Acute pyelonephritis ranges from uncomplicated infection to life-threatening emphysematous pyelonephritis, a fulminant necrotizing infection of the renal parenchyma and perinephric tissues. Most cases are caused by Gram-negative bacilli, predominantly Escherichia coli, with rising drug resistance. A structured, stepwise approach is essential for early recognition, risk stratification, and timely imaging-based intervention, particularly in acute care settings. Judicious empirical antimicrobial therapy, guided by illness severity, host factors, and local resistance patterns, is critical.
