Fig. 16

Antegrade pyelogram in an 85-year-old woman with acute on chronic renal failure and sepsis requiring nephrostomy placement. Antegrade pyelographic images demonstrate opacified renal calyces, a filling defect in the centre of a lower pole calyx (a), which persists on a delayed image (b) is consistent with a sloughed papilla as a result of necrosis (arrow), the filling defect is thought to resemble the jewel or insignia of a signet ring