11) Nonprotein nitrogen and renal function Flashcards
(89 cards)
1
Q
urinary filtrate flow
A
Bowman’s capsule
Proximal convoluted tubule (PCT)
Descending loop of Henle
Ascending loop of Henle
Distal convoluted tubule (DCT)
Collecting duct
Renal calyces
Ureter
Bladder
Urethra
2
Q
renal blood flow
A
Renal artery
Afferent arteriole
Glomerulus
Efferent arteriole
Peritubular capillaries
Vasa recta
Renal vein
3
Q
large, ——- charged molecules are repelled by the —– charge of the basement membrane
A
negatively
negative
4
Q
renal threshold
A
Concentration above which the substance cannot be totally reabsorbed and is excreted in the urine
5
Q
always reabsorbed through passive transport
A
water
urea
6
Q
2 major functions of tubular secretion
A
- Elimination of waste products not filtered by the glomerulus
- Regulation of acid-base balance in the body through secretion of H+
7
Q
nonprotein nitrogen
A
Comprises the products of catabolism of proteins and nucleic acids, which contain nitrogen but are not part of a protein molecule
8
Q
most clinically significant NPN in plasma
A
BUN
amino acids
uric acid
creatinine
creatine
ammonia
9
Q
3 NPN sources in highest amount
A
Blood urea nitrogen (BUN)
Amino acids
Uric acid
10
Q
Major nitrogen-containing metabolic product of protein catabolism in humans
A
urea/BUN
11
Q
Approximately —% of NPN is eventually excreted
A
75
12
Q
In a patient with a normal to increased GFR, approximately –% of the BUN is reabsorbed and –% is excreted.
A
40
60
13
Q
In a dehydrated patient, –% of the BUN is reabsorbed and –% is excreted.
A
70
30
14
Q
3 variables BUN depends on
A
Urea concentration
Glomerular filtration rate
Level of hydration
15
Q
azotemia
A
- An increased blood urea and other NPN compounds
- No external symptoms
16
Q
uremia
A
- An increased BUN
- More severe, now showing sx (n/v, fatigue, HTN, anorexia, uremic frost)
17
Q
A
uremic frost
18
Q
3 categories of azotemia
A
prerenal
renal
postrenal
19
Q
normal BUN:creatinine ratio
A
10:1 to 20:1
20
Q
normal BUN:Cr ratio
A
renal disease
elevated proportionally
21
Q
prerenal azotemia BUN:Cr
A
> 20:1 to 30:1
22
Q
postrenal azotemia or prerenal + renal azotemia BUN:Cr
A
high ratios with elevated Cr
23
Q
Berthelot’s reaction
A
BUN method
24
Q
sodium nitroprusside
A
BUN method
25
Nessler's rxn
BUN method
26
glutamate dehydrogenase (GLDH) procedure
BUN method
27
Diacetyl or Fearon Reaction
BUN method
28
BUN RR
7-18 mg/dL
29
BUN is stable at room temp for ---- hours, -------- refrigerated, and ----- months frozen
24 hours
several days
2-3 months
30
B U N <8-10 mg/dL
overhydration
31
BUN 50-150 mg/dL
impaired GFR
32
BUN 150-250 mg/dL
severe renal impairment
33
convert from urea to urea nitrogen
BUN = 28 g/mol
urea = 60 g/mol
34
creatinine synthesized in liver from...
Arginine
Glycine
Methionine
35
creatinine
Waste product derived from creatine and creatine phosphate which is contained in the muscle
36
precursor to creatine
phosphocreatine
37
production is proportional to the muscle mass of the individual and it is released into the body fluids at a constant rate
endogenous creatinine
38
creatinine levels affected by 3 variables
Relative muscle mass
Creatine turnover
Renal function
39
NOT affected by diet, which makes this such a desirable test to run for specimen validity
creatinine
40
ID a fluid as urine
BUN
creatinine
41
Jaffe reaction
Reaction between ---------- and picric acid in an alkaline medium (-------------) yielding a -------------- compound
creatinine
alkaline picrate
red-orange
42
decreases with age starting at 50
creatinine
43
major product of purine (adenine and guanine) catabolism
uric acid
44
precursor to uric acid
xanthine
45
hyperuricemia definition
A serum uric acid concentration of...
