Comparison of imaging findings between acute focal bacterial nephritis (acute lobar nephronia) and acute pyelonephritis: a preliminary evaluation of the sufficiency of ultrasound for the diagnosis of acute focal bacterial nephritis.

Abstract

The recommended durations of treatment for acute focal bacterial nephritis (AFBN) and acute pyelonephritis (APN) are different. This study aimed to clarify the sonographic findings used to differentiate AFBN from APN during diagnosis and to compare these findings with those obtained using computed tomography (CT). Eleven children with urinary tract infection who underwent contrast-enhanced CT and ultrasound examinations within a 24-h period were included. Diagnoses of AFBN and APN were established using CT data as the gold standard; viz., a focal area of poor enhancement is observed in AFBN but not in APN. The following ultrasound findings were evaluated: focal loss of corticomedullary differentiation (one/multiple), focal hyperechogenicity, abscess formation, and diffuse nephromegaly. Fisher's exact test was used for statistical analysis. Of the 11 patients, 8 had AFBN and 3 had APN. The two groups differed significantly in the incidence of a focal loss of corticomedullary differentiation (present/absent, 8/8 vs. 0/3; p = 0.01) but not in the incidence of focal hyperechogenicity, abscess formation, and diffuse nephromegaly (present/absent, 2/8 vs. 0/3, p > 0.99; 1/8 vs. 0/3, p > 0.99; and 5/8 vs. 3/3, p = 0.49, respectively). The poorly enhanced area used to diagnose AFBN on CT images appeared as a focal loss of corticomedullary differentiation in ultrasound examinations. CT revealed multiple lesions in two cases in which ultrasound revealed only single lesions. In our small cohort, ultrasound could be adequately used to diagnose AFBN based on the presence of a focal loss of corticomedullary differentiation. CT may not be required to differentiate AFBN from APN.