and WBC and RTE cell casts, or WBC and bacterial casts in pyelonephritis.
When mixed casts are present, there should also be homogenous casts of at least one of the cell types, and they will be the primary diagnostic marker.
The protein gels more readily under conditions of urine-flow stasis, acidity and the presence of sodium and calcium.
Tamm-Horsfall protein is found in both normal and abnormal urine but is not detected by reagent strip protein methods.
Other proteins present in the urinary filtrate, such as albumin and immunoglobulins, are also incorporated into the cast matrix.
Their shape is representative of the tubular lumen with parallel sides and somewhat rounded ends, a high refractive index and additional elements present in the filtrate.
It should be examined immediately after collection as possible under reduced light and from low-power to high-power magnification.
Crystals are formed by the precipitation of urine solutes, including inorganic salts, organic compounds and medications (iatrogenic compounds).
Crystals are usually reported as rare, few, moderate or many per hpf while abnormal crystals may be averaged and reported per lpf.
The most common crystals seen in acidic urine are urates, consisting of amorphous urates, uric acid, acid urates and sodium urates.
Amorphous urates occur in clumps resembling granular casts and appear microscopically as yellow-brown granules.
They are frequently encountered in specimens that have been refrigerated.
They are found in acidic urine with a pH greater than 5.5.
Uric acid crystals occur in a variety of shaped and appear yellow-brown or colorless.
They may be rhombic, four-sided and flat (whetstones), wedged, six-sided and in rosettes.
Increased amounts of uric acid crystals, particularly in fresh urine, are associated with increased levels of purines and nucleic acids and are seen in patients with leukemia who are receiving chemotherapy, in patients with Lesch-Nyhan syndrome and, sometimes, in patients with gout.
Acid urates appear as larger granules and may have spicules similar to the ammonium biurate crystals seen in alkaline urine.
They are rarely encountered and are frequently seen in conjunction with amorphous urates.
They are seen in less acidic urine.
They have little clinical signifance.
Sodium urate crystals are needle-shaped and are seen in synovial fluid during episodes of gout but appear in the urine.
They are rarely encountered and are frequently seen in conjunction with amorphous urates.
They are seen in less acidic urine.
They have little clinical signifance.
Calcium oxalate crystals appear either in dihydrate or monohydrate form.
The most common form of calcium oxalate crystals is the dihydrate that is easily recognized as a colorless octahedral envelope or as two pyramids joined at their bases.
Less characteristic and less frequently seen is the monohydrate form that are oval or dumbbell shaped.
Both types are frequently seen in acidic urine, but they can be found in neutral urine and even rarely in alkaline urine.
They are sometimes seen in clumps attached to mucous strands and may resemble casts.
Phosphates represent the majority of the crystals seen in alkaline urine and include amorphous phosphate, triple phosphate, calcium phosphate, calcium carbonate and ammonium biurate.
Amorphous phosphates are granular in appearance, similar to amorphous urates.
When present in large quantities following specimen refrigeration, they cause a white precipitate that does not dissolve on warming.
They can be differentiated from amorphous urates by the color of the sediment and the urine pH.
Triple phosphate (ammonium magnesium phosphate) crystals have a prism shape that frequently resembles a “coffin lid”.
As they disintegrate, the crystals may develop a feathery appearance.
Triple phosphate crystals are birefringent under polarized light.
They have no clinical significance; however, they are often seen in highly alkaline urine associated with the presence of urea-splitting bacteria.
Calcium phosphate crystals are not frequently encountered and may appear as colorless flat rectangular plates or thin prisms often in rosette formations.
The rosette forms may be confused with sulfonamide crystals when the urine pH is in the neutral range.
They have no clinical significance, though calcium phosphate is a common constituent of renal calculi.
Calcium carbonate crystals are small and colorless with dumbbell or spherical shapes.
They may occur in clumps that resemble amorphous material, but they can be distinguished by the formation of gas after the addition of acetic acid.
They are also birefringent, which differentiates them from bacteria.
Calcium carbonate crystals have no clinical significance.
