Emphysematous pyelonephritis: imaging diagnosis and follow-up

We conducted the study to evaluate the efficacy and roles of different imaging modalities in the diagnosis and follow-up of emphysematous pyelonephritis (EPN) and to correlate imaging findings with clinical outcome. Retrospective analysis of the imaging studies and clinical outcome were performed in 28 consecutive patients with EPN. They were all initially treated with CT-guided percutaneous drainage (PCD). The imaging studies performed included plain abdominal radiography (KUB) (n = 28), sonography (US)(n = 24), intravenous urography (IVU)(n = 5), retrograde pyelography (RP)(n = 20) and computed tomography (CT)(n = 28). Follow-up imaging studies included CT(n = 23) and renal scintigraphy (n = 15). The sensitivities of detecting abnormal gas in EPN on KUB and US were 66% and 88%. The mortality rate was 11%, not associated with different types, stages or renal involvement. On the follow-up CT performed within one month of PCD, type I EPN evolved into type II in 86% of the cases. On the long-term follow-up CT, renal atrophy and focal scarring were revealed in the diffuse and focal renal involvement of EPN. The mean split renal function shown on the follow-up scintigraphy was 30%. We concluded KUB and US were valuable for screening EPN, although CT was the most specific and sensitive. Follow-up CT studies not only demonstrate the response of treatment but also depict the different courses and the results of different types and renal involvement of EPN, although not associated with mortality rate.