SERUM UREA TEST

Question 1

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

Answer 1

urea

Question 2

is the major excretory product of protein metabolism.

Answer 2

Urea

Question 3

UREA

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

Answer 3

liver

Question 4

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.

Answer 4

nitrogen

blood urea nitrogen (BUN)

Urea nitrogen (urea-N)

Question 5

Urea chemical formula

Answer 5

(CO[NH2]2)

Question 6

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.

Answer 6

75%

Question 7

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_____

Answer 7

hepatic enzymes

urea cycle enzymes.

Question 8

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.

Answer 8

90%

Question 9

kidney disease is associated with accumulation of____ in blood.

Answer 9

urea

Question 10

An increase in plasma urea concentration characterizes the_____

Answer 10

uremic (azotemic) state.

Question 11

_____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.

Answer 11

Urea

40% to 70%

Question 12

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 ________

Answer 12

Glomerular filtration rate (GER).

Question 13

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

Answer 13

stage 5 chronic kidney disease (CKD)

Question 14

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.

Answer 14

creatinine

Question 15

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.

Answer 15

dialysis

renal replacement

Question 16

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

Answer 16

(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).

Question 17

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).

Answer 17

high-protein

catabolism

blood proteins

cortisol

dehydration

Question 18

An elevated concentration of urea in the blood is called______.

Answer 18

azotemia

Question 19

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.

Answer 19

uremia

uremic syndrome

Question 20

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

Answer 20

prerenal
renal
postrenal

Question 21

is caused by reduced renal blood flow.

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

Answer 21

Prerenal azotemia

Question 22

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

Answer 22

Pre renal azotemia

Question 23

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.

Answer 23

prerenal azotemia

Question 24

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

Answer 24

Renal azotemia

Question 25

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.

Answer 25

Postrenal azotemia

Question 26

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

Answer 26

Chemical and enzymatic

Question 27

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.

Answer 27

Fearon reaction

Question 28

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.

Answer 28

diacetyl diazine 540

Question 29

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

Answer 29

diacetyl

Question 30

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

Answer 30

Fearon reaction

Question 31

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.

Answer 31

urease

Question 32

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.

Answer 32

Berthelot reaction and the enzymatic assay (glutamate dehydrogenase)

Question 33

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

Answer 33

enzymatic assay with glutamate dehydrogenase

Question 34

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.

Answer 34

nitrogen nitrogen concentration

Question 35

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

Answer 35

2.14

Question 36

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____

Answer 36

millimoles per liter 0.357

Question 37

Urea concentration may be measured in (3)

Answer 37

plasma, serum, or urine

Question 38

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.

Answer 38

plasma

Question 39

A ____ sample is recomended.

Answer 39

non-hemolyzed

Question 40

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

Answer 40

bacterial decomposition

Question 41

______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.

Answer 41

Timed urine