Ammonium biurate crystals exhibit the characteristic yellow-brown color of the urate crystals seen in acidic urine.
They are frequently described as “thorny apples” because of their appearance as spicule-covered spheres.
Ammonium biurate crystals resemble other urates in that they dissolve at 60°C and convert to uric acid crystals when glacial acetic acid is added.
Ammonium biurate crystals are almost always encountered in old specimens and may be associated with the presence of the ammonia produced by urea-splitting bacteria.
Abnormal urine crystals are found in acidic urine or rarely in neutral urine and can be caused by a variety of compounds, particularly when they are administered in high concentrations.
Cystine crystals appear as thick or thin colorless hexagonal plates, and they may disintegrate in the presence of ammonia.
They may be difficult to differentiate from colorless uric acid crystals.
Cystine crystals are found in the urine of persons who inherit a metabolic disorder that prevents reabsorption of cystine by the renal tubules (cystinuria).
Cholesterol crystals resembling a rectangular plate with a notch in one or more corners, but they are rarely seen unless refrigerated and more commonly found in droplet form.
Cholesterol crystals are highly birefringent with polarized light.
They are associated with disorders producing lipiduria, such as the nephrotic syndrome, and are seen in conjunction with fatty casts and oval fat bodies.
Crystals of radiographic contrast media have a very similar appearance to cholesterol crystals and also are highly birefringent.
Differentiation is best made by comparison of the other urinalysis results, examining the patient history, and observing for accompanying substances.
Tyrosine crystals appear as fine colorless to yellow needles that frequently form clumps or rosettes.
They are usually seen in conjunction with leucine crystals in specimens with positive chemical test results for bilirubin.
Tyrosine crystals may also be encountered in inherited disorders of amino-acid metabolism.
Leucine crystals are yellow-brown spheres that demonstrate concentric circles and radial striations.
They are seen less frequently than tyrosine crystals and, when present, should be accompanied by tyrosine crystals.
Bilirubin crystals appear as clumped needles or granules with the characteristic yellow color of bilirubin.
Bilirubin crystals are present in hepatic disorders producing large amounts of bilirubin in the urine.
In disorders that produce renal tubular damage, such as viral hepatitis, bilirubin crystals may be found incorporated into the matrix of casts.
Sulfonamide crystals appear in a variety of crystal shapes and colors.
Shapes most frequently encountered include needles, rhombics, whetstones, sheaves of wheat and rosettes with colors ranging from colorless to yellow-brown.
This is commonly found in patients treated for UTIs.
Inadequate patient hydration was and still is the primary cause of sulfonamide crystallization.
The appearance of sulfonamide crystals in fresh urine can suggest the possibility of tubular damage if crystals are forming in the nephron.
Ampicillin crystals appear as colorless needles that tend to form bundles following refrigeration.
Precipitation of antibiotics is not frequently encountered except for the rare observation of ampicillin crystals following massive doses of this penicillin compound without adequate hydration.
Contaminants of all types can be found in urine, particularly in specimens collected under improper conditions or in dirty containers.
Starch granules are highly refractile spheres, usually with a dimpled center.
They resemble fat droplets when polarized, producing a Maltese cross formation, and may also occasionally be confused with RBCs.
Starch granule contamination may occur when cornstarch is the powder used in powdered gloves.
Oil droplets and air bubbles also are highly refractile.
They may resemble RBCs to inexperienced laboratory personnel.
Oil droplets may result from contamination by immersion oil or lotions and creams.
Air bubbles occur when the specimen is placed under a cover slip.
Pollen grains appear as spheres with a cell wall and occasional concentric circles.
Their large size may cause them to be out of focus with true sediment constituents.
Hair and fibers from clothing and diapers are long and refractile.
They may be mistaken for casts, so they are differentiated by being birefringent under polarized light.
Fecal artifacts may appear as plant and meat fibers or as brown amorphous material in a variety of sizes and shapes.
Improperly collected specimens or rarely the presence of a fistula between the intestinal and urinary tracts may produce fecal specimen contamination.
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