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Emergency Medicine Atlas > Part 2. Specialty Areas > Chapter 21. Microscopic Findings >

Microscopic Urinalysis

Uses

To evaluate for the presence of cells, casts, and crystals. See Figs. 21-1, 21-2, 21-3, 21-4, and 21-5.

Figure 21.1

Calcium Oxalate Crystals Calcium oxalate crystals come in two shapes. The classically described octahedral, or envelope-shaped, crystals are made of calcium oxalate dihydrate. Calcium oxalate monohydrate crystals are needle-shaped. They are seen in acid or neutral urine. They may be found in the urine of patients with ethylene glycol ingestion. In addition, the urine of patients with ethylene glycol ingestion may also fluoresce under a Wood's lamp. (From Susan K. Strasinger: Urinalysis and Body Fluids, 3d ed. Philadelphia: Davis; 1994.)

Figure 21.2

Uric Acid Crystals Uric acid crystals often have a yellow hue and a variety of sizes and shapes. They are found in acidic urine. (From Susan K. Strasinger: Urinalysis and Body Fluids, 3d ed. Philadelphia: Davis; 1994.)

Figure 21.3

White Blood Cell Casts Usually two to three cells in width, white blood cell casts are indicative of upper urinary tract infection such as pyelonephritis. (Courtesy of the American Society of Clinical Pathologists.)

Figure 21.4

Red Blood Cell Casts Red blood cells casts range from 3 to 10 cells in width and are seen in glomerulonephritis. (Courtesy of the American Society of Clinical Pathologists.)

Figure 21.5

Bacteria Bacteria are often seen in urine specimens and either can be consistent with infection or may result from local contamination from surrounding skin during specimen collection. (Courtesy of Roche Laboratories, Division of Hoffman-LaRoche Inc., Nutley, NJ.)

Materials

Freshly collected urine specimen, centrifuge, graduated centrifuge tubes, glass microscope slide, coverslip.

Method

1. Pour 10 mL of freshly collected urine into a graduated centrifuge tube.

2. Centrifuge at x400 to x450 gravity for 5 min.

3. Decant 9 mL of supernatant, leaving 1 mL in the tube.

4. Resuspend the centrifuged pellet in the remaining 1 mL of urine by stirring with a pipet.

5. Place one drop of resuspended urine on a glass microscope slide.

6. Overlay with a coverslip.

7. Examine initially using scanning x10 power, emphasizing the periphery of the coverslip, since urinary elements tend to gather at the edges.

8. Switch to x40 power to focus on specific urinary elements such as cells, casts, and crystals. Use x100 power as needed for specific identification.

Synovial Fluid Analysis for Crystals

Uses

To determine the presence of uric acid crystals (in patients with gout) or calcium pyrophosphate crystals (in patients with pseudogout) in joint fluid. See Figs. 21.6A, 21.6B, 21.6C, 21.7A, and 21.7B.

Figure 21.6A

Polarized Uric Acid Crystals (x 500) Intracellular needle-like uric acid crystals are seen within the polymorphonuclear cells from the joint fluid in a patient with gout using a direct polarizing light. (From Susan K. Strasinger: Urinalysis and Body Fluids, 3d ed. Philadelphia: Davis; 1994.)

Figure 21.6B

Compensated Polarized Uric Acid Crystals (x 500) Once crystals are found with a direct polarizing light, identification is made by using a compensated polarized light. The yellow crystal is aligned parallel to the slow vibration component of the compensator (negatively birefringent). The blue crystal is perpendicular (Crossed Urate Blue). (From Susan K. Strasinger: Urinalysis and Body Fluids, 3d ed. Philadelphia: Davis; 1994.)

Figure 21.6C

Extracellular Uric Acid Crystals (x 100) Extracellular uric acid crystals are seen under compensated polarized light. Notice the change of color with crystal alignment. (From Susan K. Strasinger: Urinalysis and Body Fluids, 3d ed. Philadelphia: Davis; 1994.)

Figure 21.7A

Polarized Calcium Pyrophosphate Crystals (x 1000) Intracellular rhomboid crystals in the joint of a patient with pseudo-gout. They may also appear as rods. (From Susan K. Strasinger: Urinalysis and Body Fluids, 3d ed. Philadelphia: Davis; 1994.)

Figure 21.7B

Compensated Polarized Calcium Pyrophosphate Crystals (x 1000) The blue calcium pyrophosphate crystal is aligned parallel to the slow vibration component of the compensator (positively birefringent). (From Susan K. Strasinger: Urinalysis and Body Fluids, 3d ed. Philadelphia: Davis; 1994.)

Materials

Freshly collected joint fluid, glass microscope slide, coverslip, polarizer.

Method

1. To prevent interference from polarizing artifacts, clean the slide and coverslip with alcohol prior to using them.

2. Using freshly collected unspun joint fluid, place a drop of joint fluid on the glass microscope slide.

3. Overlay coverslip.

4. View the slide using the polarizer.

5. Scan at x10 power; x100 power is needed to see intracellular crystals.

Gram's Stain

Uses

To determine adequacy of specimen (e.g., sputum); to determine the morphology of predominant organisms in a specimen. See Figs. 21.8, 21.9, 21.10, and 21.11.

