Ureterolysis, unilateral, with or without repositioning of the ureter, for obstruction of the ureter, if: (a) the obstruction: (i) is evident either radiologically or by proximal ureteric dilatation at operation; and (ii) is secondary to retroperitoneal fibrosis; and (b) there is biopsy proven fibrosis, endometriosis or cancer at the site of the obstruction at time of surgery (Anaes.) (Assist.)