From the Guidelines
A finding of positive urine leukocytes with no bacterial growth is clinically significant and warrants further evaluation to determine the underlying cause, which may include a partially treated urinary tract infection, non-infectious inflammation, or specific infections not detected by standard culture. This condition, known as sterile pyuria, can have various implications for patient management, including the potential need for empiric antibiotic therapy or further diagnostic testing 1. The presence of white blood cells in the urine, as indicated by a positive urinalysis result, prompts the initiation of empirical antimicrobial therapy, even in the absence of bacterial growth 1.
Key considerations in the evaluation of sterile pyuria include:
- A complete urinalysis to assess for other abnormalities
- Symptom assessment to guide the need for empiric antibiotic therapy
- Possible additional testing, such as urine PCR for sexually transmitted infections like chlamydia and gonorrhea, especially in sexually active individuals
- Consideration of other potential causes, including interstitial cystitis, kidney stones, or tuberculosis
In terms of management, empiric antibiotic therapy such as nitrofurantoin 100mg twice daily for 5-7 days or trimethoprim-sulfamethoxazole 160/800mg twice daily for 3 days may be appropriate while awaiting further results, particularly if symptoms of UTI are present 1. It is essential to note that sterile pyuria can occur due to inflammation without bacterial infection or when organisms like Chlamydia, mycobacteria, or fungi are present but don't grow on standard culture media. If symptoms persist despite negative cultures, referral to a urologist or infectious disease specialist may be necessary for further evaluation and management.
From the Research
Significance of Positive Urine Leukocytes
The presence of positive urine leukocytes (white blood cells) with no bacterial growth can be significant in the diagnosis and treatment of urinary tract infections (UTIs).
- The study 2 suggests that leukocyte esterase, nitrite positivity, and the presence of leukocyte clusters can be predictive values to detect bacterial growth in urine culture.
- However, the study 3 found that elevated urine white cell count, presence of leukocyte esterase, and presence of nitrites were significantly associated with antibiotic treatment for asymptomatic bacteriuria (ASB), which may contribute to unnecessary antibiotic use.
- The study 4 used flow cytometry to analyze particles quantitatively in urine and found that leukocytes in urine were between 30 and 15,000 (x10(6)/L) at presentation, and the deepest decreases in cell counts were noted during the first 24 h after initiation of therapy.
- The study 5 evaluated the performance of a new urine cytometer and suggested cutoff values of 65 bacteria/ml and 100 WBC/ml for screening UTI, with satisfactory diagnostic performance in terms of sensitivity, specificity, and negative predictive value.
Implications for Diagnosis and Treatment
The presence of positive urine leukocytes with no bacterial growth can have implications for diagnosis and treatment:
- The study 6 found that a patient's prior urine culture results are useful in predicting the identity and susceptibility of a current positive urine culture, which can inform empirical antibiotic treatment.
- The study 2 suggests that UTI diagnosis could be made more accurately using leukocyte esterase, nitrite positivity, and the presence of leukocyte clusters, which can help reduce unnecessary antibiotic use.
- The study 3 highlights the need to consider symptoms and clinical context when interpreting urine test results, rather than relying solely on abnormal urinalysis results to drive antibiotic treatment.