Peripelvic cysts can closely mimic the sonographic changes of renal pe
lvicalyceal dilatation. Three cases are described in which a particula
r feature was the presence of linear septations extending to the hilum
which represented the walls of tubular peripelvic cysts. The cluster
of cysts centrally in the renal sinus was originally interpreted as a
dilated pelvicalyceal system. Excretion urography is usually necessary
to exclude pelvicalyceal dilatation conclusively.