Non-Protein Nitrogen and Kidney Function Flashcards
(124 cards)
1
Q
What is urea?
A
A major product of protein breakdown
2
Q
What is urea formed from?
A
Ammonia and CO2
3
Q
Where is urea formed?
A
In the liver
4
Q
What is ammonia?
A
Breakdown product of amino acid deamination
5
Q
How is urea formed?
A
Ammonia goes through the urea cycle first combining with HCO3
Goes through various reactions, eventually becoming urea
6
Q
How is urea excreted?
A
Filtered completely by kidneys
40-60% reabsorbed
7
Q
What is the normal reference range for urea?
A
2.5-8.5 mmol/L
8
Q
What is creatinine?
A
Waste product of dehydration of creatine and creatine phosphate
9
Q
Where does creatine come from?
A
Produced in the hepatocytes and moves to muscles and brain
10
Q
How is creatine phosphate made?
A
Creatine is phosphorlayed by creatine kinase (CK) with a phosphorus from ATP
11
Q
What does creatine phosphate do?
A
When ATP is depleted from the cell creatine kinase (CK) transfers the phosphate back to the ADP to make ATP
More energy for the cell!
12
Q
Why is creatinine a good indicator of kidney function?
A
It is produced at a constant rate proportional to body muscle mass
and
Nearly all of it is filtered by the kidneys
13
Q
How is creatinine excreted?
A
Nearly all of it is filtered out by the kidneys
14
Q
What is uric acid?
A
Major waste product of purine metabolism
15
Q
What are examples of purines?
A
Adenine, guanine
Components of nucleotides, nucleic acids, etc
16
Q
What increases uric acid levels?
A
Conditions with high cell turnover
Leukemia, chemotherapy
17
Q
How is uric acid excreted?
A
Completely filtered by kidneys
Almost 100% reabsorbed
Excreted
Reabsorbed
Only ~10% filtered
18
Q
What happens to uric acid at different pH levels?
Low? High?
A
High pH = soluble urate
Low pH = uric acid, likely to precipitate and crystalize
19
Q
What is the problem with uric acid at low pH?
A
It is less soluble and is likely to precipitate and crystalize
20
Q
What damage can uric acid crystals do?
A
Painful joints
Gout
Kidney damage and stones
21
Q
What is the problem with a high blood ammonia level?
A
It is toxic to the brain and CNS
22
Q
How should a sample for urea be handled?
A
Serum/plasma
Store in fridge for up to 5 days or 6 months frozen
23
Q
What is an indirect urea test actually measuring?
A
Ammonia
24
Q
What is an example of a direct urea test?
A
Diacetyl monoxime
25
How does the diacetyl monoxime test work?
Diacetyl monoxime converts urea to diazine (yellow)
Measured at 540nm
26
How can the diacetyl monoxime test be made more stable?
Use thiosemicarbazide or ferric ions to increase stability and increase sensitivity
27
What is an example of an indirect urea test?
Urease method
28
How does the urease method work?
Urease hydolyses urea into ammonia
29
How can a urease test be measured?
1. Conductivity
| 2. Photometry
30
How is a urease test measured with conductivity?
As the reaction occurs more ions are generated, increasing solution conductivity
The instrument measures the rate in conductivity change
Directly proportional to urea
31
What are 2 ways a urease test is measured with photometry?
1. Urease Berthelot
| 2. Glutamate dehydrogenase
32
How does the Urease Berthelot method work?
Ammonium (formed from urea) reacts with phenol and sodium hypochlorite to create a blue indophenol
Measured at 560 nm
33
How doe the glutamate dehydrogenase urease method work?
```
Ammmonium ions (formed from urea) are converted into glutamate by glutamate dehydrogenase
NADH is converted to NAH at the same time
```
The decrease in absorbance of NADH is measured at 340 nm
Proportional to urea
34
How should a specimen for creatinine measurement be handled?
Serum, plasma, urine
| Can be stored for 7 days
35
What does hemolysis do to creatinine results?
Falsely increased result due to release chromagens
36
What is the basic Jaffe reaction?
Creatinine reacts with picrate ions at alkaline pH to produce a red-orange creatinine picrate
37
What is the problem with the original Jaffe reaction?
Not specific for creatinine
| Also reacts with glucose, protein, etc
38
What is the more modern creatinine method?
Kinetic Rate Jaffe method
39
How does the Kinetic Jaffe method work?
Measures the change in absorbance between 2 times measured at 520 nm
40
How does the Kinetic Jaffe method account for interfering substances?
Other substances will react at different times
The differential reaction rates identifies only creatinine
41
How can enzymes be used to measure creatinine?
Vitroes uses 4 reagent enzymes to drive reactions with the end point a oxidized dye
The change in reflectance between 2 times is proportional to creatinine
42
What are the references ranges for creatinine for men, women, and children?
