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Urinalysis (cont.)

Microscopic Urinalysis Procedure

Microscopic urinalysis entails placing a few milliliters of the collected urine sample into a special test tube with a cap. The test tube is then spun down (centrifuged) for a few minutes. The liquid part of urine on the top (the supernatant) is discarded with only a drop or two remaining in the tube. The solid part at the bottom of the tube (urinary sediment) is then gently mixed with the few drops of liquid urine left on top of it. A drop of this mix is then transferred using a small pipette onto a thin glass slide and analyzed under the microscope.

The urinary sediment is analyzed to look for white blood cells, red blood cells, epithelial cells (cells that line the urethra or bladder), and bacteria in the urine. Under the microscope, an estimate of the number of these components is typically assessed and reported. The quantity of these cells may provide additional clinical information.

Other useful information detected by the microscopic urinalysis is the evaluation of cellular elements in the urine. These cellular elements may represent debris from the kidney cells due to injury, inflammation, or infection of the kidneys, and usually are formed in tube-like structures called casts. There are a number of different types of casts that may be detected in the urine, each suggesting certain possible kidney conditions.

Sometimes crystals can be seen in the urine under the microscope. Small amounts of crystals in the urine may be normal in healthy people. Some nonspecific crystals may be seen in urine as a result of the urine sample not being freshly analyzed (within 1-2 hours), being kept at a cold temperature, or from acidic (low pH) urine. In other instances, specific crystals may be detected in urine (crystalluria) as a result of different types of kidney stones. Some antibiotics and anti-viral drugs may also promote crystal formation in urine.

Medically Reviewed by a Doctor on 6/12/2014

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