Emphysematous pyelonephritis is a necrotizing kidney infection characterized by the presence of gas in renal parenchyma, collecting system or perinephric tissue. This rare affection occurs almost exclusively in patients with diabetes mellitus and is due to non-anaerobic gas-producing bacteria. This life-threatening condition leads to septic shock and multiple organ failure. Diagnosis is suspected when a pyelonephritis does not respond to correct treatment, especially with altered vital signs or a diabetic patient. Computed tomography scan permits visualization of the gas and a radiologic classification with a prognostic value. Current treatment modalities are based upon repeated clinical and scanographic evaluations. In addition to systematic antibiotic therapy, percutaneous drainage is probably the first therapeutic stage in the majority of cases, but should not delay emergent rescue nephrectomy if necessary.