Idiopathic retroperitoneal fibrosis: a challenging case in a rare disease.

Context: Retroperitoneal fibrosis is a rare but severe disease. The diagnosis is usually late when a patient is evaluated for renal insufficiency. Untreated cases may develop serious complications or advance to end-stage renal disease.

Case Report: We report a 66-year-old man who presented with worsening kidney function. He was successfully given the diagnosis of idiopathic retroperitoneal fibrosis. Prednisone (1 mg/kg per day) was initiated. The patient's symptoms continued to improve at 1 month with stable kidney function.

Conclusion: Clinicians should have high index of suspicion for retroperitoneal fibrosis when patients present with an elevated erythrocyte sedimentation rate (ESR) or C-reactive protein (CRP) and renal insufficiency from obstructive uropathy. The diagnosis of retroperitoneal fibrosis is primarily made from imaging by computed tomography (CT) scan. Biopsy should be performed in patients who do not have typical findings on CT scan and to exclude the possibility of immunoglobulin G4 (IgG4)-related disease.