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Compendium Chemistry > Body Fluids > Flashcards

Body Fluids Flashcards

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1
Q

Macroscopic exam of urine

red

black/brown

blue/green

A
  • Red urine
    • hematuria (RBCs)
    • hemoglobinuria (free hemoglobin in urine)
    • myoglobinuria
    • all 3 produce positive hemoglobin result on urine dipstick test
  • Brownish black urine:
    • alkaptonuria
    • methemoglobinuria
  • Blue/green urine
    • pseudomonas
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2
Q

Urine chemistry - glucose

A
  • Glycosuria
    • with normal renal function, glucose appears in urine at renal threshold of 180 mg/dL
    • threshold is lower in pregnancy
    • in tubular dysfunction (impaired reabsorption), glucose may appear in the urine even when serum glucose is normal
  • dipstick method is sensitive to glucose, other reducing methods do not give a positive reaction
  • copper sulfate method (Benedict reaction) underlies the Clinitest procedure:
    • detects all reducing substances (reduce copper salts) including
      • glucose
      • lactose
      • fructose
      • galactose
      • pentose
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3
Q

Ascorbate inhibits what urine test

A
  • dipstick tests including
    • glucose
    • bilirubin
    • nitrite
    • leukocyte esterase
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4
Q

Urine protein

A
  • Normal urine protein amounts to 150 mg/day and is mostly Tamm-Horsfall (tubular) protein
    • greater amounts seen following
      • exercise
      • dehydration
      • fever
    • benign types of proteinuria
      • postural and intermittent proteinuria
  • dipstick test is sensitive to albumin
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5
Q

Urine ketones

A
  • 3 major ketones in blood and urine:
    • beta hydroxybutyrate
    • acetoacetic acid
    • acetone
  • dipstick test is sensitive to acetoacetic acid
  • table test (Acetest) is sensitive to acetoacetic acid also
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6
Q

Urine hemoglobin

A
  • Hemoglobinuria must be distinguished from hematuria and myoglobinuria, which all produce positive hemoglobin dipstick
    • hematuria is confirmed by micro exam for RBCs
    • hemoglobinuria is confirmed by micro exam of urine for hemosiderin laden mononuclear cells (Prussian blue stain used)
    • myoglobinuria distinguished by history, creatine kinase, normal haptoglobin
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7
Q

Causes of rhabdomylosis

A
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8
Q

Bilirubin and urobilinogen

A
  • urinary bilirubin indicates conjugated hyperbilirubinemia because the unconjugated form does not pass through the glomerulus
  • urobilinogen is the product of hydrolysis of bilirubin by intestinal bacteria
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9
Q

nitrite in urine

A
  • indicates presence of nitrite producing organisms such as E coli
  • nitrite negative agents of UTI include enterococci, N gonorrhoea and M Tb
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10
Q

Urine leukocyte esterase

A
  • a reflection of the number of urinary neutrophils
  • trichomonads and eosinophils are possible sources of false positive results
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11
Q

Urine specific gravity

A
  • increased when the urine is concentrated
  • fixed at 1.010 in isothenuria in which tubular damage results in urine SG equaling that of the glomerular filtrate
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12
Q

urine pH

A
  • urine is usually pH 6
  • acidotic patients have urine pH < 6
  • alkalotic patients have urine pH >6
  • Renal tubular acidosis has urine that is inappropriately alkaline compared to the blood pH and the kidneys cannot acidify the urine beyond pH 6.5
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13
Q
A
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14
Q
A
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15
Q

Chemical composition of stones is studied by

A

crystallography or infrared spectroscopy

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16
Q

Majority of kidney stones are composed of

A

Calcium oxalate > CaPO4 > struvite (MgNH4PO4 or triple phosphate stones) > urate > cystine

