Emphysematous pyelitis (EP) is a benign entity. To our knowledge, it has no
t been reported frequently in the radiology literature. Previous articles h
ave not focused on EP but rather have included other gas-forming entities (
eg, emphysematous pyelonephritis [EPN]). The authors describe imaging findi
ngs in EP and distinguish them from findings in EPN in five cases. Computed
tomography is the current method for demonstrating isolated gas production
inside the urinary collecting system. The prognosis is excellent, with rap
id complete recovery after medical treatment.