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MLSCI 263 > Urinalysis + Kidney Function Tests > Flashcards

Urinalysis + Kidney Function Tests Flashcards

1
Q

Physical examination of urine

A
  • colour
  • clarity
  • volume
  • smell
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2
Q

colour of urine

A
  • major pigment = urochrome, urobilin, uroerythrin
  • intensity depends on concentration
  • normal: straw light yellow
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3
Q

clarity of urine

A
  • normal: clear, transparent

- turbidity: may result from non-pathological or pathological causes

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4
Q

inability to produce urine

A

anuresis

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5
Q

fatal urine condition if not managed immediately!

A

anuria

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6
Q

urine smell

A
  • normal: characteristic faint odour due to volatile acids
  • improper storage = bacterial growth
  • non-pathological causes = foods, intravenous meds
  • pathological disorders = UTI (ammonia), ketone production (fruity odour), amino acid disorders
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7
Q

waxy casts

A
  • end product of cast evolution
  • harder to process
  • tubular obstruction with prolonged stasis
    > chronic renal disease
    > renal failure
  • diseased, dilated tubules (“broad” casts)
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8
Q

urine pH

A
  • normal = 4.5 to 8.0; average is 5.0 to 6.0
  • pH should support findings of other lab tests
  • acid urine:
    > inhibits UTI
    > prevents formation of alkaline renal stones (calcium carbonate, calcium phosphate)
  • alkaline urine:
    > high pH may identify improper collection/ storage!!!
    > prevents precipitation ad promotes excretion of drugs
    > prevent formation of acidic renal stone (calcium oxalate, uric acid, cysteine)
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9
Q

urinalysis: microscopic examination

A
  1. prepare urine sediment on a fresh std vol of sample; 450 x g for 5 min; low speed centrifugation avoids disruption of fragile elements
  2. examine sediment on slide at low power
    > use high power to differentiate
    > report an average of two low power fields
  3. observe: cells, casts, organisms, crystals
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10
Q

what cells should NOT be present in urine?

A
  • RBCs
  • WBCs
  • renal tubule cells should not be many!
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11
Q

renal casts

A
  • cylindrical bodies formed in lumen of renal tubules; ‘casts’ of tubule shape
  • uromodulin (Tamm-Horsfall mucoprotein): secreted by renal tubule cells; denatures/precipitates at high salt, low pH, low urine flow
  • normal = 0-2 hyaline (mucoprotein) casts/low power field
  • pathological = RBC casts, WBC casts, waxy
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12
Q

most common renal casts

A

hyaline cast

granular cast

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13
Q

hyaline cast

A
  • in normal individuals
    > dehydration
    > vigorous exercise
    > stress, fever
  • increase = renal disease, congestive heart failure
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14
Q

granular cast

A
  • breakdown of trapped cellular elements, aggregated proteins
    > after strenuous exercise
  • increase = chronic renal tubule disease; acute tubular necrosis
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15
Q

RBC casts

A
  • renal disease
  • glomerulonephritis
  • tubule damage
  • nephrotic syndrome (massive protein loss in urine)
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16
Q

WBC casts

A
  • inflammation or infection

- pyelonephritis (inflammation of kidneys)

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17
Q

waxy casts

A
  • end product of cast evolution
  • tubular obstruction with prolonged stasis: chronic renal disease, renal failure
  • diseased, dilated tubules (“broad” casts)
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18
Q

acid urine

A
  • normal: uric acid, calcium oxalate

- pathological: bilirubin, drugs (sulfonamide, ampicillin); amino acids (cysteine, tyrosine, leucine)

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19
Q

alkaline urine

A
  • normal: amorphous phosphates, triple phosphates (struvite), calcium phosphate, calcium carbonate
  • pathological: important if urine sample is fresh; triple phosphates; UTI, calculi (renal stones)
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20
Q

urine pH

A
  • normal pH 4.5-8.0
  • acid urine = inhibits development of UTI; prevents formation of alkaline renal stones (Ca carbonate or Ca phosphate)
  • alkaline urine = high pH may identify improper collection/storage
    > prevents precipitation and promotes excretion of drugs
    > prevent formation of acidic renal stone (Ca oxalate, uric acid, cysteine)
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21
Q

T or F. urine pH should support findings of other lab tests

A

T!

