A man aged 50 presented with severe abdominal and back pain on the right side from LI radiating to the sacro-iliac joints and pelvis, of 4 months duration. The pain was worse at night. There was marked weight loss and anorexia. Figure 1 Large right retroperitoneal mass, displacing kidney, adjacent to markedly dilated aorta with a cal-cified wall. Figure 2 The retroperitoneal mass is of mixed attenua-tion with minimal calcific spots, very low 'fluid density' streaks and an area of fluid density below the right kidney. There is also a small fluid density collection anterior to the left psoas.