The authors report a case of transcaval ureter complicated by acute obstructive pyelonephritis in a 54-year-old patient. Transcaval ureter is a rare congenital malformation of the infra-renal inferior vena cava (IRIVC) in which the right ureter passes through a venous ring composed of localized duplication of the vena cava due to persistence of the right posterior cardinal and supracardinal veins.