NPN Compounds and Kidney Function Tests Flashcards
2 regions of the kidney
renal cortex (outer), renal medulla (inner)
functional unit of kidney
nephron
stimulates bone marrow to produce RBCs
erythropoietin
bean shaped located on either side of
spinal column
main function of kidneys
urine formation and excretion of waste products
adrenal glands secretes
aldosterone & vasopressin
prevents water loss and is also known as
vasopressin, anti-diuretic hormone
regulates water and salt in the body
aldosterone
parts of nephrons
PCT, DCT, loop of henle, glomerulus, collecting duct
promotes reabsorption of sodium and excretion of potassium
aldosterone
function of PCT
reabsorbs Na, Cl, HCO3-, Glucose, Amino acids, Proteins, Urea, & Uric acid
function of collecting duct
final site for concentration or dilution of urine
function of loop henle
site of major exchange of water and salt
NPN Compounds %
urea - 45%
uric acid - 20%
creatine - 1-2%
amino acid - 20%
creatinine - 5%
ammonia - 0.2%
plasma contain _ of NPN compound
20-35 mg/dL
ammonia is detoxified in the _ to produce _
liver, urea
most abundant NPN
urea
ammonia exist as _ in normal blood pH
ammonium ions
acute metabolic disorder of the liver & common in children
Reye’s syndrome
normal BUN-creatinine ratio
10:1 - 20:1
Major end product of protein and amino acid catabolism
BUN
Easily removed by dialysis
BUN
In BUN, approximately ____ of the nitrogen is excreted
80%
In BUN, Formed through the ______ in the liver
Krebs-Henseleit (Urea) cycle
Excreted by the kidneys – ___ reabsorbed
___ of the total are excreted through the gastrointestinal tract and skin.
40% , <10%
Clinical application of BUN measurement
- Evaluate renal function
- Assess dehydration status
- Determine the nitrogen balance in the body
- Aid in the diagnosis of renal disease
- Verify the efficacy of dialysis
In BUN, Concentration is determined by
- Renal function
- Dietary intake
- Protein catabolism rate
End (waste) product of muscle metabolism derived from creatine and creatine phosphate
creatinine
Creatine is converted to creatinine through_____
dehydration
Creatine phosphate is converted to creatinine through ____
dephosphorylation
Creatine is phosphorylated to creatine phosphate by the presence of _____
creatine kinase
Creatinine is synthesized primarily by the liver from ____
arginine, glycine and methionine
Partially secreted by the proximal tubules via the organic cation transport pathway
creatinine
Not easily removed by dialysis
creatinine
Not reabsorbed by the tubules
creatinine
Measure the completeness of 24 hour urine collection (urine creatinine).
creatinine
Index of overall renal function
creatinine
Elevated creatinine is found in ____
abnormal renal function
creatinine measurement
- Sufficiency of kidney function
- Severity of kidney damage
- Monitor progression of kidney disease
In Acute Kidney Injury, functional or structural abnormalities or markers of kidney damage (seen in blood, urine, tissue test, imaging studies) present for___
3 months
stage 1 creatinine
SCC = >0.3 mg/dL or 150-200%
UOC = <0.5 mL/kg for >6hr
Heating converts creatine to creatinine and the difference between the two samples is the _______.
creatine concentration
stage 2 creatinine
SCC = >200 - 300%
UOC = <0.5 mL/kg for >12hr
stage 3 creatinine
SCC = >300%, 4 mg/dL or acute increase of >0.5 mg/dL
UOC = <0.3 mL/kg for >24hr or anuria of >12hr
Specialized test, not part of routine testing
Creatine
In Creatine, Analyzing the sample for creatinine before and after heating in acid solution using an endpoint _____.
Jaffe method
Elevated in plasma and urine in
Muscular dystrophy, hyperthyroidism, trauma.
Increased concentration of BUN and Creatinine in the blood
Azotemia
elevated plasma urea concentration accompanied by renal failure
Uremia/Uremic syndrome
Reduced Renal Blood Flow
pre renal azotemia
Less blood delivered to the kidney
pre renal azotemia
Less Urea filtered
pre renal azotemia
causes of pre renal azotemia
Congestive heart failure
Shock
Hemorrhage
Dehydration
High protein diet or increase catabolism
True renal disease
renal azotemia
Characterized by damage within the kidney
renal azotemia
Damaged kidneys
renal azotemia
Poor excretion
renal azotemia
Increased Urea
renal azotemia
complication of renal azotemia
Coma or neuropsychiatric changes
In renal azotemia, BUN will have an ____ of _____
abrupt elevation, >100 mg/dL
In renal azotemia, Creatinine will have a ____ of ___
slow elevation, 20 mg/dL
In renal azotemia, BUA (Blood Uric Acid) =
12 mg/dL
No erythropoietin will be secreted
renal azotemia
Associated with anemia and electrolyte imbalance due to reabsorption capacity impairment
renal azotemia
Usually the result of Urinary Tract Obstruction
post renal azotemia
Urea level is higher than creatinine due to back-diffusion of urea into the circulation.
post renal azotemia
It is the major product of purine (adenine and guanine) catabolism.
uric acid
It is formed from xanthine by the action of xanthine oxidase in the liver and intestine.
