By Jillian Foglesong Stabile, MD, FAAFP, DABOM

White blood cells play an important role in your immune system, but do they belong in your urine? If you’ve seen a urinalysis report and have questions about urine WBC (white blood cells) and what high counts mean, you’re in luck. Everything you need to know about urine WBC is in this article.

What Are White Blood Cells?

White blood cells make up part of your immune response. WBCs are made in the bone marrow, and these cells circulate throughout your body before moving into various body tissues. There are several types of white blood cells, each with unique functions.

• Neutrophils: kill bacteria and fungi

• Eosinophils: destroy parasites and function in the allergic response. Also responsible for helping to remove cancer cells.

• Basophils: part of the allergic response

• Monocytes: serve as a clean-up crew by removing damaged cells

• Lymphocytes: produce antibodies to fight against infection and protect against viral infections

Why Would There Be White Blood Cells in Your Urine?

While white blood cells are a normal part of the immune system and belong in the bloodstream, they are typically only present in very small amounts in urine. If the white blood cell count in the urine is high, it may indicate that there is a need for more evaluation. On a urinalysis, the presence of white blood cells is reported as leukocytes or leukocyte esterase.

Urinary Tract Infections

The most common cause for an elevated WBC count in the urine is infection. Urinary tract infections (UTI) can happen anywhere in the urinary tract, from the bladder (cystitis) to the kidneys (pyelonephritis). In addition to having WBCs in the urine, a urinalysis may also show red blood cells (RBCs) or nitrates if an infection is present.

Sexually transmitted infections are another type of infection of the urinary tract and surrounding area that can cause WBCs in the urine. Bacterial cultures of the urine will often be negative in this case.

Kidney Stones

Kidney stones are a common and often painful condition that can lead to blockages in the urinary tract. The inflammation caused by kidney stones can lead to inflammation, which can cause a buildup of WBC in the urine. Additionally, the stones can become infected, which also causes WBC in urine. In addition to WBCs in the urine, RBCs are frequently seen in the urine when kidney stones are present. Kidney stones are typically diagnosed on imaging tests such as CT scans.

Inflammation

WBCs are a marker of inflammation as well as infection. Inflammation outside of the urinary tract can increase the risk of WBC in the urine. Many conditions, including kidney disease, infections in other parts of the body, and damage to the bladder from radiation treatment, among others, can cause inflammation in the body, which can lead to WBCs being present in the urine.

Pregnancy

During pregnancy, it is common to see an increase in white blood cells in the blood and in the urine. This often results in a higher rate of UTI diagnosis in pregnant women, even if infections are not present. For this reason, researchers have been working to establish normal ranges for WBC counts in the urine of pregnant women.

Contamination

White blood cells may be present on the skin and in vaginal secretions. If the urine touches the skin during collection, it can result in a false positive test showing WBC in the urine. To avoid this, follow all of the instructions for collection provided by your healthcare provider.

Medication

There are several medications that can cause WBC to be present in the urine. Some of these include:

• Steroids

• Non-steroidal anti-inflammatories (NSAIDs)

• Antibiotics such as penicillin or vancomycin

• Proton pump inhibitors used to treat reflux and ulcers

If WBCs are present in your urine, you can talk to your healthcare provider about whether medications may be the cause of this finding.

Cancer

Cancer is another reason why WBC may be present in the urine. Bladder cancer, other pelvic cancers, and cancers of the kidney and ureters are more likely to cause WBCs in the urine than other types of cancer. The presence of WBC in the urine of a person with a known bladder tumor may indicate a more aggressive cancer.

Autoimmune Conditions

Autoimmune conditions such as lupus, Kawasaki disease, and Sjogren’s can increase the risk of WBCs in the urine. This may be related to the generalized inflammation these conditions cause.

Interstitial cystitis is another condition that may cause WBC in the urine. This painful condition causes inflammation in the bladder lining. Symptoms mimic those of a urinary tract infection, but bacteria are not present.

White blood cells do not normally occur in the urine, and their presence often indicates an underlying medical condition. If you are concerned about high counts of WBCs in your urine, your healthcare provider can help you determine the underlying cause as well as the best way to treat the concern.

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