[US findings of junctional parenchymal defect of the kidney].

Junctional parenchymal defect (JPD) is a triangular or linear hyperechoic structure in the anterosuperior or posteroinferior surface of the kidney. The intermediate septum is a band-like cortex, running obliquely in the central echo complex. Some authors have suggested that these structures result from partial fusion of the embryonic parenchymatous masses called renunculi (renunculi theory). In a prospective study of 600 adult patients, the anterosuperior JPD of the right kidney was most frequently identified on ultrasonography (33.5%). The incidence of JPD did not depend on sex or age, and intermediate septum was frequently associated with JPD (71.4%). These data are compatible with the renunculi theory. The prominent septum of Bertin was located in the same position on the intermediate septum in the majority of cases (96.7%). Therefore, we suggest that the typical prominent septum of Bertin may be an incomplete intermediate septum. In order to differentiate JPD from pathologic conditions such as cortical scar or hyperechoic tumor, it is necessary to identify its characteristic location and shape.