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17
Q

Calcium oxalate stones

A
  • Promoted by
    • low urine volume (like other stones)
    • low citrate
    • hypercalciuria
    • oxaluria
      • oxaluria increased in patients with Crohn disease who have undergone small bowel resection or small bowel bypass or ingest excessive amounts of oxalate (rhubarb, spinach, nuts)
  • urinary pH has little effect on calcium oxalate crystalization
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18
Q

Calcium phosphate stones

A
  • Promoted by
    • low urine volume
    • hypercalciuria
    • elevated pH
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19
Q

Struvite stones promoted by

A

UTI with urea splitting organisms, which contributes to markedly alkaline pH

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20
Q

Urate stones promoted by

A

acidic pH and hyperuricosuria

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21
Q

Cystine stones promoted by

A
  • inherited disease cystinuria (not cystinosis), an AR disease with defective renal and intestinal dibasic amino acid transport
  • affects cystine, ornithine, lysine, and arginine (COLA)
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22
Q

Microscopic findings in hematuria

A
  • Glomerular bleednig
    • red cells may be polymorphic
    • cells have different Hb concentrations
    • red cell casts
    • erythrophagocytosis
  • Non glomerular bleeding
    • uniform RBCs
    • no red cell casts
    • no erythrophagocytosis
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23
Q

Hyaline casts

A
  • clear, colorless
  • nonspecific
    • renal disease
    • dehydration
    • heat related trauma
    • vigorous exercise
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24
Q

Red cell casts

A
  • Specific for glomerulonephritis
  • Lumpy edge
  • anucleate, reddish pale discs
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25
Q

White cell casts

A
  • tubulointerstitial nephritis, especally pyelonephritis
  • nucleated cells with lobated nuclei of neutrophils
26
Q

Tubular casts

A
  • renal tubular cells characterized by mononuclear, cuboidal cells
  • acute tubular necrosis
27
Q

Granular casts

A
  • renal disease
  • exercise
  • dehydration
  • heat related trauma
  • acellular
  • rough, granular surface
  • accompany hyaline casts
28
Q

Waxy casts

A
  • severe renal disease
  • acellular
  • blunt ends
  • pale yellow
  • cracks along the length
  • diameter is 2x that of nonspecific casts (hyaline and granular)
29
Q

broad casts

A
  • hyaline, granular, or waxy casts that are unusually broad and indicate ESRD
  • correspond to widely dilated collecting ducts in advanced atrophy
30
Q

fatty casts

A
  • nephrotic syndrome - lipiduria is common
  • cellular casts in which lipid droplets are absorbed
  • with polarized light the absorbed lipid has a maltese cross appearance
  • may contain oval fat bodies and/or fat globules and can be highlighted by stains for lipid
31
Q

Amorphous urine crystals

A

AKA amorphous sediment

  • crystals that have no consistent shape or size
  • usually clinically insignificant
  • in alkaline urine there may be amorphous phosphate, magnesium, and/or calcium crystals
  • in acidic urine there may be amorphous urate crystals that appear yellow brown in football-like shapes, diamonds, needles, cubes, dumbbells, etc
32
Q

Calcium oxalate crystals

A
  • clear crystals that resemble envelopes, forming in acidic urine
    • found in oxaluria, which may be indicative of
      • high oxalate intake (rhubarbs, cabbage, asparagus)
      • small bowel disease (e.g., Crohn)
      • renal failure
      • diabetes
      • ethylene glycol
      • acetazolamide therapy
33
Q

cystine crystals

A
  • colorless hexagonal plates observed in cystinuria
34
Q

Triple phosphate (magnesium ammonium phosphate)

A
  • crystals resemble coffin lids in alkaline urine
  • usually clinically significant
35
Q

biurate crystals

A
  • resemble thorn apples
  • yellow brown rounded structures with thornlike excrescences
  • form in alkaline urine
  • usually clinically insignificant
36
Q

Tyrosine crystals

A
  • thin needles in clumps like sheaves of wheat
  • seen in
    • tyrosinosis
    • hyperbilirubinemia
    • liver disease (also may be seen with leucine crystals- depicted in image)
37
Q

