<s>[INST] <<SYS>> This is a medical question of type : causes <</SYS>> What causes Retroperitoneal fibrosis ? [/INST] What causes retroperitoneal fibrosis? The cause of retroperitoneal fibrosis is unknown in many cases (idiopathic). Some cases occur in association with other factors, including: Asbestos exposure Smoking Neoplasms (tumor) Infections Trauma Radiotherapy Surgery Use of certain drugs </s>