From the Guidelines
The presence of white blood cells (leukocytes) only in urine on microscopic analysis, without bacteria or other abnormalities, is called sterile pyuria and requires further evaluation by a healthcare provider. This finding can be caused by various conditions, including urinary tract infections that haven't grown in culture, kidney stones, interstitial cystitis, certain medications, or partially treated infections 1. Less commonly, it may indicate tuberculosis of the urinary tract, kidney disease, or certain sexually transmitted infections.
Key Considerations
- The patient should provide a clean-catch urine sample for culture and sensitivity testing to rule out infection 1.
- The doctor may recommend additional tests such as imaging studies or cystoscopy depending on the patient's symptoms and medical history 1.
- While waiting for evaluation, the patient should stay well-hydrated and take acetaminophen or ibuprofen if they have discomfort.
- Sterile pyuria occurs because white blood cells can migrate into the urinary tract in response to inflammation even when no bacterial infection is present 1.
- This finding alone doesn't necessarily indicate a serious condition but should not be ignored, especially if the patient has symptoms like pain, frequency, or urgency with urination.
Evaluation and Management
- The initial evaluation should include a thorough history, physical examination, urinalysis, and serologic testing prior to any initial imaging 1.
- The patient's risk factors for significant disease should be taken into consideration, and high-risk patients should be considered for full urologic evaluation after one properly performed urinalysis documenting the presence of at least three red blood cells per high-power field 1.
- The patient should be referred for further urologic evaluation if they have gross hematuria, even if self-limited 1.
- The patient's urine culture results should be used to guide antibiotic therapy, and a Gram stain of uncentrifuged urine should be requested if urosepsis is suspected 1.
From the Research
White Blood Cells in Urine
- The presence of white blood cells in urine can indicate a urinary tract infection (UTI) 2, 3, 4, 5, 6
- Studies have shown that various antibiotics, such as sulfonamides, trimethoprim-sulfamethoxazole, nitrofurantoin, and nalidixic acid, are effective in treating UTIs 2, 3, 4, 5
- However, the presence of white blood cells in urine alone may not be a definitive indicator of a UTI, as other factors can also cause this condition
Antibiotic Treatment
- Trimethoprim-sulfamethoxazole is a commonly used antibiotic combination for treating UTIs, but it may have a higher risk of side effects, such as hyperkalaemia and acute kidney injury, especially in older patients 6
- Nitrofurantoin is another antibiotic that has been shown to be effective in treating UTIs, with a lower risk of side effects compared to trimethoprim-sulfamethoxazole 4
- Sulfonamides are also effective in treating UTIs, but may not be as effective as trimethoprim-sulfamethoxazole or nitrofurantoin in some cases 2, 5
Microanalysis
- Microanalysis of urine can help identify the presence of white blood cells and other abnormalities, such as bacteria or protein, which can indicate a UTI 2, 3, 4, 5, 6
- However, the results of microanalysis should be interpreted in conjunction with other clinical findings and medical history to determine the underlying cause of the condition.