Which laboratory test is part of evaluating suspected pyelonephritis?

• A. Urine dipstick (nitrites, leukocyte esterase)
• B. CBC
• C. MRI pelvis
• D. Serum amylase

Answer: (A)

Evaluating suspected pyelonephritis relies on confirming infection in the urinary tract. A urine dipstick that checks nitrites and leukocyte esterase is a practical first-step test. Nitrites appear when common urinary pathogens (especially gram-negative rods like E. coli) reduce nitrates to nitrites in the bladder. A positive nitrite test strongly suggests a bacterial infection of the urinary tract. Leukocyte esterase signals the presence of white blood cells in the urine, reflecting inflammation from infection. Together, these dipstick findings support the diagnosis and help guide initial management while awaiting culture results. Other tests listed are less directly informative: a CBC can show a systemic response but is nonspecific; MRI pelvis is not used to diagnose pyelonephritis; serum amylase is unrelated to urinary tract infection.