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Urinary Pathophysiology > Azotemia, Specific Gravity, Proteinuria > Flashcards

Azotemia, Specific Gravity, Proteinuria Flashcards

1
Q

what is specific gravity used to measure?

A

urine concentration

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2
Q

what is the gold standard for urine solute concentration?

A

osmolality

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3
Q

what is osmolality?

A

number of solute particles per liter of solution

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4
Q

what does osmolality measure?

A

vapor pressure or freezing point depression

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5
Q

what is specific gravity?

A

density of solution as compared to (distilled) water

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6
Q

what is specific gravity affected by?

A

temperature
number and size of particles

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7
Q

what is used to measure specific gravity?

A

refractometers

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8
Q

what is isosthenuria?

A

same concentration as original glomerular filtrate

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9
Q

what is hyposthenuria?

A

excess water is eliminated from body and added to glomerular filtrate

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10
Q

what specific gravity and mOsm is isosthenuria?

A

1.008-1.012
300 mOsm

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11
Q

what specific gravity and mOsm is hyposthenuria?

A

<1.008
<300mOsm

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12
Q

what is hypersthenuria?

A

concentrated urine: water resorbed from filtrate to meet body’s needs

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13
Q

what specific gravity is hypersthenuria in a dog?

A

> 1.030

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14
Q

what specific gravity is hypersthenuria for a horse?

A

> 1.020

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15
Q

what specific gravity is hypersthenuria for a cat?

A

> 1.040

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16
Q

what specific gravity is hypersthenuria for a cow?

A

> 1.026

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17
Q

is there a normal range for specific gravity of urine?

A

no: must take into account hydration status, electrolyte balance, and concentration of nitrogen waste products (urea and creatinine) in blood

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18
Q

when should urine be hypersthenuric?

A

when the animal is:
dehydrated
hypovolemic
decreased cardiac output

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19
Q

urine specific gravity value between hypersthenuric and isostheuric referred to as _____________________

A

minimally concentrated urine

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20
Q

what does poorly concentrated urine in an animal that should be concentrating urine indicate?

A

renal tubular dysfunction

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21
Q

what complicates using urine specific gravity to evaluate the kidneys?

A

2/3 of nephrons (maybe more in cats) must be lost before you detect a problem
animals with glomerular disease may still be able to concentrate urine

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22
Q

some ____________ of the filtered water is reabsorbed in the proximal tubules by osmosis

A

60-70%

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23
Q

what is reabsorbed in the proximal tubules other than water?

A

Na (60%)
Cl
HCO3

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24
Q

how does water move out of the the proximal tubule?

A

aquaporins
leaky tight junctions

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25
Q

the increased oncotic pressure in peritubular capillaries favors ____________________________

A

movement of H2O into the capillary

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26
Q

what does increased concentration of the remaining filtrate in the proximal tubule promote?

A

passive reabsorption of K, Cl, Ca, and urea by diffusion

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27
Q

what are the nitrogenous waste products?

A

urea
creatinine

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28
Q

what is used in serum chemistries to asses glomerular filtration rate function?

A

nitrogenous waste products
serum phosphorous
SDMA

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29
Q

what is azotemia?

A

increase urea and/or creatinine

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30
Q

what is azotemia usually a sign of?

A

decreased glomerular filtration rate

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31
Q

what is produced by protein (amino acid) catabolism?

A

ammonia

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32
Q

how is ammonia transported to the liver?

A

portal blood

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33
Q

what converts ammonia to urea?

A

liver

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34
Q

what are the main causes of increased urea?

A

decreased renal urea excretion
modulated by tubular reabsorption and recycling of urea
mild increases caused by increased protein catabolism

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35
Q

amount of reabsorption is inversely related to _____________________

A

urine flow rate

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36
Q

what are some causes of increased protein catabolism?

A

hemorrhage into gut: bacteria catabolize hemoglobin
fever, burns, tissue necrosis, infection
starvation

37
Q

how would liver failure affect the blood urea nitrogen level?

A

decreased BUN

38
Q

what makes up urea excretion through the gastrointestinal tract in ruminants?

A

urea from blood diffuses into rumen
urea is secreted by salivary gland

39
Q

what happens to urea in the rumen?

A

microorganisms breakdown urea and use NH3 to make amino acids

40
Q

what can blunt the rise in blood urea nitrogen in ruminants?

A

urea going into gastrointestinal tract

41
Q

does urea metabolism occur in hindgut fermenters?

A

some does

42
Q

what makes creatinine a good measure of glomerular filtration rate?

A

freely filtered, no tubular reabsorption

43
Q

what is the energy storage molecule produced from creatinine?

A

phosphocreatine

44
Q

other than being freely filtered and not reabsorbed, what makes creatinine a good indicator of GFR?

A

not affected by diet or gastrointestinal hemorrhage
not significantly changed by muscle disease

45
Q

what spontaneously degrades into creatinine and what does creatinine do after?

A

phosphocreatine and creatine
freely escapes from muscle

46
Q

what is prerenal azotemia caused by?

A

decreased renal perfusion: hypovolemia and/or decreased cardiac output
increased production of urea

47
Q

what is renal azotemia caused by?

