Most patients have significant leukocytosis, pyuria with leukocyte casts in the urine, and bacteria on a gram stain of unspun urine. Hematuria may be present. Symptoms usually subside over a few days. Pathophysiology Acute pyelonephritis is a bacterial infection of the kidney with acute inflammation of the pyelocaliceal lining and renal parenchyma centrifugally along medullary rays. The etiology is from infected urine in the lower tract.
Women are much more commonly affected than men.
The typical age is 15-40. Predisposing factors include reflux, obstruction, calculi, altered bladder function, altered host resistance, pregnancy and congenital urinary tract abnormalities. There are three main pathophysiologies for acute pyelonephritis. The most common is an ascending bacterial infection, usually of P-fimbriated E. coli which adhere to the mucosa. The initial colonization of the walls of the ureter is in areas of turbulent flow which leads to paralysis of peristalsis.