Renal function, in nephrology, is an indication of the state of the kidney and its role in 
renal physiology.The most common cause of an elevated B.Urea( azotemia) is poor kidney function, 
although a serum 
creatinine level is a somewhat more specific measure of renal
function .A greatly elevated BUN (>60 mg/dL) generally indicates a moderate-tosevere degree of renal failure.Kidney function tests is a number of clinical laboratory tests that measure the levels of 
substances normally regulated by the kidneys can help determine the cause and extent 
of kidney dysfunction.Creatinine clearance rate (CCr or CrCl) is the volume of 
blood plasma that is cleared of creatinine per unit time and is a useful measure for 
approximating the GFR.Normal human adult blood should contain between (15-40) mg/dl.