ASCP Urinalysis/Body Fluids

Flashcard maker : Lily Taylor
What is he major functional unit of the kidney?
nephron
Approximately how many nephrons are there per kidney?
1 million
The nephron is composed of?
glomerulus, renal tubules
What is a glomerulus composed of?
capillary vessels
What is the function of a glomerulus?
non-selective filter of plasma substances less than 70k MW
What substances comprise the glomerular fjiltrate?
water, glucose, electrolytes, amino acids, urea, uric acid, creatinine, ammonia
What is the function of the proximal tubule?
reabsorbs water, NaCl, HCO3, K, Ca, amino acids, PO4, protein, glucose
Glucose is a threshold substance that reabsorbs within the proximal tubule at?
160 – 189 mg/dl or less
What does the descending loop of henle reabsorb?
water
What doesn’t the descending loop of henle reabsorb?
solutes
What does the ascending loop of henle reabsorb?
solutes (Na, Cl, Ca, Mg)
What doesn’t the ascending loop of henle reabsorb?
water
What do the distal and collecting tubules reabsorb?
Na
What do the distal and collecting tubules secrete?
K, NH4, H+
Potassium ions are exchanged for what in the distal and collecting tubules?
Na ions
What is the rate of filtration of the glomerulus?
120 ml/min or 1/5 of renal plasma
What is the normal amount of urine excreted per day?
1200 – 1500 ml/day
Polyuria is defined as?
greater than 2500 ml of urine excreted per day (excess urine excretion)
What conditions can cause polyuria?
diabetes insipidus, diabetes mellitus, diuretics, caffeine, alcohol
Oliguria is defined as?
less than 500 ml of urine excreted per day (decreased urine excretion)
What conditions can cause oliguria?
dehydration, vomiting, diarrhea, burns, perspiration
Anuria is defined as?
complete cessation of urination
What conditions can cause anuria?
kidney damage, decreased blood flow to kidneys
Nocturia is defined as?
increased urine volume at night?
Urine is composed of?
urea, uric acid, creatinine, inorganic solids (Cl, Na, K), water
What is a metabolic waste product produced in liver from breakdown of protein?
urea
Aldosterone is secreted from?
adrenal cortex
What is the function of aldosterone?
increases the rate of sodium reabsorption
Arginine Vasopressin (AVP/ADH) is secreted from?
posterior pituitary gland
What is the function of AVP?
reabsoprtion of water from the distal tubules
A deficiency of AVP occurs in what condition?
diabetes insipidus
Erythropoietin (EPO) is secreted from?
kidney
What is the function of EPO?
stimulates production of erythrocytes
What type of urine specimen is considered ideal?
first morning (most concentrated)
What type of urine specimen is ideas for a bacterial culture?
midstream clean catch
Catheterization involves?
inserting a catheter directly into the bladder via the urethra
Catheterization avoids?
external contamination (may introduce an infection though)
Pediatric urine specimens are collected by?
placing a plastic collection bag over the genital area (many sources of contamination associated with this collection method)
Suprapubic aspiration specimens are collected by?
inserting a needle through the suprapubic abdominal area directly into the bladder
Suprapubic aspirations avoid?
external contamination
What are negative aspects of suprapubic aspirations?
invasive, may introduce infection
What is the optimal specimen collection method for bacterial cultures?
suprapubic aspiration
24 hour urine specimens are used for?
quantitative urine studies
How is the completeness of a 24 hour urine determined?
creatinine levels (should be greater than 1.0 mg/dl)
Urines should be analyzed within what timeframe of voiding?
1 hour
What values increase as a result of prolonged sitting of urine specimens?
nitrite (bacterial growth), pH (urea is converted into ammonia), turbidity (bacterial growth/amorphous material)
What values decrease as a result of prolonged sitting of urine specimens?
glucose (glycolysis due to bacteria/yeast), ketones (volatization), bilirubin (exposure to light), urobilinogen (oxidation), cells/casts (lysis)
Urines can be preserved for how long?
24 hours
What is the preservation method of choice for urines?
refrigeration
What may result if urines are preserved in a refrigerator?
precipitation of amorphous crystals
A fruity odor associated with urine can be attributed to the presence?
ketones
An ammonia-like odor associated with urine can be attributed to?
the age of the urine (old)
A mousy odor associated with urine can be attributed to what condition?
