Chapter 25

### Uses

To evaluate for the presence of cells, casts, and crystals.

### Materials

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

### Method

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

2. Centrifuge at ×400 to ×450 gravity for 5 minutes.

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 ×10 power, emphasizing the periphery of the coverslip, since urinary elements tend to gather at the edges.

8. Switch to ×40 power to focus on specific urinary elements such as cells, casts, and crystals. Use ×100 power as needed for specific identification.

###### Figure 25.1.

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 lamp. (From Susan K. Strasinger. Urinalysis and Body Fluids. 3rd ed. Philadelphia, PA: Davis; 1994.)

###### Figure 25.2.

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. 3rd ed. Philadelphia, PA: Davis; 1994.)

###### Figure 25.3.

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. (Photo contributor: the American Society of Clinical Pathologists.)

###### Figure 25.4.

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

###### Figure 25.5.

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. (Photo contributor: Roche Laboratories, Division of Hoffman-LaRoche Inc., Nutley, NJ.)

### Uses

To determine the presence of uric acid crystals (in patients with gout) or calcium pyrophosphate crystals (in patients with pseudogout) in joint fluid.

### Materials

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