From the Guidelines
A negative urinalysis with a positive urine culture typically indicates an asymptomatic bacteriuria, which is the presence of bacteria in the urine without symptoms of a urinary tract infection. This condition generally requires treatment only in specific patient populations, such as pregnant women, patients undergoing urologic procedures, or those with certain risk factors like immunosuppression, as stated in the revised AAP guideline on UTI in febrile infants and young children 1.
Key Points to Consider
- The standard treatment for those who need it is a short course of antibiotics, with options including nitrofurantoin, trimethoprim-sulfamethoxazole, or fosfomycin, based on culture sensitivity results.
- This discrepancy between tests occurs because urinalysis primarily detects inflammation (leukocyte esterase, nitrites, white blood cells) while cultures identify actual bacterial growth, even at levels that don't trigger inflammatory markers.
- Bacteria may be present without causing inflammation if the infection is early, the bacterial load is low, or the organisms don't produce nitrites.
- In non-pregnant, non-immunocompromised adults without symptoms, watchful waiting is often appropriate as the body may clear the bacteria naturally without intervention, as suggested by the guideline's emphasis on clinical criteria to establish a threshold to decide whether to obtain a urine specimen 1.
Clinical Implications
- The guideline recommends that if urinalysis of fresh urine is negative for leukocyte esterase and nitrites, it is reasonable to follow the clinical course without initiating antimicrobial therapy, recognizing that a negative urinalysis result does not rule out a UTI with certainty 1.
- However, the presence of a positive urine culture should prompt consideration of the patient's overall clinical picture and risk factors to determine the need for treatment.
From the Research
Urinalysis and Urine Culture Results
- A negative urinalysis result indicates that there are no visible signs of infection, such as blood, protein, or leukocytes, in the urine 2.
- A positive urine culture result, on the other hand, indicates that bacteria are present in the urine, even if the urinalysis is negative 3.
Implications of Positive Urine Culture with Negative Urinalysis
- The presence of bacteria in the urine, as indicated by a positive urine culture, can still cause infection, even if the urinalysis is negative 4, 5.
- In some cases, a positive urine culture with a negative urinalysis may indicate a low-level infection or a infection that is not causing significant inflammation 6, 2.
Treatment and Management
- Antibiotic treatment is still necessary, even if the urinalysis is negative, to prevent the spread of infection and to treat the underlying bacterial cause 4, 6.
- The choice of antibiotic and duration of treatment will depend on the type of bacteria present, as well as the patient's overall health and medical history 4, 3.
Risk Factors for Postoperative Infection
- Positive stone culture, stone burden, and multiple access tracts are independent risk factors for postoperative systemic inflammatory response syndrome (SIRS) 2, 3.
- Achieving a negative urine culture before percutaneous nephrolithotomy (PCNL) is not a necessary condition, and patients can safely undergo surgery after 5 days or more of sensitive antibiotic treatment without the need for a negative urine culture result 3.