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163 Cards in this Set
- Front
- Back
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Ureters move urine to the bladder by ______ and _______
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gravity, peristalsis
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What is the fundamental urine-producing unit of the kidney?
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the nephron
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List the components of the nephron
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glomerulus, Bowman's capsule, proximal convoluted tubule, Loop of Henle, distal convoluted tubule, collecting duct
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What are the 5 major functions of the kidney?
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Regulation of water/electrolyte content, maintenance of acid/base balance, retention of vital substances, excretion of waste products/toxins/drugs, endocrine function
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(T/F) It is normal to see protein in the urine
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False
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The glomerulus selectively filters molecules by _______ and _______.
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size, charge
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What does the macula densa detect? Where is it located?
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decrease in sodium and chloride ions, distal convoluted tubule
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What is renin? Where is it released?
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an enzyme that converts angiotensinogen to angiotensin I, the juxtaglomerular apparatus
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Urine is composed of _____ water and ______ solutes
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95%, 5%
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How can you determine if a particular body fluid is urine?
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urea, creatinine
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Urine volume depends on what factors?
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fluid intake, fluid loss (non-renal), hormones, dissolved solids, diuretics
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Oliguria
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decreased urine output, happens in burn patients, with diarrhea and vomiting
adults < 400 mL/24 hours |
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Anuria
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Cessation of urine flow, happens with damage to kidney or renal flow
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Nocturia
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Frequent urination at night
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Polyuria
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Increased urine output
Happens with diabetes (mellitus or insipidus), diuretics (including caffeine and alcohol) >2.5 L per 24 hours in adults |
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Preservation of urine is required if the sample is not run within __________.
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2 hours
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Causes for UA rejection
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sample not preserved properly, foreign material in the sample (i.e. feces, paper, etc.), cup not labeled properly (i.e. label on the lid)
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When should a urinalysis be read if the urine is not preserved?
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ideally read within 30 minutes, may be read unpreserved within 2 hours, refrigeration or chemical preservative necessary beyond 2 hours
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Changes that occur in unpreserved urine
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pH, glucose, bilirubin, ketones, bacterial multiplication, crystals precipitate or solubilize, cell/cast disintegration
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Methods of urine preservation
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physical: refrigeration, freezing
chemical: toluene, thymol |
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How long can refrigeration preserve urine?
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6-8 hours
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What are the limitations of refrigeration as a method of urine preservation?
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Precipitation of crystals leading to turbidity (amorphous material)
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What are the limitations of freezing as a method of urine preservation?
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Increases the specific gravity, destroys formed elements
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What molecules does toluene help preserve in urine? How does it work?
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Acetone, protein and other reducing substances (such as glucose). It creates a thin layer over the urine.
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What is the major disadvantage of toluene as a urine preservative?
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fire risk
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What is the major disadvantage of thymol as a urine preservative?
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It creates false positive results for protein tests
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What does chloroform preserve in a urine sample?
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aldosterole
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What does formaldehyde preserve in a urine sample?
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Formed elements
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What does boric acid preserve in a urine sample?
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Most chemicals and formed elements
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What is the disadvantage of boric acid as a urine preservative?
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It precipitates uric acid
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What time should a urine specimen be collected if possible? Why?
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The first morning specimen because it is most concentrated (and bacteria have had most time to incubate)
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What is a random urine specimen? What is important to note with a random urine specimen?
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A specimen obtained at any time during examination, important to note dietary intake and physical activity
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A fasting specimen is the _____ voided specimen after fasting. It is often used for ______ monitoring.
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second, glucose
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Postprandial urine specimens are collected _____ hours after a meal. These samples are often using to check glucose when monitoring ________.
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2, insulin therapy
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A 24 hour specimen is necessary for quantitative determination of ________.
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protein
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Procedure for the 24 hour timed urine collection
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Empty bladder completely (discard) at beginning of 24 hour time collection
Collect all urine during following 24 hours, including that voided exactly at the end of the 24 hour period (on the second day) in the container |
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Clean catch mid-stream specimen
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A specimen obtained from the middle part of the first urine to avoid collecting normal flora from the area surrounding the urethra
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Procedure for clean catch mid-stream
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Genital area cleaned with soap and water and rinsed well, urinate a small amount and discard, collect following urine in sterile container
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The physical examination of urine includes:
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volume, color, appearance, foam, odor, specific gravity
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Factors that affect urine color
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metabolism, physical factors, diet, pathologic conditions
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What is urochrome?
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A product of endogenous metabolism produced at a consistent rate
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What happens to urochrome if urine remains at room temperature for a prolonged time?
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It increases
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The intensity of yellow in a urine sample may give an indication of ________.
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concentration
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Pale to colorless urine may indicate what?
