Urine Specific Gravity and Its Significance
Urine Specific Gravity
Sample for Urine Specific Gravity
- A random urine sample can be taken.
Indications for Urine Specific Gravity
- Urine analysis is part of the routine diagnostic profile.
- This gives an idea about kidney function.
- This also gives an idea about the hydration status.
Precautions for Urine Specific Gravity
- Urine collected after the I/V administration of iodine-containing radiopaque material gives high values of specific gravity.
- Glucose and the protein in the urine also have a high value.
- Diabetic patient with hyperglycemia gives high value.
- Patients after contrast radiography and dextran infusion may have high specific gravity.
- The temperature also has an effect on the specific gravity, as it is increased in the cold.
- In the case of detergent in the container may give high specific gravity.
- Diuretics and antibiotics give rise to high specific gravity.
Definition of specific gravity:
- Urine-specific gravity is the measure of the kidney’s ability to concentrate urine.
- The important process of reabsorption by the kidneys is often the first renal function to become impaired.
Urine Specific gravity facts:
- So the specific gravity will detect dehydration or abnormality in the antidiuretic hormone.
- Urine is a solution of minerals, salts, and other compounds dissolved in water.
- Specific gravity = water + dissolved chemicals.
- So specific gravity is the measure of the density of dissolved substances in the urine.
- Specific gravity is the weight of urine compared to distilled water, which has a specific gravity of 1.000.
- The specific gravity of the plasma entering the glomerulus is 1.010.
Types of urine according to the specific gravity:
- The urine-specific gravity is fixed and remains constant at around 1.010.
- It is not influenced by water intake or dehydration.
- Normal kidneys concentrate the urine in dehydration.
- It is the urine that has not greater and not less than the protein-free plasma specific gravity.
- It is urine with a specific gravity of 1.010 (1.008 to 1.012).
- It suggests renal damage.
- These patients need medical check-ups and workups.
- Specific gravity is low = <1.010 (1.001 to 1.010).
- It occurs in the following conditions:
- Diabetes inspidus. This is due to the absence or decrease of ADH. Without ADH, the kidneys produce an excessive amount of urine that is not reabsorbed.
- Glomerulonephritis and pyelonephritis. Specific gravity is low with decreased urine volume.
- Severe renal damage. There is a disturbance in both concentrating and diluting abilities of urine.
- Increased specific gravity is > 1.010 (1.025 to 1.035).
- It is seen in the following conditions:
- Diabetes mellitus.
- Increased secretion of ADH.
- The diuretic effect of stress of the surgical procedure.
- Excessive loss of water due to dehydration, fever, diarrhea, and vomiting.
- Toxemia of pregnancy.
- Cardiac diseases like congestive heart failure.
Random sample = 1.003 to 1.035.
- Most random sample = 1.015 to 1.025.
- A specific gravity of 1.023 or higher is generally considered normal.
- Specific gravity >1.035 is usually seen in the renal pyelogram (IVP).
- Specific gravity <1.003 is not urine.
Specific gravity depends upon the following:
- The state of hydration.
- Urine volume.
- High specific gravity indicates concentrated urine.
- Low specific gravity indicates dilute urine.
- The reflectometer can read specific gravity.
Normal urine specific gravity
|Adult||1.005 to 1.030 (mostly = 1.010 to 1,025)|
|Newborn||1.001 to 1.025|
|Older people||Value decreases|
|Concentrated urine||1.025 to 1.030|
|Diluted urine||1.001 to1.010|
Lab procedure to find the specific gravity of urine:
- The Hydrometer checks the specific gravity but needs an abundant quantity of urine.
- Absorbent cellulose strip impregnated with bromthymol blue, polymethyl vinyl ether, and or maleic anhydride and sodium hydroxide.
- The color changes to dark blue at a low specific gravity of 1.000.
- Yellow-green at a specific gravity of 1.030.
- Machine-readable devices are available from the Clinitek system, Bayer Diagnostics, and Elkhart Ind.
- If the urinometer does not measure the specific gravity, dilute urine 1:2.
- Now multiply the reading by 2.
The Increased specific gravity is seen in the following:
- Decreased renal blood flow.
- Diabetes mellitus.
- Excessive water loss in fever, vomiting, and diarrhea.
- Toxemia of pregnancy.
- Congestive heart failure.
- Water restriction.
The Decreased specific gravity is seen in the following:
- Diabetes insipidus.
- Early chronic failure.
- Severe renal damage.