The present case was an asymptomatic 9-year-old boy who had a horseshoe kidney with a left infrarenal mass-like lesion detected by screening sonography at school.

• 马蹄型肾及左下腔静脉的形成都发生在胚胎第七周的时候，两者的合并出现，系因该期胚胎形成过程之受到干扰的可能性极大。