Ureteral Diseases of Extrinsic Origin

The ureter is the central structure of the retroperitoneal space and the pelvic cavity. Any expansive or infiltrative pathological process in these regions may have an impact on the ureter. Most extrinsic disorders, whether tumoral or not, compress without direct extension and frequently displace the ureter. However, the mechanism of ureteral involvement by extrinsic malignancies can be different (Marincek et al. 1993; Talner 1990): — Direct tumoral involvement of the ureteral wall (serosal, intramural, mucosal, or a combination of all of them) — Metastatic extension to periureteral lymph nodes or periureteral fatty tissue with frequent desmoplastic reaction, so-called malignant retroperitoneal fibrosis (RPF) — Mucosal or intramural metastases may be isolated or associated with retroperitoneal metastases. Their patterns are described in Chap. 6