White blood cells (WBCs), also known as leukocytes, are components of the body’s immune system. These cells circulate throughout the bloodstream and tissues, acting as a defense against infections and inflammation. While a small presence of WBCs in urine can be normal, elevated levels may indicate an underlying health issue. This article explains when the presence of WBCs in urine warrants concern and outlines the steps for diagnosis and management.
Understanding White Blood Cells in Urine
When an infection or inflammation occurs in the urinary tract or kidneys, the body dispatches white blood cells to the affected area, leading to their presence in urine. A small number, typically 0-5 white blood cells per high-powered field (HPF) in a microscopic urine examination, is considered a normal finding. However, a significant increase in these cells, often termed pyuria, indicates a potential problem within the urinary system. Pyuria is generally defined as 10 or more white blood cells per cubic millimeter of urine, or more than 3 WBCs per HPF in unspun urine.
Common Causes of Elevated White Blood Cells in Urine
Elevated white blood cells in urine often stem from the body’s response to infection or inflammation within the urinary tract. Urinary Tract Infections (UTIs) are the most common cause, where bacteria entering the urethra multiply in the bladder, prompting an immune response and WBC presence. These infections can affect any part of the urinary system, including the bladder (cystitis) or spread to the kidneys. Kidney infections, also known as pyelonephritis, are a more serious UTI where bacteria infect the kidneys, resulting in higher WBC concentration.
Sexually Transmitted Infections (STIs), such as chlamydia and gonorrhea, can also cause inflammation in the urinary tract, leading to elevated WBC counts. Kidney stones, while not infections themselves, can irritate the urinary tract lining, cause inflammation, or obstruct urine flow, increasing infection risk and WBC appearance. Non-infectious inflammatory conditions, such as interstitial cystitis (a chronic bladder condition), can also lead to WBCs in urine due to bladder wall inflammation. Certain medications, including some nonsteroidal anti-inflammatory drugs (NSAIDs) or specific antibiotics, can induce kidney inflammation and elevate WBC levels. External contamination, such as vaginal discharge during menstruation, can also result in WBCs appearing in a urine sample without indicating a true urinary tract issue.
Recognizing When to Be Concerned
The presence of white blood cells in urine becomes concerning when accompanied by specific symptoms, often indicating an active infection or inflammation requiring medical attention. Common symptoms include a painful or burning sensation during urination (dysuria), an increased urge to urinate, or a feeling of incomplete bladder emptying. Urine that appears cloudy, has a strong or foul odor, or contains visible blood (hematuria) also indicates a potential problem. Systemic symptoms like fever, chills, nausea, or vomiting, especially when combined with lower back or side pain (flank pain), may signal a more widespread or severe infection, such as a kidney infection.
It is important to differentiate between symptomatic and asymptomatic findings of WBCs in urine. If WBCs are detected during a routine check-up without symptoms, this is known as sterile pyuria and may have various non-bacterial causes, including certain STIs, viral infections, or some medications. While trace amounts of WBCs without symptoms or during menstruation might not always be alarming, any persistent or symptomatic presence of WBCs in urine should prompt a consultation with a healthcare professional to determine the underlying cause and receive guidance.
Diagnosis and Management
When seeking medical attention for elevated white blood cells in urine, a healthcare professional will begin with a urinalysis. This involves examining a urine sample for WBCs, along with other markers like nitrites or leukocyte esterase, which can suggest a bacterial infection. If a bacterial infection is suspected, a urine culture may be performed to identify the specific bacteria causing the infection and determine which antibiotics will be most effective. If a urinary obstruction, kidney stones, or other structural issues are suspected, imaging tests such as an ultrasound or CT scan of the kidneys and bladder may be recommended to visualize the urinary tract.
Treatment for elevated WBCs in urine is tailored to the identified underlying cause. For bacterial infections like UTIs, a course of antibiotics is prescribed. The duration and type of antibiotic will depend on the severity of the infection and the specific bacteria identified by the urine culture.
If kidney stones are causing the issue, management may involve pain relief, increasing fluid intake to help pass smaller stones, or medical procedures for larger stones. For STIs, specific antibiotic or antiviral medications will be administered. Following the healthcare professional’s recommendations for diagnosis and treatment is important to prevent complications and ensure effective resolution.