urine

• Urine composition is 97% water and 5% solutes, which vary and are influenced by dietary intake, physical activity, body metabolism, endocrine functions and even body position.
• The major organic component in urine is urea, which makes up 60 to 90% of total organic substances.
• Other organic substances in urine include uric acid, hippuric acid, creatinine, carbohydrates, pigments, fatty acids, mucin, enzymes, hormones.
• The major inorganic component in urine is chloride, which makes up 25 to 30% of total inorganic substances.
• Chain of Custody is the process that provides documentation of proper sample identification from the time of collection to the receipt of laboratory results.
• Prostatic Infection is indicated when the number of white blood cells and bacteria in the third specimen is 10 times greater than that of the first specimen.
• Urine begins and ends with an empty bladder and requires a preservative depending on the test to be performed.
• The second specimen is a control for bladder and kidney infection.
• The temperature of urine collection should be within 4 mins of 32.5 to 37.7 o C.
• Urine after prostatic massage should be examined microscopically and compared to the number of white blood cells and bacteria in the first and third specimens.
• The required volume of urine sample is 30 to 45 ml.
• Bluing agent is added to the toilet water reservoir to prevent specimen adulteration.
• If the result from the third specimen is positive for white blood cells and bacteria, the test is invalid.
• Other inorganic substances in urine include sulfate, phosphate, ammonium, magnesium, calcium.
• The principal salt in urine is NaCl.
• Urine volume is excreted by the kidneys in response to the body’s state of hydration, which includes fluid intake, fluid loss from non-renal sources, variations in ADH secretion, and the need to excrete increased amount of dissolved solids.
• Normal daily urine volume ranges from 600-2000 ml, with a normal average daily volume of 1200-1500 ml.
• Oliguria is defined as <400 ml/day in adults, <0.5 ml/kg/hr in children, and <1 ml/kg/hr in infants.
• Polyuria is defined as >2.5 L/day in adults, 2.5-3 ml/kg/day in children.
• Oliguria is commonly seen in dehydration due to excessive water loss from vomiting, diarrhea, perspiration or severe burns, and can also be caused by kidney or decreased blood flow to the kidneys.
• Polyuria can be caused by diabetes insipidus, which can be artificially induced by diuretics, caffeine or alcohol.
• Specimen collection for urine testing requires a properly labeled container, wide-mouthed with a secure lid, and a wide, flat bottom, and should be sterile for microbiologic analysis.
• Specimen integrity in urine testing begins as soon as the urine is voided, and changes in unpreserved urine include increased odor, bacteria multiplication, pH change, nitrite change, color change, clarity change, glucose change, ketone change, and bilirubin change.
• Specimen preservation in urine testing involves changes in preserved urine, which include increased odor, bacteria multiplication, pH change, nitrite change, color change, clarity change, glucose change, ketone change, and bilirubin change.
• Fractional Specimen involves at least 2 voided collection series of blood and urine samples are collected at specific time intervals to compare concentration of a substance in urine with its concentration in the blood.
• Trichomonas immobilization may be misidentified as WBC in urine.
• Saccomanno (50% ethanol + 2% carbowax) preserves cellular elements and is used for cytology studies.
• First morning urine is the ideal specimen for routine UA and Pregnancy test.
• Bottle Method is the most-commonly used method for urine collection, performed via midstream clean catch.
• Na propionate is the preservative in the yellow plain UA tube.
• Second morning urine is the 2nd voided urine after a period of fasting, useful for glucose determination.
• Gray C&S tube sample is stable at room temperature for 48 hours, decreases pH, and should not be used if urine is below min fill line.
• Commercial tablet preservatives are convenient when ref is not possible and may contain one or more of the preservatives including NaF.
• Random Urine Specimen is collected anytime and is the most commonly received specimen, useful for routine screening tests.
• Phenol does not interfere with routine tests, but causes odor change.
• Toluene does not interfere with routine tests, floats on urine surface, and clings to glassware.
• Boric acid preserves CHONS and formed elements well, does not interfere with routine analyses other than pH, and may precipitate crystals when used in large amounts.
• Ureteral Catheterization involves catheter insertion up the ureter.
• NaF prevents glycolysis and is a good preservative for drug analysis, but may interfere with reagent strip tests for glucose, blood and leukocytes.
• Urethral Catheterization involves catheter insertion up to the urinary bladder.