Which of the following statements about pyelonephritis is incorrect?

A、Chronicpyelonephritisusuallyhasanacuteonset,andonlylocalizingurinarytractsigns.;
B、Acutepyelonephritisisacommonsuppurativeinflammationofthekidneyandismostlycausedbybacterialinfection.;
C、Thebacteriacanenterintotheurinarytractbyascendinginfectionandhaematogenousinfection.;
D、Refluxnephropathyisthemostcommoncauseofchronicpyelonephritis.