Chronic periaortitis is a clinico-pathological entity encompassing idiopathic retroperitoneal fibrosis and perianeurysmal retroperitoneal fibrosis. The treatment of this disease is generally based on the use of glucocorticoids, which are often effective. However, prolonged steroid treatments are usually needed to achieve a sustained remission; additionally, patients frequently develop disease relapses following treatment discontinuation, therefore they may be exposed to high cumulative doses of glucocorticoids.

Preliminary data reported in the literature show that methotrexate may be effective in combination with prednisone for retroperitoneal fibrosis. In addition, methotrexate is often used as a steroid-sparing agent in different inflammatory diseases.

The aim of this study is to evaluate whether a treatment with low-dose prednisone plus methotrexate is non-inferior to conventional dose-prednisone in achieving remission in retroperitoneal fibrosis patients.

Inclusion Criteria:

• New diagnosis of idiopathic retroperitoneal fibrosis or chronic periaortitis; written informed consent

Exclusion Criteria:

• Secondary forms of retroperitoneal fibrosis (e.g. drugs, surgery, neoplasms, infections)
• Previous medical therapy for retroperitoneal fibrosis
• Renal failure with creatinine >2 mg/dl which proved not to be reversible after ureteral decompression
• Hypersensitivity to the study drugs
• Pregnancy
• Active infections or malignant neoplasms