Study on the utility of ultrasonography in the differential diagnosis of febrile urinary tract infection

Abstract

Background and Purpose: Differentiating acute pyelonephritis from acute focal bacterial nephritis (AFBN) in cases of febrile urinary tract infection (fUTI) is crucial for determining therapeutic strategy. Currently, the gold standard for diagnosing AFBN is the detection of a localized low-absorption area on contrast-enhanced CT. The purpose of this study was to evaluate the utility of ultrasonography (US) in the diagnosing AFBN, with a particular focus on its positive predictive value (PPV). Methods: A retrospective study was conducted on 103 children hospitalized with first-episode fUTI between September 2020 and August 2023. Results: Of the 10 patients who met the US diagnostic criteria for AFBN—defined by an indistinct focal mass and local blood flow defects—contrast-enhanced CT was performed in 9. In all cases, a mass-like heterogeneous contrast-impaired area was observed in the region identified on US. The PPV of US for diagnosing AFBN was found to be 100%. Conclusion: These findings suggest that contrast-enhanced CT may not be necessary when AFBN is suspected based on US findings.