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Clinical Biochem > Urinalysis > Flashcards

Urinalysis Flashcards

1
Q

What is the normal range for pH dipstick results

A

4.5-8.0

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2
Q

What are sources of error for the pH dipstick

A

increased alkalinity - bacterial growth (increased sitting), pH >8.5 is not possible and must be due to improper storage

increased acidity - improper reagent strip dipping technique (protein buffer can run onto pad and falsely decrease the pH)

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3
Q

What is the clinical significance of pH dipstick results

A

can correlate with acidosis or alkalosis if kidney function is normal

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4
Q

What is the normal result for the leukocyte dipstick

A

negative

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5
Q

What are sources of error for the leukocyte dipstick

A

false positive - coloured urine, contamination with an oxidizing agent

false negative - high concentration of proteins ( >5g/L), glucose (>30g/L), ascorbic acid, cephalexin, cephalothin, high specific gravity, lymphocytes that do not produce leukocyte esterase, not mixing before dipping the reagent stick

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6
Q

What is the normal result for the nitrite dipstick

A

negative

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7
Q

What are the sources for error for the nitrite dipstick

A

false positive - coloured urine, improper storage resulting in bacterial growth

false negative - urine not held in bladder for a sufficient time, high concentration ascorbic acid, high specific gravity

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8
Q

What is the clinical significance of leukocyte dipstick results

A

infection or inflammation

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9
Q

What is the clinical significance of nitrite dipstick results

A

gram negative bacteria infection
may aid in the diagnosis of asymptomatic cystitis, evaluation of antibiotic treatment and screening of urine for culture

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10
Q

What is the normal result for the protein dipstick

A

negative

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11
Q

What are the sources of error for the protein dipstick

A

false positive - coloured urines, highly buffered alkaline urines, high specific gravity, prolonged dipping of the dip stick

false negative - proteins other than albumin

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12
Q

What is the clinical significance of protein dipstick results

A

renal disease such as glomerulonephritis and nephrotic syndrome

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13
Q

What is the normal result for the glucose dipstick

A

negative

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14
Q

What are sources of error for the glucose dipstick

A

false positive - contamination with oxidizing agents or peroxide

false negative - low temperature, high specific gravity, high concentration of ketones or ascorbic acid, bacterial growth (glycolysis)

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15
Q

What is the clinical significance of the glucose dipstick

A

uncontrolled diabetes mellitus, renal disease, pregnancy

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16
Q

What is the normal result for the ketone dipstick

A

negative

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17
Q

What are sources of error for the ketone dipstick

A

false positive - coloured urine, bacterial growth, presence of MESNA or captopril

false negative - bacterial growth can break down acetoacetic acid

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18
Q

What is the clinical significance of the ketone dipstick

A

uncontrolled diabetes mellitus, insulin, inherited metabolic disorder, dieting, starvation, pregnancy, vomiting, diarrhea, strenuous exercise

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19
Q

What is the normal result for the blood dipstick

A

negative

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20
Q

What are sources of error for the blood dipstick

A

false positive - contamination of oxidizing agents, bacterial peroxidases, myoglobin, menstrual contamination

false negative - increased specific gravity, high concentrations of ascorbic acid, not mixing before dipping reagent strip

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21
Q

What is the clinical significance of the blood dipstick

A

hematuria - renal stones, glomerulonephritis, pyelonephritis, strenuous exercise

hemoglobinuria - IVH, transfusion reaction, severe burns, infection

myoglobinuria - observed in rhabdomyolysis, trauma and crush injuries, is toxic to nephron tubules and may cause acute renal failure

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22
Q

What is the normal result for the urobilinogen dipstick

A

negative (<16 umol/L)

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23
Q

What are sources of error for the urobilinogen dipstick

A

false positive - coloured urines, porphobilinogen

false negative - acidic urine, exposure to light, storage at room temperature

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24
Q

What is the clinical significance of the urobilinogen dipstick

A

hemolytic disorders, liver disease excluding hepatobiliary obstruction

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25
Q

What is the normal result for the bilirubin dipstick

A

negative

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26
Q

What are the sources of error for the bilirubin dipstick

A

false positive - coloured urines

false negative - exposure to light and storage at 4C, high concentrations of ascorbic acid or nitrites

