KIDNEY FUNCTION TEST Flashcards
The functional units of each kidney or the nephrons are composed of five basic parts namely
glomerulus, proximal convoluted tubule, loop of henle, distal convoluted tubule, and collecting duct
what enzyme is primarily secreted in the kidney, catalyzes the synthesis of the active vitamin D
enzyme 1-a hydroxylase
how many liters of water are filtered daily in humans
180 liters
in 180 liters of water filtered everyday, how many are reabsorbed by the proximal convoluted tubule
150 liters - others absorbed 5 liters
what are the functions of the kidneys
elimination of waste products
maintenance of blood volume
maintenance of electrolyte balance
maintenance of acid-base balance
endocrine function (erythropoietin secretion)
the human kidneys receive approx 25% of the blood pumped, what is the total renal blood flow
approx 1200 ml.mn
the human kidneys receive approx 25% of the blood pumped, what is the total renal plasma flow
600-700 ml/mn
this part of nephron is for immediate reabsorption of essential substances
PCT
this part of nephron is for final adjustment of the urinary composition
DCT
this part of nephron facilitates in major exchanges of water and salts place between the blood and the medullary interstitium; this exchange maintains the osmotic gradient concentration in the medulla, which is necessary for renal concentration
ascending and descending loop of henle in juxtamedullary nephron
this part of nephron serves as nonselective filter of plasma substances
glomerulus
give the NPN’s and their corresponding percentage
urea - 45%
amino acid - 20%
uric acid - 20%
creatinine - 5%
creatine - 1%
ammonia - 0.2%
routine markers for GFR
clearance and cystatin C
secondary markers for GFR
beta-trace protein
considered the best overall indicator of the level of kidney function
GFR
GFR decreases by _____ after age 20-30 yrs
1 ml/mn/yr
how many liters of glomerular filtrate are produced daily
150 liters
must know:
180 liters of water are filtered daily
150 reabsorbed ng PCT (5 reabsorbed sa iba)
150 rin ang nagagawang glomerular filtrate
the rate at which creatinine and urea are removed or cleared from the blood into the urine is termed as
clearance
it represents the volume of plasma that would contribute in all the solute excreted
clearance test
clearance test is expressed in
ml/mn
representing the volume of plasma that would be totally cleared of the solute in one minute
relationship of clearance and plasma concentration
inversely proportional - as clearance of substance declines the concentration in plasma increases
🔹 If the kidneys efficiently clear a substance (high clearance) → Less of it remains in the plasma, so its plasma concentration is low.
🔹 If clearance declines (low clearance) → The kidneys aren’t removing the substance well, so more stays in the plasma, leading to a higher plasma concentration.
volume of plasma from which a measured
amount of substance can be completely eliminated into the urine per unit of time expressed in
mililiters per minute
clearance test
this clearance test is not routinely done because of the necessity for continuous intravenous infusion, which requires an intravenous infusion and timed urine collections over many hrs
inulin clearance - reference method
doses of inulin clearance
priming - 25 ml of 10 % inulin solution
continuous - 500 ml of 1.5% inulin solution
disadvantage of inulin clearance test
use of IV infusion
ref range of inulin clearance test
male = 127ml/mn
female 118 ml/mn
this clearance test provides an estimate of the amount of plasma that must flow tru the kidney glomeruli per minutes
ESTIMATE - creatinine clearance
It is an excellent measure of renal function; ________is freely filtered by the glomeruli, minimally secreted in
the tubules but not reabsorbed.
creatinine
creatinine is not reabsorbed by the tubules but some are minimally secreted, how can we prevent the secretion to increase accuracy?
inhibition of tubular secretion using cimetidine - improves clearance estimate of GFR in patients with mild to moderate renal impairment
increased creatinine clearance is found in what circumstances
high cardiac output
pregnancy
burns
carbon monoxide poisoning
decreased creatinine clearance is found in what circumstances
impaired kidney function
shock, dehydration
hemorrhage
congestive heart failure
this clearance test become the standard lab method for determining GFR
creatinine clearance
one of the first clearance test but is not used nowadays as it’s not accurate
urea clearance
this clearance can demonstrate progression of renal disease or response to therapy.
