2- Plasma urea and Blood Urea Nitrogen (BUN) : The normal value
of blood urea is 15-40 mg/dl. Normal value of BUN is 8-13 mg/dl.
3- Glomerular Filtration Rate (GFR): This is measured by studying
the clearance of a substance which is ideally freely filtered through
the glomerulus; and not reabsorbed or excreted by the renal tubules
(e.g. inulin). In practice, we use endogenous creatinine which is
filtered through the glomerulus but some excretion occurs by the
renal tubules, so creatinine clearance slightly overestimates GFR.
Normal creatinine clearance in adult male is 90 -150 ml/minute. To
estimate creatinine clearance, the patient should collect 24 hours urine
from which V and U could be estimated then, blood is withdrawn for P
estimation.
C= UXV
P
C= creatinine clearance
U= urine concentration of creatinine
V= urine flow rate (minute or second)
P= plasma concentration of creatinine