Pus cells in urine are white blood cells (WBCs) that have entered the urinary tract. Their presence signals that the body’s immune system is actively responding to an irritant, inflammation, or an infection somewhere along the urinary system. These immune cells are the body’s primary defense mechanism, migrating to neutralize a threat. Finding an elevated number of these cells suggests an active biological process requiring attention.
Identifying Pus Cells in Urine
The formal medical term for an abnormally high number of white blood cells (leukocytes) in the urine is pyuria. These immune cells are referred to as “pus cells” because they are the main component of pus, a fluid formed when these cells die while fighting infection or managing tissue damage.
Healthy urine contains a minimal amount of these cells. The normal range is considered to be fewer than five white blood cells per high-power field (WBCs/HPF) when viewed under a microscope. A count exceeding this threshold is clinically recognized as pyuria. This suggests a localized immune response is occurring within the kidneys, bladder, ureters, or urethra.
Common Reasons for Elevated Levels
The most frequent cause for elevated white blood cells in the urine is a bacterial Urinary Tract Infection (UTI). Bacteria, such as Escherichia coli, colonize the urethra or bladder, triggering a massive influx of leukocytes. This immune response results in a significant increase in pus cells flushed out with the urine. A kidney infection, known as pyelonephritis, is a more serious UTI where bacteria have ascended to the kidneys, leading to a more intense immune reaction and higher pus cell counts.
Elevated pus cells can also occur without a typical bacterial infection, a condition called sterile pyuria. Causes include irritation from kidney stones, which create physical trauma and inflammation as they move through the urinary tract. Chronic inflammatory conditions, such as interstitial cystitis, can also lead to pyuria.
Other Causes of Pyuria
Sexually transmitted infections like chlamydia or gonorrhea may cause inflammation in the urethra that results in an elevated leukocyte count. Systemic diseases, including autoimmune disorders like systemic lupus erythematosus, can affect the kidneys and lead to pyuria. Certain medications, notably nonsteroidal anti-inflammatory drugs (NSAIDs), are occasionally associated with kidney inflammation. In rare cases, genitourinary tuberculosis or a tumor in the urinary tract may be the underlying cause.
How Doctors Test for Pyuria
Healthcare providers diagnose elevated white blood cells through a laboratory test called a urinalysis. This process begins with an initial dipstick test, a rapid screening tool that checks for leukocyte esterase. This enzyme is released by white blood cells, and a positive dipstick result indicates leukocytes are present in the urine.
The urine sample is then sent for microscopic examination to confirm and quantify the severity. A laboratory technician examines the urine sediment under a high-power microscope to physically count the white blood cells. This count provides the definitive measure of pyuria, reported as the number of WBCs per high-power field.
If pyuria is confirmed, a urine culture is typically performed, especially if a bacterial infection is suspected. This test involves placing the sample on a growth medium to see if bacteria multiply and to determine the specific species responsible. Identifying the type of bacteria allows the healthcare provider to select the most effective antibiotic treatment.
Addressing the Underlying Cause
Treatment for pyuria depends entirely upon identifying and addressing the underlying cause of the inflammation or infection. If diagnostic tests confirm a bacterial infection, such as a UTI, the patient will be prescribed a course of antibiotics. Completing the entire course of medication is important to ensure the total eradication of the bacteria.
For non-infectious causes, such as kidney stones or interstitial cystitis, the approach shifts to managing the specific condition. This may involve pain management, anti-inflammatory medications, or other therapies to reduce tissue irritation. If a medication is found to be the cause, a physician may recommend stopping or substituting the drug.
Consulting a healthcare provider is necessary for proper diagnosis, as self-treating can delay effective care. Follow-up testing is often recommended after treatment to confirm that the pyuria has resolved and that the pus cell level has returned to the normal range.