So acute pyelonephritis is a type of upper urinary tract infection.

急性肾盂肾炎是一种上尿路的感染。

All right, as a quick recap: acute pyelonephritis is typically a bacterial infection of the upper urinary tract, which usually develops from a lower urinary tract infection, especially in individuals with vesicoureteral reflux.

得！快速回顾一下：急性肾盂肾炎是一种典型的上尿路细菌感染，通常由下尿路感染发展而来，尤其在膀胱输尿管反流患者中。