Splenorenal fusion: heterotopia simulating a primary renal neoplasm.

We report an instance of splenic heterotopia arising within the left kidney of an otherwise normal female infant. Embryologic considerations suggest that fusion of nephrogenic mesoderm and splenic anlage in the second month of gestation accounts for the observed findings. Although splenic-mesonephric (splenogonadal) fusion is a well-characterized, although rare, malformation, we were unable to find any previous description of splenic-metanephric fusion.