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27
Q

What is the clinical significance of the bilirubin dipstick

A

hepatobiliary obstruction, gallstones, tumors in the bile duct, some liver disease such as hepatitis or cirrhosis

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28
Q

What is the normal result for specific gravity

A

1.005 - 1.030

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29
Q

What are the sources of error for the specific gravity dipstick

A

false increase - high concentration of proteins

false decrease - highly buffered alkaline urine (add 0.005 if pH is >/= 6.5 when read visually)

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30
Q

What is the clinical significance of the specific gravity dipstick

A

patient hydration status, ability of the kidney to concentrate urine, presence of ketones increases specific gravity

a value of 1.000 can be correlated with specimen adulteration

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31
Q

What is the normal colour/turbidity of urine

A

unremarkable/clear

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32
Q

What is the expected frequency of hyaline casts in urine

A

occasional

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33
Q

What is the expected frequency of granular casts in urine

A

occasional

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34
Q

What is the expected frequency of white cell casts in urine

A

negative

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35
Q

What is the expected frequency of red cell casts in urine

A

negative

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36
Q

What is the expected frequency of waxy casts in urine

A

negative

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37
Q

What is the expected frequency of fatty casts in urine

A

negative

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38
Q

What is the expected frequency of mixed cellular casts in urine

A

negative

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39
Q

What is the expected frequency of white cells in urine

A

occasional

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40
Q

What is the expected frequency of red cells in urine

A

occasional

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41
Q

What is the expected frequency of epithelial cells in urine

A

occasional

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42
Q

What is the expected frequency of renal epithelial cells in urine

A

negative

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43
Q

What is a clean catch or midstream urine

A

a method of collecting urine to reduce bacterial contamination from the skin. The genital area is cleaned and a urine specimen is collected part way through voiding the bladder

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44
Q

When is suprapubic aspiration most often used

A

to collect urine from infants for culture

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45
Q

When should urines be processed

A

within 2 hours of collection

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46
Q

What are the benefits and risks of refrigerating a urine sample

A

decreases bacterial growth but promotes crystal formation

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47
Q

What causes cloudyness in urine

A

amorphous urates (in acidic urine), amorphous phosphates (in alkaline urine), white or red cells in significant numbers

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48
Q

What causes an amber colour in urine

A

bilirubin or dehydration

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49
Q

What causes an orange colour in urine

A

bilirubin, carrots, riboflavin, rhubarb

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50
Q

What causes a pink/red colour in urine

A

red blood cells (if cloudy), hemoglobin (if clear), myoglobin, porphyrins, beets, methyldopa, senna

51
Q

What causes a brown to red colour in urine

A

porphobilin

52
Q

What causes a brown to black colour in urine

A

bilirubin, melanin, methemoglobin, iron compounds, levodopa, quinine

53
Q

What causes a blue/green colour in urine

A

biliverdin, pseudomonas, methylene blue

54
Q

What is the reaction for the pH dipstick

A

a double indicator principle using both bromothymol blue and methyl red

55
Q

What are interferences of the pH dipstick

A

none known

56
Q

What is the reaction for the leukocyte dipstick

A

esterases in the leukocytes hydrolyze an ester in the test pad to produce an aromatic compound which reacts with a diazonium salt to produce an azo dye

57
Q

What is the reaction of the nitrite dipstick

A

Enterobacteriaceae reduce dietary nitrate in urine into nitrite, at an acidic pH nitrite reacts with an aromatic amine to form a diazonium compound which couples with an aromatic compound to produce a pink colour

colour development is not proportional to the number of bacteria present, any pink colour should be marked as positive

58
Q

What is the reaction of the protein dipstick

A

the indicator dye releases protons in response to the proteins which are anionic and causes a colour change

59
Q

What is pre-renal proteinuria

A

overflow proteinuria is caused by an increase in low molecular weight plasma proteins excreted in the urine, these proteins pass through the healthy glomeruli but due to increased concentrations it exceeds the reabsorption capability of the tubules

LMW proteins can be: acute phase reactants, hemoglobin, myoglobin or monoclonal free light chainsWh

