Retroperitoneal Fibrosis: Beware of Lymphoma.

Retroperitoneal fibrosis is a rare disease manifesting as chronic soft tissue fibrosis in the retroperitoneum, with potential anatomic and/or functional compromise of adjacent organs. It can be primary (idiopathic) or secondary to other conditions such as cancers, radiotherapy, surgery, traumatisms, infections, autoimmune disorders, or drugs. We report herein a 54-year-old patient with symptomatic retroperitoneal fibrosis leading to bilateral hydronephrosis and renal failure, in whom, after a complex diagnostic workup and protracted clinical course, a follicular lymphoma in the retroperitoneal was identified. The patient was treated with rituximab and cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy protocol, with a resolution of hydronephrosis and lower back pain. We include a thorough literature review on etiopathogenesis, diagnosis, therapy, and prognosis of retroperitoneal fibrosis. A meticulous search for malignancy is necessary for this rare condition that, if positive, may have significant therapeutic and prognostic implications.