CLINICAL LAB SCIENEC

306
ESSENTIALS OF CLINICAL LABORATORY SCIENCE
In the Lab
(including but not limited to mucoprotein), forming casts shaped by the walls of the
tubules. When increased numbers of red and white cells are also present in the
tubules, they may become trapped in the protein. The protein and the cells may then
decompose and form a variety of casts identified by their appearances. Casts are
categorized as shown in Table 12-6. Images of the casts are shown in Figures 12-22
through 12-25.
Normal Crystals—Formed Elements in Urine
Figures 12-26 through 12-29 show crystals that are found in normal urine samples. Calcium
carbonate and ammonium biurate crystals are found predominantly in alkaline
urine. Crystals that form in alkaline urine may be dissolved by the use of strong acids
such as hydrogen chloride. Amorphous (without shape) phosphate and triple phosphate
crystals are common in alkaline urine, and sometimes calcium carbonate crystals
will be found in neutral or slightly alkaline urine samples. Uric acid and calcium
oxalate crystals will be chiefly found in acid urine, along with amorphous urates (Table 12-7).
Urine specimens that have been refrigerated or for which testing has otherwise been
delayed will often form crystals called amorphous sediment from the dissolved chemicals
present in the sample. This may cause the urine sample to become completely
cloudy, but the phenomenon can be reversed by warming of the sample through
immersing the specimen tube in warm water for a few minutes. Acid urine specimens,
a normal condition as most urine samples will be pH 5.0 to 6.0, will yield amorphous
urates, while alkaline specimens will provide amorphous phosphates.
Table 12-6 Examples of Casts with Descriptions and Conditions under Which Formed
Cast Classification Descriptions Conditions Associated with Casts
Hyaline
Granular
RBC
WBC
Epithelial cell
Waxy
Transparent and colorless, visible under low
light levels in microscopic examination
Granules from breakdown of cells and
metabolic components
Glycoprotein entraps intact RBCs; cast
appears often as bright red
Outline of transparent material with visible
WBCs within the cast
Cylindrical form of epithelial cells where
nuclei may be visualized
Appearance is consistent in appearance
with a broken and splintered wax tube and
contains few or no inclusions
Occasional hyaline cast is normal; increased in extreme
exercise and stress, but also found in chronic renal
disease, congestive heart failure (poor circulation),
glomerulonephritis, and pyelonephritis
Previously classifi ed as fi nely and coarsely granular casts,
but this terminology seldom used today
Blood transfusion incompatibility, trauma and strenuous
exercise, glomerulonephritis
Pyelonephritis chiefl y from bacterial ascension from
bladder infection
Damage to renal tubules; renal epithelial cells may be
visualized within the cast
Broken areas with sharp ends appear much as a broken
piece of glass
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