Diagnostic significance of the determination of renal tubular function in kidney disease

Determination of renal tubular function, including phenol red excretion test, kidney concentrated dilution test, urine osmotic pressure, urine concentration dilution test, free water clearance rate measurement, renal tubular glucose absorption determination of tubular Determination of ammonia hippuric acid excretion bicarbonate reabsorption excretion (alkali load) test, now commonly used tests are described below.


(1) of phenol red excretion test phenol red, also known as phenol sulfur peptide (PSP), is harmless to human body's pigment. Phenol red injected into the body, about 94% from the urine. Determination of phenol red excretion in the urine, can be used as a rough indicator to determine the excretion of proximal tubule function. 15min after the phenol red injection of the normal adult, the excretion of 28% to 51%, an average of 35%; the 2h excreted a total of 63% to 84%, an average of 70%. Low excretion of the elderly. Clinical practice, often for 15 min excretion <25%, the 2h excretion of <55%, row tubular secretion function to reduce the boundaries. Phenol red excretion rate, seen in glomerular, tubular or renal interstitial lesions.


(2) renal concentrated dilution test kidney (urine) enrichment experiments, the ability to observe the body's water shortage situation, the distal tubules to concentrate urine. 3 times normal urine specimens, at least a relative density of> 1.026 (the elderly in more than 1.020); urine relative density <1.020, indicating poor renal concentration. The extreme damage of the renal function, urinary maximum relative density of 1.010; uremia, urine relative density of 1.010 ~ 1.012; glomerulonephritis, pyelonephritis, hypokalemia and hyperkalemia, kidney disease, but also showed relative density of urine abnormalities .


(3) free water clearance rate of free water clearance (CH2O) per minute cleared from plasma to urine and pure water, to better reflect the kidney to regulate fluid balance in the body dry and too much water than urine osmolality the ability, it can more accurately determine the severity of the renal concentration and dilution function and renal disease. Normal CH2O 25 ~ 100ml / h. CH2O positive on behalf of the renal diluting capacity, a negative value on behalf of renal concentration capacity equal to or close to zero indicates that the kidney can not concentrate and dilute urine in the function of serious injury.


(4) determination of renal tubular glucose reabsorption With the constant increase in plasma glucose concentration, renal tubular reabsorption of glucose values ​​also increased when the blood glucose concentration exceeds a certain limit, renal tubular reabsorption capacity of saturated can not be too much sugar reabsorption to the urine. At this point, the amount of filtrate reabsorption of glucose, known as renal tubular glucose reabsorption (TMG). TMG significantly reduced, seen in severe acute glomerulonephritis and chronic glomerulonephritis; renal arteriosclerosis, chronic pyelonephritis, caused by the occlusion of part of the glomerular or tubular ischemia, TMG can be reduced.