PKU (phenylketonuria)
A maple syrup like odor associated with urine can be attributed to what condition?
maple syrup disease
What compound gives urine its normal color?
urochrome
What type of urine specimen may be more on the alkaline side?
postprandial (2 hours after eating)
What is the typical pH of a normal urine?
6.0
The pH of a random urine can range from?
4.5 – 8.0
What can cause a urine to be cloudy?
cells, casts, crystals, bacteria
The presence of what substances can cause urine to appear more red?
hemoglobin, RBCs, myoglobin, porphyrin, uroerythrin
The presence of what substances can cause urine to appear more red-brown?
hemoglobin, RBCs, myoglobin
The presence of what substances can cause urine to appear more yellow-brown/amber-yellow-green?
bilirubin, biliverdin
The presence of what substance can cause urine to appear more yellow-orange?
bilirubin, urobilin, pyridium (drug)
The presence of what substances can cause urine to appear bright yellow?
vitamin C
The presence of what substances can cause urine to appear dark yellow?
concentrated specimen, bilirubin, urobilin
The presence of what substances can cause urine to appear brown-black?
methemoglobin (oxidized RBCs), homogentistic acid (alkaptonuria), melanin
The presence of what substances can cause urine to appear blue?
indican (tryptophan metabolic disorder)
The presence of what substances can cause urine to appear green/blue-green?
old urine, psuedomonas
The presence of what substances can cause urine to appear port wine?
porphyrin
The urine pH of a vegetarian is usually more?
alkaline
What can cause urine to become more acidic?
metabolic or respiratory acidosis, high protein diet, cranberry juice
Specific gravity measurements can help determine?
the concentration and dilution function of the kidney tubules
What is the normal specific gravity of urine?
1.002 – 1.035
What is the highest specific gravity value that the kidneys can concentrate?
1.040
Increased specific gravity values can be attributed to?
large amounts of glucose, radio-opaque dyes (renal x-ray procedures)
Decreased specific gravity values can be attributed to?
diabetes insipidus
Specific gravity is proportional to?
color (the higher the SG the deeper the color)
What is the defect associated with diabetes mellitus?
decreased insulin
What is the defect associated with diabetes insipidus?
decreased AVP/ADH
What symptoms are seen in both diabetes insipidus and mellitus?
polyuria, polydipsia
What substances are increased in the urine of an individual with diabetes mellitus?
specific gravity, glucose, ketones
What substances are decreased in an individual with diabetes insipidus?
specific gravity
Urinary measurments of glucose and ketones are normal in what type of diabetes?
insipidus
Refractometers measure?
the refractive index of urine
Corrections must be made with refractometers in the case of?
large amounts of protein
How do you correct a SG value higher than 1.035?
dilute the urine specimen 1:2 with water and multiply the last 2 digits of the result by 2
What is the principle of the measurement of protein in the urine?
protein error of indicators
What causes the change in color indicating the presence of protein on a urine dipstick?
albumin binding to the dye which shifts the dye’s spectrum os the color changes from yellow to green
The presence of protein in the urine can be quantified by?
precipitation methods (sulfosalicylic acid)
How can highly alkaline urine affect protein measurements?
false positive
How can sulfosalicylic acid and penicillin affect protein measurements?
false positive
What is the best single indicator of renal abnormalities?
proteinuria
Proteinuria is associated with what conditions?
multiple myeloma, orthostatic proteinuria, strenuous exercise
What is orthostatic proteinuria?
a benign condition which results in proteinuria after standing
Periodic monitoring of microalbuminuria benefits patients with what conditions?
diabetes, hypertension, peripheral vascular disease
What substance is in such low quantities that routine reagent strips cannot detect its presence?
microalbumin
What is the methodology behind the measurement of glucose on a dipstick?
glucose oxidase (double) sequential enzyme reaction)
A positive copper reduction test with a negative dipstick test indicates?
a sugar (or other reducing substance) other than glucose
Which is more sensitive: copper reduction test or glucose dipstick?
dipstick
What interferes with the measurement of glucose on a dipstick?
bleach (false positive)
What is the purpose for using a clinitest tablet?
to detect the presence of other reducing sugars as well as glucose
What is the methodology behind the clinitest tablet?
benedict’s copper reduction test (CuSO4 + NaOH + reducing substance = Cu2O)
In benedict’s copper reduction test sugars and other reducing substances reduce what substance into?