Urine Microscopy in acute renal failure

  • RBCs
  • Casts
  • Erythrophagocytosis
  • Granulocytes
A
38
Q

Light criteria

A

help to classify effusions as exudative or transudative

40
Q

Distinguishing transudates and exudates

A
  • Light criteria
  • exudate:
    • specific gravity > 1.016
    • pleural fluid protein > 3 G/dL
    • pleural fluid cholesterol > 45 mg/dL
    • pleural fluid bilirubin:serum bilirubin ratio >0.6
  • Caused by
    • Transudates:
      • CHF
      • cirrhosis
      • nephrotic syndrome
    • Exudates
      • result from nearly all other causes:
        1. bacterial pneumonia
        2. malignancy (usually bloody)
        3. tuberculosis
        4. pulmonary embolus
        5. collagen vascular diseases (especially rheumatoid arthritis)
        6. pancreatitis (classically left sided)
        7. esophageal perforation
        8. chylothorax
        9. asbestos exposure
        10. postmyocardial infarction (Dressler syndrome)
        11. uremia
        12. ovarian fibromas (Meigs syndrome)
41
Q

Chylous effusion

A
  • aka chylothorax
  • caused by
    • lymphatic (thoracic duct) obstruction
    • malignancy (lymphoma and bronchogenic carcinoma)
    • trauma
    • surgery
    • infection
    • sarcoidosis
    • lymphangioleiomyomatosis of the lung
  • creamy top layer of chylomicrons may form if fluid is allowed to stand
42
Q

Chylous versus pseudochylous effusions

A
43
Q

pseudochylous effusions

A
  • result from gradual accumulation of lipids from cellular breakdown in
    • TB
    • rheumatoid pleural effusion
    • myxedema
45
Q

CHF pleural effusion

A
  • In treated CHF, a transudate may be converetd into exudate
  • effusions tend to be larger on or confined to the right hemithorax
46
Q

Parapneumonic effusions

A
  • usually sterile or contain few bacteria
  • empyema = bacterial pneumonia
    • >100,000 neutrophils/mL
    • pH < 7.2
    • bacteria on gram stain
47
Q

Tuberculosis associated pleural effusions

A
  • lymphocyte predominant and contain a paucity of mesothelial cells
  • adenosine deaminase (ADA) elevated
48
Q

Pulmonary embolism effusion

A
  • 50% associated with effusion
  • most are exudates, bloody and may demonstrate marked mesothelial cell hyperplasia often with atypia
49
Q

Collagen vascular disease effusion

A
  • may cause pleuritis and an exudate especially in rheumatoid arthritis
  • often demonstrate
    • pH < 7.2
    • LDH > 700
    • glucose < 30
    • micro shows fibrin, relative paucity of mesothelial cells and occasional histiocytes, some multinucleate
50
Q

Pleural fluid microscopy

A
  • neutrophils suggest empyema when numerous, but often predominate in early course of PE associated effusion
  • lymphocytic pleural effusions suggest tuberculous effusions, lymphatic obstruction
  • mesothelial cells are decreased or absent in rheumatoid pleuritis, tuberculosis, and postpleurodesis pleuritis
  • eosinophils are common if there has been prior instrumentation or introduction of air into pleural space
51
Q

Xanthochromia

A
  • pink or yellow tinged fluid following centrifugation
    • pink xanthochromia indicates free hemoglobin and is detected following subarachnoid hemorrhage
    • yellow xanthochromia indicates bilirubin derived from hemoglobin metabolism and begins 12 hours after a bleed, peaking at 72 hours and disappearing in 2-4 weeks
    • artifactual xanthochromia may be due to
      • serum hyperbilirubinemia
      • CSF protein > 150 mg/dL
      • carotinoids
      • melanin
      • rifampin
      • delay >1 hour prior to exam
52
Q

blood in CSF

A
  • If fluid becomes progressively less from tube 1 to tube 4, is likely due to traumatic tap
  • if xanthochromia is present, then it is probably truly bloody
  • erythrophagocytosis and hemosiderin are also evidence of traumatic tap
53
Q

