From the Guidelines
A large number of white blood cells (WBCs) in urine, known as pyuria, indicates inflammation in the urinary tract and requires medical evaluation, as it is a hallmark of true urinary tract infection (UTI) and helps distinguish UTI from asymptomatic bacteriuria 1. The most common cause of pyuria is a UTI, which typically requires antibiotic treatment.
- Common antibiotics prescribed include nitrofurantoin, trimethoprim-sulfamethoxazole, or ciprofloxacin, though the specific choice depends on patient factors and local resistance patterns.
- While waiting for medical care, patients should increase fluid intake to help flush bacteria from the system. Other potential causes of pyuria include kidney stones, interstitial cystitis, sexually transmitted infections, or kidney disease.
- Accompanying symptoms like painful urination, frequency, urgency, blood in urine, fever, or flank pain should prompt immediate medical attention. The presence of WBCs in urine occurs because the immune system sends these cells to fight infection or respond to inflammation, and they subsequently appear in urine samples.
- Even without symptoms, pyuria requires evaluation as it may indicate a "silent" infection that could lead to kidney damage if left untreated, and the minimum laboratory evaluation for suspected UTI should include urinalysis for determination of leukocyte esterase and nitrite level by use of a dipstick and a microscopic examination for WBCs 1. If pyuria is present (≥ 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 1.
From the Research
Large Numbers of WBCs in Urine
- A large number of white blood cells (WBCs) in urine can be an indication of a urinary tract infection (UTI) 2, 3.
- UTIs can be caused by bacteria such as Escherichia coli, and symptoms may include dysuria, frequency, and lower abdominal pain 2, 4.
- The presence of WBCs in urine can be detected through urinalysis, and quantitative leukocyte counts can be performed using flow cytometry 3.
- A study found that leukocyte counts in urine decreased significantly during the first 24 hours of antibiotic treatment in women with UTIs, and returned to normal values at the end of treatment in successful outcomes 3.
- It is essential to diagnose and treat UTIs promptly to prevent complications such as pyelonephritis, sepsis, and kidney damage 2, 5, 4.
- Antibiotic therapy is the recommended treatment for UTIs, and the duration of treatment varies depending on the type of infection and the specific antibiotic used 2, 5, 4.