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Questions and Answers
What does red, clear urine most likely indicate?
What is the normal range of white blood cells (WBCs) reported in urine sediment?
Which type of white blood cells predominates in urine sediment?
What condition is indicated by an increase in urinary leukocytes?
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Which staining method is preferred for identifying eosinophils in urine sediment?
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What is the primary reason a microscopic examination of urine is conducted?
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During the microscopic examination, what is the appropriate magnification to use for scanning in high power?
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Why are stains not typically used in microscopic examinations of urine?
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What types of cells can be considered normal in urine sediment?
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What happens to Red Blood Cells in hypersthenuric urine?
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Which microscopy technique is typically used for routine analysis of urine?
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What characteristic of Red Blood Cells is noted under a high power objective?
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What is the correct procedure for decanting the urine after centrifugation?
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What is the appearance of transitional epithelial cells characterized by?
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Which of the following conditions may indicate a malignancy or viral infection in transitional epithelial cells?
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In which part of the renal tubule do you find larger and columnar renal tubular epithelial cells?
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What does an increased number of renal tubular epithelial cells normally indicate?
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Which type of renal tubular epithelial cell has a cuboidal shape and at least one straight edge?
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What is a common cause of pyuria associated with inflammation of the bladder?
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Which type of epithelial cell originates from the renal tubules in the kidneys?
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The presence of clumps of WBCs in urine is indicative of which condition?
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What appearance is characteristic of squamous epithelial cells in urine sediment?
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What suggests that a urine sample may not be a mid-stream collection based on squamous cells?
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Which condition is characterized by the presence of WBC casts in urine?
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What type of epithelial cells can indicate the presence of an autoimmune disease in urine?
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What feature distinguishes a clue cell from typical squamous epithelial cells?
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Which condition is NOT associated with the presence of oval fat bodies in urine?
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What does a positive Sudan III or Oil Red O stain indicate?
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In urine analysis, what would explain the presence of bacteria with a negative nitrite test?
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What characteristic distinguishes yeast from red blood cells in urine analysis?
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Which of the following is NOT a common source of renal fragments indicating severe tubular injury?
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Which microorganism is most commonly associated with urinary tract infections?
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What could potentially cause the appearance of yeast in a urine sample?
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Which of the following conditions is least likely to result in fat droplets in urine?
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Study Notes
Microscopic Examination
- A microscopic examination is performed when one or more chemical tests are positive: blood (RBCs), leukocyte esterase (WBCs), protein, nitrite (bacteria)
- The microscopic examination is a standard part of urinalysis, used to analyze the makeup of urine sediment after centrifugation
Procedure
- Pour urine into a conical tube, centrifuge, and discard the supernatant
- Apply the sediment to a glass slide using a pipette, then cover with a coverslip
- Scan the entire preparation for at least 10 low-power fields (10X) and 10 high-power fields (40X)
Stains
- Microscopic examination can be performed with or without stains, stains help to improve cellular detail
- Common stains include Sternheimer-Malbin, Sedi-stain, Sudan III or IV, and Oil Red O
Microscope Techniques
- Bright-field microscopy is used for routine analysis, where objects appear dark against a light background
- Phase contrast microscopy uses a phase condenser ring to enhance visualization of elements with low refractive indexes; this is useful for visualizing hyaline casts, mixed cellular casts, mucous threads, and Trichomonas
- Polarizing microscopy uses polarizing filters to identify cholesterol Maltese crosses and enhance visualization of lipids and crystals; lipids exhibit birefringent Maltese crosses, and this technique can also bring out cast details
Normal Sediment
- Normal sediment may contain small amounts of: red blood cells (RBCs), white blood cells (WBCs), epithelial cells, amorphous urates, and amorphous phosphates
Red Blood Cells
- RBCs are smooth, non-nucleated, biconcave discs, approximately 7 μm in diameter
- Reported as an average of 10 high-power fields (hpf), with a normal range of 0-3/hpf
- In concentrated urine (hypersthenuric urine), RBCs shrink due to water loss and appear crenated (irregularly shaped)
- Red/pink, cloudy urine indicates intact red cells (hematuria), while red, clear urine indicates hemoglobin (hemoglobinuria)
White Blood Cells
