Renal cortical scarring in acute pyelonephritis.

A series of 14 patients with acute pyelonephritis was evaluated for the formation of renal scarring by serial computed tomography (CT) and intravenous urography. Although the urography results were normal, CT showed renal parenchymal atrophy (cortical scarring) in 6 patients. Cortical scarring was observed to occur after 61 to 187 days, and it was slower to develop in the patients with recurrent fever lasting for 2 weeks or more in total than in those with fever for less than 2 weeks. Scarring was significantly more frequent in patients with severe renal involvement than in those with mild involvement, and scars developed at the sites of the most extensive lesions seen on the initial CT scans. Cortical scars were detected in 6 of the 7 patients in whom the lesions occupied 30% or more of the renal parenchyma. We conclude that the extent of the initial renal parenchymal involvement was the most important determinant of eventual scar formation.