Available histopathologic evidence suggests that most cases of the disease called idiopathic retroperitoneal fibrosis are essentially identical to those referred to as idiopathic mediastinal fibrosis, perianeurysmal retroperitoneal fibrosis, and inflammatory aneurysm of the aorta. The name "chronic periaortitis" includes all of these variants and "chronic periarteritis" refers to the uncommon associated involvement of coronary arteries. It has been proposed that the cause of the disease is a local autoallergic reaction to components of atherosclerotic plaques. Some recent evidence supports that view, but as yet there is no definite proof. Surgical ureterolysis is the treatment of choice in typical uncomplicated cases, but an important characteristic of the disease is its sensitivity to corticosteroids.