CSF protein

A
  • 15-45 mg/dL normally
  • increased CSF protein is seen in presence of most CNS pathology
  • Albumin permits assessment of integrity of BBB
  • when BBB intact, the ratio of CSF: serum albumin is < 1:230
54
Q

CSF leak diagnosis

A
  • e.g., rhinorrhea or otorrhea
  • diagnosis:
    • glucose measurement - usually lower in CSF
    • protein electrophoresis - twin transferrin peak (with Beta2 transferrin) and prealbumin bands
55
Q

CSF glucose levels

A
  • normally 60% of serum levels, varying from 40-80%
  • hypoglycorrhachia (< 30%) seen in bacterial meningitis
56
Q

CSF in multiple sclerosis

A
  • CSF:serum IgG is elevated when there is intrathecal Ig production or increased permeability of the BBB
  • can exclude the effect of increased permeability by using albumin CSF: serum ratio as a control
  • the IgG index is obtained by dividing the CSF igG/serum IgG ratio by the ratio of CSF albumin/serum albumin
  • intrathecal IgG synthesis (CSF IgG index) has a sensitivity of 90% for MS
  • Oligoclonal bands
    • several distinct bands in the gamma region
    • by agarose gel electrophoresis has a sensitivity of 50-75% and specificity of 95-97% for MS
    • Isoelectric focusing ismore sensitive (90%) and specific (95%)
    • the CSF banding pattern must be compared to simultaneous serum protein electrophoresis; if similar bands are identified in the serum, then the CSF bands are discounted
57
Q

CSF microscopy

A

Normal cell count is 0-5/mL for adults and 0-20/mL for neonates

58
Q

CSF fluid differential counts in meningitis (bacterial, viral, fungal/mycobacterial)

A
59
Q

Peritoneal fluid chemistry

A
  • serum ascites albumin gradient is the most useful index for distinguishing portal HTN related ascites from others
  • the serum ascites albumin gradient is the difference between the albumin measured in serum and that measured in ascites fluid
  • In portal HTN, the serum ascites albumin gradient is >1.1 g/dL
60
Q

Peritoneal fluid microscopy

A
  • infection is suggested if there are > 250 neutrophils/mm3; in such cases, neutrophils usually comprise over 70% of all nucleated cells
  • in spontaneous bacterial peritonitis, the ascites gram stain is often negative because low bacterial counts
  • a floridly positive gram stain indicates secondary bacterial peritonitis
61
Q

Synovial fluid chemistry

  • inflammatory
  • septic arthritis (labs and overlap with other entities)
A
  • inflammation in synovial fluid reduces its viscosity because of degradation of hyaluronic acid, forming basis for the mucin clot test
  • septic arthritis
    • low glucose
    • low pH
    • high lactate levels
    • overlap with rheumatoid arthritis and gout
62
Q

Synovial fluid microscopy

A
  • The cell count and differential are useful for distinguishing between inflammatory and noninflammatory conditions
  • In the presence of significant neutrophilic inflammation, immediate treatment decisions depend largely upon the presence or absence of crystals
  • Synovial fluid gram stain is positive in only ~50% of cases of septic arthritis
  • Monosodium urate crystals are found in gout
    • needle shaped rods (2-20 um in length)
    • negative birefringence = yellow when parallel to the compensator and blue when perpendicular
  • Calcium pyrophosphate crystals are found in pseudogout (aka, calcium pyrophosphate deposition disease)
    • rods or rhomboids (2-20 um and weak positive birefringence, appearing blue when parallel to the compensator and yellow when perpendicular)
63
Q
A
64
Q

Synovial fluid differential counts (WBC count, neutrophils, glucose difference, macroscopic appearance)

A

Compendium Chemistry (13 decks)

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