Leukocytes, commonly known as white blood cells, are often found in urine tests and can indicate various conditions, from common infections to other underlying health issues. Understanding why these cells might appear in urine is a common concern.
What Are Leukocytes
Leukocytes are a fundamental component of the body’s immune system, serving as cellular defenders against infection and foreign invaders. These specialized cells circulate throughout the bloodstream and tissues, identifying and neutralizing harmful microorganisms like bacteria, viruses, and parasites. Their primary role involves engulfing pathogens and regulating inflammatory responses to protect the body.
Why Leukocytes Appear in Urine
The presence of leukocytes in urine, known as pyuria, typically signals an inflammatory response within the urinary tract. The most frequent cause is a urinary tract infection (UTI), where bacteria multiply in the urethra, bladder, or kidneys. The body dispatches white blood cells to combat these invading microorganisms.
Beyond common UTIs, leukocytes can appear due to more extensive infections like pyelonephritis (kidney infection). Inflammation of other urinary system parts, such as cystitis (bladder inflammation) or urethritis (urethral inflammation), can also increase leukocyte count. These inflammatory conditions trigger an immune response, even without bacterial infection.
Kidney stones, which are hard deposits of minerals and salts that form inside the kidneys, can also cause leukocytes by irritating the urinary tract lining. Sexually transmitted infections (STIs) can lead to inflammation and pyuria, particularly if they affect the urethra. Certain medications, such as some nonsteroidal anti-inflammatory drugs (NSAIDs), may also induce sterile pyuria, meaning leukocytes are present without a bacterial infection.
Contamination during urine collection is another consideration, especially in females, where vaginal discharge can introduce white blood cells into the sample. Less common causes include interstitial nephritis, an inflammatory kidney condition, or systemic diseases affecting kidney function. While leukocytes in urine often point to an infection, other non-infectious causes must also be considered during diagnosis.
How Leukocytes in Urine Are Detected
Detecting leukocytes in urine typically begins with a urinalysis, a common diagnostic test. Patients are usually instructed to provide a “midstream clean catch” sample to minimize contamination. The initial step involves a dipstick test, which uses a chemically treated strip that changes color in the presence of leukocyte esterase, an enzyme found in white blood cells.
If the dipstick test indicates leukocyte esterase, a microscopic examination of the urine sediment is usually performed. A laboratory technician views a concentrated drop of urine under a microscope to count the white blood cells present. This method provides a more precise quantification of leukocytes and can also identify other elements like bacteria, red blood cells, or crystals.
If an infection is suspected, a urine culture may be performed. This involves placing a small portion of the urine sample on a special growth medium to allow any bacteria present to multiply. The culture helps identify the specific type of bacteria causing the infection and determines which antibiotics would be most effective for treatment.
Understanding Your Results and Next Steps
Interpreting the presence of leukocytes in urine requires considering the quantity detected, which can range from trace amounts to large numbers. Trace or small amounts might not always indicate a significant problem, especially if no other symptoms are present. However, moderate to large numbers typically suggest an active inflammatory or infectious process within the urinary tract.
A healthcare provider will evaluate the leukocyte count in conjunction with other factors, including any reported symptoms such as painful urination, frequent urges, or fever. They will also consider other findings from the urinalysis, like the presence of nitrites or red blood cells. The complete clinical picture helps determine the underlying cause and guide further diagnostic steps.
If leukocytes are found, seeking medical attention is important for an accurate diagnosis. Common treatments for bacterial infections causing pyuria involve specific antibiotics prescribed by a doctor. For non-infectious causes, treatment focuses on managing the underlying condition, such as addressing kidney stones or adjusting medications. Following up with a healthcare professional ensures appropriate management and helps prevent potential complications.