What are the implications of leukocytes (white blood cells) in urine?

From the Guidelines

The presence of leukocytes in urine is a strong indicator of a urinary tract infection (UTI) and requires prompt evaluation and treatment, especially in frail or comorbid older individuals, as suggested by the most recent study 1. The implications of leukocytes in urine are significant, as they can indicate inflammation or infection in the urinary tract. According to the latest guidelines 1, the presence of leukocytes, along with symptoms such as frequency, incontinence, urgency, or costovertebral angle pain/tenderness, warrants antibiotic treatment.

Key Considerations

• The evaluation of UTI should include urinalysis for determination of leukocyte esterase and nitrite level by use of a dipstick and a microscopic examination for WBCs, as recommended by 1 and 1.
• If pyuria (≥10 WBCs/high-power field or a positive leukocyte esterase or nitrite test is present on dipstick), a urine culture (with antimicrobial susceptibility testing) should be ordered, as suggested by 1 and 1.
• The most recent study 1 provides a comprehensive approach to managing urinary infections in frail or comorbid older individuals, emphasizing the importance of considering symptoms, urinalysis results, and other factors when deciding to prescribe antibiotics.

Treatment Approach

• Antibiotic treatment should be prescribed based on the presence of symptoms and urinalysis results, as outlined in the latest study 1.
• Common antibiotics prescribed for UTI include nitrofurantoin (Macrobid), trimethoprim-sulfamethoxazole (Bactrim), or ciprofloxacin, depending on the severity and type of infection.
• It is essential to complete the full course of antibiotics, even if symptoms improve, to ensure effective treatment and prevent recurrence.
• Drinking plenty of water (2-3 liters daily) can help flush out bacteria and support the recovery process.

Special Considerations

• In some cases, leukocytes can be present without bacteria (sterile pyuria), which may indicate other conditions like kidney stones, interstitial cystitis, or certain sexually transmitted infections that require different treatments.
• The immune system sends white blood cells to fight infection or inflammation in the urinary tract, and the presence of leukocytes in urine can be an indicator of this response.

From the Research

Implications of Leukocytes in Urine

The presence of leukocytes (white blood cells) in urine, also known as leukocyturia, can have several implications for patient health. Some of the key implications include:

• Infection of the urinary tract: The most common cause of leukocyturia is an infection of the urinary tract, often accompanied by bacteriuria 2.
• Diagnostic evaluation: When contamination has been excluded, leukocyturia in the absence of significant bacteriuria mandates a further diagnostic evaluation 2.
• Urinary tract infection (UTI) diagnosis: Leukocytes in urine can be used as an indicator of UTI, with a sensitivity and specificity of 62.7% and 100%, respectively 3.
• Antimicrobial stewardship: The presence of leukocytes in urine can help guide antimicrobial therapy, reducing unnecessary antibiotic exposure 4.

Leukocyte Parameters and UTI Diagnosis

Studies have investigated the use of leukocyte parameters in urine to diagnose UTIs. Key findings include:

• A leukocyte cutoff value of 87.2/μL had a sensitivity and specificity of 98.33% and 95%, respectively, for UTI diagnosis 5.
• The use of certain cutoffs for bacterial and leukocyte parameters in urine flow cytometry demonstrated very good performance in detecting acquired symptomatic UTIs 5.
• Adapted cut-off values for leukocyte counts in different clinical presentations can help exclude significant bacterial growth in urine culture 6.

Clinical Presentations and Leukocyte Counts

Leukocyte counts in urine can vary depending on clinical presentation. For example:

• In female, younger, and dysuric patients, higher cut-offs for UFC leucocytes (169/μL, 169/μL, and 205/μL) exhibited high sensitivity 6.
• In patients with urinary frequency, significant bacterial growth in urine culture was more common (61.5%) 6.
• The predictive accuracy of UFC leucocyte and UFC bacterium counts was good for significant bacterial growth in urine culture (AUC ≥ 0.88) across different clinical presentations 6.