Men 50 - 120 umol/L
Women 40 - 100 umol/L
Children 30-70 umol/L
43
Define clearance
The volume of plasma from which a measured amount of substance can be cleared by the kidneys into the urine per unit of time
44
What is creatinine clearance used for?
Assessing glomerular filtration rate
Volume of plasma filtered by kidneys per minute
45
What is the calculation for creatinine clearance?
U x V x 1.73
--------------------------------------
P x 86400 s. A
```
U = urine creatinine umol/L
V = 24hr urine volume
P = plasma creatinine umol/L
A = patients body surface area m^2
```
46
What are the specifications made to the patient for a 24 hour creatinine clearance collection?
No coffee, tea, meat, or medication
Ensure adequate hydration
Blood collected at mid-way point
47
What is the reference range in adults for creatinine clearance?
1.20 - 2.30 mL/sec
48
What might a decreased creatinine clearance mean?
Decreased kidney function
49
How is an estimated GFR done?
Calculate value based on serum creatinine
50
What is considered and abnormal eGFR?
Below 60 mL/min
51
How should a specimen for uric acid measurement be handled?
Avoid hemolysis
| Do not use sodium fluoride, inhibits enzyme reaction
52
Why should tubes containing ammonia not be used for indirect urea measurement?
These methods convert urea into ammonia so ammonia from the tube will be measured and a false high result will be given
53
What are 2 ways to measure uric acid?
1. Caraway (old)
| 2. Uricase
54
How does the Caraway method work?
Uric acid reduces phosphotungstic acid into tungsten blue
| Measured at 700nm
55
What is the problem with the Caraway method?
Not specific for uric acid
Other reducing substances will also reduce the reagent and give a false high result
ex: ascorbic acid, cysteine
56
How does the uricase method work?
Uricase converts uric acid into allantoin and H2O2
57
What are 2 ways of measuring the uricase method?
1. Direct photometry
| 2. Adding peroxidase and oxidizing a chromagen
58
How does measuring the uricase method directly work?
Uric acid is measured at 287 nm
| The absorbance before and after is measured and the change is noted
59
How does measuring the usicase method by adding pexoidase work?
Peroxidase causes H2O2 to oxidize a dye
| Reflecance measured at 670 nm
60
How should a specimen for ammonium analysis be handled?
Plasma (heparin, EDTA, oxalate)
Collected on ice and spun cold
Tested immediately or frozen
61
What is the most common way to measure ammonia? How does it work?
Glutamate dehydrogenase
GLDH converts ammonia to glutamate, while converting NADH into NAD
Decrease in absorbance of NADH measured at 340 nm = ammonia
62
Define azotemia
Increased blood urea
63
What pre-renal causes may cause increase urea?
Decreased renal blood flow
- dehydration, cardiac failure
Increased protein metabolism
- high protein diet, starvation, fever
64
What renal causes may cause increased urea?
Renal failure
| nephrosis, nephrosclerosis, glomerulonephritis
65
What post-renal causes may cause increased urea?
Urine output obstruction
| - kidney stones, enlarged prostate, tumors
66
When might low urea levels be seen?
Advanced liver disease
| Hemoldialysis
67
Why would severe liver disease cause low urea levels?
Decreased synthesis in liver from ammonia due to failure
68
What pre-renal causes might cause increased creatinine?
Dehydration, circulatory collapse, muscular dystrophy
69
What renal causes might cause increased creatinine?
Nephrosis
Glomerular nephritis
Nephrosclerosis
Kidney issues
70
What post renal causes might cause increased creatinine?
Urine output obstruction
| - kidney stones, tumors
71
What might be the cause of both urea and creatinine being increased?
Renal and post-renal disorders
72
What might be the cause of urea being increased but creatinine being normal?
High protein, dehydration
73
What would be the cause of urea being normal but creatinine being increased?
Unlikely
Repeat, check sample
74
What is the reference range for uric acid in males and females?
Male 200 - 500 umol/L
| Female 150 - 450 umol/L
75
What is hyperuricemia?
Increased uric acid levels
76
What is gout?
Deposition of monosodium urate crystals in tissues surrounding joints
77
What causes gout?
Uric acid
Increased purine production
Under-secretion of uric acid (renal disorder)
78
What might cause hyperuricemia?
Increased tissue destruction (chemo, radiation, leukemia)
Retention of uric acid, renal disorder, drugs
79
What is a definitive for gout?
Observance of MSU crystals in synovial fluid
| Long needle that display birefringence under polar microscope
80
What is the reference range for ammonia?
10 - 45 umol/L
81
What might cause increased ammonia?
Liver disorders (hepatitis, cirrhosis, Reye's syndrome)
82
What is Reye's syndrome?
Sudden severe liver damage usually in children following a viral infection (mainly influenza B), and drugs like asprin
83
What are some major renal conditions?
1. Acute glomerularnephritis
2. Nephrotic syndrome
3. Pyelonephritis (infection)
4. Cystitis
84
What is the major finding in acute glomerular nephritis?
