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seen in patients with nephrotic syndrome or other glomerular diseases associated with significant
proteinuria. Granular casts are observed in a number of disorders and are thought to be formed from
partially degraded cellular casts, or are protein-derived casts. Hyaline casts are not thought to be
indicative of any disease process, but increased numbers may be seen in concentrated urine specimens.
Waxy casts and broad casts are most often observed in advanced renal failure. Increased numbers of RTE
cells are indicators of renal tubular injury. Increased numbers of RTE may be caused by drugs with renal
tubular toxicity (eg, cyclosporine A, aminoglycosides, cisplatin, radio-contrast media, acetaminophen
overdose), interstitial nephritis, hypotension (surgical, sepsis, obstetric complications), or heme pigments
from hemoglobinuria or myoglobinuria from rhabdomyolysis (eg, alcoholism, heat stroke, seizures, sickle
cell trait). Newborns often shed RTE cells in their urine. The presence of squamous cells suggest that the
specimen may not have been an optimal clean-catch specimen and could be contaminated with skin flora.
Recommendations by an American Urological Association panel, based upon careful review of all
available published outcome studies that contained results of detailed hematuria workups within actual
patient populations, are that patients with more than 3 RBCs per high-power field in 2 out of 3 properly
collected urine specimens should be considered to have microhematuria and, hence, evaluated for possible
pathologic causes. However, the panel also noted that there is no absolute lower limit for hematuria, and
risk factors for significant disease should be taken into consideration before deciding to defer an
evaluation in patients with only 1 or 2 RBCs per high-power field. High-risk patients, especially those
with a history of smoking or chemical exposure, should still be considered for a full urologic evaluation
even after a properly performed urinalysis documented the presence of at least 3 RBCs per high-power
field. In certain patients, even 1 or 2 RBCs per high-powered field might merit evaluation.(1) Osmolality:
Osmolality is an index of the solute concentration of osmotically active particles, principally sodium,
chloride, potassium, and urea; glucose can contribute significantly to the osmolality when present in
substantial amounts. The ability of the kidney to maintain both tonicity and water balance of the
extracellular fluid can be evaluated by measuring the osmolality of the urine. More information
concerning the state of renal water handling or abnormalities of urine dilution or concentration can be
obtained if urinary osmolality is compared to serum osmolality. Normally, the ratio of urine osmolality to
serum osmolality is 1.0 to 3.0, reflecting a wide range of urine osmolality. Reference Values: 0-12
months: 50-750 mOsm/kg >12 months: 150-1,150 mOsm/kg Please note above the age of 20 there is an
age-dependent decline in the upper reference range of approximately 5 mOsm/kg/year. Protein: This test
detects the presence of overt proteinuria (>300 mg/day). However, normal urinary protein excretion is
180 mg/dL); this
is most commonly, although not exclusively, seen in diabetes. Reference Values: < or =15 mg/dL pH:
Urine pH is affected by diet, medications, systemic acid-base disturbances, and renal tubular function. pH
may affect urinary stone formation. For example, urine pH 6.0 may reduce the tendency for uric acid stone formation. Ketones: Produced
during metabolism of fat, increased ketones may occur during physiological stress conditions such as
fasting, pregnancy, strenuous exercise, and frequent vomiting. In diabetics who are unable to efficiently
utilize glucose due to a lack of insulin, starvation, or with other abnormalities of carbohydrate or lipid
metabolism, ketones may appear in the urine in large amounts before serum ketone is elevated. Bilirubin:
Bilirubinuria is an indicator of liver disease and biliary tract obstruction. Hemoglobin: Hemoglobinuria is
an indicator of intravascular hemolysis. The test is equally sensitive to myoglobin as to hemoglobin. The
presence of hemoglobin, in the absence of RBCs, is consistent with intravascular hemolysis. RBCs may
be missed if lysis occurred prior to analysis; the absence of RBCs should be confirmed by examining a
fresh specimen. The presence of myoglobin may be confirmed by MYOU/9274 Myoglobin, Urine.
Reducing Substances: Urine can contain a variety of reducing substances (sugars [glucose, galactose,
sucrose, fructose, lactose, maltose], ascorbic acid, drugs, etc), compounds so termed because of their
ability to reduce cupric ions. The primary reducing substances of medical significance are the sugars,
glucose (diabetes), and galactose (galactosemia). Other sugars may be found but are not of clinical
significance. Because glucose also is detected by glucose-specific dipstick reagents, the test for reducing
substances is performed to detect galactose.
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