Image Quiz

What is the diagnosis?

The answer to the Image Quiz Jan 28, 2012 is crossed-fused renal ectopia. 

This is a renal scan. What is the diagnosis? More on cross-fused ectopia:

• Crossed ectopy = kidney located on the opposite side of the midline from its ureter.
• In 90% of crossed ectopy, there is at least partial fusion of the kidneys (the remainder demonstrate two discrete kidneys on the same side, crossed-unfused ectopy)
• Due to improper renal ascent in embryogenesis (4th-8th week of fetal life - normally, the kidney reaches its appropriate position at L2 level at the end of the 2nd month)
• Fusion of the kidneys within the pelvis leads to crossed-fused renal ectopia.
• Abnormally situated umbilical artery prevents normal cephalic migration. Another theory is that the ureteric bud crosses to the opposite side and induces nephron formation in the contralateral metanephric blastema.

• Incidence: 1 out of 1,000 births.
• 2:1 male to female ratio
• A single renal mass with two collecting systems is located on one side of the abdomen.
• Left-to-right ectopy three times more common.