Idiopathic presacral retroperitoneal fibrosis: report of two cases.

Retroperitoneal fibrosis is characteristic plaques of dense fibrous tissue, typically extending from the level of the kidney down to the sacral promontory. Involvement of the presacral space is extremely rare in retroperitoneal fibrosis. We report two cases of idiopathic retroperitoneal fibrosis manifested by a presacral mass.