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large fluid intake, diabetes mellitus, alcohol consumption
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Dark yellow to brown red urine may indicate what?
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concentrated urine, decreased fluid intake, fever, dehydration
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Yellow-brown to "beer brown" colored urine may indicate what?
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Presence of bilirubin
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Clear red color may indicate the presence of what in a urine sample?
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hemoglobin
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A cloudy red or smoky red color in urine may indicate what?
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hematuria
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A dark yellow/amber/orange color in a urine sample may indicate what?
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bilirubin, pyridium, high concentration
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A red/pink/brown color in a urine sample may indicate what?
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blood, porphobilinogen (port wine)
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Abnormal urine color may interfere with what?
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the colorimetric readings of the urine dipstick
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A brown/black color in a urine sample may indicate what?
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Melanin, homogentistic acid (alkaptonuria), medications (levopoda)
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A blue/green color in a urine sample may indicate what?
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Medication, bacterial infection (Pseudomonas)
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If a urine specimen is old, what type of odor will it have? Why?
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ammonical/pungent due to the break down/conversion of urea into ammonia by bacteria
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A sweet/fruity odor of urine results from the presence of _______. This occurs in conjunction with what conditions?
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ketones
diabetes mellitus, prolonged vomiting, starvation, strenous exercise |
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Yellowish foam in the urine may indicate what?
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bilirubin
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Large amounts of white foam in the urine may indicate what?
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High concentrations of protein
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Turbidity of urine may occur due to:
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refrigeration, white blood cells, kidney stones, yeast cells, high number of bacteria, high number of mucus threads
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Define specific gravity
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The ratio of the weight of a fixed volume of solution to that of the same volume of water at a specified temperature (usually room temperature - 20 degrees Celsius)
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The specific gravity gives an indication of what?
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The ability of the kidneys to concentrate or dilute urine, may also reflect the degree of hydration
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Isosthenuric urine has a specific gravity of what?
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1.010
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Hyposthenuric urine has a specific gravity of what?
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below 1.010
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Hypersthenuric urine has a specific gravity of what?
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above 1.010
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What are the different methods to measure the urine specific gravity?
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urinometer, refractometer, reagent strip, falling drop method, weighing technique
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What is contained in a urinometer? Where does the urinometer float in water?
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Mercury and air, at the 1.000 mark
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Describe the temperature correction for the urinometer.
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Each 3 degrees Celsius changes the reading by 0.001
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What corrections must be performed for a urinometer?
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abnormal dissolved substances and temperature
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Sources of error for urinometer
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Temperature differences, proteinuria (if not corrected), glycosuria (if not corrected), X-ray contrast media, chemical preservatives
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In refractometry, the degree of refraction is proportional to the __________.
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specific gravity (amount of solute concentration)
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Reagent strips are a/an ________ method of measuring specific gravity.
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indirect
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Reagents strips actually measure _____ when testing for specific gravity.
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ionic concentration
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Urine specific gravity is used to obtain information about the state of the ______ and _______ of the patient.
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renal epithelium and hydration
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How should urinalysis reagent strips be stored?
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With a desiccant and secured cap to avoid moisture, in a dark bottle to avoid degradation by light, at room temperature
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Before performing a urine dipstick, what should be done to the sample?
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The sample should be mixed by gentle swirling or inversion
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To prevent the flow of urine between urine dipstick pads, what should be done during urinalysis?
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The edge of the dipstick should be run against the rim of the container as the strip is withdrawn and the side of the strip should be blotted (paper towel, gauze, etc.)
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Sources of error in urine dipstick chemical analysis
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Leaving strip in urine too long
not wicking excess urine from strip not adhering to reading rxn times poor light source when reading rxns testing sample at refrigerated temp masking of rxn color by dye given to patient |
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Quality assurance of urine dipsticks
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test with both positive and negative controls once per shift or every 24 hours and each time a new bottle is opened
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Describe the chemical test strip method for measuring specific gravity
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ionic solutes cause hydrogen ions to be released from a polyelectrolyte in the pad, resulting in a change in the pad's pH which causes a color change
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Causes of a falsely elevated specific gravity on a urine dipstick
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moderate or high levels of protein
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Falsely decreased specific gravity on a urine dipstick may be caused by:
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highly alkaline urine
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The normal pH of a first morning urine specimen is between ____ and ____.
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5, 6
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Following meals, what can happen to the pH of urine?
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It may be increased (alkaline tide)
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The normal range of urine pH is ______. The physiological range is ______.
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5.0-7.0, 4.5-8.0
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The chemical reaction for pH in the urine dipstick
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a double pH indicator system of methyl red (red to yellow change in pH 4.0-6.0) and bromothymol blue (yellow to blue change in pH of 6.0-9.0)
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Interference for pH reading on urine dipstick
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run-over from other reagent pads
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Clinical significance of urine pH
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indicator of acid-base disorders
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An acid or alkaline pH of urine in the absence of respiratory or metabolic disorders may indicate what?