A

renal parenchymal disease: glomerular, inflammation, tubular necrosis, parenchymal scarring

48
Q

what are some causes of decreased glomerular filtration rate?

A

replacement of nephrons with fibrosis, cells, inflammatory cells
tubules plugged by cells, casts, crystals
back-pressure counteracts pressure from renal blood flow
tubuloglomerular feedback

49
Q

what fraction of nephrons must be lost to compromise concentrating ability?

A

2/3

50
Q

what fraction of nephrons must be lost to see renal azotemia?

A

3/4

51
Q

what causes post-renal azotemia?

A

obstruction of urinary tract
rupture of urinary tract

52
Q

how does rupture of urinary tract lead to azotemia?

A

urea and creatinine reabsorbed from fluid in abdominal cavity
urea is reabsorbed more quickly because it diffuses across cell membranes

53
Q

is an animal with rupture of the urinary tract usually still urinating?

A

yes

54
Q

what is the level of creatinine in abdomen compared to creatinine in the blood in a uroabdomen?

A

> 2x that in blood

55
Q

what are some lab abnormalities you see with a uroabdomen?

A

low Na and Cl
high K, urea, creatinine, and phosphorous

56
Q

what rises less in ruminants with a uroabdomen?

A

BUN
K
phosphorous
due to salivary gland secretion

57
Q

what is SDMA?

A

methylated arginine

58
Q

when does SDMA increase?

A

GFR decreases by 25-40%

59
Q

what can cause SDMA to be high other than renal disease?

A

slightly higher in growing puppies
dehydration
endothelial dysfunction and cardiovascular disease in people

60
Q

what is the hallmark of glomerular disease?

A

proteinuria

61
Q

can patients with glomerular disease concentrate their urine?

A

yes
unless downstream failing too

62
Q

what makes up the glomerular filtration barrier?

A

fenestrated endothelium
basement membrane
podocyte foot processes separated by gaps

63
Q

what proteins can go through the glomerular filtration barrier?

A

small and/or positively charged ones pass freely

64
Q

what proteins are usually excluded from the glomerular filtration barrier?

A

large and/or negatively charged molecules

65
Q

what is the role of the proximal tubule with protein?

A

takes up rogue proteins through pinocytosis

66
Q

what is the normal amount of protein in urine?

A

<20mg/kg/day

67
Q

what are the semiquantitative methods for detecting proteinuria?

A

dipstick
sulfosalicylic acid turbidometric test

68
Q

is dipstick or sulfosalicylic acid turbidometric test more sensitive?

A

dipstick a bit more sensitive

69
Q

what protein does dipstick primarily detect?

A

albumin

70
Q

what is the gold standard quantitative test for protein in urine?

A

protein:creatinine ratio

71
Q

what does a protein:creatinine ratio require?

A

chemistry analyzer with microprotein assay

72
Q

in the protein:creatinine ratio, what does creatinine correct for?

A

urine concentration

73
Q

why do we look for proteinuria?

A

glomerular disease
tubular disease

74
Q

what happens in glomerular disease that leads to proteinuria?

A

disruption of glomerular wall
loss of negative charges

75
Q

can you get hypoalbuminemia with glomerular disease and tubular disease?

A

yes glomerular disease
no tubular disease

76
Q

what is physiologic proteinuria?

A

transient overload of tubule absorptive capacity

77
Q

what can cause physiologic proteinuria?

A

+/- strenuous exercise (not proven in domestic animals)
neonatal absorption of colostrum
seizures

78
Q

what is the mechanism of post-renal pathologic proteinuria with inflammation/infection in bladder/urethra/prostate?

A

increased vascular permeability

79
Q

what is the most reliable way to know if you have inflammation in the urinary tract?

A

increased white blood cells in the urine sediment

80
Q

what is the mechanism of post-renal pathologic proteinuria with hemorrhage?

A

loss of plasma proteins

81
Q

what are the etiologies of post-renal pathologic proteinuria with hemorrhage?

A

tissue trauma
tumor
stones
coagulation defect

82
Q

what are the etiologies of post-renal pathologic proteinuria with inflammation/infection?

A

infection
tissue necrosis
trauma
neoplasia

83
Q

what are the types of red supernatant?

A

hemoglobinuria
myoglobinuria

84
Q

what is mild proteinuria?

A

UPC <2.0
1-2+ on dipstix or SSA test

85
Q

what are some causes of mild proteinuria?

A

artifact from highly concentrated urine
pre-renal or post-renal problem
early glomerular disease
tubular disease
systemic disease affecting blood vessels

86
Q

what is marked proteinuria?

A

UPC >2.0, usually >5.0
3-4+ dipstix or SSA test

87
Q

what is marked proteinuria a hallmark of?

A

glomerular disease

88
Q

what should you rule out with marked proteinuria?

A

hemoglobinuria
myoglobinuria
glomerular disease

89
Q

is pitting edema in hypoproteinemic patients with protein-losing glomerulopathy seen in chronic or acute kidney disease?

A

chronic

Urinary Pathophysiology (11 decks)

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