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Abstract There are currently no available data on the relationship between sonographic temporary nephromegaly in children during their first febrile urinary tract infection (fUTI) and recurrent fUTI. For this analysis, a multicenter retrospective cohort study of 343 children who underwent renal ultrasound during their first fUTI was conducted between 2013 and 2020. Sonographic temporary nephromegaly was defined as increased renal length during the initial fUTI, followed by normal renal length after antibiotic treatment. Compared with children without sonographic temporary nephromegaly (n = 307), the duration of fever and intravenous antibiotics was significantly longer, and C-reactive protein, creatinine, and the proportion of children who had recurrent fUTI were significantly higher, in those with sonographic temporary nephromegaly (n = 36). In an additional analysis of 100 patients who received voiding cystourethrography, a logistic regression model confirmed that the odds of vesicoureteral reflux (VUR) were significantly higher in children with temporary nephromegaly or those who experienced fUTI recurrence. In nine out of 16 children with VUR who had temporary nephromegaly, the reason for receiving voiding cystourethrography was recurrent fUTI. Our results suggest that sonographic temporary nephromegaly during an initial fUTI is predictive for recurrence and VUR, and that in children with temporary nephromegaly, VUR may be detectable before fUTI recurrence.

Abstract Galactose-deficient IgA1 (Gd-IgA1) is important in the pathogenesis of IgA nephropathy (IgAN). A Gd-IgA1-specific monoclonal antibody (KM55) has revealed glomerular Gd-IgA1 deposition solely in patients with IgAN and IgA vasculitis with nephritis (IgAV-N). However, this specificity is controversial and has not been demonstrated in pediatric patients. Here, we conducted double-immunofluorescence staining of IgA and Gd-IgA1 in 60 pediatric patients with various glomerular diseases. We divided patients into four groups: (1) patients with IgAN and IgAV-N (n = 23); (2) patients with immunocomplex-mediated glomerulonephritis accompanied by IgA deposition, including lupus nephritis, membranoproliferative glomerulonephritis, and membranous nephropathy (n = 14); (3) patients with other glomerular diseases involving IgA deposition, including idiopathic nephrotic syndrome (INS), oligomeganephronia, Alport syndrome, dense deposit disease, and crescentic glomerulonephritis (n = 11); and (4) patients with IgA-negative diseases including INS, membranoproliferative glomerulonephritis, membranous nephropathy, oligomeganephronia, Alport syndrome, C3 glomerulonephritis, poststreptococcal acute glomerulonephritis, and hemolytic uremic syndrome (n = 12). KM55 staining revealed Gd-IgA1-positive findings in 23/23 patients in Group 1 and 13/14 patients in Group 2, but not in patients in Groups 3 or 4. Therefore, KM55 may detect incidental IgA deposition in pediatric patients. Gd-IgA1 may be involved in the pathogenesis of these immune-related diseases; alternatively, KM55 may recognize IgA-related immunocomplexes in a non-specific manner.