Kinetics of Biomarkers in Acute Pyelonephritis

Inclusion Criteria: * \> 18 years * Flank/loin pain or tenderness, or both and fever \> 38°C during the last 48 hours and pyuria Exclusion Criteria: * Pregnancy * Presence of indwelling catheters * Known polycystic kidney disease or any malformation of the urinary tract, or single kidney; renal transplant recipients; acute or chronic renal failure requiring dialysis * Recent discharge from hospital (during the last 10 days); ongoing antibiotic treatment * Known severe immunosuppression: Receiver of solid-organ or hematopoietic stem cells transplants; neutropenia ( \< 1 G neutrophils / L); chronic (more than 14 days) use of systemic glucocorticoids (\>10 mg/d of prednisone); active use of immunosuppressive therapy for the treatment of auto-immune or inflammatory disease; HIV infection with \< 350 CD4+ cells / ml or unknown CD4+ status * Pyelonephritis initially identified as complicated: obstruction of urinary tract, urinary stone; history of renal infection in the last 15 days * Patient with severe sepsis or septic shock