Acute pyelonephritis

Acute pyelonephritis is an acute suppurative inflammation caused by bacterial invasion of the renal pelvis, calyces, and renal parenchyma. The disease course does not exceed 6 months. There are two routes of infection: 1. Ascending infection: bacteria enter the renal pelvis through the ureters and then invade the renal parenchyma. Seventy percent of acute pyelonephritis cases originate from this route. 2. Hematogenous infection: bacteria enter the renal tubules through the bloodstream and invade the renal pelvis from the tubules, accounting for about 30%, mostly staphylococcal infections. Urinary tract obstruction and urinary stasis are the most common causes of acute pyelonephritis; simple pyelonephritis is rare.