Urine crystals, miscellaneous findings, and reporting results

Crystals

Crystals are common in urine specimens, particularly if the specimen has been allowed to cool. Cooling causes solid crystals to precipitate out of the urine, which changes the urine’s appearance from clear to cloudy. The presence of most crystals is not clinically significant unless the crystals are found in large numbers. With only rare exceptions, abnormal crystals are seen in acidic urine. Abnormal crystals may be present because of certain disease states or an inherited metabolic condition. They may also be iatrogenic, which means they are present because of medication or treatment. Identification of crystals begins with noting the pH of the urine specimen. A history of medications and recent diagnostic testing may be helpful too.

Crystals are reported as occasional, few, moderate, or many per high-power field. At times, crystals can be amorphous, or lacking a defined shape. Frequently crystals are difficult to identify without additional chemical testing. Amorphous urates are found in acidic urine, whereas amorphous phosphates are found in alkaline samples.

Miscellaneous findings

Oval fat bodies are formed when renal tubular epithelial cells or macrophages absorb fats. The fat droplets in the cells vary in size. They are characteristic of kidney distress.

A few bacteria may be found in normal urine specimens. High bacterial counts in a urine specimen without white blood cells may indicate that the specimen sat at room temperature and the bacteria multiplied. Urine specimens with a putrid odor, numerous white blood cells, and bacteria are common in UTIs. Bacteria are seen under high-power magnification. They are often motile (moving).

Spermatozoa can be found in the urine specimens of both male and female patients. In a specimen from a female, their presence represents vaginal contamination. Sperm usually have pointed, oval heads and long, whiplike tails. They may be motile in fresh urine.

Trichomonas vaginalis is the most commonly encountered protozoan in urine. It is frequently a vaginal contaminant but may also be found in urine specimens from male patients. When urine is fresh and warm, trichomonas may be motile and move rapidly when viewed under the microscope. Trichomonas organisms are pear-shaped protozoa with four flagella, or whiplike tails. They are larger than round epithelial cells but smaller than squamous cells. Trichomonas organisms die when the specimen cools.

Mucous threads can be found in most urine specimens. They appear as pale, irregular, threadlike structures with tapered ends. Beginners often confuse hyaline casts with mucous threads. They are frequently seen in patients with inflammation and in specimens contaminated with vaginal secretions.

Artifacts and contaminants are often found in urine sediment. Training is required to tell them apart from significant structures. Fibers are common in the sediment and come from clothing, diapers, or digested plant material:

• Clothing fibers often are long and twisted and sometimes are colored. Diaper fibers can be confused with casts.
• Plant fibers appear in the urine because of fecal contamination.
• Hair is distinct not only because of the visible rough look to the strand but also because of the large size.
• Air bubbles are common if the coverslip was improperly placed over the sediment. Air bubbles are structureless, refractile (refracting light, causing a glow) and have a dark outline.

Understanding the results of a microscopic examination

The medical assistant should understand how the microscopic findings of the sediment are reported. First, the sediment is examined under the low-power objective and low light to locate casts, generally found around the edges of the coverslip. From 10 to 15 low-power fields are scanned, and the number of casts is counted and reported.

Red and white blood cells, epithelial cells, yeasts, bacteria, and crystals are identified using the high-power objective and increased light. From 10 to 15 high-power fields should be scanned and the number counted, averaged, and reported. The method of counting varies considerably among laboratories. It is important that all workers in the same laboratory use the same counting and reporting systems.

The numbers of casts, RBCs, and WBCs are counted, totaled, and averaged. They are reported using numeric ranges based on the average seen (e.g., range of 0-1, 1-2, 2-5, 5-10, 10-20, and so forth; also, too numerous to count [TNTC]). Microscopic examination of epithelial cells is similar. Epithelial cells are counted, totaled, and averaged. Then they are reported as occasional, few, moderate, or many per high-power field (e.g., 1-3 occasional, 4-6 few, 7-12 moderate, >12 many). Miscellaneous elements seen in urine are counted, averaged, and estimated. Reports will be estimated as occasional (not seen in every field), few (covers less than one-fourth of the field), moderate (covers approximately one-half of the field), and many (covers the entire field).