retroperitoneal fibrosis, a chronic inflammatory process, usually of unknown cause, in which fibrous tissue surrounds the large blood vessels in the lower lumbar area. It frequently causes constriction of the midportion of the ureters, which may lead to hydronephrosis and azotemia. Occasionally the fibrosis spreads upward to involve the duodenum, bile ducts, and superior vena cava. Symptoms include low-back and abdominal pain; weakness; weight loss; fever; and, with urinary tract involvement, frequency of urination, hematuria, polyuria, or anuria. Methysergide, taken to prevent migraine headaches, is one known cause of this condition. Treatment includes stopping methysergide and instituting surgical release of the ureters from the fibrosis with transplantation laterally or intraperitoneally.