uric acid
Uric acid is transported to kidney and filtered (___)
70%
1g of uric acid is excreted normally and 98% is reabsorbed in the ___ and ____
PCT & DCT
Uric acid is in the form of ______() in plasma
monosodium urease (95%)
Pain & inflammation of joints by precipitation of sodium urates in tissues
gout
When value is _____, uric acid crystals may form and precipitate in the tissues and contribute to formation of gout and stones in the kidney
> 6.8 mg/dL
Primarily seen in men and first diagnosed between 30-50 of age
gout
presence of “birefringent crystal in synovial fluid”
gout
Increased risk of renal calculi/nephrolithiasis
gout
Gout causes ___ increase of uric acid
25-30%
Occurs in patients on chemotherapy for diseases such as leukemia & multiple myeloma.
Increased Nuclear Metabolism
Causes elevated levels of uric acid because filtration and secretion are hindered.
Chronic renal disease
In Increased Nuclear Metabolism, Allopurinol inhibits ____, an enzyme in the uric acid synthesis pathway, which is used to treat these patients.
xanthine oxidase
In Chronic renal disease, BUA is
> 10 mg/dL
Can cause urinary tract calculi
Chronic renal disease
Inborn error of purine metabolism
Lesch-Nyhan Syndrome
In Lesch-Nyhan Syndrome, It is deficient of
hypoxanthine-guanine phosphoribosyl transferase (HGPRT)
other causes of Lesch-Nyhan Syndrome
Secondary to glycogen storage disease
Toxemia of pregnancy and lactic acidosis
Increased dietary intake
Ethanol consumption
Best overall indicator of the level of kidney function
GFR
Disorder of reabsorption in the PCT of the kidney
fanconi’s syndrome
6-mercaptopurine, azathioprine
Chemotherapy
Measures the clearance of substances not bound to protein.
GFR
GFR decreased by 1.0 mL/minute/year after age ___ years.
20-30
In GFR, _____of glomerular filtrate is produced daily.
150L
In GFR, About ___ of water is filtered daily
180L
In GFR, ___ is reabsorbed in the PCT
150L
In GFR, ___ in the descending loop of henle of cortical nephrons
5L
Removal of the substance from plasma into urine over a fixed time (24hrs).
clearance
In Clearance, Plasma concentration is _____ to clearance
inversely proportional
In Clearance, formula is affected by ______ and correction for _____should be included in the formula
body surface area, body mass
Reference method of clearance test
inulin clearance test
exogenous substance (never produced by the body)
inulin clearance test
Introduced via IV (____mL of ___% inulin soln.)
inulin clearance test, 500 , 1.5
Not routinely done due to the necessity for continuous IV inclusion
inulin clearance test
Alternatives to Inulin
Radioactive marker: 125I-iothalamate & 99mTc-DTPA
Iohexol and Chromium 51-labelled EDTA
Nonradiolabeled iothalamate
Best alternative method to inulin
Creatinine clearance
Excellent measure of renal function
Creatinine clearance
endogenous substance freely filtered by the glomeruli but not reabsorbed.
Creatinine
Production & excretion of creatinine are directly related to
muscle mass
Excretion is not routinely affected by diet
creatinine clearance
In creatinine clearance, Approximately ___of creatinine is excreted per day
1.2-1.5 g
Major limitation of creatinine clearance
urine collection should be accurate (timing)
Demonstrate progression of renal disease or response to therapy
Urea clearance
Not reliable GFR – urea is freely filtered but variably reabsorbed by the tubules
Urea clearance
Low molecular weight protease inhibitor and produced at a constant rate by all nucleated cells.
Cystatin C
Indirect estimate of GFR
Cystatin C
Freely filtered by the glomerulus but completely reabsorbed by the tubules
Cystatin C
Presence of Cystatin C in urine denotes that there is a damage in the
PCT
Only kidney function test that should not be measured in urine.
Cystatin C
Not affected by muscle mass, age, diet, and gender
Cystatin C
AKA Prostaglandin D synthase
BTP
A low molecular weight glycoprotein (____amino acid)
BTP, 168
Belongs to the lipocalin protein family
BTP
Isolated primarily from CSF
BTP
Accurate marker for CSF leakage
BTP
Freely filtered by the glomerulus but completely reabsorbed and catabolized by the proximal tubule.
BTP
BTP in serum correlates significantly with ___. However, BTP is ___ diagnostic efficient test for GFR.
serum Cystatin C, GFR, urine microproteins // not a
Increased in B-trace protein
Renal disease (because of reduced filtration in the presence of constant production)
In clearance, time required to collect urine
1440 minutes
In clearance, ave. body surface of adult individual (___ for pediatric)
1.73, 0.717
Uric acid is measured to:
assess inherited disorders of purine metabolism
to confirm diagnosis and monitor treatment of gout
to assist in the diagnosis of renal calculi
to prevent uric acid nephropathy during chemotherapeutic treatment
and to detect kidney dysfunction
In Creatine, Elevated in plasma and urine in
Muscular dystrophy, hyperthyroidism, trauma.
Plasma creatinine concentration is a function of:
relative muscle mass
rate of creatine turnover
and renal function
