Q
You undertake a DMSA scan for a 3 year old girl with recurrent infections. Which of the following abnormalities is this most likely to represent?
"Right-sided crossed kidney ectopy without fusion in a 13-year-old girl (confirmed with CT images). "
© Greirosu et al.
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Correct Answer:
Explanation
Importantly, DMSA scans are taken with a Gamma camera behind the patient, therefore the left kidney typically appears on the left side of the image and the right kidney appears on the right side of the image. With that in mind, this DMSA shows a left kidney in the normal position with a right kidney that has crossed the midline and appears in continuity with the left. As the right kidney has crossed the midline this would be called a right sided fused ectopic kidney.
Crossed fused kidney is the second most common congenital fusion abnormality with an incidence between 1/1300-1/7500, after Horseshoe kidney which is much more common with an incidence of around 1/400. Crossed fusion kidneys typically occur where the ectopic kidney that has crossed the midline is fused to a kidney in its normal position. Crossed fused kidneys are typically asymptomatic.
Of crossed fused kidney's McDonald and McClellan classified six types, shown in the answer image below. The most common of these is unilateral fused kidney with inferior ectopia, with unilateral fused kidney with superior ectopy being the least common.
