Leukocytes in urine, also known as white blood cells, are a component of the body’s immune system. Their presence in urine often signals an underlying health issue.
Understanding Leukocytes in Urine
Leukocytes are a type of white blood cell produced in the bone marrow, circulating throughout the bloodstream and tissues to identify and attack foreign invaders like bacteria and viruses. They act as the body’s defense mechanism, responding to inflammation or infection by migrating to the affected area.
Under normal circumstances, very few, if any, leukocytes should be present in urine. A typical range for leukocytes in urine is considered to be 0 to 5 white blood cells per high-powered field (HPF) when examined under a microscope. An elevated level, often referred to as pyuria when exceeding 5 leukocytes per HPF or 10,000 leukocytes per milliliter of urine, indicates inflammation or infection within the urinary tract.
Common Causes of Leukocytes in Urine
The most frequent cause of leukocytes in urine is a urinary tract infection (UTI), which occurs when bacteria enter the urinary tract and multiply, typically in the bladder or urethra. The body’s immune response to this bacterial invasion leads to an increased presence of white blood cells in the urine.
Kidney infections, also known as pyelonephritis, represent a more serious form of UTI where bacteria ascend from the lower urinary tract to the kidneys. This severe infection triggers a significant immune response, causing leukocytes to appear in the urine. Occasionally, bacteria from other parts of the body can reach the kidneys through the bloodstream, leading to such an infection.
Bladder inflammation, or cystitis, can also lead to leukocytes in urine. While often caused by bacterial UTIs, bladder inflammation can also occur without a bacterial infection, a condition known as interstitial cystitis.
Kidney stones are another common cause, as they can irritate the urinary tract lining and obstruct urine flow. This blockage can lead to urine stagnation, increasing the risk of bacterial accumulation and subsequent infection.
Sexually transmitted infections (STIs), such as chlamydia and gonorrhea, can cause inflammation in the urinary tract, resulting in leukocytes in the urine even without the typical bacterial infection seen in UTIs, a condition known as sterile pyuria. Additionally, certain medications, including some nonsteroidal anti-inflammatory drugs (NSAIDs), aspirin, penicillin-based antibiotics, steroids, and diuretics, can lead to increased leukocyte levels in urine as a side effect. Other less common causes include certain cancers of the bladder, prostate, or kidney, and some autoimmune conditions like systemic lupus erythematosus.
Associated Symptoms and Diagnostic Steps
The presence of leukocytes in urine often accompanies a range of symptoms. Common indicators include a painful or burning sensation during urination, a frequent urge to urinate (even with little urine produced), and cloudy or foul-smelling urine.
Other symptoms that may point to a more widespread or severe issue include lower abdominal discomfort, back pain, flank pain, nausea, vomiting, and fever or chills. Blood in the urine, known as hematuria, can also occur.
The initial step in diagnosing leukocytes in urine typically involves a urinalysis, a test that examines the urine’s contents. This test includes a visual examination for clarity and color, a dipstick test that chemically detects substances like leukocyte esterase (an enzyme found in white blood cells), and a microscopic examination to count the actual number of white blood cells. A positive leukocyte esterase result or a count of 10 or more white blood cells per cubic millimeter in a urine specimen indicates pyuria.
If leukocytes are detected, a urine culture may be performed to identify specific bacteria or other pathogens causing an infection. This culture grows any microorganisms present to determine the exact cause and guide appropriate treatment. Further diagnostic steps, such as blood tests or imaging studies like ultrasounds or CT scans, may be ordered if kidney stones, blockages, or other underlying conditions are suspected. These additional tests help to visualize the urinary tract and detect any structural abnormalities.
When to Seek Medical Attention
Discovering leukocytes in urine generally warrants a consultation with a healthcare professional. This is especially true if their presence is accompanied by symptoms such as painful or frequent urination, cloudy urine, lower abdominal or back pain, or fever.
Prompt medical attention is important because untreated conditions causing leukocytes in urine can lead to complications. For instance, an untreated urinary tract infection can advance to a more serious kidney infection, potentially leading to kidney damage. In some cases, infections can even spread to the bloodstream, resulting in a severe condition requiring immediate medical intervention.
Healthcare providers can accurately determine the cause of leukocytes in the urine and recommend the most effective course of action, which may involve antibiotics for bacterial infections, or other treatments for conditions like kidney stones or inflammation.