Figure 21.8

Gram's Stain—Staphylococcus pneumoniae Gram-positive, kidney-shaped diplococci of S. pneumoniae. (Courtesy of Roche Laboratories, Division of Hoffman-LaRoche Inc. Nutley, NJ.)

Figure 21.9

Gram's Stain—Staphylococcus aureus Small clusters of gram-positive cocci seen in S. aureus infection. (Courtesy of Roche Laboratories, Division of Hoffman-LaRoche Inc. Nutley, NJ.)

Figure 21.10

Gram's Stain—Gram-Negative Rods Gram-negative rods of Pseudomonas aeruginosa. (Courtesy of Roche Laboratories, Division of Hoffman-LaRoche Inc. Nutley, NJ.)

Figure 21.11

Gram's Stain—Neisseria gonorrhoeae Multiple gram-negative, intracellular diplococci from a patient with N. gonorrhoeae. (Courtesy of Morse, Moreland, Thompson: Atlas of Sexually Transmitted Diseases. London: Mosby-Wolfe; 1990.)

Materials

Freshly collected specimen to be examined, glass microscope slide, crystal violet, Gram's iodine, acetone-alcohol (acetone, 30 mL, and 95% alcohol, 70 mL), safranin, Bunsen burner.

Method

1. Put specimen on dry, clean glass microscope slide and allow to air dry.

2. Heat-fix specimen by gently passing over flame.

3. Cover specimen with crystal violet for 1 min.

4. Rinse off completely with water; do not blot.

5. Cover specimen with Gram's iodine for 1 min.

6. Rinse off completely with water; do not blot.

7. Decolorize for 30 s with gentle agitation in acetone-alcohol.

8. Rinse off completely with water; do not blot.

9. Cover with safranin for 10 to 20 s.

10. Rinse off completely with water and let air-dry.

Dark-Field Examination

Uses

To examine lesions (chancres, mucous patches, condyloma lata, skin rash) for the presence of Treponema pallidum (Fig. 21.12).

Figure 21.12

Dark-Field Microscopy Examined under a dark-field microscope at x40 or x100 power, spirochetes appear as motile, bright corkscrews against a black background. (Courtesy of Morse, Moreland, Thompson: Atlas of Sexually Transmitted Diseases. London: Mosby-Wolfe; 1990.)

Materials

Compound microscope with dark-field condenser (dark-field microscope), glass microscope slide, coverslip, physiologic saline.

Method for Obtaining and Viewing the Specimen

1. From chancre or condyloma lata:

a. Gently abrade the lesion with a dry gauze.

b. Dab away any bleeding.

c. Touch slide to exudative fluid in base of lesion.

d. Overlay coverslip and view immediately under dark-field microscope using x40 and x100 objectives.

2. From mucous patch:

a. Touch slide to mucous patch.

b. Overlay coverslip and view immediately under dark-field microscope using x40 and x100 objectives.

3. From skin lesion:

a. Gently scrape surface of skin lesion with edge of a number 15 scalpel blade.

b. Dab away any bleeding.

c. Touch slide to exudative fluid rising from skin lesion.

d. Overlay coverslip and view immediately under dark-field microscope using x40 and x100 objectives.

Vaginal Fluid Wet Mount

Uses

To examine for clue cells, Trichomonas, and sperm. See Figs. 21-13, 21-14, and 21-15.

Figure 21.13

Clue Cells "Glitter cell" or "clue cell": Epithelial cell covered with adherent bacteria in a wet mount of a vaginal specimen from a patient with Gardnerella vaginalis (also known as nonspecific vaginitis or bacterial vaginosis). Note the refractile appearance, indistinct borders, and ragged edges of the epithelial clue cell. (Courtesy of Curatek Pharmaceuticals.)

Figure 21.14

Trichomonas Saline wet mount demonstrating oval-bodied, flagellated trichomonads. They are similar in size to leukocytes and can be distinguished from them by their motility and presence of flagella. (Courtesy of H. Hunter Hansfield: Atlas of Sexually Transmitted Diseases. New York: McGraw-Hill; 1992.)

Figure 21.15

Spermatozoa Spermatozoa may be motile or immotile. (From Susan K. Strasinger: Urinalysis and Body Fluids, 3d ed. Philadelphia: Davis; 1994.)

Materials

Aqueous sodium chloride, glass microscope slide, coverslip.

Method

1. Place a drop of saline onto the middle of the glass slide. (Alternative method: Place several drops of saline in a small glass test tube and place the swab in the tube. The swab can then be wiped onto a slide at a later time.)

2. Mix a small amount of vaginal fluid to be examined into the saline drop.

3. Overlay a coverslip.

4. Examine directly through microscope at x40 and x100 (oil immersion).

Potassium Hydroxide Mount

Uses

To examine for yeast and fungus. See Fig. 21.16.

Figure 21.16

Candida albicans Potassium hydroxide preparation of vaginal secretions from a patient with vaginal candidiasis due to Candida albicans. Note the pseudohyphae characteristic of this organism. (Courtesy of H. Hunter Hansfield: Atlas of Sexually Transmitted Diseases. New York: McGraw-Hill; 1992.)

