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What Causes White Blood Cells (WBCs) in the Urine?

Nov 13, 2017

White blood cells are also called leukocytes. This is one of the blood cell types, along with platelets and red blood cells. White blood cells are used to kill infections located in the body. It's normal to have a few white blood cells in your urine because the kidneys do not filter these cells as a part of their jobs. There are, however, certain circumstances in which white blood cells can be found in the urine.

What Causes White Blood Cells in Urine?

Under specific circumstances, white blood cells in the urine can be possible. They include several possibilities, including the following:

1.   Bladder Infection

You can often have white blood cells in the urine if you have a bladder infection. The infection can lead to irritation of the lining of the bladder so that white blood cells become present. In a bladder infection, you will have pain in the bladder, burning on urination, and frothy or cloudy urine. This condition is also called cystitis and is common in boys during adolescents, but when in adult, it is more common in women. The effective treatment is to drink a lot of fluids and to take antibiotics. Things like bladder problems, having sexual intercourse, and pregnancy issues can increase the chance of having a bladder infection.

2.   Urinary Tract Infection

This is an infection of the urinary system. It happens when bacteria from the stool travel up the urethra, particularly when urinating or during sex. This type of infection can lead to white blood cells in your urine as well as pain and burning when you urinate. Like bladder infection, you need to use antibiotics and drink a lot of water.

3.   Kidney Infection

Kidney infections are also known as pyelonephritis and they can be serious if left untreated. The infection results from bacteria spreading up the ureters from the bladder and into the kidneys themselves. This can lead to dysfunction of the kidneys and an infection that yields white blood cells in urine. An infection of the kidney can happen if you have a kidney stone or a ureteral stone that slows the passage of urine through the urinary tract. The urine that is trapped in the kidneys becomes infected and white blood cells flood the area. You can have pain in the flank area of the back along with increased frequency of urination, burning on urination, and cloudy urine. You need to take antibiotics consistently for few days before the medications take hold and the symptoms abate.

4.   Medications

Certain medications are likely to cause white blood cells in the urine. Some of these include medications for pain and medications that thin the blood. Antibiotics can also cause this problem. Medications you take for arthritis can also lead to retention of urine, blood disorders, and allergic reactions as a side effect.

5.   Other Possible Causes

There are other causes you might want to consider. These include the following:

  • Holding your urine. If you do not urinate frequently, this can cause the bladder to stretch and weaken so that white blood cells leak into the urine. Bacteria can grow within the bladder, leading to an infection.
  • Obstruction of the urinary tract. Any kind of obstruction, such as bladder tumors, kidney tumors, or stones in the kidney can cause excessive numbers of white blood cells in the urine.
  • Pregnancy. While you are pregnant, it is not uncommon to have an elevated protein level and a high white blood cell count in the urine. This may be due to bacterial contamination from the vagina.
  • Sexual intercourse. Sex can cause bacteria to be pushed into the urethra. This can lead to infection so that there are more white blood cells in urine.
  • Excessive amount of exercise. Too much strenuous exercise can lead to an increase in white blood cells. This is not dangerous, but you should tell your doctor if you exercise excessively.
  • Blood disorders. If you have problems with the clotting of your blood or are a victim of sickle cell anemia, there may be leakage of blood into the urinary tract, which includes having extra urine white blood cells.
  • Cancers. Cancer of the kidneys, prostate, or bladder can cause it because they result in inflammation or obstruction of the urinary tract. This may mean you will need chemotherapy, surgery, or radiation therapy.

Regardless of the causative condition, the doctor may evaluate the urine further in the laboratory if white blood cells are found. The treatment used is based on what the doctor finds during the evaluation. If there is an infection, the doctor may order a course of antibiotics in order to treat the infection. If antibiotics don't cure the infection, the doctor may look for other causes of why you might have too many white blood cells in the urinary tract.

How to Test White Blood Cells in Urine

The doctor may order a leukocyte esterase test, also called an LE test. This is a test that helps detect white blood cells in the urinary tract. Leukocyte esterase is a type of enzyme found in many types of white blood cells.

In order to have the test, you will need to give a sterile urine specimen from a first morning specimen. There are normally a few white blood cells as seen under the microscope and if so, the test is considered negative for infection. The test will become positive if there are a lot of white blood cells in the urine.

However, the test can be falsely positive under certain circumstances. Vaginal secretions or bloody vaginal discharge from infections like trichomonas can yield a false positive test. If you take in too much vitamin C or have too much protein in the urine, it can also affect the result.