An Atypical Presentation of Retroperitoneal Fibrosis.

A 69-year-old man with a psoriatic arthritis treated with infliximab for 1 month presented to the urology clinic for lower urinary tract symptoms. He was found to have a new diagnosis of elevated creatinine. Computed tomography of the abdomen and pelvis revealed bilateral severe hydronephrosis with abnormal soft tissue thickening of the right renal pelvis and proximal ureter. Bilateral stents were placed after ureteroscopy demonstrated no abnormalities. A computed tomography-guided biopsy of the peri-ureteral lesions revealed fibroadipose tissue with sclerosis and extensive chronic inflammation consistent with retroperitoneal fibrosis. Infliximab was discontinued and the patient was started on corticosteroids. Follow-up magnetic resonance imaging of the abdomen and pelvis at 2 months revealed total resolution of soft tissue and inflammation along the proximal ureter bilaterally. Repeat imaging demonstrated no hydronephrosis after stents removal, and the patient's creatinine remains normal at 12 months follow-up.