A urinalysis showing WBCs with positive leukocyte esterase most strongly supports which condition?

• A. RBC casts
• B. Proteinuria without leukocytes
• C. Hematuria without leukocytes
• D. WBCs and positive leukocyte esterase

Answer: (D)

Leukocyte esterase in urine comes from neutrophils; a positive test means there are white blood cells in the urine, i.e., pyuria. When you see white blood cells alongside a positive leukocyte esterase, the finding points most strongly to an inflammatory or infectious process in the urinary tract, commonly a urinary tract infection.

RBC casts suggest glomerular disease, not primarily infection. Proteinuria without leukocytes doesn’t indicate inflammation in the urine, and hematuria without leukocytes points away from an infectious process. So the combination of WBCs and positive leukocyte esterase is the pattern most consistent with pyuria due to a urinary tract infection.