SEMINAR ON TUBULAR FUNCTION TEST

Presented by: Nidhi kumari B.Sc (MLT) 3rd year

Moderated by : Dr.seema

FUNCTION OF TUBULES(a) When the glomerular filtrate is formed, it

contain almost all the crystalloids of plasma. In the proximal convoluated tubules, about 70% water ,sodium, and chloride as well as 100% glucose , amino acids and potassium are reabsobed.

(b) Urea , phosphate and calcium are partially absorbed.

(c) The major processes occuring in renal tubules are reabsorption or secretion of solutes and reabsorption of water.

RENAL THRESHOLD AND TUBULAR MAXIMUM(a) Compounds whose excretion in urine is

dependent on blood level are known as threshold substances at normal level or low plasma level they are completely reabsorbed and not excreted in urine.

(b) The maximum reabsorptive capacity of the substances is known as the tubular maximum or Tm.

(c) The renal threshold of a substance is the plasma level above which the compound is excreted in urine.

VARIOUS TUBULAR FUNCTUON TESTS:

(a) Specific Gravity test : The simplest test of tubular function is the measurement of the specific gravity of urine. It depends on the concentration of solutes, where as osmolality depends on the osmotically active particles. In moderate form of kidney damage the blood level of urea and creatinine may be within the normal limit.

CONCENTARTION TEST

Principle : This test is based on the ability of kidney to concentrate urine, and based on measuring sp.gr of urine . They are simple, easy to carry out and extremely important.

(a) Fishberg concentration test : most commonly used test and easy to carry out.

PROCEDURE : The patient is allowed tono food or water after a meal at 6 pm. The next day at 7 am , the bladder is emptied and specimen is discarded and second specimen is collected at 8 am and sp.gr is measured

INTERPRETATION : If the function is normal sp.gr should be >1.025.

Impaired gravity is less than 1.020 Severe renal damage sp.gr is fixed at 1.010

WATER DILUTION TEST Principal : The ability of kidney to eliminate

water is tested by measuring the urinary output after ingesting a large volume of water.

Procedure : The patient remains in bed through out the procedure because the elimination of water is maximal in the horizontal position. On the day before the test the patient has an evening meal. On the morning of test patient has to advised to empty bladder at 8am which is discarded.

Then make patient to drink 1200ml of water with in half n hour. Then bladder is empty at 9am, 10am, 11am and 12pm. Then the voluma and sp.gr of the four specimen is measured.

INTERPRETATION : If the renal function is normal more than 80% water is voided and sp.gr should be < 1.003.

If renal function is impaired < 80% water is exrected in 4hrs.

If severe renal damage then sp.gr is fixed at 1.010.

TEST FOR TUBULAR EXCRETION AND REABSORPTIONPSP TEST (PHENOL SULPHTHALAMINE TEST)Principal : The reserve function of secretion of

foreign non endogenous materials by tubular epithelium is most conventially tested by the use of certain dyes and measuring their rate of excreation.

Procedure : 1ml of psp is injected intravenously normal kidney excrete 30-50% of dye in 1st 15 minute .if amount of dye excreated is less than 20% in 1st 15 minute. It will show renal impairement.

TUBULAR PROTEINURIAThis occurs when functional nephrons are

reduced , GFR is decreased and remaining nephrons are over working. The tubular reabsorption mechanism is impaired , so low molecular weight proteins appear in urine. Tubular damage results in the release of intracellular components to the urinary tract and may be used as markers of tubular damage.

NEPHRON LOSS PROTEIN URIAThere is decrease in number of functioning

nephorns. The compensatory rise in glomerular filtration by other nephorns increases the filitered load of proteins. Even if there is no glomerular permeability changes , tubular proteinuria is seen.

UROGENIC PROTEINURIAThis is due to inflammation of lower urinary

tract , when proteins are secreted into the tract . Acculumation of proteins in tubular lumen can tigger inflammation reaction.