Which diagnosis is suggested by nitrite-positive, leukocyte esterase-positive urine with 25-40 WBC/hpf and moderate bacteria in a young woman?

• A. Glomerulonephritis
• B. Upper urinary tract infection
• C. Lower urinary tract infection
• D. Nephrolithiasis

Answer: (C)

Nitrite-positive and leukocyte esterase–positive urine with pyuria and bacteria points to a bacterial urinary tract infection. Leukocyte esterase indicates white blood cells in the urine (pyuria), and nitrite positivity comes from bacteria that reduce nitrates to nitrites—most commonly gram-negative organisms like E. coli. The finding of 25–40 WBCs per high-power field confirms significant inflammation, and the presence of bacteria supports an active infection. In a young woman, this pattern most often represents a lower urinary tract infection (cystitis) presenting with symptoms such as dysuria, frequency, and urgency. Upper urinary tract infection (pyelonephritis) would typically accompany systemic signs like fever and flank pain, and glomerulonephritis or nephrolithiasis would show different urine findings (eg, RBCs, protein, casts, or intense colicky pain with hematuria). Thus, the best-fit diagnosis is a lower urinary tract infection.