Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

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.
Reference Values:
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