Compression from extra-ureteric masses (retroperitoneal fibrosis or malignant conditions of pelvis and retroperitoneal space) is a chronic inflammatory process of the retroperitoneal space causing partial or complete obstruction of one or both ureters over the lower lumbar vertebrae.
There are numerous causes of retroperitoneal fibrosis in the adult (RPF). Malignant diseases (Hodgkin lymphomas, carcinoma of the breast, carcinoma of the colon should be suspected and ruled out) or inflammatory bowel disease, aortic aneurism, etc. Some medications have also been implicated such as ergot (used for migraine control).
The symptoms are non specific and include low back pain, malaise, anorexia, weight loss, and in several cases uremia.
For the diagnosis we need intravenous urography, and CT or MRI scan at least. A retrograde urogram is necessary when real function is poor and is the best way to elimitate the length of the ureter involved. There is a medical treatment based on corticosteroids and immune response modulators but even nowadays we do not avoid surgical treatment.
Recently this tends to be endoscopic with placement of permanent endoureteric prosthesis (stents) that are made from a special material that avoids encrustations and last for years. Also, an open procedure is possible with mobilization of the ureter(s) and wrapping them in omentum in order to protect them.