Urine Specific Gravity Tests - An Overview

What Is a Urine Specific Gravity Test?

Urine-specific gravity test is a noninvasive and painless procedure that helps the doctor check the patient's health and other urologic abnormalities. The most significant thing the doctor checks in the patient's urine sample is the specific gravity. Urine-specific gravity is nothing but a medical term that compares the density of water and urine. If the urine is excessively concentrated, it signifies that the kidneys are not functioning well or the patient is not drinking a sufficient quantity of water. Patients suffering from diabetes insipidus can also have concentrated urine and excessive thirst.

What Are the Uses of a Urine-Specific Gravity Test?

It is important to first understand the role of the kidneys before learning about the importance of the urine-specific gravity test. The kidneys are paired organs that function as filtration units and regulate the body's electrolyte levels. A urine-specific gravity is a fast and easy method to help the doctor know whether the kidneys cannot function properly. The patient will have to take the test multiple times during the day. The test is usually done in patients diagnosed with the following conditions:

• Dehydration.

• Congestive heart failure.

• Shock.

• Diabetes insipidus.

• Kidney failure.

• Overhydration.

• Urinary tract infections.

• Low sodium levels or hyponatremia.

• Raised sodium levels or hypernatremia.

• Renal artery stenosis (narrowing of the arteries of the kidneys).

• Presence of sugar in the kidneys.

• Diarrhea.

• Vomiting.

How Should the Patient Prepare for the Urine Specific Gravity Test?

The doctor might provide certain instructions before the test for the patient to follow. First, the patient will be asked to prepare a list of all the medications. Next, the doctor might ask the patient to stop taking certain drugs that might interfere with the test results, especially the ones containing dextran or sucrose. The urine-specific gravity test can not be done immediately if the patient has undergone the procedure involving intravenous administration of the radioactive contrast dye. The test can only be done after three days if the patient is completely alright. The patient will be asked to take a balanced diet a few days before the test, which implies that the patient must stop taking foods that change the urine color. Such foods include:

• Blackberries.

• Beets.

• Carrots.

• Fava beans.

• Rhubarb.

How Is the Urine Specific Gravity Test Performed?

A urine-specific gravity test is a simple procedure in which the urine sample contains one to two ounces of urine. The patient must ensure that the urine sample is collected in the morning because the urine is most concentrated at that time. The doctor provides a sterile cup or a container to collect the urine sample. The steps of a specific gravity urine test are listed below:

1. First, the patient must clean the genitals from front to back with an antibacterial wipe to reduce bacterial contamination of the urine sample.

2. Urinate a small amount and then keep the cup near the urethra. Finally, urinate in the cup to collect the urine sample. This is known as the clean catch method.

3. The doctor will finally send the urine sample to the laboratory for examination and evaluation.

4. The laboratory technician uses a refractometer to project light into the urine sample to evaluate its density. This method is better than the dipstick method used in urinalysis.

5. Though several at-home tests are available, they are unreliable and do not provide a sterile environment compared to laboratory tests.

6. In addition to the urine-specific gravity test, osmolality tests can also be done to know how the kidneys change the urine concentration.

What Happens in the Test Results?

The specific gravity of the urine can also be measured by urine color. For example, dark urine has higher specific gravity, whereas if it appears light, it has lower specific gravity. Hence, the patient must always stay hydrated. Urine-specific gravity provides an accurate measurement of the overall concentration of the urine. The doctor checks the ratio of the density of the patient's urine and the density of water. If the kidneys function well, the ratio usually ranges from 1.002 to 1.003. High urine specific gravity might occur due to the presence of the following substances in the urine:

1. Proteins.

2. Glucose.

3. Bilirubin.

4. Red blood cells (RBCs).

5. White blood cells (WBCs).

6. Bacteria.

7. Crystals.

The doctor might use the urine-specific gravity test results and urinalysis results to diagnose the underlying urologic conditions. Abnormalities in the urine-specific gravity test results might indicate the following:

• Excess toxins in the blood.

• Kidney diseases.

• Urinary tract infections.

• Cerebral injuries in patients with diabetes insipidus.

What Symptoms Occur if the Urine Specific Gravity Levels Are Not in the Normal Range?

Primary central diabetes insipidus and nephrogenic diabetes are the most common conditions that alter the fluid and electrolyte levels of the body. The patient might have the following signs and symptoms if the urine-specific gravity levels fluctuate:

• Weakness.

• Nausea.

• Vomiting.

• Loss of appetite.

• Confusion.

• Muscle cramps.

What Are Some of the Factors That Affect the Test Results?

The factors that affect the test results or produce inaccurate results are listed below:

1. The urine sample gets exposed to light and temperature changes.

2. Bacterial growth.

3. Alkaline pH.

4. Presence of glucose in the urine.

5. Contrast agents.

6. Exercises.

7. Medications like Ibuprofen and Metronidazole.

How to Lower the Urine Specific Gravity?

If it appears dark in color due to high specific gravity, the doctor might suggest the following:

• Drink plenty of clear fluids, mainly water.

• The patient must include water-rich foods like soups in the diet.

• In critical situations, the patients must be hospitalized and given fluids intravenously.

• Stay hydrated while exercising.

Conclusion

A urine-specific gravity test is a reliable procedure that helps the doctor to diagnose kidney diseases based on the specific gravity of urine. There are several factors responsible for the variations in urine-specific gravity. Therefore, patients with chronic kidney disease and changes in urine color must consult a urologist at the earliest to learn more about the procedure.