Pediatric Ectopic Kidney

  • Etiology:
    — Pronephros – Disappears by fifth week, failure of this stage leads to renal agenesis or renal hypoplasia
    — Mesonephros – Regresses by twelfth week leaving behind vas and epididymis and seminal vesicles and ejaculatory ducts, failure of this stage leads to renal agenesis or renal hypoplasia
    — Metanephros – Ureteric bud appears, ureteric bud invaginates nephrogenic blastema, renal ascent, failure of this stage leads to renal ectopia
  • Imaging of Pelvic kidney:
    — Usually the kidney in the pelvis measures shorter than the kidney in its normal position
  • Imaging of Crossed fused ectopia:
    — Cross fused ectopia occurs when one kidney crosses midline and fuses with the other
    — Usually the left kidney is the kidney that crosses midline and fuses its superior pole with the inferior pole of the right kidney
    — 3 times more common on the right
  • DDX:
  • Complications:
  • Treatment: None
  • Clinical: 1/900 births

Radiology Cases of Ectopic Kidney

Radiology Cases of Pelvic Kidney

CT of pelvic kidney
Coronal image (above) from a CT with contrast of the abdomen shows a normal appearing kidney in the left renal fossa and the absence of a kidney in the right renal fossa. An axial image from the same exam (below) shows the right kidney to be located in the pelvis.
IVP of pelvic kidney
AP image from the excretory phase of a vintage intravenous pyelogram shows a normal position of the right kidney in the right renal fossa. The left renal fossa is empty and the left kidney can be found in the left pelvis, over the left side of the sacrum.

Radiology Cases of Cross Fused Ectopia

Angiogram of cross fused renal ectopia
AP image from a selective angiogram injection of the left renal artery shows fusion of the medial aspect of the left kidney, which has crossed the midline, to the medial aspect of the right kidney, causing the right kidney to be displaced laterally. A right hemivertebra is also present just above the T10 vertebral body.

Gross Pathology Cases of Ectopic Kidney

Gross Pathology Cases of Cross Fused Ectopia

Pathology image of Wilms tumor and renal crossed fused ectopia
Post-mortem gross pathological images obtained anteriorly (on the left) and posteriorly (on the right) show a mass in the upper pole of the right kidney. The upper pole of the left kidney is fused to the lower pole of the right kidney.