Emphysematous pyelonephritis (EPN) is an acute gas forming necrotizing infection of the renal parenchyma with high mortality. Although its incidence is relatively low, it mostly occurs in patients wiith diabetes mellitus. The aim of the study is to identify the risk factors related to mortality and assess the outcome of managements according to the radiologic classification.

The clinical records of 23 patients diagnosed with EPN were reviewed retrospectively. The cases were grouped into two types on the basis of computed tomography scan. Type 1 EPN was defined as renal necrosis and gas formation with total absence of fluid content. Type 2 EPN was defined as the presence of renal or perirenal fluid in association with bubbly or loculated gas pattern. The patients' symptoms, performed investigations, and treatments were analyzed.

All patients had diabetes mellitus. Escherichia coli (78.6%) was the most common pathogen in urine and blood cultures. The factors showing statistically significant differences between survivors and non-survivors were age (P=0.013), the presence of obstructive uropathy (P= 0.008), and type 1 group (P=0.030). Multivariate logistic regression showed that factor significantly related to death was age (odds ratio=1.20, 95% confidence interval 1.01-1.38, P=0.037). Conservative treatment including antibiotics and percutaneous drainage was successful in type 2 group. Overall mortality was 26.1%; all expired patients were from type 1 group. The mortality of conservative treatment and nephrectomy in type 1 group was 83.3% and 20.0%, respectively.

These results suggest that old age is a significant risk factor for mortality in patients with EPN. Nephrectomy should be considered as the main treatment option in patients with type 1 EPN.