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

MRI of pediatric cross fused renal ectopia — Coronal (above) and axial (below) T1 MRI with contrast of the abdomen and pelvis show the left kidney crossing to the right side of the abdomen with the upper poles of both kidneys being fused to each other.

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.

VCUG of cross fused renal ectopia — AP image from a voiding cystourethrogram exam shows the contrast filled bladder in the midline. There is bilateral vesicoureteral reflux into non-dilated renal collecting systems. The right renal collecting system and right ureter are normally positioned in the middle of the right side of abdomen while the left renal collecting system and left ureter are abnormally positioned in the lower right side of the abdomen. The C-shaped contrast-filled structure to the right of the bladder is sigmoid colon that was filled during a previously performed vaginogram through a rectovaginal fistula.

Gross Pathology Cases of Ectopic Kidney

Gross Pathology Cases of Cross Fused Ectopia and Wilms Tumor

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.