Retroperitoneal Fibrosis Due to Opium Abuse: A Case Series and Literature Review.

Retroperitoneal fibrosis (RPF) is a rare condition with an unclear etiology, presenting with the development of aberrant chronic nonspecific fibroinflammatory tissue in the retroperitoneal space, which can result in entrapment and obstruction of the retroperitoneal structures. RPF is a subtype of chronic periaortitis, and can be divided into two types: primary (or idiopathic) and secondary. RPF is usually idiopathic, but can also be secondary to malignancies, certain drugs, infections, surgery, and trauma. The systemic clinical manifestations are nonspecific and include low-grade fever, fatigue, anorexia, weight loss, and myalgia. We report five patients admitted to our hospital with clinical, laboratory, imaging, and pathologic findings compatible with RPF, and we describe their treatment and follow-up. We were suspicious that the impurities of some types of opium have an important role in the pathogenesis of RPF. Some of our patients used opium again after the follow-up period; however, they used a different type with a different origin, and we were surprised to see that RPF did not form again.