Red blood cell casts in urine
85
What is the major finding in nephrotic syndrome?
High proteinuria
86
What is the major finding in pyelonephritis?
White blood cell casts with increased WBCs in urine
87
What is the major finding in cystitis?
Increased WBCs but no casts in urine
88
Where does the urea cycle occur and what waste product is produced?
Occurs in the hepatocytes
| Produces urea
89
Describe the role of creatine in neural and muscle cells and the creation of creatinine
Creatine is phosphorlyated into creatine phosphate
Creatine phosphate can have the phosphate released to ADP to create ATP (energy)
Creatinine is the waste product
90
TRUE OR FALSE
Most substances are reabsorbed in the proximal convoluted tubules
True
91
TRUE OR FALSE
In alkalosis the kidney decreases the rate of absorption of bicarbonate ion
True
92
TRUE OR FALSE
The preferred anticoagulant for serum urea by the urease method is sodium fluoride
False
NaF inhibits urease
Serum or heparinized plasma
93
TRUE OR FALSE
In the dry chemistry method for ammonia a semipermeable membrane separates the NH3 from the rest of the specimen prior to its reaction with bromophenol blue
True
94
TRUE OR FALSE
In nephrotic syndrome there is increased permeability of the glomeruli in the pelvis or calyces of the kidney or in the ureter
True
95
TRUE OR FALSE
Nephrolithiasis is a condition where there are one or more stones in the pelvis or calyces of the kidney or in the ureter
True
96
TRUE OR FALSE
In the urea cycle 2 molecules of waste ammonia eliminated by the formation of urea
False
1 molecule
97
TRUE OR FALSE
Creatine kinase is the high energy storage compound found in muscles and neurons
False
CK is the enzyme
Creatine phosphate is the storage compound
98
TRUE OR FALSE
Ammonia is toxic because it enter the neurons and reduces ATP production
True
99
TRUE OR FALSE
The direct urea method measures urea by determining the rate of change in the conductivity due to production of ions as the urease reaction procedes
False
This is an indirect method
100
TRUE OR FALSE
Glomerular filtration rate is the volume of plasma in mL filtered by the glomerulus per unit of time
True
101
TRUE OR FALSE
The kidney is responsible for the secretion of rennin
True
102
TRUE OR FALSE
Deamination of amino acids produces ammonia
True
103
TRUE OR FALSE
Urea formation takes place in the kidneys
False
Liver
104
The Berthelot method is a modification of the urease method for urea
True
105
TRUE OR FALSE
An indirect method for urea uses a coupled enzyme reaction - urease first, then glutamate dehydrogenase
True
106
TRUE OR FALSE
Hemolysis of the specimen will cause a significant positive error in some urease based methods
False
107
TRUE OR FALSE
Both the CX and the Vitros use the Jaffe reaction for measurement of creatinine
False
Vitros uses 4 coupled reactions to get the leuco dye
108
TRUE OR FALSE
Uricase methods generate allantoin and hydrogen peroxide
True
109
TRUE OR FALSE
Renal function failure will usually be indicated by a high serum creatinine level and low serum urea
False
Both high due to decreased filtration
110
TRUE OR FALSE
The uricase method suffers from heavy positive interference from reducing substances in the specimen
False
The old phosphotungstate method would
111
TRUE OR FALSE
In the Vitros method for urea the ammonia reacts with a red colored chromogen and reflectance is measured
True
112
TRUE OR FALSE
Picric acid is used in the measurement of uric acid
False
Creatinine
113
TRUE OR FALSE
Reagent strips for measurement of urine creatinine contain 3,5-dinitrobenzoic acid
True
114
TRUE OR FALSE
The diacetyl monoxime method condenses urea with ustable diacetyl to form a yellow diazine derivative measured at 540 nm
True
115
TRUE OR FALSE
Nephrosclerosis is another term for malignant hypertension
True
Hypertension produces necrosis of renal arterioles that results in protein and red cells in the urine
116
TRUE OR FALSE
Increased plasma ammonia indicates end stage renal failure
False
Liver faliure
117
Hardening of the kidnes associated with hypertension and disease of renal arterioles is called glomerulonephritis
False
Nephrosclerosis
118
TRUE OR FALSE
Net filtration pressure inside the glomerulus is about 10 mmHg
True
119
TRUE OR FALSE
Nephrotic syndrome is also called nephrosis
True
120
TRUE OR FALSE
Blood creatinine levels are affected by thyroid hormones
False
Formed at a constant rate dependent upon muscle mass
121
TRUE OR FALSE
Creatinine is produced in the liver
False
Neurons and muscles
122
TRUE OR FALSE
Uric acid is a waste product of pyrimidine metabolism
False
Purine metabolism
123
TRUE OR FALSE
Uric acid is insoluble in acid solution
True
124
TRUE OR FALSE
Thiosemicarbazide is incorporated into the reagents in the diacetyl monoxime method to improve color stability and intensity
True
