Table 1 Huang’s classification

Class1

Gas is confined within the renal pelvis

Class2

Gas confined to renal parenchyma

Class3A

Gas and pus spread to the perirenal area (within the renal fascia)

Class3B

Gas or pus extends outside the perirenal space (outside the renal fascia)

Class4

Emphysematous pyelonephritis in bilateral or unilateral renal patients