Microscopic Urinalysis Overview
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Questions and Answers

What is the purpose of microscopic examination of urine?

To detect and identify insoluble materials present in the urine.

Midstream clean-catch specimen minimizes external contamination of the sediment.

True

What is the standard volume of urine specimen required for examination?

10-15 ml

Which of the following are constituents of urine sediment?

<p>All of the above</p> Signup and view all the answers

What type of microscopy is most commonly used in routine urinalysis?

<p>Bright-field microscopy</p> Signup and view all the answers

Centrifugation is done for ____ minutes at an RCF of 400.

<p>5</p> Signup and view all the answers

What appearance do red blood cells have under microscopic examination?

<p>Smooth, non-nucleated, biconcave disks measuring approximately 7 mm in diameter.</p> Signup and view all the answers

What must be noted if the volume of urine specimen is less than 10-15 ml?

<p>The specimen used should be noted on the report form.</p> Signup and view all the answers

What is meant by 'crenated RBCs'?

<p>Cell shrinkage due to loss of water (hypersthenuric).</p> Signup and view all the answers

Which of the following are constituents found in urine sediment? (Select all that apply)

<p>Epithelial cells</p> Signup and view all the answers

What is the purpose of microscopic examination of urine?

<p>To detect and identify insoluble materials present in the urine.</p> Signup and view all the answers

Hyaline casts disintegrate rapidly in dilute alkaline urine.

<p>True</p> Signup and view all the answers

What is the standard volume of urine specimens for analysis?

<p>10-15 ml</p> Signup and view all the answers

Which microscopy technique is most commonly used for routine urinalysis?

<p>Bright-field microscopy</p> Signup and view all the answers

What type of microscopy enhances visualization of elements with low refractive indices?

<p>Phase-contrast microscopy</p> Signup and view all the answers

What is the appearance of red blood cells under microscopic examination?

<p>Smooth, non-nucleated, biconcave disks measuring approximately 7 mm in diameter.</p> Signup and view all the answers

Crenated RBCs indicate cell enlargement due to excess water.

<p>False</p> Signup and view all the answers

Study Notes

Microscopic Examination of Urine

  • The purpose is to detect and identify insoluble materials present in urine.
  • These materials include red blood cells (RBCs), white blood cells (WBCs), epithelial cells, casts, bacteria, yeast, parasites, mucus, spermatozoa, crystals, and artifacts.

Macroscopic Screening

  • Specimen Preparation:
    • Specimens should be examined while fresh or adequately preserved.
    • Formed elements, primarily RBCs, WBCs, and hyaline casts, disintegrate rapidly, particularly in dilute alkaline urine.
    • A midstream clean-catch specimen minimizes external contamination of the sediment.
  • Specimen Volume:
    • The standard volume is 10-15 ml.
    • If a volume of 10-15 ml is not possible (e.g., pediatric patients), the volume of the specimen used should be noted on the report form.
  • Centrifugation:
    • Centrifugation for 5 minutes at an RCF of 400 produces an optimum amount of sediment with the least chance of damaging the elements.

Sediment Examination Techniques

Sediment Stains

  • Stains can be used to enhance visualization of specific elements in the urine sediment.

Microscopy

  • Bright-field microscopy:
    • Most common technique, used for routine urinalysis.
  • Phase-contrast microscopy:
    • Enhances visualization of elements with low refractive indices, such as hyaline casts, mixed cellular casts, mucous threads, and Trichomonas.
  • Polarizing microscopy:
    • Aids in the identification of cholesterol in oval fat bodies, fatty casts, and crystals.
  • Dark-field microscopy:
    • Aids in the identification of Treponema pallidum.
  • Fluorescence microscopy:
    • Allows visualization of naturally fluorescent microorganisms or those stained by a fluorescent dye, including labeled antigens and antibodies.
  • Interference-contrast:
    • Produces a three-dimensional microscopy image and layer-by-layer imaging of a specimen.

Urine Sediment Constituents

Red Blood Cells (RBCs)

  • Appear smooth, non-nucleated, biconcave disks measuring approximately 7 mm in diameter.
  • Must be identified under high power objective (HPO).
  • Crenated RBCs:
    • Cell shrinkage due to loss of water (hypersthenuric).
  • Ghost cells:
    • Cell swelling and lysis due to hypotonic urine.