>7.0 mg/dL in men
>6.0 mg/dL in women
46
gout (primary hyperuricemia) patient population
men 30 to 50 years of age
7 times more common in men
47
Occurs when monosodium urate precipitates in supersaturated body fluids
gout
48
precipitate acute attacks of gout
Alcohol
High-protein diets (organ meats)
Stress
Acute infection
Surgery
Certain medications
49
gout tx
Diet adequate (not high) in protein
No alcohol
Normal weight maintenance
Drug therapy if needed
50
Chemotherapy and radiation therapy in cancer patients (leukemia, lymphoma, multiple myeloma, polycythemia) can cause...
secondary hyperuricemia
| Increased cell destruction of endogenous nucleic acids
51
tx for secondary hyperuricemia
Allopurinol
52
Enzyme deficiency of HGPRT (biosynthesis of purines)
Lesch-Nyhan Syndrome
53
Lesch-Nyhan patient population
X-linked genetic disorder almost exclusively in males
54
characteristics of Lesch-Nyhan
“Sandy diaper” uric acid crystals
Mental retardation
Abnormal muscle movements
Pathological aggressiveness
Self-mutilation
55
causes of hypouricemia
Severe hepatocellular disease
Defective renal tubular reabsorption of uric acid
Fanconi’s syndrome
Wilson disease
Uricosuric drugs (Allopurinol)
Alzheimer’s
Parkinson’s
56
Phosphotungstic acid
uric acid method
57
allantoin
uric acid method
58
uric acid sample handling
- Uric acid is susceptible to bacterial action, so specimens should be refrigerated
- Hemolysis and bilirubin ↓ uric acid
59
renal clearance
The rate at which the kidneys remove a substance from the plasma or blood.
60
why is creatinine a good indicator of GFR?
- Freely filtered by the glomeruli
- Not reabsorbed by the tubules
- Released into the plasma at a constant rate
61
formula for CrCl
clearance = UV/P
U = urine concentration in mg/dL
P = plasma concentration in mg/dL
V = urine flow in mL/minute (1440 min/24h)
62
Creatinine clearance has to be corrected to an adult body surface area (BSA) of ------m2.
1.73
UV/P(1.73/BSA) = ClCr
| Dubois formula
63
Use to estimate glomerular filtration rate from the serum creatinine level in patients with chronic renal disease and those at risk for CKD
eGFR
64
In patients 18 years of age and older, the --------- equation is the best means currently available to use creatinine values as a measure of renal function.
Modification of Diet in Renal Disease (MDRD) Study Equation
65
Normal protein:creatinine ratio
<1:10
66
Gold standard for measuring glomerular filtration rate
inulin clearance
67
- Water loading to stimulate diuresis
- Bladder catheterization to assure completeness of collection
- Careful timing of blood samples
inulin clearance
| invasive
68
Single-chained, non-glycosylated, low-molecular-weight protein synthesized by all nucleated cells
cystatin C
additional GFR measure
69
Used primarily to test for renal tubular function in renal transplant patients when decreased tubular function indicates early rejection
BMG
70
based on the “protein error of indicators.”
urinalysis protein mat
71
microalbuminuria definition
30-300 mg albumin/g creatinine
72
Most often associated with children and young adults following a group A streptococcal infection (e.g., strep throat)
Acute glomerulonephritis (AGN)
73
glomeruonephritis secondary conditions
Edema—Especially periorbital (around eyes), knees, and ankles
HTN from mild to moderate
Electrolyte imbalance (Na+ and K+)
74
Dysmorphic RBCs, RBC Casts
glomerulonephritis
75
Associated with end stage of persistent glomerular damage with irreversible loss of renal tissue and chronic renal failure
Chronic Glomerulonephritis (CGN)
76
May occur as a complication of glomerulonephritis or as a result of circulatory disorders that affect blood pressure and flow of blood to the kidney (DM, SLE)
nephrotic syndrome
77
s/s nephrotic syndrome
Massive proteinuria (>3 g/day)
Pitting edema
Hyperlipidemia—Fat droplets, oval fat bodies
Hypoalbuminemia
Renal epithelial, waxy, and fatty casts
78
Inflammatory process involving a bacterial infection of the renal tubules by gram-negative bacteria
pyelonephritis
79
pyelonephritis-causing organisms
Escherichia coli
Klebsiella
Proteus
Enterobacter
80
Most common cause is vesicoureteral reflux nephropathy.
chronic pyelonephritis
81
**CKD Stage GFRs**
At increased risk
1
2
3
4
5
**CKD Stage GFRs**
At increased risk — >90
1 — >90
2 — 60-89
3 — 30-59
4 — 15-29
5 — <15
82
Acute increase in the serum creatinine level of 25% or more and GFR <10 mL/min.
renal failure
83
majority of kidney stones
75% calcium oxalate with or without phosphate
84
4 factors that influence formation of kidney stones
- Increase in concentration of chemical salts as a result of dehydration or increase in salts in the diet
- Change in urinary pH
- Urinary stasis
- Presence of a foreign body
85
DM nephropathy protein/albuminuria
Proteinuria > 0.5g/day
or
Albuminuria ~300 mg/day
86
dialysis
larger macromolecules are separated from low-molecular-weight compounds by their rate of diffusion through a semipermeable membrane
87
formula for urea reduction ration (URR) in dialysis pts
URR = (predialysis BUN - postdialysis BUN)/predialysis BUN (100)
88
most widely used method in assessing dialysis adequacy
urea kinetic modelling (UKM)
89
dialysis pts are prone to...
coronary artery disease
left ventricular hypertrophy