urea
in advance renal failure, this clearance test is a better estimate of GFR than creatinine
urea clearance test
as renal function diminishes, the fraction of urea reabsorbed declines progressively, while the tubular secretion of creatinine increases
relationship of urine flow to urea concentration
inversely - the faster the rate of urine flow, the less urea is reabsorbed and vice versa
is used to evaluate potential living kidney transplant donors
Iothalamate
is a nearly ideal substance for the measurement of clearance
creatinine
It is an endogenous metabolic product synthesized at a constant rate for a given individual and cleared essentially
only by glomerular filtration
creatinine clearance
it is a low molecular weight protease inhibitor
cystatin C
produced in constant rate of all nucleated cells
cystatin C
cystatin C - its synthesis is strongly influenced by what interleukins
IL 10
it is COMPLETELY REABSORBED and catabolized by the PCT, hence, its presence in the urine denotes damage of that tubule
Cystatin C
serum level is an indirect estimate of GFR
cystatin C
why do serum creatinine is higher in males than females?
due to muscle mass correlation
it is a reliable marker for a starting renal disease especially in predisposed individuals such as those with diabetes mellitus
cystatin C
recommended to assess GFR among pediatric, elderly, and renal transplant patients
cystatin C
increased cystatin C is observed in
acute and chronic failure, and diabetic nephropathy
the modified cystatin C equation is used in what population
if a child is younger than 14 yrs old
a low molecular weight glycoprotein
beta trace protein
belongs to lipocalin protein family and functions as prostaglandin D synthase
beta trace protein
aside from cystatin C that is completely absorbed by the tubules and catabolized by the proximal convoluted tubules, what is the other clearance protein that has the same characteristics?
beta trace protein
beta trace protein’s plasma concentration originates from
brain
The National kidney foundation recommends what clearance test to be calculated each time creatinine level is reported
estimated glomerular filtration rate (eGFR)
the equation for eGFR used to predict GFR is based on
serum creatinine, age, body size, gender, and race without the need for a 24 hr urine collection, which when improperly collected causes inaccurate test results
what clearance test does not need a 24 hr urine collection, and can replace traditional testing such as creatinine clearance test and result in earlier detection of CKD
eGFR
this formula is one of the first formulas used to estimate GFR
cockcroft-gault formula
this formula of GFR predicts creatinine clearance and the results are not corrected for body surface area
cockcroft-gault formula
this equation or formula for GFR assumes that women will have 15% lower creatinine clearance than men at the same level of serum creatinine
cockcroft-gault formula
this formula for GFR was developed in the study of chronic renal insufficiency
MDRD
The __ formula was validated in a large population that included both Black and White
individuals
MDRD
this GFR formula does not require patient weight and is corrected for body surface area.
MDRD
The four-variable MDRD equation
includes___ as variables
age, race,gender, and serum creatinine
is a low-molecular-weight protein produced at a steady rate by most body tissues and is used as clearance test
cystatin C
Levels of __rise more quickly than creatinine levels in acute kidney injury (AKI)
cystatin C
this clearance test Plasma concentrations appear to be unaffected by diet, gender, race, age, and muscle mass.
cystatin C
defined as the random fluctuation around a homeostatic setting point
biologic variation
what is the difference between “within-subject” and “between-subject”
within-subject means
- biologic fluctuation around the homeostatic setting point for a single individual
between-subject means
- differences between the homeostatic setting points of multiple individuals
given the biologic variation of creatinine and cystatin C, what can u say to both?
creatinine is more helpful in monitoring renal function over time for a given individual
cystatin C is potentially more useful for detecting minor renal impairment
is a small, nonglycosylated peptide found on the surface of most nucleated cells
b2-microglobulin/;
β2-M is easily filtered by the glomerulus, and __% is reabsorbed by the proximal tubules and catabolized
99.9
Measurement of serum __ is used clinicaly to assess renal tubular function in renal transplant patients, with elevated levels indicating organ rejection.
