Acute pyelonephritis is defined as inflammation of the renal pelvis and kidney arising rapidly, most commonly from an ascending bacterial infection that colonizes the lower urinary tract and spreads upward, or less commonly via hematogenous spread. As an upper urinary tract infection, it is distinguished mechanistically and clinically from lower urinary tract infection by anatomical location, by predisposing structural/functional factors such as vesicoureteral reflux and urinary obstruction, and by the systemic inflammatory response it provokes (leukocytosis, fever, flank pain) versus the localized presentation of lower UTI. This places acute pyelonephritis within nephrology/urology as a category of upper urinary tract infection defined by route of bacterial ascent, immune-mediated tissue response, and its potential to progress to chronic or complicated renal disease.
Acute pyelonephritis is defined as inflammation of the renal pelvis and kidney arising rapidly, most commonly from an ascending bacterial infection that colonizes the lower urinary tract and spreads …