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Questions and Answers
Which microscopy technique is used to produce a 3D microscopic image showing very fine structural detail by splitting the light rays?
Which microscopy technique is used to produce a 3D microscopic image showing very fine structural detail by splitting the light rays?
- Bright-field microscopy
- Dark-field microscopy
- Fluorescence microscopy
- Interference contrast microscopy (correct)
What property allows some atoms to absorb light at a particular wavelength and emit light of a longer wavelength, commonly used in the visualization of microorganisms?
What property allows some atoms to absorb light at a particular wavelength and emit light of a longer wavelength, commonly used in the visualization of microorganisms?
- Absorption
- Fluorescence (correct)
- Refraction
- Reflection
Which microscopy technique aids in visualizing specimens that cannot be seen easily with a bright-field microscope, such as Treponema pallidum?
Which microscopy technique aids in visualizing specimens that cannot be seen easily with a bright-field microscope, such as Treponema pallidum?
- Bright-field microscopy
- Dark-field microscopy (correct)
- Fluorescence microscopy
- Interference contrast microscopy
What is the ideal specimen collection method for urinalysis that minimizes external contamination?
What is the ideal specimen collection method for urinalysis that minimizes external contamination?
What can refrigeration of urine specimens potentially cause according to the provided text?
What can refrigeration of urine specimens potentially cause according to the provided text?
What technique allows the visualization of naturally fluorescent microorganisms or those stained by fluorescent dye, aiding in the detection of bacteria and viruses?
What technique allows the visualization of naturally fluorescent microorganisms or those stained by fluorescent dye, aiding in the detection of bacteria and viruses?
Which type of microscope is commonly used for routine urinalysis?
Which type of microscope is commonly used for routine urinalysis?
What type of microscope enhances the visualization of elements with low refractive indices?
What type of microscope enhances the visualization of elements with low refractive indices?
What property of sediments may indicate the presence of elements that can refract light in two dimensions?
What property of sediments may indicate the presence of elements that can refract light in two dimensions?
Which structure can be identified using the polarizing microscope due to its ability to aid in the identification of cholesterol?
Which structure can be identified using the polarizing microscope due to its ability to aid in the identification of cholesterol?
Under which type of microscope might sediments appear birefringent?
Under which type of microscope might sediments appear birefringent?
What is adjusted on the bright-field microscope to control the light when examining sediments?
What is adjusted on the bright-field microscope to control the light when examining sediments?
What causes red blood cells to swell and lyse rapidly in hypotonic urine?
What causes red blood cells to swell and lyse rapidly in hypotonic urine?
How can one confirm that a sediment in urine is red blood cells and not yeasts?
How can one confirm that a sediment in urine is red blood cells and not yeasts?
Which stain is most frequently used for identifying white blood cells, epithelial cells, and casts in urine sediment?
Which stain is most frequently used for identifying white blood cells, epithelial cells, and casts in urine sediment?
What does Oil Red O and Sudan III stain in urine sediment?
What does Oil Red O and Sudan III stain in urine sediment?
Why might a urine specimen appear red and hazy?
Why might a urine specimen appear red and hazy?
How do red blood cells in hypotonic urine differ from dysmorphic red blood cells?
How do red blood cells in hypotonic urine differ from dysmorphic red blood cells?
What is the recommended urine volume for testing before decanting to the centrifuge tube?
What is the recommended urine volume for testing before decanting to the centrifuge tube?
What effect does refrigeration have on urine samples according to the text?
What effect does refrigeration have on urine samples according to the text?
What is the purpose of gentle agitation during resuspension of the urine before testing?
What is the purpose of gentle agitation during resuspension of the urine before testing?
How does delay in testing affect urine samples according to the text?
How does delay in testing affect urine samples according to the text?
What is the recommended RCF (Relative Centrifugal Force) for centrifuging urine samples?
What is the recommended RCF (Relative Centrifugal Force) for centrifuging urine samples?
How can the obstruction of microscopic examination due to refrigeration be corrected according to the text?
How can the obstruction of microscopic examination due to refrigeration be corrected according to the text?
What type of crystals exhibit a 'coffin lids' appearance?
What type of crystals exhibit a 'coffin lids' appearance?
Which type of crystal is commonly associated with urea-splitting organisms in recurrent urinary tract infections?
Which type of crystal is commonly associated with urea-splitting organisms in recurrent urinary tract infections?
Which type of crystal is characterized by a 'spicule-covered sphere' appearance?
Which type of crystal is characterized by a 'spicule-covered sphere' appearance?
