We report two cases of ruptured pyogenic liver abscesses where one patient survived and the other died. We suspected that infection with gas-producing bacteria was the cause of the latter outcome, and we reviewed 47 case reports of ruptured pyogenic liver abscesses. Of the 47 cases, we determined that 77.6% included gas-producing pathogens. Moreover, the presence of gas-producing pathogens was associated with a mortality of 22.2%, whereas there were no deaths in cases with no gas-producing pathogens.