RADIOLOGY: ABDOMEN: Case# 32983: RETROPERITONEAL FIBROSIS. Left flank pain. R/O pancreatic and renal cell carcinoma. There is a cuff of tissue around the distal thoracic/proximal abdominal aorta. This is uniform in thickness and well-demarcated. The aorta runs centrally through this and is of uniform and normal caliber (3 cm AP). A fleck of mural calcification is noted on the inner aspect of this tissue (image #13). The lesion extends inferiorly to the level of the renal artery. The intra-abdominal aorta is of normal caliber. No thrombus is seen within it. Small scattered flecks of mural calcification are seen in the distal aorta.