Retroperitoneal fibrosis is a rare, in most cases idiopathic, pathology, although it has been associated with medications, neoplasms and other connective tissue diseases. In terms of histopathology, inflammation and deposits of fibrotic tissue in the retroperitoneum are observed and, characteristically, this covers the urethra, provoking acute obstructive kidney damage, the most frequent manifestation of the disease. The definitive diagnosis is obtained solely via biopsy, and the basis of treatment is corticotherapy, although in severe cases, and where resistance to corticosteroids exists, other treatments have been used, such as immunomodulators. Occasionally, surgical interventions are necessary to manage complications. The case of a 50-year-old man who came to the Hospital emergency service due to abdominal pain is presented. Paraclinical studies showed azotemia, and diagnostic images showed left hydronephrosis with a component of interaortocaval and periaortic soft tissue. A retroperitoneal biopsy was conducted, and a diagnosis of idiopathic retroperitoneal fibrosis was made. Bilateral nephrostomies were put in place and treatment with corticosteroids was initiated