Which crystal dissolves in dilute acetic acid and resembles sulfonamide crystals?
Which crystal dissolves in dilute acetic acid and resembles sulfonamide crystals?
Which crystal requires acetic acid to dissolve and can be differentiated from amorphous urates by color and urine pH?
Which crystal requires acetic acid to dissolve and can be differentiated from amorphous urates by color and urine pH?
Which crystal can be distinguished from amorphous material by gas formation after the addition of acetic acid?
Which crystal can be distinguished from amorphous material by gas formation after the addition of acetic acid?
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Study Notes
Microscopy
- Dark-field microscopy enhances visualization of specimens that cannot be seen with bright-field microscopy, used for unstained specimens, and aids in the identification of Treponema pallidum (spirochete).
- Fluorescence microscopy allows visualization of naturally fluorescent microorganisms or those stained with fluorescent dye, including labeled antigens and antibodies, and detects bacteria and viruses within cells and tissues through immunofluorescence.
- Interference contrast microscopy produces 3D microscopic images showing fine structural detail by splitting the light ray so that beams pass through different areas of the specimen, and layer-by-layer imaging of a specimen; objects appear bright against a dark background.
Routine Urinalysis
- Urine should be examined immediately, as some sediments or cells will disintegrate rapidly; refrigeration can cause precipitation of amorphous and other non-pathologic crystals.
- Midstream clean catch is the ideal specimen, as it minimizes external contamination of the specimen.
- Urine volume for examination: 10-15mL (average: 12mL); centrifugation: 400 RCF for 5 min; decant: 0.5-1.0mL supernatant; resuspend: gentle agitation.
Types of Microscopes
- Bright-field microscopy is used for routine urinalysis; sediments viewed under this microscope appear dark against a light background.
- Phase-contrast microscopy enhances visualization of elements with low refractive indices, such as hyaline casts, mixed cellular casts, mucus threads, and Trichomonas vaginalis.
- Polarizing microscopy aids in the identification of cholesterol in oval fat bodies, fatty casts, crystals, and lipids, and uses polarized light; sediments may appear birefringent, a property indicating that the element can refract light in two dimensions at 90 degrees to each other, producing characteristic colors in crystals and Maltese-cross formation in lipids.
Red Blood Cells (RBCs)
- RBCs in hypotonic or hyposthenuric (diluted) urine appear as "ghost cells" because they absorb water, causing them to swell and lyse rapidly, releasing hemoglobin and leaving only the cell membrane.
- Dysmorphic RBCs are seen with glomerular membrane damage; the number and appearance of RBCs must be considered, as an abnormal urine concentration affects RBC appearance.
Sediment Stains
- Sternheimer-Malbin stain: uses crystal violet and Safranin, delineates structure and contrasting colors of the nucleus and cytoplasm, and identifies WBCs, epithelial cells, and casts.
- Toluidine Blue stain: enhances nuclear detail, differentiates WBCs and renal tubular epithelial (RTE) cells.
- Oil Red O and Sudan III lipid stains: stain triglycerides and neutral fats orange-red, but do not stain cholesterol, which is capable of polarization; Maltese-cross formation is observed on a polarizing microscope.
Urine Sediments
- RBCs: appear as ghosts or dysmorphic cells in hypotonic or hyposthenuric urine.
- WBCs: average cells/HPF; Pus cells.
- Epithelial Cells: semiquantitative/LPF.
- Bacteria: semiquantitative/HPF; differentiates gram-positive (blue) from gram-negative (red) bacteria.
- Amorphous crystals: semiquantitative/LPF; seen in neutral or alkaline urine, granular in appearance, cause white precipitate/sediment that does not dissolve by warming.
Urinary Crystals
- Alkaline urine: amorphous phosphates, granular in appearance, cause white precipitate/sediment that does not dissolve by warming.
- Ammonium biurate: associated with the presence of ammonia produced by urea-splitting organisms, exhibits characteristic yellow-brown "thorny apple" appearance.
- Triple phosphate: ammonium magnesium phosphate, colorless, three to six-sided prisms with oblique ends, referred to as "coffin lids".
- Struvite (MAP): presence of urea-splitting organisms, usually seen in recurrent urinary tract infection.
- Calcium phosphate: apatite or hydroxyapatite, colorless, flat rectangular plates or thin prisms, often in rosette formation, resembles sulfonamide crystals.
- Calcium carbonate: small and colorless, with dumbbell or spherical shape, may occur in clumps that resemble amorphous material, but can be distinguished by the formation of gas after the addition of acetic acid.
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