Classification CT findings Recommended management
Class I gas limited to the collecting system medical management alone or medical management combined with percutaneous drainage
Class II gas limited to the renal parenchyma alone  
Class IIIA perinephric extension of gas or abscess medical management plus percutaneous drainage,  non-responders in this group required nephrectomy
Class IIIB Extension of gas beyond the Gerota fascia
Class IV EPN in a solitary kidney or bilateral EPN
Table 1: Classification of EPN according to CT findings with the recommended management for each.