55 years old female patient develops a fever and pyuria.

　Laboratory studies show a leukocyte count of 15,000/μL, a blood urea nitrogen level of 20 mg/dL, and a serum creatinine concentration of 1.2 mg/dL. The urine culture grows Escherichia coli. Treatment with trimethoprim-sulfamethoxazole is started.

　3 days later, the fever and pyuria have resolved and the leukocyte count is 10,000/μL, blood urea nitrogen level is 24 mg/dL, serum creatinine is 1.4 mg/dL, serum creatine phosphokinase is 25 mg/dL. Urinalysis shows no leukocytes in high-power fields.