Ultrasonography in crossed renal ectopia.

Five cases of crossed renal ectopia, three fused and two unfused, which were identified sonographically are presented. Bowel occupying the contralateral renal fossa can mimic mass or kidney and lead to confusion. A crossed-fused kidney can mimic a single kidney with a duplicated system or a kidney with a renal mass. A characteristic anterior and/or posterior notch provides a major clue to the correct diagnosis. In addition, correlation with plain radiographs and/or barium studies demonstrating bowel in the contralateral renal fossa, as well as real-time examination demonstrating peristalsis, should aid in the correct diagnosis.