A higher white blood cell (WBC) count in urine can be an unexpected finding on a routine test. This result often prompts questions about its meaning and potential health implications. This article explains what an elevated WBC count in urine signifies and explores its common underlying reasons.
Understanding White Blood Cells
White blood cells, also known as leukocytes, are a fundamental part of the body’s defense system. These cells circulate throughout the bloodstream and tissues, acting as primary responders to infection and inflammation. They neutralize threats like bacteria, viruses, or other irritants.
While white blood cells are crucial for immune responses, their presence in urine typically indicates an underlying issue. A healthy urinary tract is considered sterile, meaning it should not contain many of these immune cells. Even a small number of white blood cells can be normally present, but elevated amounts suggest the body is reacting to something within the urinary system.
Interpreting Urine White Blood Cell Counts
The presence of white blood cells in urine is detected through a urinalysis. A dipstick test screens for leukocyte esterase, an enzyme found in white blood cells, indicating their presence. This initial screening is followed by a microscopic examination of the urine sediment, which allows for a direct cell count.
A normal urine sample typically contains less than 5 WBCs per high-power field (HPF) when viewed under a microscope. An abnormally high number of white blood cells in urine is medically termed pyuria. Pyuria is defined as 10 or more white blood cells per cubic millimeter of urine, or more than 10 WBCs per HPF. While an elevated count points to inflammation or infection, it is an indicator, not a definitive diagnosis, and requires further investigation.
Common Causes of Elevated Urine WBCs
A high white blood cell count in urine can stem from various conditions, most commonly involving the urinary tract. Urinary tract infections (UTIs) are a frequent cause, occurring when bacteria enter and multiply within the urinary system. These infections can affect the urethra (urethritis), bladder (cystitis), or kidneys (pyelonephritis).
Kidney infections, or pyelonephritis, are a serious type of UTI where bacteria ascend from the bladder to the kidneys. These infections cause inflammation and an increase in urine white blood cells. Kidney stones can also cause elevated WBCs by irritating the urinary tract lining or by creating an obstruction that predisposes to infection. Blockages from stones can trap urine, fostering bacterial growth and an inflammatory response.
Beyond infections, bladder inflammation not caused by bacteria can also lead to increased urine WBCs. Conditions such as interstitial cystitis, a chronic bladder condition, or inflammation from certain medications or radiation therapy, can trigger an immune response. These non-infectious processes cause white blood cells to accumulate in the urine.
Sexually transmitted infections (STIs) are another source of elevated white blood cells in urine, particularly those affecting the urethra or genital tract. Common STIs like gonorrhea, chlamydia, and trichomoniasis can cause inflammation in the urinary system, leading to pyuria. Inflammation in nearby organs, such as appendicitis or diverticulitis, might indirectly contribute to elevated WBCs in urine due to their proximity.
Sometimes, a high white blood cell count in a urine sample can be due to contamination during collection. In females, vaginal discharge or menstrual blood can introduce white blood cells into the urine sample. Proper clean-catch collection techniques are essential to minimize such contamination and ensure accurate test results.
Next Steps After a High Reading
A high white blood cell count in urine indicates the need for further medical evaluation. Consult a healthcare professional, as they can accurately interpret results in the context of individual symptoms and medical history. Self-diagnosis or self-treatment should be avoided.
The healthcare provider will often recommend additional tests to pinpoint the underlying cause. A common follow-up is a urine culture, which specifically identifies the type of bacteria present and determines the most effective antibiotic if an infection is confirmed. Imaging studies, such as ultrasounds or CT scans, may be ordered to check for kidney stones, structural abnormalities, or inflammation within the urinary system.
Blood tests might also be performed to assess for systemic infections or kidney function. Treatment for an elevated urine white blood cell count depends on the identified cause. Bacterial infections are typically managed with antibiotics.
Other conditions, like non-infectious inflammation or kidney stones, may require different medications or interventions. Seek immediate medical attention if a high urine WBC count is accompanied by severe symptoms such as a high fever (above 101°F or 38.3°C), intense pain, persistent nausea or vomiting, or confusion. These could signal a more serious condition like a kidney infection or sepsis.