Presentation
Middle-aged septic female with know history of renal stone disease. Hypotensive on admission.
Patient Data

Extensive bilateral renal stone disease.
Obstructing ureteric stone in the distal right ureter causing a mild nephrohydroureter.
Gas in both kidneys and large volume gas in the right retroperitoneum as well as in the right ureter.
Case Discussion
Advanced case of emphysematous pyelonephritis. The vast majority occur in those with diabetes mellitus and/or urolithiasis.
In this case it is present bilaterally and on the right has perforated the renal capsule to extend in the most profound fashion into the retroperitoneum. This is termed class 4: the highest class of the disease.
In fact, the gas serves to illustrate the anatomy of the retroperitoneal spaces and confines of Gerota's fascia.