What laboratory finding could still be negative in a child with a Urinary Tract Infection (UTI)?

• A. Leukocyte esterase
• B. Pyuria
• C. White blood cells (WBCs)
• D. Hematuria

Answer: (B)

In the context of a urinary tract infection (UTI) in children, while pyuria (the presence of pus or white blood cells in urine) is commonly associated with these infections, it is possible for a child to have a UTI without pyuria being present. This scenario may arise in the early stages of the infection or in situations where the immune response is weak or atypical.

Other laboratory findings, such as leukocyte esterase, white blood cells (WBCs), and hematuria, are more likely to present in the setting of a UTI. Leukocyte esterase, for instance, typically indicates the presence of white blood cells, which are a response to infection. Similarly, the detection of white blood cells in a urinalysis is a direct indicator of inflammation or infection in the urinary tract. Hematuria, or blood in the urine, can also be present with UTIs, reflecting inflammation or injury to the urinary tract.

Thus, while pyuria is often expected, its absence does not rule out the possibility of a UTI, making it the laboratory finding that could be negative in such a case.