Yokoyama T, Takemura Y, Irabu H, et al. - Given that the gold standard for the diagnosis of acute pyelonephritis (APN) in children is the finding of both pyuria (P) and bacteriuria (B), researchers examined APN patients who visited the hospital over 14 years to identify specific clinical features of APN(P(−);B(−)). In total, 171 APN patients were involved, and 29 of these were APN(P(−);B(−)). Compared with the patients with pyuria and/or bacteriuria, APN(P(−);B(−)) individuals were older and had a longer duration between onset of fever and diagnosis. They also exhibited higher C-reactive protein levels. APN(P(−);B(−)) ind had elevated levels of urinary α-1 microglobulin and urinary β-2 microglobulin. APN is difficult to diagnose in febrile patients who do not have pyuria or bacteriuria, but as these patients are at the same risk for VUR as APN patients with pyuria and bacteriuria, a comprehensive history of clinical course and urinary chemistry may help in the diagnosis.