60
Q

What are two examples of renal proteinuria

A

glomerular leakage and tubular proteinuria

61
Q

What is glomerular leakage

A

selective - the slits between the glomerular membrane podocytes are still intact but are wider than usual. Large molecules pass through the damaged glomeruli and are excreted, there is still some size selectivity

nonselective - proteins of any size can pass through the damaged glomerulus

62
Q

What is tubular proteinuria

A

glomeruli are healthy but the renal tubules cannot reabsorb the low molecular weight What is the expected frequency of in urine proteins such as B2-microglobulin and immunoglobulin

rare, might be caused by heavy metal poisoning and nephrotoxic drugs

63
Q

What is post-renal proteinuria

A

proteins found in the urine originate from the urinary tract as a result of inflammation, malignancy or injury. Uromodulin is produced by the renal tubular epithelial cells in the loop of henle and is always present

64
Q

What is the reaction of the glucose dipstick

A

based on a double sequential enzyme reaction, glucose oxidase catalyzes the oxidation of glucose to form gluconic acid and hydrogen peroxide then peroxidase catalyzes the oxidation of a chromogen via the hydrogen peroxide

65
Q

What is the reaction of the ketone dipstick

A

based on the development of colours ranging from beige to purple when acetoacetic acid reacts with nitroprusside

acetone does not react unless glycine is added to the reagent pad

66
Q

What is the reaction of the blood dipstick

A

based on the peroxidase-like activity of hemoglobin which catalyzes the reaction of cellular peroxide and a chromogen, will detect both intact RBC and free hemoglobin

sensitivity of ~ 5 RBC/L

67
Q

What is the reaction of the urobilinogen dipstick

A

based on the ehrlich reaction, in an acid medium p-diethylaminobenzaldehyde with a colour enhancer reacts with urobilinogen to produce a pink colour

68
Q

What is the reaction of the bilirubin dipstick

A

bilirubin reacts with a diazonium salt in an acidic medium to form an azo dye

69
Q

What is the reaction of the specific gravity dipstick

A

the test pad contains a polyelectrolyte and a pH indicator maintained at an alkaline pH, ionic solutes in the urine cause protons to be released from the pad which causes the surrounding pH to decrease and the bromothymol blue indicator changes from blue-green to yellow-green

70
Q

What is a polarizing microscope used for

A

to detect birefringent urine elements such as uric acid and cholesterol

71
Q

What is the morphology of a hyaline cast

A

there is a visible protein matrix, it appears translucent and is easier to see in subdued light or phase contrast

stain uniformly, pale pink or pale purple but sometimes do not stain at all

72
Q

What is the clinical significance of a hyaline cast

A

they are not clinically significant and can be observed after exercise or stress

increased hyaline casts will be seen along with other cast types in pathological conditions

73
Q

What is the morphology of granular casts

A

contain many fine or coarse granules that are usually evenly dispersed over the cast, can also include degenerated cell remnants

74
Q

What is the clinical significance of granular casts

A

found in normal urine (following strenuous exercise) as well as in urine from individuals with renal disease

75
Q

What is the morphology of RBC casts

A

intact erythrocytes can sparsely populate or completely fill the cast, unstained the cast will appear yellow or reddish brown, stained the RBCs appear purple or colourless within the pink matrix

76
Q

What is the clinical significance of RBC casts

A

indicates bleeding in the nephron, most commonly observed in glomerulonephritis and are associated with proteinuria

77
Q

What is the morphology of WBC casts

A

intact leukocytes can sparsely populate or completely fill the cast, usually composed of neutrophils and thus can look granular, staining can aid in identifying the multi-lobed nucleus,

should correlated with free leukocytes in the urine and urine dipstick

78
Q

What is the clinical significance of WBC casts

A

indicates infection of inflammation in the nephron, commonly observed in pyelonephritis an can also be seen in acute interstitial nephritis and glomerulonephritis

79
Q

What is the morphology of epithelial cell casts

A

they contain renal tubular epithelial cells

80
Q

What is the clinical significance of epithelial cell casts

A

present in advanced renal tubular disease resulting in stasis, tubular disease may also be caused by heavy metals, drugs, viral infection, transplant rejection, can also be seen in pyelonephritis with leukocyte casts

