Leukocytes, or white blood cells, are integral components of the immune system, defending against invaders like bacteria and viruses. Produced in the bone marrow, these cells are the primary responders to inflammation or infection. The presence of white blood cells in the urine is called leukocyturia, typically found during a routine urinalysis. While a small number may be normal, an elevated count suggests the body is mounting an immune response, often signaling a problem within the urinary tract or kidneys.
How Leukocytes Are Measured
The detection of leukocytes typically involves two distinct testing methods performed as part of a complete urinalysis. The first is the urine dipstick test, a rapid screening tool utilizing a chemically treated strip. This strip checks for leukocyte esterase, an enzyme released by neutrophils when they are present in the urine. A positive dipstick result indicates the likely presence of leukocytes, suggesting inflammation or infection along the urinary tract.
If the dipstick is positive, or if symptoms suggest a urinary tract issue, a microscopic analysis of the urine sediment is performed to quantify the exact number of cells. The urine is spun down in a centrifuge, and the solid elements are viewed under a high-power microscope. The result is reported as the number of white blood cells per high-power field (HPF). A significant finding, sometimes called pyuria, is generally considered to be greater than five white blood cells per HPF.
Primary Causes of High Leukocytes
The detection of an elevated leukocyte count in the urine is not a diagnosis in itself but a sign of inflammation, which can stem from a wide range of causes categorized as infectious or non-infectious. By far the most common infectious cause is a Urinary Tract Infection (UTI), where bacteria enter the urethra and multiply. This triggers a massive immune response that sends white blood cells to the bladder or urethra lining. A more serious infection, known as pyelonephritis, occurs when the bacteria travel upward to infect the kidneys, typically causing a much higher and more symptomatic leukocyte count.
Certain sexually transmitted infections (STIs) like chlamydia and gonorrhea can also cause inflammation in the urethra, leading to leukocyturia without the typical bacterial presence seen in a standard UTI. In men, inflammation of the prostate gland, known as prostatitis, will often manifest with an increased number of leukocytes in the urine.
Non-infectious causes are sometimes referred to as sterile pyuria, meaning white blood cells are present without a detectable bacterial infection in a standard urine culture. Kidney stones are a frequent non-infectious cause, as their movement or obstruction causes mechanical irritation and inflammation, drawing leukocytes to the area.
Other Non-Infectious Triggers
Other potential causes of leukocyturia include:
- Interstitial nephritis, which is inflammation of the kidney tubules often triggered by certain medications, such as NSAIDs or specific antibiotics.
- Sample contamination, particularly in women, where vaginal discharge or menstrual blood can mix with the urine during collection.
- Autoimmune diseases or tumors in the urinary tract.
- Recent strenuous exercise.
When to Seek Medical Attention
While a slightly elevated leukocyte count might be transient, the presence of certain accompanying symptoms necessitates prompt medical consultation to prevent complications. Immediate attention should be sought if the leukocyturia is accompanied by signs of a more serious infection, such as a fever, chills, or pain in the flank or back area, which may suggest pyelonephritis or a kidney infection. Severe pain or burning during urination (dysuria), along with a frequent or urgent need to urinate, are common indicators that a symptomatic urinary tract infection is present.
The visualization of blood in the urine (hematuria) is another symptom that warrants rapid evaluation alongside an increased leukocyte count. Even when white blood cells are found unexpectedly during a routine test without symptoms (asymptomatic leukocyturia), follow-up is advisable. A provider will want to rule out silent inflammation, especially in high-risk groups like pregnant women, or investigate underlying issues such as kidney problems.
Treatment Approaches Based on Underlying Cause
The therapeutic strategy for elevated leukocytes is entirely dependent on accurately identifying the underlying source of the inflammation. If the cause is determined to be a bacterial infection, such as a UTI or pyelonephritis, the mainstay of treatment involves the use of antimicrobial medications. A healthcare provider will often order a urine culture to identify the specific type of bacteria causing the infection, which then guides the selection of the most effective antibiotic.
For non-infectious causes like kidney stones, the treatment focuses on managing the pain and facilitating the stone’s passage, which can include increasing fluid intake and using pain-relieving medication. Larger stones that cannot pass naturally may require procedures such as lithotripsy, which uses shock waves to break the stone into smaller fragments, or surgical removal. If the leukocyturia is linked to interstitial nephritis caused by a medication, the intervention involves adjusting or discontinuing the offending drug and providing supportive care to allow the kidney to recover.
In all scenarios, the diagnosis and subsequent treatment plan must be carefully overseen by a healthcare professional. Self-treating based only on the presence of leukocytes can mask a more serious condition. Addressing the root cause, whether it is an infection, an obstruction, or drug-induced inflammation, is necessary to resolve the underlying issue.