Acute Lobar Nephronia in Children

Urinary tract infection (UTI) is one of the most common bacterial infections in febrile children, especially in those aged 2 years or younger. The association between UTI and congenital abnormalities, like vesicoureteral reflux (VUR), may put children at high risk for acute pyelonephritis (APN) and subsequent renal scarring. Moreover, it has been believed that post-pyelonephritic renal scarring with recurrences, especially in the presence of high-grade VUR, may cause future medical problems such as hypertension and/or impaired kidney function, which has been the driving force behind the comprehensive investigation and treatment of first-episode febrile UTI in children. Acute lobar nephronia (ALN) is a localized, nonliquefactive, severe interstitial bacterial infection of renal parenchyma, generally affecting one or more renal lobules. It is considered as at the midpoint in the spectrum of upper UTI between APN and intrarenal abscess. ALN was first described in adults by Rosenfield et al in 1979 and was subsequently reported in children by Lawson et al in 1985. Histologically, ALN discloses localized hyperemia, interstitial edema, and leukocytic infiltration. The histopathologic features of APN are similar to, but less severe than, those of ALN, whereas intrarenal abscess shows tissue necrosis and liquefaction within the infectious areas. ALN is not a rare condition in children. It is probably an underdiagnosed disorder. However, it is important to differentiate ALN from non-ALN UTI and intrarenal abscess, not only because these conditions are pathologically different, but also because they may be managed differently. ALN has recently been diagnosed with increasing frequency in children, as a result of the advancement of noninvasive imaging modalities. The characteristic appearance of a focal mass in the kidney with ill-defined margins is the hallmark of sonographic findings of ALN. Depending on the stages of ALN, sonographic appearance includes hypoechogenic, isoechogenic, and hyperechogenic lesions. However, the sensitivity of this sonographic characteristic for the diagnosis of ALN is low and not satisfactory. Computed tomography (CT) is considered to be the most sensitive and accurate imaging modality for the diagnosis of ALN. However, it raises costs and radiation