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Chemistry 1 > Non-Protein Nitrogen and Kidney Function > Flashcards

Non-Protein Nitrogen and Kidney Function Flashcards

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1
Q

What is urea?

A

A major product of protein breakdown

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2
Q

What is urea formed from?

A

Ammonia and CO2

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3
Q

Where is urea formed?

A

In the liver

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4
Q

What is ammonia?

A

Breakdown product of amino acid deamination

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5
Q

How is urea formed?

A

Ammonia goes through the urea cycle first combining with HCO3

Goes through various reactions, eventually becoming urea

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6
Q

How is urea excreted?

A

Filtered completely by kidneys

40-60% reabsorbed

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7
Q

What is the normal reference range for urea?

A

2.5-8.5 mmol/L

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8
Q

What is creatinine?

A

Waste product of dehydration of creatine and creatine phosphate

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9
Q

Where does creatine come from?

A

Produced in the hepatocytes and moves to muscles and brain

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10
Q

How is creatine phosphate made?

A

Creatine is phosphorlayed by creatine kinase (CK) with a phosphorus from ATP

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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!

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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

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13
Q

How is creatinine excreted?

A

Nearly all of it is filtered out by the kidneys

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14
Q

What is uric acid?

A

Major waste product of purine metabolism

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15
Q

What are examples of purines?

A

Adenine, guanine

Components of nucleotides, nucleic acids, etc

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16
Q

What increases uric acid levels?

A

Conditions with high cell turnover

Leukemia, chemotherapy

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17
Q

How is uric acid excreted?

A

Completely filtered by kidneys
Almost 100% reabsorbed
Excreted
Reabsorbed

Only ~10% filtered

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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

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19
Q

What is the problem with uric acid at low pH?

A

It is less soluble and is likely to precipitate and crystalize

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20
Q

What damage can uric acid crystals do?

A

Painful joints
Gout
Kidney damage and stones

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21
Q

What is the problem with a high blood ammonia level?

A

It is toxic to the brain and CNS

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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

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23
Q

What is an indirect urea test actually measuring?

A

Ammonia

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24
Q

What is an example of a direct urea test?

A

Diacetyl monoxime

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25
Q

How does the diacetyl monoxime test work?

A

Diacetyl monoxime converts urea to diazine (yellow)

Measured at 540nm

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26
Q

How can the diacetyl monoxime test be made more stable?

A

Use thiosemicarbazide or ferric ions to increase stability and increase sensitivity

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27
Q

What is an example of an indirect urea test?

A

Urease method

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28
Q

How does the urease method work?

A

Urease hydolyses urea into ammonia

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29
Q

How can a urease test be measured?

A
  1. Conductivity

2. Photometry

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30
Q

How is a urease test measured with conductivity?

A

As the reaction occurs more ions are generated, increasing solution conductivity

The instrument measures the rate in conductivity change

Directly proportional to urea

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31
Q

What are 2 ways a urease test is measured with photometry?

A
  1. Urease Berthelot

2. Glutamate dehydrogenase

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32
Q

How does the Urease Berthelot method work?

A

Ammonium (formed from urea) reacts with phenol and sodium hypochlorite to create a blue indophenol

Measured at 560 nm

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33
Q

How doe the glutamate dehydrogenase urease method work?

A 
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

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34
Q

How should a specimen for creatinine measurement be handled?

A

Serum, plasma, urine

Can be stored for 7 days

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35
Q

What does hemolysis do to creatinine results?

A

Falsely increased result due to release chromagens

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36
Q

What is the basic Jaffe reaction?

A

Creatinine reacts with picrate ions at alkaline pH to produce a red-orange creatinine picrate

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37
Q

What is the problem with the original Jaffe reaction?

A

Not specific for creatinine

Also reacts with glucose, protein, etc

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38
Q

What is the more modern creatinine method?

A

Kinetic Rate Jaffe method

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39
Q

How does the Kinetic Jaffe method work?

A

Measures the change in absorbance between 2 times measured at 520 nm

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40
Q

How does the Kinetic Jaffe method account for interfering substances?

A

Other substances will react at different times

The differential reaction rates identifies only creatinine

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41
Q

How can enzymes be used to measure creatinine?

A

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

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42
Q

What are the references ranges for creatinine for men, women, and children?

A

Men 50 - 120 umol/L
Women 40 - 100 umol/L
Children 30-70 umol/L

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43
Q

Define clearance

A

The volume of plasma from which a measured amount of substance can be cleared by the kidneys into the urine per unit of time

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44
Q

What is creatinine clearance used for?

A

Assessing glomerular filtration rate

Volume of plasma filtered by kidneys per minute

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45
Q

What is the calculation for creatinine clearance?

A

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
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46
Q

What are the specifications made to the patient for a 24 hour creatinine clearance collection?