β2-M
is a low-molecular-weight protein (16.9 kDa) associated with acute skeletal and cardiac muscle injury.
myoglobin
__functions to bind and transport oxygen from the plasma
membrane to the mitochondria in muscle cells.
Myoglobin
also referred to as microalbuminuria
albuminuria
Urine albumin measurement is important in the management of patients with __
diabetes mellitus
is the first FDA-cleared test used to determine if critically ill patients are at risk for developing moderate to severe AKI in the 12 hrs following administration of the test
NeproCheck
this kidney function test permits a detailed, in depth assessment of renal status with an easily obtained specimen
urinalysis
kidney function test that serves as a quick indicator of an individual’s glucose status and hepatic-biliary function
urinalysis
is a 25-kDa protein expressed by neutrophils and epithelial cells including those of the proximal tube
neutrophil gelatinase-associated lipocalin
if the urine is not being able to test within the time limit, it can be stored at what temp for how many hrs
2-8 for 8 hrs
markers for renal blood flow
urea, creatinine, uric acid
major end product of protein (dietary) and amino acid catabolism
blood urea nitrogen
it is 45% of the total NPN and approx. 80% of the nitrogen excreted
BUN - urea
how blood urea nitrogen is synthesized
synthesized in the liver from carbon dioxide and ammonia or deamination of amino acids through the ornithine or kreb’s henseleit cycle
you know that urea is reabsorbed in the proximal convoluted tubule passively right?
then how do urea being reabsorbed actively and where?
in the collecting duct using urea transporter
the FIRST metabolite to elevate in kidney disease
urea
is urea easily removed during dialysis?
yes
good indicator of nitrogen intake and the state of hydration
urea
about how many gram of urea is excreted daily in stable nitrogen balance?
25g
formula to obtain UREA from BUN
2.14 * BUN = urea mg%
ref range of BUN
8-23 mg/dl (2.9-832 mmol/L)
BUN:Creatinine ratio
10:1 - 20:1
anticoagulant that must NOT be used in BUN determination
fluoride and citrate - inhibits urease
what are added in BUN determination to enhance color development
thiosemicarbazide and ferric ions
what is forbidden in patients to drink before BUN determination
alcohol intake - ethanol lowers urea by more than 10%
fasting not required
direct method of BUN
diacetyl monoxime method
diacetyl monoxime method of BUN will produce what ___
yellow diazine derivative
urease are prepared from __
jack beans
In enzymatic method (indirect method) of BUN determination, after urease reaction, the ammonia produced are can be treated with ___ reagents
berthelot reagents
what’s the UV enzymatic method of BUN called
GLDH - glutamate dehydrogenase method
the reference method of BUN determination
isotope dilution mass spectrometry (IDMS )
It determines unique spectroscopy fragments through mass spectrometry and quantification using isotopically labeled compound
isotope dilution mass spectrometry
despite being the reference method of BUN - IDMS is not recommended for the reason of ____
the assay is expensive
increased BUN is found in
chronic renal disease
stress
burns
high protein diet
dehydration
decrease BUN is found in
poor nutrition
hepatic disease
impaired absorption (celiac disease)
pregnancy
clinically, BUN rises in response to
renal dysfunction
low BUN is not generally considered abnormal renal fucntion
true or false
true
why is there a decreased BUN when there’s severe hepatic disease
because of a decline in the capacity of the liver to generate urea from ammonia
it is the end product of muscle metabolism derived from creatine (a-methyl guanidoacetic acid)
creatinine
what are the 3 amino acids that produces creatinine
methionine, arginine and lysine
is creatinine easily removed by dialysis
nope - not easily
is creatinine can be reused in the body’s metabolism
nooo - solely a waste product
commonly used to monitor renal function; an index of of overall renal function
creatinine
a measure of the completeness of 24 hr urine collection
creatinine
creatinine is can be used to determine fetal age, aside from that it can determine ___ in of a fetal as well
fetal kidney
the amount generated in an individual is proportional to the mass of skeletal muscle present
creatinine
is a functional or structural abnormalities or markers of kidney damage including abnormalities in blood, urine, or tissue tests or imaging studies present for less than 3 months
acute kidney injury
acute kidney injury is also called as
acute kidney failure
A 24-hour urine sample with < 0.8 g/day of creatinine indicates
that some of the urine was probably discarded
patients taking what antibiotic may have falsely increased results when the jaffe reaction is used
cephalosporin
what is the principle behind the direct jaffe method of creatinine
creatinine + alkaline picrate = red-orange tautomer of creatinine picrate
interferences of direct jaffe method for creatinine determination that will result to false increased level
ascorbate
glucose
uric
a-keto acids
interferences of direct jaffe method for creatinine determination that will result to false decreased level
hgb and bilirubin
what are the chemical methods of creatinine determination
folin wu method
lloyd or fuller’s earth method
jaffe reagent
kinetic jaffe method
folin wu method
sensitive or specific?
