Occult Blood in Urine Tests: What You Need to Know

What is "occult blood"?

Hello Dr.
Lee: Recently, the company I work for conducted employee health screenings.
During the urine dipstick test, the technician mentioned that I had "occult blood." Could you please explain what this indicates? Thank you!

Tina, 40~49 year old female. Ask Date: 2000/09/07

Dr. Li Yuqi reply Family Medicine

There are many causes of urinary occult blood, and the incidence of positive results is more than ten times higher in female patients compared to male patients.
The reasons for this include: (1) Gender differences: Women have a regular menstrual cycle that can interfere with testing.
(2) Suboptimal specimen collection: A midstream urine sample should be collected (i.e., discarding the initial portion of urine before collecting the sample for testing), as using either the initial or final portion of urine can lead to inaccuracies.
If a positive result for urinary occult blood is found, it is recommended to retest approximately one week after the menstrual period, as over ninety percent of cases will return to normal.

Reply Date: 2000/09/07

More Info

Understanding the presence of occult blood in urine tests is crucial for assessing urinary tract health and identifying potential underlying conditions. Occult blood, or "OB," refers to blood in the urine that is not visible to the naked eye but can be detected through laboratory testing. This finding can indicate various medical issues, ranging from benign to serious.

When a urine test shows a positive result for occult blood, it typically means that there is a small amount of blood present in the urine. The causes of this can vary widely and may include:
1. Urinary Tract Infections (UTIs): Infections in the bladder or kidneys can lead to inflammation and bleeding, resulting in the presence of blood in the urine.

2. Kidney Stones: The formation of stones in the kidneys or urinary tract can cause irritation and bleeding, leading to a positive occult blood test.

3. Trauma or Injury: Any injury to the urinary tract, whether from an accident or a medical procedure, can result in blood being present in the urine.

4. Glomerular Diseases: Conditions affecting the kidneys' filtering units, such as glomerulonephritis, can lead to blood in the urine.

5. Cancer: In some cases, the presence of occult blood can be an early sign of bladder or kidney cancer.

6. Menstruation: For women, it is important to consider the timing of the urine test in relation to their menstrual cycle, as menstrual blood can contaminate the urine sample.

When you receive a report indicating the presence of occult blood, it is essential to follow up with your healthcare provider for further evaluation. They may recommend additional tests, such as:
- Urinalysis: A comprehensive analysis of urine to check for other abnormalities, such as protein, glucose, or signs of infection.

- Imaging Studies: Ultrasound or CT scans can help visualize the kidneys and urinary tract to identify stones, tumors, or other structural issues.

- Cystoscopy: A procedure that allows direct visualization of the bladder and urethra, which can help identify sources of bleeding.

It is also important to consider factors that may affect the test results. For instance, vigorous exercise, dehydration, or certain medications can lead to transient hematuria (blood in urine). Therefore, if the test is positive, it may be advisable to repeat the test after a short period, especially if there are no accompanying symptoms such as pain or changes in urination.

In summary, a positive occult blood test in urine indicates the presence of blood that requires further investigation to determine the underlying cause. While some causes may be benign, others could indicate more serious conditions. Regular follow-up and communication with your healthcare provider are essential to ensure appropriate management and care. If you have any concerns or experience symptoms such as pain, changes in urination, or unexplained weight loss, it is crucial to seek medical attention promptly.

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