A

No coffee, tea, meat, or medication
Ensure adequate hydration
Blood collected at mid-way point

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47
Q

What is the reference range in adults for creatinine clearance?

A

1.20 - 2.30 mL/sec

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48
Q

What might a decreased creatinine clearance mean?

A

Decreased kidney function

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49
Q

How is an estimated GFR done?

A

Calculate value based on serum creatinine

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50
Q

What is considered and abnormal eGFR?

A

Below 60 mL/min

51
Q

How should a specimen for uric acid measurement be handled?

A

Avoid hemolysis

Do not use sodium fluoride, inhibits enzyme reaction

52
Q

Why should tubes containing ammonia not be used for indirect urea measurement?

A

These methods convert urea into ammonia so ammonia from the tube will be measured and a false high result will be given

53
Q

What are 2 ways to measure uric acid?

A
  1. Caraway (old)

2. Uricase

54
Q

How does the Caraway method work?

A

Uric acid reduces phosphotungstic acid into tungsten blue

Measured at 700nm

55
Q

What is the problem with the Caraway method?

A

Not specific for uric acid
Other reducing substances will also reduce the reagent and give a false high result

ex: ascorbic acid, cysteine

56
Q

How does the uricase method work?

A

Uricase converts uric acid into allantoin and H2O2

57
Q

What are 2 ways of measuring the uricase method?

A
  1. Direct photometry

2. Adding peroxidase and oxidizing a chromagen

58
Q

How does measuring the uricase method directly work?

A

Uric acid is measured at 287 nm

The absorbance before and after is measured and the change is noted

59
Q

How does measuring the usicase method by adding pexoidase work?

A

Peroxidase causes H2O2 to oxidize a dye

Reflecance measured at 670 nm

60
Q

How should a specimen for ammonium analysis be handled?

A

Plasma (heparin, EDTA, oxalate)
Collected on ice and spun cold
Tested immediately or frozen

61
Q

What is the most common way to measure ammonia? How does it work?

A

Glutamate dehydrogenase

GLDH converts ammonia to glutamate, while converting NADH into NAD

Decrease in absorbance of NADH measured at 340 nm = ammonia

62
Q

Define azotemia

A

Increased blood urea

63
Q

What pre-renal causes may cause increase urea?

A

Decreased renal blood flow
- dehydration, cardiac failure

Increased protein metabolism
- high protein diet, starvation, fever

64
Q

What renal causes may cause increased urea?

A

Renal failure

nephrosis, nephrosclerosis, glomerulonephritis

65
Q

What post-renal causes may cause increased urea?

A

Urine output obstruction

- kidney stones, enlarged prostate, tumors

66
Q

When might low urea levels be seen?

A

Advanced liver disease

Hemoldialysis

67
Q

Why would severe liver disease cause low urea levels?

A

Decreased synthesis in liver from ammonia due to failure

68
Q

What pre-renal causes might cause increased creatinine?

A

Dehydration, circulatory collapse, muscular dystrophy

69
Q

What renal causes might cause increased creatinine?

A

Nephrosis
Glomerular nephritis
Nephrosclerosis

Kidney issues

70
Q

What post renal causes might cause increased creatinine?

A

Urine output obstruction

- kidney stones, tumors

71
Q

What might be the cause of both urea and creatinine being increased?

A

Renal and post-renal disorders

72
Q

What might be the cause of urea being increased but creatinine being normal?

A

High protein, dehydration

73
Q

What would be the cause of urea being normal but creatinine being increased?

A

Unlikely

Repeat, check sample

74
Q

What is the reference range for uric acid in males and females?

A

Male 200 - 500 umol/L

Female 150 - 450 umol/L

75
Q

What is hyperuricemia?

A

Increased uric acid levels

76
Q

What is gout?

A

Deposition of monosodium urate crystals in tissues surrounding joints

77
Q

What causes gout?

A

Uric acid

Increased purine production
Under-secretion of uric acid (renal disorder)

78
Q

What might cause hyperuricemia?

A

Increased tissue destruction (chemo, radiation, leukemia)

Retention of uric acid, renal disorder, drugs

79
Q

What is a definitive for gout?

A

Observance of MSU crystals in synovial fluid

Long needle that display birefringence under polar microscope

80
Q

What is the reference range for ammonia?

A

10 - 45 umol/L

81
Q

What might cause increased ammonia?

A

Liver disorders (hepatitis, cirrhosis, Reye’s syndrome)

82
Q

What is Reye’s syndrome?

A

Sudden severe liver damage usually in children following a viral infection (mainly influenza B), and drugs like asprin

83
Q

What are some major renal conditions?

A
  1. Acute glomerularnephritis
  2. Nephrotic syndrome
  3. Pyelonephritis (infection)
  4. Cystitis
84
Q

What is the major finding in acute glomerular nephritis?

