Host and Bacterial Markers that Differ in Children with Cystitis and Pyelonephritis.

OBJECTIVE: To determine whether treatment for urinary tract infections in children could be individualized using biomarkers for acute pyelonephritis. STUDY DESIGN: We enrolled 61 children with febrile urinary tract infections, collected blood and urine samples, and performed a renal scan within 2 weeks of diagnosis to identify those with pyelonephritis. Renal scans were interpreted centrally by 2 experts. We measured inflammatory proteins in blood and urine using LUMINEX or an enzyme-linked immunosorbent assay. We evaluated serum RNA expression using RNA sequencing in a subset of children. Finally, for children with Escherichia coli isolated from urine cultures, we performed a polymerase chain reaction for 4 previously identified virulence genes. RESULTS: Urinary markers that best differentiated pyelonephritis from cystitis included chemokine (C-X-C motif) ligand (CXCL)1, CXCL9, CXCL12, C-C motif chemokine ligand 2, INF γ, and IL-15. Serum procalcitonin was the best serum marker for pyelonephritis. Genes in the interferon-γ pathway were upregulated in serum of children with pyelonephritis. The presence of E coli virulence genes did not correlate with pyelonephritis. CONCLUSIONS: Immune response to pyelonephritis and cystitis differs quantitatively and qualitatively; this may be useful in differentiating these 2 conditions.