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22
Q

measure of urine concentration based on its density; affected by # of solutes and their MW

A

urine specific gravity

1.002 -1.040

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23
Q

2 methods of measuring urine specific gravity

A
  • polyelectrode pH indicator (~ionic strength)

- refractive index

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24
Q

urine glucose

A
  • normally absent
  • glucosuria = DM
  • detected by glucose oxidase method (linked to peroxidase rxn)
  • other sugars may appear in urine = not detected
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25
Q

urine ketones

A
  • ketonuria
  • when ketonemia >70mg/dL exceeds renal threshold
  • ketones react with sodium nitroprusside => colour
26
Q

urine nitrite

A
  • identify asymptomatic UTI: NO3 -> NO2 (dye colour increases)
  • but not all bacteria have nitrate reductase
  • false positives: foods or dyes => red
27
Q

leukocyte esteerase

A
  • detects intact and lysed WBCs; infection; increased dye colour
  • normal is <10 WBCs/uL
  • pathology is > 20 BCs/uL (bacteria, pyuria)
28
Q

these often detect asymptomatic UTI

A

urine nitrite

leukocyte esterase

29
Q

urine blood

A
  • intact RBCs in urine = hematuria

- early indicator of disease but not severity

30
Q

urine bilirubin, urobilinogen

A
  • hemoglobin -> heme -> bilirubin -> urobilinogen

indicator of liver disease (should be REALLY LOW; should not be a colour change on dipstick)

31
Q

urine proteins

A
  • normal <150 mg/day
  • proteinuria = increased protein in urine due to glomerular or tubular damage
  • detected by indicator dye tetrabromophenol blue
  • FIRST indication of renal disease
    > diabetic nephropathy
    > edema and nephrotic syndrome (up to 5 g/day!)
  • albumin, Bence-Jones proteins, uromodulin mucoproteins, B2-microglobulin and other small MW proteins
32
Q

Albustix detect

A
  • for albumin only; >50 mg/day
  • qualitative dipstick tests may miss low [albumin]; most only detect >250 mg/day
  • microalbuminuria = 15-300 mg/day
33
Q

albuminuria

A
  • increase urine [albumin] more important than total urine protein
  • powerful indicator of diabetic nephropathy; glomerulus affected first
34
Q

Bence Jones proteins

A
  • low MW proteins arising from overproduction of light chain kappa and lambda immunoglobulin para-proteins
  • precipitate at 40-60 Cc
  • redissolve at 10C
35
Q

most abundant protein in urine

A
  • uromodulin (Tamm-Horsfall) mucoprotein
  • 20-70 mg/day
  • mucoprotein (85kD): 30% carb (forms a gel)
    > affects water impermeability (mutants cant concentrate urine)
    > secreted by renal distal tubule and collecting duct cells
  • inhibits viral hemagglutination, formation of calcium stone, development of UTI
36
Q

B2 microglobulin and other small MW proteins

A
  • present due to defective tubule reabsorption due to tubule damage arising from:
    > heavy metal poisoning (lead)
    > Wilson’s disease: tissue deposition of copper
    > Fanconi’s syndrome: proximal tubule malabsorption
37
Q

aminoaciduria

A
  • normal is 1-2% of total nitrogen in urine due to AA
  • overflow aminoaciduria = increase [plasma amino acid]
    > inborn error
    > excessive breakdown of body protein
    > increase protein diet
  • renal aminoaciduria: not absorbed in tubule ; renal tubular disease
38
Q

ig light chain damage nephrons when they deposit in ells and become trapped in hyaline casts = block tubules

