Crossed Fused Renal Ectopia

Michael P. D'Alessandro, M.D.
Peer Review Status: Internally Peer Reviewed

Etiology/Pathophysiology:
Due to abnormal ascent of the kidneys, resulting in abnormalities in renal position, rotation and fusion. Renal ectopic by definition refers to abnormal position of the kidneys. The most common site of an ectopic kidney is in the pelvis, rarely it can be too high and in the chest - a thoracic kidney.

When an ectopic kidney crosses over to the contralateral side it is called crossed renal ectopia and the kidney lies below the contralateral kidney. There is usually fusion between the 2 kidneys and in doing this the crossed lower kidney malrotates so the pelves point to the midline and the crossed kidney's drainage is to the side it would drain to if it had not malrotated. More common in males and more common on the right. Fifty percent of patients have associated genitourinary, skeletal and cardiac valvular defects.

Pathology:
Not applicable

Imaging Findings:
The ectopic kidney crosses the midline and its upper pole fuses with the lower pole of the contralateral kidney. The kidneys ureters drain to their respective sides.

DDX:

• Not applicable

References:
See References Chapter.

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