How common is renal ectopia?
The prevalence has been estimated at 1:500 to 1:2000, although this is probably underestimated since renal ectopy is often clinically silent.
What are renal problems that have been associated with renal ectopia?
obstruction, reflux with subsequent infection.
If a surgeon were to intervene on this kidney, why might CT angiography be useful?
Ectopic kidneys often have variant blood supply. Kidneys begin their development supplied by the iliac arterial system, and as they ascend, they exchange those arteries for supply from the aorta. If the kidney does not ascend, it may retain purely iliac artery blood supply or it may have a mixture of supply from the aorta and iliac arteries.
The right kidney has not ascended to its normal position in the right upper quadrant, and instead has only risen as high as the lower lumbar spine and sacrum ( closer to a "sacral kidney" than a "pelvic kidney").
The collecting system is oriented anteriorly, which is the normal orientation as a kidney ascends. As a kidney ascends, it rotates medially into its normal position.
The ectopic kidney receives arterial supply from the distal aorta, but its renal vein crosses behind the kidney to drain into the ipsilateral proximal common iliac vein.
This was an isolated finding, and the study was otherwise normal: no other abnormality in the kidneys, ureter, or bladder.