sensitive
not specific
what are the adsorbent of lloyd or fuller’s earth method
lloyd’s reagent - sodium aluminum silicate
fuller’s earth reagent - aluminum magnesium silicate
purpose of adsorbent in lloyd or fuller’s earth method
removes interferences present in the specimen
are utilized to separate creatinine from the adsorbent which is then made to react with the freshly made jaffe reagent
elution techniques
disadvantage of llod or fuller’s earth method
a time-consuming method and not really automated; not routinely performed
composition of jaffe reagent (alkaline picrate)
saturated picric acid
10% NaOH
principle of kinetic jaffe method
serum is mixed with alkaline picrate solution and the rate of change in absorbance is measured between two points
interferences in kinetic jaffe method
a-keto acids and cephalosporins
this type of method for creatinine determination is used to eliminate non-specificity of the jaffe reaction and is more specific than jaffe test
enzymatic method
what are the enzymatic method of creatinine determination
creatinine aminohydrolase - CK method
creatinase-hydrogen peroxide method
creatinine amidohydrolase/iminohydrolase method
what is the reference method of creatinine determination
IDMS - isotope dilution mass spectrometry
this enzymatic method of creatinine determination requires large volume of pre incubated samples and is not widely used
creatinine aminohydrolase- CK method
this enzymatic method of creatinine determination has the potential to replace jaffe method and is more specific than jaffe method
creatinase-hydrogen peroxide method
creatinase is also known as
creatinine aminohydrolase/iminohydrolase
this enzymatic method of creatinine determination used the consumption of NADH to measure the concentration of creatinine at decrease absorbance at 340 nm
creatinine amidohydrolase/iminohydrolase method
principle of IDMS for creatinine determination
a known amount of a C13 isotope-enriched creatinine is added to the sample and the mass spectrum is determined
increased serum creatinine is found in
impaired renal function
chronic nephritis
congestive heart failure
decreased serum creatinine
decreased muscle mass
advanced and severe liver disease
pregnancy
inadequate dietary protein
why do elevated plasma creatinine concentration is associated with abnormal renal function, especially the glomerular function
since creatinine is freely filtered out of the blood and not reabsorbed,
If plasma creatinine is high, it suggests that the kidneys are not effectively filtering creatinine out of the blood, which indicates impaired glomerular function (GFR is reduced)
plasma creatinine is a relatively insensitive marker and may not be measurably increased until renal function has deteriorated more than _____%
50
describe the creatinine level of a plasma if the renal function is normal but has muscular disease
within the reference limit or normal
kapag may muscle disease usually increased and creatinine, however, in severe muscle wasting, production of creatinine could be reduced to less than ____% of the amount predicted from the body weight
25
___ and ___, in the face of elevated BUN and creatinine, is indicative of renal disease,
strongly suggest tubular failure
Hyperphosphatemia and hypocalcemia
Hyperphosphatemia → Proximal tubule dysfunction (↓ phosphate excretion).