Microscopic Examination of Urine

  • The purpose of a microscopic examination of urine is to identify insoluble materials, including:
    • Red blood cells (RBCs)
    • White blood cells (WBCs)
    • Epithelial cells
    • Casts
    • Bacteria
    • Yeast
    • Parasites
    • Mucus
    • Spermatozoa
    • Crystals
    • Artifacts

Macroscopic Screening

  • Urine specimens should be examined while fresh or adequately preserved.
  • A midstream clean-catch specimen minimizes external contamination.
  • The standard volume for centrifugation is 10-15 mL.
  • If a full 10-15 mL volume isn't possible, note the volume on the report form.

Sediment Examination Techniques

Sediment Stains

  • Staining helps identify microscopic elements

Microscopy

  • Bright-field microscopy: Most common technique used for routine urinalysis
  • Phase-contrast microscopy: Enhances visualization of elements with low refractive indices (e.g., hyaline casts, mucous threads, Trichomonas)
  • Polarizing microscopy: Identifies cholesterol in oval fat bodies, fatty casts, and crystals
  • Dark-field microscopy: Aids in the identification of Treponema pallidum
  • Fluorescence microscopy: Visualizes naturally fluorescent microorganisms or those stained by a fluorescent dye (including labeled antigens and antibodies)
  • Interference-contrast: Produces a three-dimensional microscopy image and layer-by-layer imaging of a specimen

Urine Sediment Constituents

Red Blood Cells (RBCs)

  • Appear smooth, non-nucleated, biconcave disks measuring approximately 7 mm in diameter.
  • Must be identified under high-power objective (HPO).
  • Crenated RBCs: Cell shrinkage due to water loss (hypersthenuric urine).
  • Ghost cells: Cell swelling and lysis due to water gain (hypotonic urine).

White Blood Cells (WBCs)

  • Larger than RBCs (~12 µm in diameter) and have a nucleus.
  • Neutrophils are the most common type.
  • Eosinophils may indicate an allergic or parasitic infection.
  • Lymphocytes can be seen in conditions like urinary tract infection or glomerulonephritis.

Epithelial Cells

  • Squamous epithelial cells: Derived from the lining of the urethra and vagina.
  • Transitional epithelial cells: From the lining of the bladder and renal pelvis.
  • Renal tubular epithelial cells: From the lining of the renal tubules (can indicate renal damage).

Casts

  • Formed in the renal tubules from protein (mainly Tamm-Horsfall protein).
  • Hyaline casts are most common and usually considered normal at low levels.
  • Cellular casts consist of RBCs, WBCs, or epithelial cells.
  • Granular casts contain granules and may indicate renal disease.
  • Waxy casts are dense and associated with severe renal disease.

Bacteria

  • May be present in urine, but need to differentiate between normal flora and true infection.
  • Can indicate a urinary tract infection.

Yeast

  • Candida albicans is most common.
  • Associated with diabetes, immunosuppression, or antibiotics.

Parasites

  • Trichomonas vaginalis is most common.
  • Can be found in urine or vaginal secretions.

Mucus

  • Mucus threads are common and do not usually indicate pathology.

Spermatozoa

  • May be present in urine after sexual activity.

Crystals

  • Can be normal or abnormal and usually appear in acidic urine.

Artifacts

  • Foreign materials like fibers, hair, or air bubbles.
  • Differentiate from true urine elements.

Reporting Urine Sediment Results

  • Casts: Report the average number per low-power field (/lpf).
  • RBCs and WBCs: Report the average number per high-power field (/hpf).
  • Epithelial cells, crystals, and other elements: Use semi-quantitative terms (rare, few, moderate, many) or as 1+, 2+, 3+, 4+ per lpf or hpf.

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AUBF Microscopic Examination of Urine PDF

Description

This quiz focuses on the microscopic examination of urine, aimed at detecting various insoluble materials. You'll learn about specimen preparation, screening techniques, and the importance of volumes in urine analysis. Test your knowledge on identifying elements such as RBCs, WBCs, and crystals.

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