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CC LAB > SERUM UREA TEST > Flashcards

SERUM UREA TEST Flashcards

1
Q

The NPN compound present in highest concentration in the blood is____.

A

urea

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2
Q

is the major excretory product of protein metabolism.

A

Urea

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3
Q

UREA

It is formed in the_____ from amino groups t-NH2) and free ammonia generated during protein catabolism.

A

liver

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4
Q

Since historic assays for urea were based on measurement of_____, the term _______ has been used to refer to urea determination.

_______ is a more appropriate term.

A

nitrogen

blood urea nitrogen (BUN)

Urea nitrogen (urea-N)

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5
Q

Urea chemical formula

A

(CO[NH2]2)

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6
Q

Urea (CO[NH22) is the major nitrogen-containing metabolic product of protein catabolism in humans, accounting for more than _____of the nonprotein nitrogen eventually excreted.

A

75%

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7
Q

The biosynthesis of urea from amino nitrogen-derived ammonia is carried out exclusively by______ of the urea cycle.

During the process of protein catabolism, amino acid nitrogen is converted to urea in the liver by the action of the so-called_____

A

hepatic enzymes

urea cycle enzymes.

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8
Q

More than_____ of urea is excreted through the kidneys, with losses through the gastrointestinal tract and skin accounting for most of the remaining minor fraction.

A

90%

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9
Q

kidney disease is associated with accumulation of____ in blood.

A

urea

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10
Q

An increase in plasma urea concentration characterizes the_____

A

uremic (azotemic) state.

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11
Q

_____is neither actively reabsorbed nor secreted by the tubules but is filtered freely by the glomeruli.

In a normal kidney,____ to ____ of the highly diffusible urea moves passively out of the renal tubule and into the interstitium, ultimately to re-enter plasma.

A

Urea

40% to 70%

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12
Q

The back diffusion of urea is also dependent on urine flow rate, with less entering the interstitium in high flow states (eg, pregnancy) and vice versa.

Consequently, urea clearance generally underestimates ________

A

Glomerular filtration rate (GER).

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13
Q

In_____________ , the osmotic duresis in the remaining functional nephrons limits the back diffusion of urea so that urea clearance approaches inulin clearance.

A

stage 5 chronic kidney disease (CKD)

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14
Q

Measurement of blood and plasma urea has been used for many years as an indicator of kidney function.

However, It is generally accepted that______ measurement provides better information in this respect.

A

creatinine

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15
Q

Plasma and urinary urea measurement may still provide useful clinical information in particular circumstances, and the measurement of urea in_____ fluids is widely used in assessing the adequacy of_____ therapy.

A

dialysis

renal replacement

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16
Q

A number of extrarenal factors influence the circulating urea concentration, limiting its value as a test of kidney function. For example, plasma urea concentration is increased by

A

(1) a high-protein diet
(2) increased protein catabolism
(3) reabsorption of blood proteins after gastrointestinal hemorrhage
(4) treatment with cortisol or its synthetic analogues
(5) dehydration
(6) decreased perfusion of the kidneys (e.g., heart failure).

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17
Q

A number of extrarenal factors influence the circulating urea concentration, limiting its value as a test of kidney function. For example, plasma urea concentration is increased by

(1) a_____ diet
(2) increased protein____
(3) reabsorption of______ after gastrointestinal hemorrhage
(4) treatment with____ or its synthetic analogues
(5)_____
(6) decreased perfusion of the kidneys (e.g., heart failure).

A

high-protein

catabolism

blood proteins

cortisol

dehydration

18
Q

An elevated concentration of urea in the blood is called______.

A

azotemia

19
Q

Very high plasma urea concentration accompanied by renal failure is called____, or the_____.

This condition is eventually fatal if not treated by dialysis or transplantation.

A

uremia

uremic syndrome

20
Q

Conditions causing increased plasma urea are classified according to cause into three main categories:

A

prerenal
renal
postrenal

21
Q

is caused by reduced renal blood flow.

Less blood is delivered to the kidney; consequently, less urea is filtered.

A

Prerenal azotemia

22
Q

Causative factors include congestive heart failure, shock, hemorrhage, dehydration, and other factors resulting in a significant decrease in blood volume.

A

Pre renal azotemia

23
Q

The amount of protein metabolism also induces_____ changes in blood urea concentration.

A high-protein diet or increased protein catabolism, such as occurs in stress, fever, major illness, corticosteroid therapy, and gastrointestinal hemorrhage, may increase urea concentration.

A

prerenal azotemia

24
Q

causes of elevated urea include acute and chronic renal failure, glomerular nephritis, tubular necrosis, and other intrinsic renal disease.

A

Renal azotemia

25
Q

can be due to obstruction of urine flow anywhere in the urinary tract by renal calculi, tumors of the bladder or prostate, or severe infection.

A

Postrenal azotemia

26
Q

(2) methods are the two principal approaches that have been used to quantify urea in body fluids.

A

Chemical and enzymatic

27
Q

Most chemical methods for urea are based on the ______ in which diacetyl condenses with urea to form the chromogen diazine, which absorbs strongly at 540 nanometers.

A

Fearon reaction

28
Q

Most chemical methods for urea are based on the FEARON REACTION in which_____condenses with urea to form the chromogen____, which absorbs strongly at_____ nanometers.

A

diacetyl

diazine

540

29
Q

Fearon reaction

Because_____is unstable, it is usually generated in the reaction system from diacetyl monoxime and acid.

A

diacetyl

30
Q

Although once widely used, the method has largely been superseded by enzymatic approaches.

A

Fearon reaction

31
Q

Enzymatic methods for the measurement of urea are based on preliminary hydrolysis of urea with_______ to generate ammonium ion, which is then quantified.

This approach has been used in end-point, kinetic, conductimetric, and dry chemistry systems.

A

urease

32
Q

Spectrophotometric approaches to ammonium quantitation include the_______ and ______ with_______.

This latter approach has been accepted as a reference method and adapted to a range of analytical platforms.

A

Berthelot reaction and the enzymatic assay (glutamate dehydrogenase)

33
Q

This approach has been accepted as a reference method and adapted to a range of analytical platforms.

A

enzymatic assay with glutamate dehydrogenase

34
Q

Assays for urea were originally performed on a protein- free filtrate of whole blood and based on measuring the amount of_____ in the sample.

Current analytic methods have retained this custom and urea often is reported in terms of _____ rather than urea concentration.

A

nitrogen

nitrogen concentration

35
Q

Urea nitrogen concentration can be converted to urea concentration by multiplying by_____

A

2.14

36
Q

In the International System of Units (SI), urea is reported in units of_______.

Urea nitrogen concentration expressed in milligrams per deciliter may be convened to urea concentration in millimoles per liter by multiplying by____

A

millimoles per liter

0.357

37
Q

Urea concentration may be measured in (3)

A

plasma, serum, or urine

38
Q

If_____ is collected, ammonium ions and high concentrations of sodium citrate and sodium fluoride must be avoided; citrate and fluoride inhibit urease.

Although the protein content of the diet influences urea concentration, the effect of a single protein-containing meal is minimal and a fasting sample is not required usually.

A

plasma

39
Q

A ____ sample is recomended.

A

non-hemolyzed

40
Q

urea is susceptible to______, so samples (particularly urine) that cannot be analyzed within a few hours should be refrigerated.

A

bacterial decomposition

41
Q

______samples should be refrigerated during the collection period.

Methods for plasma or serum may require modification for use with urine specimens because of high urea concentration and the presence of endogenous ammonia.

A

Timed urine

CC LAB (46 decks)

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