How long does it take a bladder infection to get to kidneys?

Varies: As long as it takes bacteria to reach kidney. Can be within hours if bladder reflux is present. Usually 1 - 3 days after bladder becomes inflammed and ureral valve in bladder becomes swollen ; permits reflux up to kidney. Some bacteria have hair-like projections on their wall and can 'crawl' like little caterpillars thru ureteral valves ; up ureter to kidney. Also depends upon body's resistance.