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An inability of the kidney to secrete or reabsorb acid or base
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pH is important in the identification of ______ in the urine.
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crystals
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Alkaline urine may indicate what?
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kidney dysfunction, urinary tract infection, old specimen allowed to stand at room temperature
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A urine pH greater than 8.0 generally indicates what?
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an improperly preserved specimen
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A normal protein measurement in urine is what?
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0 or trace
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Trace proteinuria may occur in an otherwise healthy patient when?
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overnight, after moderate exercise or secondary to fever
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Sulfosalicylic acid is a confirmatory test for _______. This is measured by looking at the ______ following the reaction.
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protein, turbidity
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Chemical reaction for protein
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Anions of proteins react with tetra-bromophenol blue indicator to cause a color change
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A highly alkaline urine will do what to the protein measurement on a urine dipstick?
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falsely elevate the result (the high pH causes a color change even without protein)
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The following will cause a falsely elevated result for protein in a urine dipstick:
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alkaline pH, highly pigmented specimen, quaternary ammonium compounds, drugs such as phenazopyridine, chlorhexidine or bleach
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Interferences for the SSA protein test
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turbid urine, uncentrifuged urine, x-ray media, drugs, tolbutamide metabolites, cephalosporin, penicillin, sulfonamides, highly alkaline urine (negative bias)
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SSA is more sensitive for ______ than dipsticks
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globulins
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What is microalbumin?
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albumin concentrations in urine below the detection limit of a regular UA dipstick
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Microalbumin is useful for what?
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Early detection of kidney damage, especially from undiagnosed type II diabetes mellitus
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The microalbumin Micral test uses what method?
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a specific immunochemical assay in which albumin binds to an antibody. The bound and unbound antibody then migrate up the strip. Bound antibody causes an enzymatic color change.
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Range of microalbumin test
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0 to 10 mg/dL
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The microalbumin immunodip strip uses what method?
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immunochromographic technique where migration is controlled by particle size. Albumin binds to blue latex coated with antibody. Bound particles are able to migrate further up the strip.
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Mild to moderate proteinuria is defined as:
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Protein > 100 mg/24 hours (trace to 2+).
Associated with UTI, nephritis, glomerular or tubular damage, diabetic nephropathy, multiple myeloma |
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Severe proteinuria is defined as:
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Protein > 3.5 g/24 hours (3+ to 4+)
Associated with nephrotic syndrome (secondary to glomerular or tubular damage) |
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Monoclonal globulins and Bence-Jones proteins are excreted in ______.
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multiple myeloma
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Damage to the glomerulus may be caused by:
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amyloid, toxic substances, immune complexes, high blood pressure, high glucose
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Tubular proteinuria due to defective tubular reabsorption may be due to:
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chronic - heavy metals, Fanconi's syndrome, cirrhosis, chronic pyelonephritis
acute - bacterial infections, burns, acute pancreatitis |
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Normal renal plasma threshold for glucose
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160-180 mg/dL
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Usually all glucose is ______ in the proximal convoluted tubules
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reabsorbed
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When testing for glucose in the urine, it is recommended that the specimen is ________.
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fasting
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(T/F) Glucose in the urine is diagnostic for diabetes mellitus
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False
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A baby born to a woman suffering from gestational diabetes is more likely to develop ______ and _______ later in life.
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obesity, type 2 diabetes
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Glycosuria without hyperglycemia indicates what?
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Impaired reabsorption in the renal tubules
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Hyperglycemia of non-diabetic origin is associated with what?
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Hormonal function (not insulin)
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The glucose dipstick is diagnostically sensitive to what level?
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100 mg/dL
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(T/F) The urine dipstick detects all reducing sugars
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False, the urine dipstick detects glucose only
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Causes of false negatives on the glucose urine dipstick
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high specific gravity, ascorbic acid, high ketones, some bacteria
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Causes of false positives on glucose dipstick
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oxidizing agents (i.e. bleach), some bacteria
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Reagents in the glucose dipstick
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glucose oxidase, peroxidase, chromogen, buffer
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The urine dipstick uses what reaction set to measure glucose?
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glucose oxidase, peroxidase
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The primary cause of a false negative glucose dipstick result
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Leaving a specimen unpreserved for greater than one hour (bacteria/cells use up glucose)
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The clinitest or copper reduction test is a confirmatory test for what?
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Glucose
This test also detects other reducing sugars |
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What common sugar is not a reducing substance?
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sucrose
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The clinitest is primarily used to test urine from infants for what?
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Sugars excreted due to in-born errors of metabolism
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In the clinitest, copper sulfate (which is a blue color) is converted to ________ (which is a green to orange color).
