Acute gas-producing bacterial renal infection: Correlation between imaging findings and clinical outcome

PURPOSE: To correlate imaging findings of types I and II emphysematous pyelonephritis (EPN) with clinical course and prognosis. MATERIALS AND METHODS: The imaging studies and clinical outcome in 38 patients with EPN were retrospectively studied. The imaging studies performed included radiography (n = 33), computed tomography (n = 31), and ultrasonography (n = 35). RESULTS: Two types of EPN were identified. Type I EPN was characterized by parenchymal destruction with either absence of fluid collection or presence of streaky or mottled gas. Type II EPN was characterized as either renal or perirenal fluid collections with bubbly or loculated gas or gas in the collecting system. The mortality rate for type I EPN (69%) was higher than that for type II (18%). Type I EPN tended to have a more fulminant course with a significantly shorter interval from clinical onset to death (P < .001). CONCLUSION: Two distinct types of EPN can be seen radiologically, and the differentiation is important due to the prognostic difference.