Hypocalcemia → Impaired vitamin D activation (by the proximal tubules), thus failed reabsorption of calcium
low ratio (BUN:CREA) <10:1
low protein diet - kasi diba from protein ang urea
acute tubular necrosis - tubular necrosis di nare-reabsorbed si urea
repeated dialysis - readily removed kasi si urea sa dialysis
hepatic disease - hindi nacoconvert ni liver si ammonia to urea
ending mababa si urea
high ratio (BUN:CREA) >20:1 with normal creatinine
pre renal azotemia
dehydration
catabolic states
GI hemorrhages
high protein diet
pre-renal azotemia means
—-> Less blood reaching the kidneys → Less filtration → BUN accumulates in plasma.
—> due to low perfusion, kidney will keep sodium and water to maintain the volume, and urea follows water. Thus, increase in urea
dehydration
—> kidney will keep sodium and water, urea will follow water thus increase on its level
GI HEMORRHAGES
–> In GI bleeding, blood is digested in the stomach and intestines, breaking down into proteins (hemoglobin → amino acids), then metabolized in the liver
high protein diet
–> alam mo na yan, labyu, syempre dahil breakdown ng protein si urea, duh, basic
causes of high ratio (BUN:CREA) >20:1 with high creatinine
post renal azotemia - usually caused by urinary obstruction by stones/tumors.
Preventing urine getting out the kidney ang ending elevated bun and crea
prerenal azotemia with renal disease
renal failure
it is the major product of purine (adenine and guanine) catabolism
blood uric acid
final breakdown of nucleic acids catabolism in humans
blood uric acid
how do uric acid are formed
formed from xanthine by the action of xanthine oxidase in the liver and intestine
95% of uric acid exist as
monosodium urate
uric acid is derived from 3 sources, what are they
catabolism of ingested nucleoproteins
catabolism of endogenous nucleoproteins
direct transformation of endogenous purine nucleotides
conditions that has hyperuricemia
gout
increased nuclear metabolism
chronic renal disease
lesch-nyhan syndrome
other causes
conditions that has hypouricemia
fanconi’s syndrome
wilson’s disease
hodgkin’s disease
it is a disease found primarily in males and first diagnosed between third and fifth decades of life
`gout
a condition characterized by pain and inflammation of the joints (acute inflammatory arthritis)
gout
it is characterized by the presence of “birefringent crystals in the synovial fluid” - definitive diagnosis
gout
persons with gout are highly susceptible to what type of stone
nephrolithiasis - kidney stones
value or amount of serum uric acid to form and considered as gout
7.5 mg/dl
hyperuricemia condition that is seen in leukemia, lymphoma, multiple myeloma or polycythemia, and hemolytic and megaloblastic anemias
increased nuclear metabolism
what is the treatment for increased nuclear metabolism
allopurinol drug
a hyperuricemia that is due to decreased GFR and tubular secretion
chronic renal disease
a hyperuricemia that is an inborn error of purine metabolism and is characterized by the deficiency of hypoxanthine guanine phosphoribosyl transferase
lesch-nyhan syndrome
from the book of rodriguez, what are the conditions under hypouricemia
fanconi’s syndrome
wilson’s disease
hodgkin’s disease
describe the plasma uric acid of a newborn
elevated and gradually decreasing in the succeeding year
Uric acid is stable in both serum and urine for how many days at room temperature
3 days
the anticoagulant that cannot be used for uric acid determination
potassium oxalate
major interferences of uric acid determination
ascorbic acid and bilirubin
what is the principle behind the chemical methods of blood uric acid determination
reduction-oxidation reaction
what are the method under chemical method that uses sodium cyanine
folin, brown, newton, and benedict method
what are the method under chemical method that uses sodium carbonate
archibald, caraway, henry method
is the incubation period of chemical method for uric acid determination after the addition of an alkali to inactivate non uric reactants
lagphase
principle behind the enzymatic method - uricase method
the enzyme uricase will oxidizes uric acid to form allantoin. Then spectrophotometry at 293 mm, allantoin can’t absorb light at this wavelength, so the sudden decrease of absorbance after the initial absorbance is proportional to the concentration of uric acid.
