The aim of this study is to evaluate the impact of the duration of antibiotic therapy on the risk of recurrence in kidney graft pyelonephritis. The secondary objectives are to identify the factors associated with the duration of antibiotic therapy in acute kidney graft pyelonephritis, identify the factors associated with recurrence of acute kidney graft pyelonephritis within 3 months, evaluate the impact of the duration of antibiotic therapy on antibiotic-related complications and assess the impact of the duration of antibiotic therapy on the progression of renal function after acute kidney graft pyelonephritis.

Inclusion Criteria:

• Adult patients
• Kidney transplant recipients with a functional graft.
• Hospitalization with acute pyelonephritis (APN) defined by fever OR chills (noted in the clinical records) AND bacteriuria AND exclusion of another obvious cause of fever. (For rehospitalizations, also include cases where antibiotic therapy was initiated based on suspicion, even in the absence of documented infection.)

Exclusion Criteria:

• Age < 18 years.
• Vacationing patient or lost to follow-up with follow-up < 3 months.

Every patient with AGPN during the study period