A 58-year-old woman with diabetes mellitus presented to the emergency department with fever and dysuria. Laboratory results showed elevations of the white blood cell count, creatinine, and the CRP, as well as a thrombocytopenia. An abdominal radiograph showed air in the left kidney (Fig. 1). A non-contrast computed tomography (CT scan) revealed swelling of the left kidney with air in the left perirenal space consistent with emphysematous pyelonephritis. The patient was treated with antibiotics, but required a left radical nephrectomy. The pathology showed renal emphysematous changes and papillary necrosis with tubular destruction. Urine and wound cultures revealed Citrobacter diversus and Enterococcus species.