Urinary Pathophysiology > Azotemia, Specific Gravity, Proteinuria > Flashcards

Azotemia, Specific Gravity, Proteinuria Flashcards

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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
the increased oncotic pressure in peritubular capillaries favors ____________________________
movement of H2O into the capillary
26
what does increased concentration of the remaining filtrate in the proximal tubule promote?
passive reabsorption of K, Cl, Ca, and urea by diffusion
27
what are the nitrogenous waste products?
urea creatinine
28
what is used in serum chemistries to asses glomerular filtration rate function?
nitrogenous waste products serum phosphorous SDMA
29
what is azotemia?
increase urea and/or creatinine
30
what is azotemia usually a sign of?
decreased glomerular filtration rate
31
what is produced by protein (amino acid) catabolism?
ammonia
32
how is ammonia transported to the liver?
portal blood
33
what converts ammonia to urea?
liver
34
what are the main causes of increased urea?
decreased renal urea excretion modulated by tubular reabsorption and recycling of urea mild increases caused by increased protein catabolism
35
amount of reabsorption is inversely related to _____________________
urine flow rate
36
what are some causes of increased protein catabolism?
hemorrhage into gut: bacteria catabolize hemoglobin fever, burns, tissue necrosis, infection starvation
37
how would liver failure affect the blood urea nitrogen level?
decreased BUN
38
what makes up urea excretion through the gastrointestinal tract in ruminants?
urea from blood diffuses into rumen urea is secreted by salivary gland
39
what happens to urea in the rumen?
microorganisms breakdown urea and use NH3 to make amino acids
40
what can blunt the rise in blood urea nitrogen in ruminants?
urea going into gastrointestinal tract
41
does urea metabolism occur in hindgut fermenters?
some does
42
what makes creatinine a good measure of glomerular filtration rate?
freely filtered, no tubular reabsorption
43
what is the energy storage molecule produced from creatinine?
phosphocreatine
44
other than being freely filtered and not reabsorbed, what makes creatinine a good indicator of GFR?
not affected by diet or gastrointestinal hemorrhage not significantly changed by muscle disease
45
what spontaneously degrades into creatinine and what does creatinine do after?
phosphocreatine and creatine freely escapes from muscle
46
what is prerenal azotemia caused by?
decreased renal perfusion: hypovolemia and/or decreased cardiac output increased production of urea
47
what is renal azotemia caused by?
renal parenchymal disease: glomerular, inflammation, tubular necrosis, parenchymal scarring
48
what are some causes of decreased glomerular filtration rate?
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
what fraction of nephrons must be lost to compromise concentrating ability?
2/3
50
what fraction of nephrons must be lost to see renal azotemia?
3/4
51
what causes post-renal azotemia?
obstruction of urinary tract rupture of urinary tract
52
how does rupture of urinary tract lead to azotemia?
urea and creatinine reabsorbed from fluid in abdominal cavity urea is reabsorbed more quickly because it diffuses across cell membranes
53
is an animal with rupture of the urinary tract usually still urinating?
yes
54
what is the level of creatinine in abdomen compared to creatinine in the blood in a uroabdomen?
>2x that in blood
55
what are some lab abnormalities you see with a uroabdomen?
low Na and Cl high K, urea, creatinine, and phosphorous
56
what rises less in ruminants with a uroabdomen?
BUN K phosphorous due to salivary gland secretion
57
what is SDMA?
methylated arginine
58
when does SDMA increase?
GFR decreases by 25-40%
59
what can cause SDMA to be high other than renal disease?
slightly higher in growing puppies dehydration endothelial dysfunction and cardiovascular disease in people
60
what is the hallmark of glomerular disease?
proteinuria
61
can patients with glomerular disease concentrate their urine?
yes unless downstream failing too
62
what makes up the glomerular filtration barrier?
fenestrated endothelium basement membrane podocyte foot processes separated by gaps
63
what proteins can go through the glomerular filtration barrier?
small and/or positively charged ones pass freely
64
what proteins are usually excluded from the glomerular filtration barrier?
large and/or negatively charged molecules
65
what is the role of the proximal tubule with protein?
takes up rogue proteins through pinocytosis
66
what is the normal amount of protein in urine?
<20mg/kg/day
67
what are the semiquantitative methods for detecting proteinuria?
dipstick sulfosalicylic acid turbidometric test
68
is dipstick or sulfosalicylic acid turbidometric test more sensitive?
dipstick a bit more sensitive
69
what protein does dipstick primarily detect?
albumin
70
what is the gold standard quantitative test for protein in urine?
protein:creatinine ratio
71
what does a protein:creatinine ratio require?
chemistry analyzer with microprotein assay
72
in the protein:creatinine ratio, what does creatinine correct for?
urine concentration
73
why do we look for proteinuria?
glomerular disease tubular disease
74
what happens in glomerular disease that leads to proteinuria?
disruption of glomerular wall loss of negative charges
75
can you get hypoalbuminemia with glomerular disease and tubular disease?
yes glomerular disease no tubular disease
76
what is physiologic proteinuria?
transient overload of tubule absorptive capacity
77
what can cause physiologic proteinuria?
+/- strenuous exercise (not proven in domestic animals) neonatal absorption of colostrum seizures
78
what is the mechanism of post-renal pathologic proteinuria with inflammation/infection in bladder/urethra/prostate?
increased vascular permeability
79
what is the most reliable way to know if you have inflammation in the urinary tract?
increased white blood cells in the urine sediment
80
what is the mechanism of post-renal pathologic proteinuria with hemorrhage?
loss of plasma proteins
81
what are the etiologies of post-renal pathologic proteinuria with hemorrhage?
tissue trauma tumor stones coagulation defect
82
what are the etiologies of post-renal pathologic proteinuria with inflammation/infection?
infection tissue necrosis trauma neoplasia
83
what are the types of red supernatant?
hemoglobinuria myoglobinuria
84
what is mild proteinuria?
UPC <2.0 1-2+ on dipstix or SSA test
85
what are some causes of mild proteinuria?
artifact from highly concentrated urine pre-renal or post-renal problem early glomerular disease tubular disease systemic disease affecting blood vessels
86
what is marked proteinuria?
UPC >2.0, usually >5.0 3-4+ dipstix or SSA test
87
what is marked proteinuria a hallmark of?
glomerular disease
88
what should you rule out with marked proteinuria?
hemoglobinuria myoglobinuria glomerular disease
89
is pitting edema in hypoproteinemic patients with protein-losing glomerulopathy seen in chronic or acute kidney disease?
chronic

Urinary Pathophysiology (11 decks)

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