81
Q

What is the morphology of fatty casts

A

casts that contain unstained spherical, highly refractile fat droplets, neutral fats and triglycerides can be stained orange with Sudan II or Oil Red O, cholesterol can demonstrate as Maltese-cross under polarizing lights

should be accompanied by proteinuria and oval fat bodes, free fat droplets

82
Q

What is the clinical significance of fatty casts

A

most commonly associated with nephrotic syndrome but may be observed in toxic tubular necrosis, diabetes mellitus, and crush injuries

83
Q

What is the morphology of waxy casts

A

more refractile than hyaline casts, may have broken ends, colourless or uniform purple

84
Q

What is the clinical significance of waxy casts

A

found in extreme urine stasis and are associated with chronic renal failure

85
Q

What is the morphology of erythrocytes

A

appear as small, biconcave discs lacking nuclei but varies based on the urine specific gravity, can be crenated (hypersthenuria) or large and empty (hyposthenuria)

staining varies based on pH, pink purple (neutral pH), pink or unstained (acidic pH) or, purple (alkaline pH)

86
Q

What is the clinical significance of erythrocytes

A

macroscopic hematuria (>100 cells/HPF) indicates glomerular disease or trauma and coagulation disorders

microscopic hematuria indicates early glomerular disease, malignancy or renal calculi

87
Q

What is the morphology of leukocytes

A

larger than erythrocytes, round with multi-lobed nuclei, the neutrophils cytoplasm stains light purple and contain large purple staining granules

in hyposthenuria WBCs may swell and appear as glitter cells
neutrophil lysis is increased in alkaline urines and hyposthenuria

88
Q

What is the clinical significance of leukocytes

A

Pyuria is found in infection (pyelonephritis, cystitis, urethritis) and inflammation (glomerulonephritis, lupus, interstitial nephritis) of the genitourinary system

other leukocytes cell types may be seen in urine
eosinophils are associated in drug-induced interstitial nephritis (differentiate from neutrophils with Hansel stain)
lymphocytes are found in increased numbers in renal transplant rejection

89
Q

What is the morphology of squamous epithelial cells

A

large irregularly shaped cells with abundant light blue cytoplasm, small dense nuclei stain that stain dark orange-purple

90
Q

What is the morphology of transitional epithelial cells

A

these cells are smaller than squamous cells and have various shapes, cytoplasm stains light purple and nuclei are well defined and stain blue-purple

91
Q

What is the clinical significance of squamous epithelial cells

A

cells originate in the female genitalia and urethra and the lower urethra of men. They are not clinically significant

92
Q

What is the clinical significance of transitional epithelial cells

A

cells originate in the renal calyx, bladder and ureters. Increased numbers are found following catheterization

93
Q

What is the morphology of renal tubular epithelial cells

A

smaller than squamous cells and have various shapes, columnar with coarse granules cytoplasm stains light purple with an eccentric blue-purple nuclei

94
Q

What is the clinical significance of renal tubular epithelial cells

A

cells originate from the proximal and distal convoluted tubules and collecting ducts of the nephron the presence of these cells indicates tubular damage

95
Q

What is the morphology of oval fat bodies

A

renal tubular cells that have absorbed lipids, cells are highly refractile and the eccentric nucleus of the cell may be obscured

confirmation of the presence of fatty droplets composed of triglycerides or neutral fats can be performed by staining with Sudan III or oil red O

fatty drops composed of cholesterol appear as maltese crosses under polarized light

96
Q

What is the clinical significance of oval fat bodies

A

lipiduria is associated with nephrotic syndrome as well as severe tubular necrosis and diabetes mellitus and trauma to long bones

usually seen with free fat droplets and fatty casts

97
Q

What are calcium oxalate crystals

A

typically found in acidic urine but can be present at other pHs

colourless, birefringent and soluble in HCl

dihydrate form is octrahedral (envelope)

monohydrate is oval/dumbbell shaped

monohydrate form is significantly increased in ethylene glycol poisoning

98
Q

What are uric acid crystals

A

found in acidic urine (<5.5)

colourless to yellow, birefringent and soluble in alkali

four sided flat plates, rhombic, wedges and rosettes

increased amounts associated with cytotoxic drugs and gout

99
Q

What are amorphous urate crystals

A

found in acidic urine (<5.5)

pink or pink-orange in colour, yellow-brown granules, birefringent, soluble with alkali, can convert to uric acid with HCl