A

Bence Jones proteins

39
Q

a defense protein

A
  • uromodulin

- inhibit mechanisms of pathogens; prevents formation of stone

40
Q

non-protein nitrogen

A
  • metabolic waste
    > majority from protein metabolism as urea; remainder from…
    > muscle turnover as creatinine
    >nucleic acid (purine) metabolism as uric acid
41
Q

marker of impaired renal function, ___ is cleared from the blood by kidneys

A

NPN = non-protein nitrogen

42
Q

source of urea

A
  • product of protein breakdown in liver

AAas -> ammonia
-> urea cycle -> urea

43
Q

urea in liver failure

A

urea formation is impaired

44
Q

what does an increase in serum [urea] mean?

A

decrease in renal clearance
marker of renal function!!!
- not detected until GFR function is decreased by 25-50%

45
Q

product of muscle turover

A

creatinine (creatine phosphate)

46
Q

increase serum creatinine

A
  • significantly impaired renal function

- >75% function lost!

47
Q

creatinine

A
  • constant production varies with muscle mass; not activity
  • cleared from blood by the kidney
  • ALWAYS present in urine at constant rate (useful to use as reference)
  • serum levels not affected by diet
48
Q

T or F. Serum creatinine alone is a sensitive indicator of renal function

A

F!

- clearance must drip to 25% of normal before serum creatinine is increased so not very sensitive

49
Q

Jaffe reaction

A

creatinine and picrate ion (OH-) => creatinine picrate (A500); a yellow colour
- suitable for urine, protein-free filtrate of plasma or serum

  • subject to interferences
  • negative interference with bilirubin (yellow) but can be managed w buffers or ferricyanide to oxidize to biliverdin
50
Q

enzyme-linked rxns for determining creatineine

A

NADH ; inversely proportional

the more creatinine the less absorption

51
Q

uric acid

A

NPN waste product derived from purine nucleic acids

- adenosine and guanosine

52
Q

increase in [uric acid]

A

impaired renal function or …

53
Q

forms of uric acid

A

keto form and lactim (enol uric acid; weakly acidic and forms salts with Na+ and K+)

54
Q

this eliminates nitrogen from purine metabolism

A

uric acid

55
Q

uricase or urate oxidase

A
  • converts uric acid to allantoin (less liquid waste)

- step missing in humans

56
Q

what causes hyperuricemia?

A
  • decrease renal excretion
  • acidosis
  • enhanced cellular breakdown
  • increased dietary intake of precursors (rich man’s disease; organ meats?)
  • inborn error: Lesch-Nyhan syndrome (self-mutilation)
    > enzyme def in uric acid metabolism
  • gout
57
Q

what is gout?

A
  • painful!
  • 3-25x increase in plasma uric acid
    > deposits in joints
  • rich man’s disease (diet)
  • neuts ingest urate crystals -> chemotactic factor -> arthritis; supersaturation of uric acid = crystals
58
Q

what can gout be due to?

A
  • deficiency in plasma urate binding protein

- local effects of pH, cold, trauma

59
Q

uricosuria

A
  • high urine [uric acid]
  • increased uric acid production => renal excretion
  • poor water solubility => urate crystals in urine
    > at low pH soluble Na+ and K+ salts => precipitate = stones
  • lithium sometimes treatment
  • influenced by diet
60
Q

lithium urate

A

most soluble salt and can promote uric acid excretion

61
Q

uric acid methodology

A

HPLC methods - reversed-phase columns (retention time <6 min)

uricase-catalyzed oxidation
> advantage = specific and can be done directly on serum without protein precipitation
- inversely proportional (high activity of enzyme means that lots of urate present and this is measured at A292 so decrease in absorbance bc converted to allantoin)

peroxide coupling from uricase oxidation to methanol oxidation = chromagen; directly proportional (visible light)

MLSCI 263 (31 decks)

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