Retroperitoneal fibrosis (RPF) is a rare autoimmune disorder that is defined by a fibrotic reaction in the retroperitoneum (the compartment of the abdomen where the adrenals, kidneys, ureters, large blood vessels and bladder are found). The exact cause of this problem is not known although several risk factors do exist. RPF is most frequently a problem due to the manner in which it wraps around the organs in the retroperitoneum, specifically the ureter, causing urinary obstruction and hydronephrosis (swelling of the kidney). Treatment of RPF may be undertaken in conjunction with a rheumatologist. Temporary measures may be required to relieve urinary obstruction, with either ureteral stent placement or nephrostomy drainage. Medical therapy may consist of oral steroids. When ureteral obstruction occurs in RPF, surgical ureterolysis (freeing of the ureters) is typically required. This surgery separates the affected ureter(s) from the fibrotic reaction and brings them into the abdomen. Often they are then wrapped in fat (omental wrap). This surgery is performed via a robotic approach. See Other Robotic Procedures for more information.