Kidney function tests urea measurement

Early kidney disease is difficult to detect. The urinalysis is normal in early lead nephropathy and the blood urea nitrogen and serum creatinine increase only when two-thirds of kidney function is lost. Measurement of creatinine clearance can often detect earlier disease as can other methods of measurement of glomerular filtration rate. An abnormal Ca-EDTA mobilization test has been used to differentiate between lead-induced and other nephropathies, but this procedure is not widely accepted. A form of Fanconi syndrome with aminoaciduria, glycosuria, and hyperphosphaturia indicating severe injury to the proximal renal tubules is occasionally seen in children. 

Following synthesis, urea is transported in the bloodstream to the kidneys, which filter it for excretion. Measurements of blood urea nitrogen (BUN) levels provide a sensitive clinical test of kidney function, because filtration and removal of urea are impaired in cases of kidney malfunction. Analogously, blood ammonia measurements are a sensitive test of liver function. 

Renal function is an indication of the physiological state of the kidney glomerular filtration rate (GFR) describes the flow rate of Altered fluid through the kidney, while creatinine clearance rate (Ccr) is the volume of blood plasma that is cleared of creatinine per unit time, and is a useful measure for approximating the GFR. Most clinical tests use the plasma concentrations of the waste substances of creatinine and urea, as well as electrolytes, to determine renal function. The nephron is the functional unit of the kidney (Figure 10.1) it consists of two parts ... 

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