Crystal Information and Courses from MediaLab, Inc.

In an undiluted specimen, count and differentiate red cells and white cells at the same time. You can count red cells on a hand counter and use the differential counter for white cells. If you cannot differentiate white cells from red cells in the undiluted specimen, a plain capillary tube may be filled with crystal violet acetic acid diluent which is subsequently expelled from the tube. A very thin coating of the diluent will remain on the inside of the tube. CSF is drawn halfway up into the tube, which is then rocked back and forth to mix. The hemacytometer is then filled with the fluid containing stained white blood cells and lysed red cells. If cells are numerous and overlapping and it is necessary to focus through several planes in order to see all of the cells, a dilution must be made. When macroscopic appearance is turbid, milky or bloody, a significant dilution is usually necessary.

The urine microscopic exam is performed on a centrifuged urine sediment. The sediment contains all the formed elements or insoluble materials that have accumulated in the urine through its passage from the kidney to the lower urinary tract. These formed elements include cells, casts, crystals and miscellaneous structures.

The sediment may be examined using both brightfield and phase-contrast microscopy. With the brightfield microscope, subdued light must be used. Some structures will be missed if there is too much light in the field. Fine focus throughout the examination to identify structures in different focal planes. Scan the slide on low power for quantification of casts, crystals and elements that are present in only a few fields. Use high power to identify casts and count red blood cells, white blood cells and epithelial cells.

Leucine crystals indicate a problem with the metabolism of the amino acid leucine. These crystals are round to oval with radiating bands going from a center point out to the periphery, often referred to as a "wagon wheel." These crystals are soluble in hot alcohol and alkali.

The characteristics of the more common types of abnormal crystals are summarized in the table below. Crystal Color Significance Leucine Yellow Metabolism Tyrosine Colorless–yellow Liver disease (rare) Cystine Colorless Cystine metabolism Cholesterol Colorless Renal tubular disease Bilirubin Gold-orange Increased bilirubin High doses of ampicillin, sulfonamide drugs or other drugs may also result in urine crystal formation. It is important to check the patient’s current medications when unusual crystals are found in the urine specimen.

Cholesterol crystals may be seen in renal tubular disease. These crystals look like plates of glass, sometimes with a notch out of one corner. Under polarized light, they exhibit a stained glass effect. These crystals are rarely seen unless the specimen has been refrigerated, because the lipids remain in droplet form. Large amounts of protein, lipid droplets, fatty casts or oval fat bodies should be found along with cholesterol crystals. Cholesterol crystals are found in acid or neutral urine.

Cystine crystals indicate an abnormality in metabolism of the amino acid cystine. These crystals appear as colorless, refractile, hexagonal plates with even sides. Cystine crystals sometimes occur in pairs. They produce a red color in the nitroprusside reaction. Cystine may be confused with the hexagonal forms of uric acid but does not polarize light. Cystine crystals occur in acid urine.

The results of this specimen are abnormal but the abnormalities correlate with each other. The turbidity can be explained by the presence of bacteria and crystals. The presence of RBCs in the microscopic explains the blood found on the dipstick. The casts, bacteria and WBCs can account for the increased protein. The results may be reported.

Crystals are not usually present in freshly voided urine, but can appear in urine left at room temperature for several hours. Most crystals form due to changes in urine pH and temperature after collection. Diagnostically significant crystals may indicate the presence of a metabolic disorder, renal calculi formation, or provide information that can be used to regulate medications.

Calcium carbonate crystals appear as tiny dumbbells or small colorless spheres.

Identification of crystals found in the urine sediment requires knowledge of the urinary pH. Large crystals are identifiable under low power. High power magnification is required for smaller crystals. Most crystals can be identified by morphology alone. Urine pH and reagent strip results can provide supporting information. If further examination is necessary birefringence and solubility characteristics should be performed.

Crystals found in normal alkaline urine include triple phosphate, ammonium biurate, calcium carbonate, amorphous phosphates, and calcium oxalate. This slide shows an example of triple phosphate crystals. These may appear as four to six sided prisms resembling coffin lids. They indicate either stasis of the bladder or a stale sample.

Ammonium biurate crystals commonly occur in the form of "thorn apples," as shown here, or in polyhedral shapes. They are deeply colored from a dark yellow to brown. They sometimes appear in clumps or clusters. This crystal occurs only in stale urine.

The number of bacteria, yeast, crystals and mucous must be estimated. Examine 10 fields under high power (40X) magnification. Use phase-contrast if needed. Determine the average of each element found and record the findings according to the following criteria: Element fills <1/4 of each field = trace Element fills about 1/4 of each field = 1+ Element fills about 1/2 of each field = 2+ Element fills about 3/4 of each field = 3+ Element fills total field = 4+

Cornstarch, talcum powder, and other starch materials may be mistaken for crystals. A drop or two of dilute iodine solution will stain the talcum particles blue-black.

Some starch granules from dusting powders have faint concentric striations, others do not. External contaminants (ie. those that enter the urine specimen during collection, transportation, or while being examined on the slide) must be differentiated from crystals and other clinically significant findings.