Understanding Urine Specific Gravity

What specific gravity classification is associated with dilute urine?

Which specific gravity range is typical for most random urine specimens?

What is the specific gravity of a first morning urine specimen generally considered to be?

Which classification indicates a specific gravity higher than 1.010?

What implication does a specific gravity below 1.002 have regarding urine samples?

What is indicated by a fixed urine specific gravity (SG) of 1.010?

Which condition is associated with a low specific gravity (SG) of urine?

Excessive water loss is likely to cause which of the following urine specific gravities?

What role does antidiuretic hormone (ADH) play in urine specific gravity?

Which condition might impair the release of aldosterone and lead to a higher urine specific gravity?

What primarily influences the specific gravity of a solution?

Which of the following statements regarding specific gravity of urine is accurate?

What is one of the primary functions of measuring specific gravity in urine?

Larger molecules influence specific gravity in what way compared to smaller molecules?

How does the specific gravity of a solution relate to distilled water?

Definition

Specific gravity (SG) is a measure of the density of a solution compared to distilled water.
It is measured in relation to the density of water, which has an SG of 1.000.
SG of urine is influenced by the number and size of dissolved particles.
Larger particles contribute more to SG than smaller particles.

Functions

Determine kidney's concentrating ability: This helps assess how well the kidneys are able to regulate the concentration of urine.
Ensure accurate chemical tests: Accurate chemical tests rely on adequate urine concentration.

Specific Gravity Ranges

Isosthenuric: 1.010 (urine has the same SG as plasma ultrafiltrate)
Hyposthenuric: < 1.010 (dilute urine)
Hypersthenuric: > 1.010 (concentrated urine)

Normal Specific Gravity Range

Random specimen: 1.002 to 1.035; most commonly between 1.015 to 1.030.
First morning specimen: This is usually the most concentrated.
If a urine sample has an SG below 1.002 then it may not actually be urine.

Low Specific Gravity

Indicates a loss of the kidneys' ability to concentrate urine.
Clinical causes:
- Tubular damage: Damage to the renal tubules can impair their reabsorption ability.
- Diabetes insipidus: A condition where the body doesn't produce sufficient antidiuretic hormone (ADH), which is essential for water reabsorption.
- Large volume, low SG urine production: This is a consequence of impaired water reabsorption, leading to dilute urine.
- Decrease in ADH: ADH helps the kidneys to reabsorb water. A decrease in ADH levels will result in more dilute urine.

High Specific Gravity

Indicates that the urine is more concentrated than usual.
Clinical causes:
- Adrenal insufficiency: This can impair the release of aldosterone, which is essential for sodium retention and water reabsorption.
- Hepatic disease: Liver diseases can affect the body's ability to regulate fluid balance.
- Excessive water loss: This can be caused by conditions like severe vomiting, diarrhea, or excessive sweating, leading to concentrated urine.

Fixed Urine SG

A consistent urine SG of 1.010 (isothenuric) indicates severe renal damage.
The kidneys are unable to concentrate or dilute the filtrate, leading to a constant SG.

This quiz covers the concept of specific gravity (SG) of urine and its implications for kidney function. You'll learn about the ranges of SG and how it reflects the concentration ability of the kidneys. Test your knowledge with questions about normal ranges and factors affecting urine SG.