[en] Retroperitoneal fibrosis is an uncommon inflammatory disease which is characterized by the development of a fibrous process that surrounds the major vessels and organs located within the retroperitoneum. Isolated as an idiopathic expression or associated with several other diseases in its secondary form, retroperitoneal fibrosis remains relatively of rare occurrence and as a result, is devoid of either diagnostic or therapeutic definitive recommendations. We report the observation of one case admitted in the emergency room for abdominal pain induced by left hydronephrosis. Radiographic exploration with contrast-enhanced studies evidenced retroperitoneal fibrosis causing left ureteric obstruction. Therapeutic approach was based on corticosteroids and ureteral drainage which prevented recurrence while fibrosis was almost reversed six months later.