Imaging results

All abdominal CT scans were independently reviewed. If performed elsewhere, we requested that the referring hospitals provide these CT images. The following variables from these imaging studies were assessed: localization of the soft tissue mass; the presence of extrinsic ureteral obstruction; the presence of hydroureteronephrosis (unilateral or bilateral and, if unilateral, which site was affected); the presence of renal atrophy (described as kidney length ≤8.5 cm); the presence of infrarenal aneurysmal aortic dilation, defined as aortic diameter ≥30 mm; and any other relevant intra-abdominal findings. During follow-up, CT-documented mass regression was categorized as follows: no regression, moderate regression (<50% mass reduction), significant regression (>50% mass reduction) and complete regression (no identifiable or measurable mass).