2. Why Important?
• Mostly the kidney diseses are asymptomatic
or have vague/nonspecific symptoms so Renal
function tests are useful tests for estimation of
renal function before any radiological
procedure, in chronic diseases which effect
kidney like HTN, DM and for general
wellbeing.
3. FUNCTIONS OF KIDNEY
• Excretes the waste products of metabolism
• Precisely regulates the body’s concentration
of water and salt
• Maintains the appropriate acid base balance
of plasma
• Serves as an endocrine organ, secreting such
hormones as erythropoietin, renin, and
prostaglandins.
• Conversion of Vit D into active Vit D3 form
4. Kidney carries out filtration of
blood to form urine!
The total blood volume is circulated through
the kidneys about 300 times each day
serves to convert more than 1700 liters of
blood per day into about 1 liter of a highly
specialized concentrated fluid called urine.
5. Basic RFTs
• In Blood sample:
BUN/UREA
Serum Creatinine
BUN and creatinine rise in kidney dyfunction.
6. BUN-Blood urea Nitrogen and Urea
• Urea is a relatively nontoxic substance made
by the liver to dispose of ammonia resulting
from protein metabolism.
• The real urea concentration is BUN x 2.14
• Normal BUN range is 8-25 mg/dL
• BUN is a sensitive but not specific indicator of
renal disease—can be raised in dehydration,
CCF, Urinary tract obstruction
7. Serum creatinine
• Creatine is made by body to supply energy to
muscles. Muscles use creatine and form a
byproduct creatinine as waste of creatine,
kidney filters it from blood along with other
waste products
• In Kidney failure creatinine cannot be excreted
properly by kidney so its level rises in blood
8. Serum CREATININE
• It is generally a more sensitive and specific
test for renal function than the BUN.
• Normal range is 0.6-1.3 mg/dL
• – *non pregnant state
• % rise in urea and creatinine more useful in
kidney diseases rather than single value bc
each individual has different normal value
depending upon his age, sex and body mass
9. AZOTEMIA? & UREMIA?
• Azotemia is a biochemical abnormality that
refers to an elevation of the blood urea
nitrogen (BUN) and creatinine levels, and is
related largely to a decreased glomerular
filtration rate (GFR).
• Types of azotemia:
Prerenal azotemia (e.g., in hemorrhage,
shock, volume depletion, and congestive
heart failure)
10. Postrenal azotemia is seen whenever urine
flow is obstructed beyond the level of the
kidney
• UREMIA: When azotemia becomes
associated with a constellation of clinical
signs and symptoms and biochemical
abnormalities,it is termed Uremia.
• S&S of uremia: Nonspecific: Nausea,
vomiting, fatigue, sleep disturbances, leg
cramps, Amenorrhea etc
11.
12. Tests to estimate the rate of
filtration of blood by kidney—
Kidney function
Creatinine clearance
eGFR(Estimated GFR)
• Both tests actually estimate the kidney
function by estimating the filtration rate of
creatinine, only estimate bc using creatinine
and not whole blood as indicater which is not
absorbed by tubules after filtration and
secreted in very small amount
13. How CC is performed?
• Patient collects his urine in container for
oneday/24hours and then his blood sample
taken for serum creatinine---
• Than both urine creatinine and serum
creatinine levels put in formula to estimate
the amount of creatinine cleared from body
by kidney thus tells weather kidney
functioning normally
14.
15. eGFR
• Nowadays eGFR is used instead of CC
• Calculated by different formulas in which
modifying factors age,sex,race and surface
area applied along with serum creatinine
• Timed urine creatinine collection not required
16. What is GFR?-Glomerular filtration rate sum of the
filtration rates-amount/time filtered in all of the
functioning nephrons
