A patient with acute pyelonephritis on antibiotic therapy shows which finding as best evidence the regimen is being followed?

• A. Urine output increases to 2,000 mL/day.
• B. Flank and abdominal discomfort decrease.
• C. Bacteria are absent on urine culture.
• D. The red blood cell count is normal.

Answer: (C)

The main idea is confirming that the infection has been cleared by the antibiotic treatment. While symptoms such as pain relief and improved comfort often accompany improvement, they don’t prove that the bacteria are gone. The strongest evidence that the regimen is effectively treating acute pyelonephritis is a urine culture that shows no bacteria. A sterile urine culture means the pathogens have been eradicated by the therapy, confirming adherence and success of the regimen. Increased urine output can reflect hydration or kidney function but doesn’t prove microbiologic clearance; a normal red blood cell count isn’t a direct indicator of infection resolution.