Figure 24. Retroperitoneal fibrosis. Postcontrast CT scan shows a mass of soft-tissue attenuation (arrows) encircling the SMA in the root of the SBM. Biopsy at laparotomy revealed diffuse fibrosis of the pancreas and peripancreatic mesentery. Note the left hydronephrosis (H) caused by ureteral involvement. Ao = aorta.