at initial absorbance, di naman mamemake sure if uric acid lang ba ang nandon, kapag na spectro yon, makikita ung absorbance ng buong solution at hindi specific to uric acid lang, so mag add ng uricase to oxidize uric acid, then magiging allantoin na si uric acid. Next is re-read at 293, mao-observe doon magkakaron ng changes sa absorbance. So initial absorbance - absorbance after adding of uricase, kaya sinabi na THE DECREASE OF ABSORBANCE IS PROPORTIONAL TO THE CONCENTRATION OF URIC ACID IN THE SAMPLE
enzymatic method of uric acid uses what enzyme
uricase
ref method of uric acid determination
IDMS
it is the elevated concentrations of nitrogenous substances such as urea and creatinine in blood
azotemia
a clinical syyndrome comprised of a marker elevation in plasma urea and other nitrogenous waste products, accompanied by acidemia and electrolyte imbalance
uremia
uremia is characterized by
anemia (normocytic normochromic)
uremic frost (dirty skin)
generalized edema
foul breath
sweat is urine like odor
what does uremia caused to red blood cell appearance
changes in red cell shape
- burr cells (echinocytes)
- ellipsoidal cells
the presence of burr cells during the course of illness may signal the development of ___
renal dysfunction
acc to rodriguez, what are the excretion tests
para-amino hippurate (PAH)/ diodrast test
phenosulfonthalein (PSP) dye test
this excretion test measures the renal plasma flow
para-amino hippurate (DIODRAST TEST )
this excretion test measures the excretion of the dye proportional to renal tubular mass
phenosulfonthalein DYE test
this excretion test is for renal plasma flow that’s why it’s ref range is 600-70 ml/mn
PAH
this excretion test is for renal total blood flow that’s why its ref range is 1200 ml/mn
PSP dye test
this test reflects the function of the collecting tubules and the loops of henle
concentration test
this test used to assess the quantity of solutes present in urine which reflects the ability of the kidneys to produce a concentrated urine
concentration test
this test can detect renal damage that is not yet severe enough to cause elevated plasma urea and creatinine levels
concentration test
monitoring the concentration of what inorganic compounds in urine reveals the ability of the kidney to concentrate the ultrafiltrate in tubules
sodium and chloride
what are the most prevalent solutes excreted
urea, chloride, and sodium
sample used for concentration test
first morning urine
the simplest test of renal concentrating ability
specific gravity
it compares the weight of a fluid with that distilled water at a reference temperature
Specific gravity q
main determinant of the SG of plasma
protein
“fixation” of SG at 1.10 indicates
sever loss of concentrating ability of the kidneys
SG iso osmotic plasma = _____
SG iso osmotic urine = _____
SG iso osmotic plasma = 1.020 - 1.030
SG iso osmotic urine = 1.010
it is an expression of concentration in terms of the total number of solute particles present per kg solvent
osmolality
affected only by the number of solutes present, thus more accurate than specific gravity in assessing tubular function
osmolality
osmolality is regulated by the changes in ___
water balance
urine osmolality is due primarily to what substance
urea
serum osmolality is due primarily to what substance
chloride and sodium
in terms of molecular weight, what is the difference from SG to osmolality
osmolality is not affected by high molecular weight substances as opposed to SG such as proteins and lipids
normal ration of urine osmolality to serum osmolality is
1:1
primary organ responsible for osmotic regulation
hypothalamus
how hypothalamus respond in 1-2% increase of serum osmolality
four fold increase of AVP concentration
how hypothalamus respond in 1-2% decrease of serum osmolality
shuts off AVP synthesis
polydipsia can cause (lower, higher) plasma osmolality and will suppress __ and ___
lower plasma osmolality; thirst and AVP
describe the serum and urine osmolality of diabetes insipidus
increased serum osmolality
decrease urine osmolality
describe the serum and urine osmolality of SIADH
decrease serum osmolality and normal/increase urine osmolality