- WBCs are larger than RBCs and smaller than epithelial cells, approximately 12 μm in diameter
- Reported as an average of 10 high-power fields (hpf), with a normal range of 0-5/hpf
- Capable of migrating through tissues to sites of inflammation or infection
Neutrophils
- The predominant type of WBC found in urine sediment
- Contain granules and multilobed nuclei, making them easily identifiable
- Lyse rapidly in dilute alkaline urine and absorb water and swell in hypotonic urine
- Brownian movement of granules results in a sparkling appearance, referred to as "glitter cells"
- Stain light blue with Sternheimer-Malbin, with no pathological significance in low numbers
- High numbers are indicative of a bacterial infection
Eosinophils
- Not normally seen in urine
- Urine sediment must be concentrated and stained, preferably with Hansel or Wright's stain
- A finding of greater than 1% after counting 100 (or 500) cells is considered significant; increased numbers are associated with drug-induced interstitial nephritis, UTIs, and renal transplant rejection
Mononuclear Cells
- May be present in small numbers; include lymphocytes, monocytes, macrophages, and histiocytes
- Lymphocytes are the smallest WBCs and may be mistaken for RBCs
- Lymphocyte numbers are increased in renal transplant rejection
WBC Identification Difficulties
- Mononuclear cells can be mistaken for renal tubular epithelial cells (RTEs)
- Lymphocytes can be mistaken for RBCs
- Acetic acid or a supravital stain can be used to enhance nuclear detail if necessary
WBC Clinical Significance
- An increase in urinary leukocytes is called pyuria, which can be caused by bacterial infections or non-bacterial disorders
- Bacterial infections: pyelonephritis, cystitis, prostatitis, urethritis
- Non-bacterial disorders: glomerulonephritis, lupus erythematosus, interstitial nephritis, tumors
- Greater than 50 WBCs/hpf strongly suggests acute inflammation, particularly pyelonephritis or cystitis
- Clumps of WBCs strongly suggest a kidney origin (e.g., pyelonephritis), which is further indicated by the presence of WBC casts and WBC/epithelial casts
Epithelial Cells
- Small amounts are normal and represent the shedding of old cells
- Classified into three types based on their origin in the genitourinary system: squamous, transitional (urothelial), and renal tubular
Squamous Epithelial Cells
- The largest cell found in urine sediment
- Abundant, irregular cytoplasm with a prominent nucleus about the size of an RBC, resulting in a "fried egg" appearance
- Originate from the linings of the female urethra and vagina, and the lower portion of the male urethra
- A large number of squamous cells may indicate that the sample is not a mid-stream specimen
Clue Cells
- A specific type of squamous epithelial cell that is pathologic
- Covered with Gardnerella vaginalis coccobacillus, giving it a grainy, irregular appearance
- Usually observed in vaginal wet preparations, but small numbers may be seen in urinary sediment
Transitional Epithelial Cells
- Line the renal pelvis, calyces, ureters, bladder, and upper male urethra
- Smaller than squamous cells, with a centrally located nucleus, resulting in a "poached egg" appearance
- Alternate forms include caudate forms and syncytia (clumped transitional epithelials), which can occur during invasive urological procedures and have no clinical significance
Transitional Epithelial Cell Clinical Significance
- Small numbers are normal
- Increased numbers may indicate inflammation or infection in the areas where they originate
- Cells containing vacuoles or irregular nuclei could indicate a malignancy or viral infection
Renal Tubular Epithelial Cells
- Vary in size and shape depending on the part of the renal tubule they originate from
- Proximal convoluted tubule cells are larger and columnar
- Distal convoluted tubule cells are smaller and oval
- Collecting duct cells are cuboidal (with at least one straight edge)
- Can appear in large sheets as "renal fragments"
- Have coarsely granular cytoplasm and eccentric nuclei
Renal Tubular Epithelial Cell Clinical Significance
- The most clinically significant type of epithelial cell
- Greater than 2 RTE cells/hpf indicate tubular injury and further testing; increased RTEs are indicative of renal tubular necrosis
- Causes of renal tubular necrosis include exposure to heavy metals, drug-induced toxicity, viral infections, pyelonephritis, malignant infiltrations, and salicylate poisoning
- Renal fragments indicate severe tubular injury
Oval Fat Bodies
- Fat can be found as free droplets or within disintegrating cells
- Oval fat bodies are RTE cells containing lipids
- Confirmed with Sudan III or Oil Red O stain (orange) or polarized light (cholesterol will demonstrate a Maltese cross)
- Associated with nephrotic syndrome, severe tubular necrosis, diabetes mellitus, and trauma
Bacteria
- Urine from healthy individuals should not contain bacteria
- A few bacteria may be present due to minimal contamination during specimen collection
- These contaminant bacteria can multiply rapidly at room temperature but have no clinical significance
- Can be cocci or bacilli, and reported as few, moderate, or many/hpf
- If a UTI is suspected, bacteria should be accompanied by WBCs
- Enterobacteriaceae (gram-negative rods) are most associated with UTIs
Bacteria and Nitrite
- If bacteria are observed microscopically but the reagent strip is negative for nitrite, this could be due to:
- Excess bacteria reducing nitrite to nitrogen, which is not detected by the strip
- Bacteria lacking the enzyme needed to reduce nitrate to nitrite (only gram-negative bacteria have this enzyme)
- Insufficient incubation time for bacteria to reduce nitrate
- Patient not consuming nitrate in their diet (green vegetables)
- Patient taking antibiotics (inhibits bacterial metabolism)
Yeast
- Small, refractile oval structures, with or without budding
- Can be mistaken for RBCs, but can be distinguished by budding or by the fact that RBCs lyse in acetic acid while yeast does not
- Common in diabetics, as acidic urine containing glucose is ideal for yeast growth
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Description
This quiz covers the process of microscopic examination as part of urinalysis, including procedures, staining techniques, and microscope methods. Test your knowledge on how to analyze urine sediment and the specific stains used for better cellular visualization.
