Retroperitoneal fibrosis
Retroperitoneal fibrosis (RPF) is a rare but multifaceted disease which encompasses a range of conditions characterized by the presence of a fibro-inflammatory tissue, which usually surrounds the abdominal aorta, iliac arteries, and extends into the retroperitoneum to entrap ureters with resultant unilateral or bilateral obstruction, usually at the junction between the middle and lower thirds of the ureter. The condition is progressive: initially, the fibrous tissue is fairly cellular, later becoming relatively acellular. The mechanism by which obstruction occurs is probably due to loss of peristalsis. A histological diagnosis should be obtained if at all possible, and laparotomy is required in order to obtain a sufficiently large sample to differentiate between idiopathic and secondary causes of RPF. Treatment of idiopathic RPF is by corticosteroids in the first instance with ureteric stents or ureterolysis initially and requires regular monitoring.