Materials

Aqueous potassium hydroxide (KOH) 10%, glass microscope slide, coverslip.

Method

1. Place a drop of KOH onto the middle of the glass slide.

2. Suspend a small amount of vaginal fluid into the drop of KOH.

3. Overlay a coverslip.

4. Let sit at room temperature for 30 min; as an alternative, gently heat the slide over a Bunsen burner but do not boil.

5. Examine under microscope for hyphae and spores.

Stool Examination for Fecal Leukocytes

Uses

To evaluate a patient for the presence of fecal leukocytes. See Fig. 21.17.

Figure 21.17

Fecal Leukocytes Multiple white cells in the stool specimen from a patient with bacterial diarrhea. (Courtesy of Herbert L. DuPont, MD.)

Materials

Freshly collected liquid stool specimen, glass microscope slide, coverslip, methylene blue.

Method

1. Place a drop of liquid stool onto the glass slide.

2. Add two drops of methylene blue to the stool specimen.

3. Mix thoroughly.

4. Overlay with a coverslip.

5. Place the edge of a piece of filter paper adjacent to the coverslip to absorb any excess methylene blue.

6. Examine using x10 objective to scan specimen and x40 and x100 to identify specific leukocytes.

Skin Scraping for Dermatoses and Infestations

Uses

To determine fungal dermatoses or skin infestations. See Figs. 21-18, 21-19, 21-20, and 21-21.

Figure 21.18

Scabies Skin scraping from a patient with scabies. Note the intact mite at the lower right of the photograph, and the ova and fecal pellets. (Courtesy of the Department of Dermatology, Naval Medical Center, Portsmouth, VA.)

Figure 21.19

Scabies Adult female scabies mite. (Courtesy of Morse, Moreland, Thompson: Atlas of Sexually Transmitted Diseases. London: Mosby-Wolfe; 1990.)

Figure 21.20

Pediculosis Phthirus pubis, the crab louse. Note the short body and claw-like legs, which are ideally suited for clinging to the hair shaft. (Courtesy of the Department of Dermatology, Naval Medical Center, Portsmouth, VA.)

Figure 21.21

Pediculosis Phthirus corporis, the body louse. Note the elongated body. (Courtesy of the Department of Dermatology, Naval Medical Center, Portsmouth, VA.)

Materials

Fresh skin scraping, glass microscope slide, coverslip, 10% potassium hydroxide or mineral oil.

Method

1. Specimen collection:

a. Gently scrape skin lesion with edge of a number 15 scalpel.

2. Slide preparation:

a. Pediculosis may be seen grossly clinging to individual hairs or under low power. Live nits may fluoresce with a Wood's lamp.

b. For scabies, place a drop of KOH or mineral oil onto the slide.

c. Suspend a small amount of the scraping onto the drop.

d. Overlay a coverslip.

e. Let sit at room temperature for 30 min; as an alternative, gently heat the slide over a Bunsen burner but do not boil.

f. Examine under microscope for hyphae, spores, or infestations.

India Ink Preparation

Uses

To examine cerebrospinal fluid for organisms with capsules, particularly Cryptococcus neoformans.

Materials

India ink, glass microscope slide, coverslip. See Fig. 21.22.

Figure 21.22

India Ink Preparation Budding yeast with prominent capsule on india ink preparation from a patient with C. neoformans meningitis. (Courtesy of Morse, Moreland, Thompson: Atlas of Sexually Transmitted Diseases. London: Mosby-Wolfe; 1990.)

Method

1. Lightly centrifuge cerebrospinal fluid to concentrate cells at bottom of tube (1 to 2 min).

2. Pour off excess fluid (retain if further testing may be necessary).

3. Take a drop from the bottom of the centrifuge tube and place it in the middle of a glass microscope slide.

4. Place a drop of india ink into the specimen drop; gently mix.

5. Overlay a coverslip.

6. Examine at x10 to screen specimen, use x40 objective to confirm findings.

Wright's Stain—Thin Smear for Malaria

Uses

To evaluate for the presence of ring trophozoites. See Fig. 21.23.

Figure 21.23

Plasmodium falciparum Thin Film Ring forms (trophozoites) of P. falciparum are seen on the Wright's stain thin film in a patient with intermittent fever who had recently traveled to Africa. (Courtesy of James P. Elrod, MD, PhD.)

Materials

Air-dried blood smear, Coplin jar of Wright's stain, slide rack, pH 7.2 buffer, blotting paper.

Method

1. Place a drop of blood on the middle of a slide.

2. Hold another slide evenly on top of the slide at a 45-degree angle and drag the slide over the drop of blood to the opposite edge to spread the blood evenly.

3. Allow the blood to dry for 5 to 10 min.

4. Stain air-dried smears in a closed Coplin jar of Wright's stain for 5 min.

5. Place the slide on a rack.

6. Rinse and treat with pH 7.2 buffer primed with 1 mL Wright's stain per 400 mL for 3 min.

7. Rinse in pH 7.2 buffer for 20 s.

8. Blot dry and mount on microscope at x100 (oil immersion).