[Pyelonephritic scar formation].

Pyelonephritic scars almost never develop after urinary tract infections alone, but require in addition certain risk factors. The most important risk factors are: vesicoureteral reflux, intrarenal reflux, obstructive uropathy, and nephrolithiasis. Most of the pyelonephritic scars develop in early childhood, where we find the combination of vesicoureteral reflux, intrarenal reflux, and urinary tract infections. Urinary tract infections alone almost never result in pyelonephritic scars. After the age of 3 years the risk to develop pyelonephritic scars is not more than 10% in those with the combination of urinary tract infections and vesicoureteral reflux. In this age group the risk to develop pyelonephritic scars is not altered by antireflux operation.