A

Red blood cell casts in urine

85
Q

What is the major finding in nephrotic syndrome?

A

High proteinuria

86
Q

What is the major finding in pyelonephritis?

A

White blood cell casts with increased WBCs in urine

87
Q

What is the major finding in cystitis?

A

Increased WBCs but no casts in urine

88
Q

Where does the urea cycle occur and what waste product is produced?

A

Occurs in the hepatocytes

Produces urea

89
Q

Describe the role of creatine in neural and muscle cells and the creation of creatinine

A

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
Q

TRUE OR FALSE

Most substances are reabsorbed in the proximal convoluted tubules

A

True

91
Q

TRUE OR FALSE

In alkalosis the kidney decreases the rate of absorption of bicarbonate ion

A

True

92
Q

TRUE OR FALSE

The preferred anticoagulant for serum urea by the urease method is sodium fluoride

A

False

NaF inhibits urease

Serum or heparinized plasma

93
Q

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

A

True

94
Q

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

A

True

95
Q

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

A

True

96
Q

TRUE OR FALSE

In the urea cycle 2 molecules of waste ammonia eliminated by the formation of urea

A

False

1 molecule

97
Q

TRUE OR FALSE

Creatine kinase is the high energy storage compound found in muscles and neurons

A

False

CK is the enzyme

Creatine phosphate is the storage compound

98
Q

TRUE OR FALSE

Ammonia is toxic because it enter the neurons and reduces ATP production

A

True

99
Q

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

A

False

This is an indirect method

100
Q

TRUE OR FALSE

Glomerular filtration rate is the volume of plasma in mL filtered by the glomerulus per unit of time

A

True

101
Q

TRUE OR FALSE

The kidney is responsible for the secretion of rennin

A

True

102
Q

TRUE OR FALSE

Deamination of amino acids produces ammonia

A

True

103
Q

TRUE OR FALSE

Urea formation takes place in the kidneys

A

False

Liver

104
Q

The Berthelot method is a modification of the urease method for urea

A

True

105
Q

TRUE OR FALSE

An indirect method for urea uses a coupled enzyme reaction - urease first, then glutamate dehydrogenase

A

True

106
Q

TRUE OR FALSE

Hemolysis of the specimen will cause a significant positive error in some urease based methods

A

False

107
Q

TRUE OR FALSE

Both the CX and the Vitros use the Jaffe reaction for measurement of creatinine

A

False

Vitros uses 4 coupled reactions to get the leuco dye

108
Q

TRUE OR FALSE

Uricase methods generate allantoin and hydrogen peroxide

A

True

109
Q

TRUE OR FALSE

Renal function failure will usually be indicated by a high serum creatinine level and low serum urea

A

False

Both high due to decreased filtration

110
Q

TRUE OR FALSE

The uricase method suffers from heavy positive interference from reducing substances in the specimen

A

False

The old phosphotungstate method would

111
Q

TRUE OR FALSE

In the Vitros method for urea the ammonia reacts with a red colored chromogen and reflectance is measured

A

True

112
Q

TRUE OR FALSE

Picric acid is used in the measurement of uric acid

A

False

Creatinine

113
Q

TRUE OR FALSE

Reagent strips for measurement of urine creatinine contain 3,5-dinitrobenzoic acid

A

True

114
Q

TRUE OR FALSE

The diacetyl monoxime method condenses urea with ustable diacetyl to form a yellow diazine derivative measured at 540 nm

A

True

115
Q

TRUE OR FALSE

Nephrosclerosis is another term for malignant hypertension

A

True

Hypertension produces necrosis of renal arterioles that results in protein and red cells in the urine

116
Q

TRUE OR FALSE

Increased plasma ammonia indicates end stage renal failure

A

False

Liver faliure

117
Q

Hardening of the kidnes associated with hypertension and disease of renal arterioles is called glomerulonephritis

A

False

Nephrosclerosis

118
Q

TRUE OR FALSE

Net filtration pressure inside the glomerulus is about 10 mmHg

A

True

119
Q

TRUE OR FALSE

Nephrotic syndrome is also called nephrosis

A

True

120
Q

TRUE OR FALSE

Blood creatinine levels are affected by thyroid hormones

A

False

Formed at a constant rate dependent upon muscle mass

121
Q

TRUE OR FALSE

Creatinine is produced in the liver

A

False

Neurons and muscles

122
Q

TRUE OR FALSE

Uric acid is a waste product of pyrimidine metabolism

A

False

Purine metabolism

123
Q

TRUE OR FALSE

Uric acid is insoluble in acid solution

A

True

124
Q

TRUE OR FALSE

Thiosemicarbazide is incorporated into the reagents in the diacetyl monoxime method to improve color stability and intensity

A

True

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