Crossed fused renal ectopia: sonographic diagnosis.

Five cases of crossed fused renal ectopia, all confirmed by either computed tomographic scan or intravenous urography, were diagnosed sonographically. The sonographic appearance of this entity consists of a characteristic anterior and/or posterior notch, difference in orientation of the 2 collecting systems in the fused kidneys, and absence of a kidney in the contralateral renal fossa, or elsewhere in the body, such as the pelvis. The inability to diagnose this condition correctly may lead to the misdiagnosis of a renal mass or infiltrative disease occupying the contralateral renal fossa. Computed tomographic scans will also identify the anomaly.