cupric ion to the cuprous state (in the presence of alkali and heat)
The clinitest tablet is generally used as a screening test for?
galactosemia (a rare congenital carbohydrate metabolic condition in pediatric patients)
What is the principle of ketone testing performed with a dipstick?
sodium nitroprusside + ketone = purple color
What is the dipstick actually detecting when testing for the presence of ketones?
diacetic acid
What confirmation test is used to confirm the presence of ketones in the urine?
acetest tablets
What are the end products of fat metabolism?
acetone, diacetic acid (acetoacetate), beta-hydroxy-butyric acid
What interferes with the measurement of ketones in the urine?
highly pigmented urine, levadopa metabolites
Uncontrolled diabetes mellitus, high protein diets and GI disturbances can cause what types of results when testing for ketones?
positive
What is the 2-step enzymatic procedure that detects the presence of blood in the urine?
peroxide on strip + blood = O2, O2 + color producer = color change
What substances can result in false positive results when testing for the presence of blood?
bleach, other oxidizing substances
What substance can result in false negative results when testing for the presence of blood?
vitamin C
What other substances also exhibit peroxidase activity?
hemoglobin, myoglobin
Hematuria is associated with what clinical conditions?
systemic bleeding disorders, renal diseases, cystitis, calculi, strenuous exercise
Hemoglobinuria is associated with what clinical conditions?
hemolytic anemias, incompatible transfusions, malaria, strenuous exercise
Myoglobinuria is associated with what clinical conditions?
muscle destruction
What is the principle behind the detection of bilirubin in the urine?
(diazo reaction) diazonium salt + bilirubin = bluish purple color
Which is more sensitive in the detection of bilirubin: Ictotest tablet or dipstick?
ictotest
What substances can lead to false positives in the detection of bilirubin?
vitamin C, nitrite
Bilirubinuria is associated with what conditions?
bile duct obstruction, liver damage (hepatitis and cirrhosis)
What is the principle behind dipstick testing of urobilinogen?
(ehrlich’s reaction) para-dimethylaminobenzaldehyde in acid buffer reacts with urobilinogen
What substances lead to false negatives when testing for urobilinogen?
nitrite, formalin
What substances lead to false positives when testing for urobilnogen?
highly pigmented urine, some medications
What is the reference range for urobilinogen?
1 mg/dL or less
Increased urobilinogen can be indicative for what conditions?
liver damage, hemolytic disease
True of False: A negative urobilinogen result cannot be detected on a dipstick.
true
A negative urobilinogen result can indicate?
bile duct obstruction
During normal bilirubin metabolism hemoglobin is converted into?
unconjugated bilirubin
Unconjugated bilirubin once formed goes where and what does it become during bilirubin metabolism?
liver, conjugated bilirubin
Once bilirubin becomes conjugated in the liver it then goes where? What does it get turned into then?
intestine, urobilinogen
Once urobilinogen is formed, it is sent where?
1/2 to the feces as urobilin, 1/2 to the liver where it is reabsorbed
The 1/2 of urobilinogen that is sent the liver is excreted where?
kidney
Increased urobilinogen with no bilirubin in the urine indicates what conditions?
a hemolytic condition
Increased bilirubin and urobilinogen in the urine indicates?
liver disease
Increased bilirubin with decreased urobilinogen indicates what condition?
bile duct obstruction
What is the principle behind the detection of nitrite in urine using a dipstick?
(Griess’s reaction) nitrite reacts with amine reagent at acidic pH forming a dizaonium compound, the diazonium compound reacts with 3-hydroxy-1,2,3,4 tetrahydrobenz (h)-quinolin
What situations can cause a false negative nitrite result?
lack of dietary nitrite, urine not in bladder long enough, non-nitrate reducing bacteria present, vitamin c
What is the principle behind the detection of leukocytes in urine using a dipstick?
leukocyte esterase splits an ester to form a pyrrole compound which reacts with a diazo regent
A positive pH test correlates with what other tests?
nitrite, leukocte, microscopic
A positive protein test correlates with what other tests?
blood, nitrite, leukocyte, microscopic
A positive glucose test correlates with what other tests?
ketone
A positive bilirubin test correlates with what other tests?
urobilinogen
The leukocyte esterase test reacts with what

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