74-year-old man with IgG4-KD manifesting as perinephric lesion.Contrast-enhanced arterial phase CT image shows homogeneous, rim-like, soft-tissue mass surrounding both kidneys (arrows). Peri-aortic, soft-tissue lesion, indicating retroperitoneal fibrosis, is also observed (arrowhead). IgG4-KD = immunoglobulin G4-related kidney disease