cold temperatures enhance precipitation

100
Q

What are acid urate crystals

A

found in weakly acidic urines

larger granules with spicules

101
Q

What are sodium urate crystals

A

needle shaped

102
Q

What are amorphous phosphate crystals

A

white, granular in appearance similar to amorphous urates

cold temperatures enhance precipitation

differentiated from amorphous urates based on colour and pH

soluble with acid, insoluble at 60C

103
Q

What are ammonium magnesium phosphate (triple phosphate) crystals

A

colourless, prism shaped (coffin lids), birefringent, soluble in acetic acid

may have feathered appearance as they dissolve

104
Q

What are calcium phosphate crystals

A

rare

colourless, flat rectangular plates with one square end and one pointed end, birefringent and soluble in dilute acetic acid

105
Q

What are calcium carbonate crystals

A

rare

small colourless spheres and dumbbells, resemble amorphous phosphates, soluble in acetic acid (produces carbon dioxide)

106
Q

What are ammonium biurate

A

rare

yellow-brown spicule covered spheres often described as thorny apples, dissolve at 60C and convert to uric acid with addition of glacial acetic acid

usually seen in aged urines

107
Q

What are cystine crystals

A

rare

colourless hexagonal plates, birefringent, soluble in NaOH

cystinuria is an inherited metabolic disorder

108
Q

What are cholesterol crystals

A

rare

rectangular shaped flat plates with notched corners, highly birefringent

should be seen in conjunction with marked proteinuria as well as other signs of lipiduria

often confused with radiographic material

109
Q

What are tyrosine crystals

A

rare

colourless to yellow, thin needles forming clumps or needles

in severe liver disease tyrosine is seen along with leucine and a positive bilirubin reagent strip test

can be observed in inherited metabolic disorders

110
Q

What are leucine crystals

A

rare

brown to yellow spheres with concentric circles with striations radiating from the center of the crystal

in severe liver disease leucine is seen along with leucine and a positive bilirubin reagent strip test

can also be observed in inherited metabolic disorders

111
Q

What are bilirubin crystals

A

yellow-brown fine needle clusters or granules

seen in hepatic disorders and should correlate with a positive bilirubin reagent strip test

112
Q

What are bacteria

A

tiny spheres or rods

may indicate the presence of infection

may or may not correlate with positive nitrite and leucocyte tests

often confused with amorphous crystals

113
Q

What is yeast

A

clear, small, ovoid refractile structures

may have buds and or mycelia

commonly associated with diabetic and immunocompromised patients alongside leukocytes

may also be seen with vagina moniliasis

114
Q

What is trichomonas vaginalis

A

pear shaped cells with a waxy membrane and a long thin flagellum

a sexually transmitted parasitic infection

115
Q

What is spermatozoa

A

oval head with long tapered tails

found in specimens from males or females but may have legal implications in female specimens

116
Q

What is mucus

A

produced by the lower genitourinary system and primarily composed of uromodulin

clear, threadlike structure that is weakly refractile

117
Q

What are the expected test results for a UTI

A

Dipstick - positive leukocytes, nitrites, blood

Microscopic - increased WBC, Bacteria, RBC, transitional epithelial cells

118
Q

What is pyelonephritis

A

an inflammation of the kidney and renal pelvis due to infection, can be acute or chronic

119
Q

What are the expected test results for pyelonephritis

A

Dipstick - positive leukocytes, nitrites, blood

Microscopic - increased WBC, Bacteria, RBC, transitional epithelial cells, WBC clumps, WBC, granular and waxy casts

120
Q

What is glomerulonephritis

A

a thickening of the basement membrane, cellular proliferation. leukocyte infiltration and deterioration and scarring of the kidney

causes can be immunological, hereditary or metabolic

121
Q

What are the expected test results for glomerulonephritis

A

Dipstick - positive protein and blood, low specific gravity

Microscopic - increased WBC, RBC, increased renal tubular epithelial cells, RBC casts, occasional WBC and renal cell casts

122
Q

What is nephrotic syndrome

A

a disease of the renal parenchymal cells and is characterized by increased permeability of the glomeruli to proteins and lipids

123
Q

What are the expected test results for nephrotic syndrome

A

Dipstick - positive protein, blood

Microscopic - lipiduria, oval fat bodies, increased RBC, casts (especially fatty), renal epithelial cells

Clinical Biochem (15 decks)

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