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cuprous oxide
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Clinitest tablets contain:
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copper sulfate, sodium hydroxide, sodium carbonate and sodium citrate
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Why should you observe the clinitest as the reaction is progressing?
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To observe any pass-through effect
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Why does a pass-through effect occur in the clinitest?
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There is a very high concentration of a reducing substance in the specimen.
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If a pass-through phenomenon occurs in the clinitest, what can the technologist do?
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Perform the test again using the 2-drop method
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3 ketones that are intermediate forms of fat metabolism
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acetone, acetoacetic acid, beta-hydroxybutyrate
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What ketone has the highest concentration in the body?
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beta-hydroxybutyate
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Ketones may appear in what two states?
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carbohydrate deprivation or type I diabetes mellitus
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Chemical reaction for measuring ketones in urine dipstick
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sodium nitroprusside + acetoacetic acid --------> purple color
(in alkaline medium) |
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The ketone urine dipstick detects only _______, but the presence of ________ and ________ is assumed if the test is positive.
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acetoacetic acid, acetone, BHB
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The acetest tablet tests for ________. _______ gives this test better color differentiation than the dipstick test.
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ketones, lactose
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______ will give a false positive for blood on the urine dipstick.
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Myoglobin
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What can cause transient blood in the urine?
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strenous exercise, certain drugs, menstruation
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In hemoglobinuria, the urine will appear _____ and ______.
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clear and red
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In hematuria, the urine will appear ______ and _______.
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cloudy and red
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In myoglobinuria, the urine will appear ______ and ______.
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clear and brown (occasionally red if very high concentration)
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What can cause myoglobinuria?
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Any type of muscle injury (trauma, crush injury, prolonged coma, convulsion)
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Reaction for measuring blood in the urine
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Hemoglobin acts as a pseudo-peroxidase to catalyze redox reaction between hydrogen peroxide and tetramethylbenzidine to give a green-blue color
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Causes of false negatives in blood dipstick test
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failure to mix specimen, high specific gravity, hypertension medication, excess nitrites, high intake of ascorbic acid
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How can hemoglobinuria and myoglobinuria be differentiated using a chemical pad?
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The column test:
Add ammonium sulfate to urine and centrifuge. This precipitates the hemoglobin and leaves myoglobin in the supernatant. The supernatant is then tested. |
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In urine, bilirubin is an early sign of _______.
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liver disease
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In the intestines, conjugated bilirubin is converted to ________.
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urobilinogen then urobilin
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The reaction for measuring bilirubin in the urine
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The diazo reaction
Conjugated bilirubin + diazo salts -------> azodye (pink/purple color) |
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Interferences in bilirubin measurement
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False positive: some drugs, reddish urine False negative: ascorbic acid, light
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Confirmation test for bilirubin
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Ictotest, more sensitive than dipstick
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Interferences in ictotest
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false positive: improper timing, indican, urine pigments of phenazopyridine compounts
false negative: light exposure of sample, high concentration of ascorbic acid, nitrate |
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Urobilinogen test reactions
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Ehrlich's aldehyde reaction or azo-coupling (diazo) reaction
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Interferences in Ehrlich's reaction
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False positives: porphobilinogen, indican, p-aminosalicylic acid, sulfonamides, methyldopa, procaine, chlorpromazine, highly pigmented urine
False negatives: poor preservation |
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Ehrlich's reagent is:
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p-diethylaminobenzaldehyde
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Ehrlich's reagent reacts with urobilinogen to form what color?
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Cherry red to pink
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The Watson-Schwartz test is used to differentiate ______ and ______.
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urobilinogen, porphobilnogen
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Describe the Watson-Schwartz test
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Once a positive Ehrlich's test is performed, the specimen is divided into tube 1 and tube 2. Chloroform is added to tube one and butanol is added to tube 2. Urobilinogen is soluble in both, porphobilinogen is soluble in neither. Layer colors allow for differentiation.
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The nitrite test in urine screens for the presence of what?
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Bacteria (especially gram negative bacteria) causing a urinary tract infection
(Note: not all bacteria produce nitrites) |
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Causes of false positives in the nitrite urine dipstick test
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reddish urine, improper collection/storage leading to overgrowth
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Pyuria may be caused by
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lower UTI, pyelonephritis, acute glomerulonephritis, genital infections (contamination)
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Chemical reaction for leukocyte esterase
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Leukocyte esterase catalyzes hydrolysis of acid esters to diazonium salt resulting in a color change
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Causes of false positives for leukocyte esterase
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vaginal secretions, highly colored urines, strong oxidizing agents
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Causes of false negatives for leukocyte esterase
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high protein, very high glucose, high specific gravity, medication (cephalosporins, gentamicin, tetracycline), ascorbic acid, oxalic acid
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