How to Identify Urine Crystals

The identification of crystals in urine is done during the microscopic phase of a complete urinalysis. Crystals are identified by their shape and color as well as by the pH (acidity or alkalinity) of the urine sample. The presence--or absence--of crystals in a urine sediment is an important diagnostic aid in the treatment of disease as well as an indicator of your overall health. Crystals fall into 3 main categories: those that are present in small numbers in healthy individuals; those that are present as a result of medication or X-ray dyes; and those that indicate disease.

Things You'll Need

• Urine sample
• Urine chemistry dipstick
• Centrifuge tube
• Centrifuge
• Pipettes
• Microscope slides--preferably with wells
• Coverslips
• Microscope
• Urine reference book

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Instructions

• 1

  Before crystals can be identified in a urine sample, the urine must be checked for pH and then centrifuged for microscopic examination. Pour 10 to 15 ml of the urine sample to be examined in a clear glass or plastic centrifuge tube. Note the color and the appearance--clear, hazy, cloudy or turbid--of the urine. Dip the chemistry strip into the sample and briefly drag along the top edge of the centrifuge tube to drain excess urine from the strip. Although all the chemistry results on the dipstick are recorded during the urinalysis--glucose, protein, blood, leukocytes, nitrates, etc--only the pH of the urine determines the presence of crystals.

  Place the tube in the centrifuge and spin the sample for 5 to 10 minutes at 2000 to 3000 rpm.

• 2

  Pour off the supernatant (the clear liquid on the top), and flick or tap the tube to break up the "button" of sediment on the bottom. Using a pipette, place a drop of the sediment on the microscope slide and cover with a coverslip if not using slides with wells. Place the slide on the stage of the microscope and scan first under low power (100x) to locate crystals. If the individual is healthy there will be few crystals present. Shift the microscope objective to high power (400x) to identify crystals.

• 3

  Shift the microscope objective to high power (400x) to identify crystals. The most common crystals found in an acid urine are: 1.) uric acid: these come in a variety of shapes, although the lozenge shape is the most familiar, and are amber in color; 2.) calcium oxalate: these come in oval shapes, dumbbell shapes, and biconcave/biconvex discs; and 3.) amorphous urates: these appear as sand-like granular material with no real morphological shape.

• 4

  Identify crystals in alkaline urine. Alkaline urine (pH 7.5 to 8.5 or higher) is usually the result of the urine standing for a long period of time before testing. The pH can change due to a breakdown of some of the material present in the urine sample.
  The most common crystals present in an alkaline urine are: 1.) calcium phosphate: these can look like prisms, needles, or star-like clumps; 2.) triple phosphate: these are prism shaped and are identified as having a "coffin lid" appearance; and 3.) amorphous phosphates: often pink in color, these appear as sand-like granular material with no real morphological shape.

• 5

  Determine if the crystals are due to other causes. These could be crystals from high doses of drugs or medications such as sulfonamides, sulfadiazine, amoxicillin, or even vitamin C. X-ray dye crystals also show up in urine sediment, as well as crystals that are only present in certain disease states.