Description 

A 57-year-old woman with a 5-month history of left-upper quadrant (LUQ) abdominal pain was referred after a retroperitoneal mass was discovered on CT scan of the abdomen and pelvis. Clinical history revealed mild LUQ abdominal pain over the course of 5 months, associated with anorexia, unintended weight loss and several episodes of painless gross haematuria. Physical examination was positive for an ill-defined mass in the LUQ extending to the umbilical region. Routine laboratory tests did not reveal abnormal findings except for microscopic haematuria. CT scan images revealed a left cross ectopic kidney fusing laterally with the lower pole of right kidney in addition to a mass measuring 7.5×8.5 cm emerging from the ectopic kidney. The mass extended to the left flank crossing the abdominal aorta and passing behind the inferior mesenteric artery. This structure mimicked a horseshoe kidney (figures 1 and 2). Retrograde pyelography confirmed the …