(Lab) Determination of Urine Specific Gravity

It is the density of a solution compared to the density of a specific volume of distilled water at a similar temperature.

This test is an indication of the kidney’s ability to concentrate and excrete urine

Specific Gravity

The correlation of a higher specific gravity in the urine is _________________________ to the urine concentration

Directly proportional

The specific gravity ranges from ______________ to _____________. However, most samples fall between ___________ and ___________

Range: 1.002 to 1.035

Most samples fall between 1..015 to 1.030

It is expected that the specific gravity is higher when the specimen is ________________________ due to its concentration

First Morning Specimen

Urine specific gravity is the estimation of the concentration of solutes such as: (U, P, C, P, S)

Urea

Phosphates

Chlorides

Proteins

Sugars

Causes and increased specific gravity (9)

• AG

• DH

• DM

• DR

• F

• IS ADH

• N

• TP

• V

• Acute Glomerulonephritis

• Dehydration

• Diabetes mellitus

• Diarrhea

• Fever

• Increased Secretion of ADH

• Nephrosis

• Toxemia of pregnancy

• Vomiting

Decreased in Specific Gravity (5)

AD

CP

CF

D

HFI

ADH deficiency

Chronic pyelonephritis

Cystic Fibrosis

Diuretics

High Fluid Intake

Determination of Specific Gravity also helps to detect possible dehydration or abnormalities in the __________________ hormone and serves as an indicator of the ____________________

Anti-diuretic hormone

Renal Tubular Function

Contamination of _________ or ___________ will increase specific gravity.

Stool or Tissue

Patients intake of ___________________ and ______________ will decrease Specific Gravity

Aminoglycosides and lithium

This procedure determines the concentration of dissolved particles in urine specimen, by measurine the velocity and the angle at which the light passes through a solution .

Refractometer

Other name for Refractometer

Total Solids Meter

The Refractometer applies the principles of light by using a __________________ to direct a specific wavelength of day-light against a manufacturer-calibrated specific gravity

Principles of Light using prism

Temperature correction in the Refractometer is not done because instrument is compensated between _____ and ______

15C to 38C

The only correction for Refractometer are ____________ and ____________

Glucose and Protein

The refractometer is calibrated using:

Distilled Water

5% NaCL:

9% Sucrose:

The refractometer is calibrated using:

Distilled Water

5% NaCL: 1.022 ± 0.001

9% Sucrose: 1.034 ± 0.001

The level of which the ________________ sinks is a representative of the specimen’s specific gravity

Urinometer

The Urinometer is usually calibrated at a temperature of _______ so correction must be done

20C

The only disadvatage of the Urinometer is that it requires a large sample, with ____-____ mL

10-15 mL

For temperature Urinometer corrections, for every ___C the urine temperature is above or below 20C, 0.001 is added or subtracted from the reading

3C

For Protein and Glucose corrections of Urinometer

Protein:

Glucose:

Protein: subtract 0.003 for every g/dL

Glucose: subtract 0.004 for every g/dL

The reagent strip reaction is based on the change of _____________________ of a polyelectrolyte in an alkaline medium

pKa (dissociation constant)

In reagent strip method, the hight the concentration of th urine, the more hydrogen ions are released, thereby lowering the _____

pH

Reagent Strip Method

Incorporation of the indicator _________________ on the reagent pad measures the change in pH

Bromothymol blue

Colors and SG of Reagent Strip:

As the SG increases, from _________________ alkaline blue, it turns to shades of green, then yellow which has a SG of __________________

1.000 blue

0.005 per intervals

green - yellow

yellow (1.030)

Reference values for Reagent Strip Method

Random Urine:

24 hour Urine:

Random Urine: 1.002 - 1.035

24 hour Urine: 1.015 to 1.025