Pediatric Duplicated Kidney

Etiology: Due to splitting of metanephric blastema by abnormality of ureteric buds, there is a spectrum of duplications:
— Complete: 2 collecting systems separated by cortical band with 2 separate ureters with separate ureteral orifices
— Partial: 2 collecting systems with the 2 ureters joining before bladder with a single ureteral orifice
— Bifid collecting system: 2 collecting systems drained by 1 ureter
Wiegert-Meyer rule: Complete duplication with 2 completely separate ureters
— Upper pole: Ectopic ureter that usually inserts in bladder medial and inferior to lower pole (normal) ureter causing collecting system obstruction due to ureterocele or stenotic insertion of ureter and this ureter may insert into urethra or vagina in female
— Lower pole: Ureter inserts in bladder in normal orthotopic location and reflux usually due to short intramural tunnel which predisposes to reflux
Imaging: Drooping lily sign – obstructed nonfunctional upper pole moiety in duplex system displaces the functional opacified lower pole moiety inferolaterally
Imaging US: Interruption of central echogenic renal fat surrounding collecting system due to cortical band between two collecting systems
DDX:
Complications: Ectopic ureter can lead to infection or wetting
Treatment:
Clinical: 20% are bilateral
— Ectopic ureter can lead to infection or wetting
— Classic history is female that is always wet and has never been dry despite toilet training due to ectopic ureter inserting below bladder sphincter mechanism
— Male typically has pain or infection but not wetting

Radiology Cases of Duplicated Kidney

Radiology Cases of Duplicated Kidney With Ectopic Ureterocele

US of duplicated kidney with ectopic ureterocele and hydroureteropyonephrosis — Sagittal US of the right kidney (upper left) shows a duplicated renal collecting system with the upper pole replaced by a round structure filled with echogenic material. Sagittal US of the right upper pole ureter (upper right) shows a tortuous ureter filled with echogenic material. Transverse US of the bladder (lower left) shows a round structure in the right side of the bladder that has echogenic material in its inferior portion and anechoic material in its superior portion. Sagittal US of the right ureter and bladder (lower right) shows the tortuous right ureter filled with echogenic material on the left side of the image and the rounded structure with the fluid-fluid level in the right side of the bladder.

VCUG of ectopic ureterocele — AP images from a voiding cystourethrogram (above) show a lucent filling defect in the base of the bladder. Oblique image (below) shows reflux into an extremely dilated right renal collecting system. The right ureter inserts into a dilated structure that is inside and outside of the bladder.

IVP of bilateral duplicated kidneys and ectopic ureteroceles — Post void excretory phase image from an intravenous pyelogram exam shows bilateral duplication of the kidneys. Within the collapsed bladder are two round filling defects.

MRI of duplicated kidney with ectopic ureterocele — Axial T2 MRI without contrast of the upper abdomen (above right) shows a normal right kidney and the upper pole of the left kidney has a thin rim of parenchyma around an extremely large cyst. Axial T2 MRI of the lower abdomen (below left) shows the hydronephrotic lower pole of the left kidney which is rotated on its axis and a dilated hydroureter medial to it while the cystic structure posterior to the left kidney is the continuation of the left kidney upper pole cystic structure. Axial T2 MRI of the pelvis (below right) shows an oval cystic structure with a thin wall located posteriorly within the bladder. Coronal T2 MRI (above left) again shows the full extent of the dilated cystic structure in the upper pole of the left kidney, the midline hydroureter, and the cystic structure within the bladder.

US and VCUG of ectopic ureterocele — Sagittal US of the right kidney (above left) was unremarkable. Sagittal US of the left kidney (above right) shows a duplicated kidney with hydronephrosis of the upper pole. Sagittal US of the bladder (below left) shows a round thick walled lesion at the base of the bladder. AP image from a voiding cystourethrogram exam (below right) shows a round filling defect on the left side of the bladder.

VCUG of ectopic ureterocele and urachal diverticulum — Lateral image from a voiding cystourethrogram exam shows a round lucency / filling defect near the trigone of the bladder. There is also contrast filling a blind ending tubular tract at the dome of the bladder.

Radiology Cases of Duplicated Kidney with Multicystic Dysplastic Kidney

US of duplicated kidney with multicystic dysplastic kidney in the lower pole — Sagittal US of the left kidney shows a normal appearing upper pole. The lower pole has two large cysts, of different sizes, that do not communicate.

Radiology Cases of Duplicated Kidney with Everting Ectopic Ureterocele

US and VCUG of duplicated kidney with everting ectopic ureterocele — Sagittal US of the upper pole of the left kidney (above left) shows a duplicated kidney with hydronephrosis of the upper pole collecting system. Sagittal US of the bladder (above right) shows a large cystic structure at the base of the bladder. AP image of the bladder (below left) obtained at the start of filling of the bladder during a voiding cystourethrogram (VCUG) shows a large filling defect in the base of the bladder. AP image of the bladder (below right) obtained during the voiding phase of the VCUG shows the previously seen filling defect in the base of the bladder has everted out of the bladder and now appears as a contrast filled structure to the left of the bladder.

VCUG of an everting ectopic ureterocele — Sagittal US of the right (above left) and left (above right) kidneys shows parenchymal bars of tissue between the upper and lower poles of each kidney. Transverse US of the bladder (middle left) shows a round cystic structure on the right side of the bladder. Sagittal US of the bladder (middle right) shows the right ureter in continuity with the cystic structure within the bladder. AP image of the bladder (below left) obtained at the start of filling the bladder during a voiding cystourethrogram (VCUG) shows a round filling defect in the right base of the bladder. AP image of the bladder (below right) obtained during the voiding phase of the VCUG shows the previously seen filling defect in the base of the bladder has everted out of the bladder and now appears as a contrast filled structure to the right of the bladder.

Radiology Cases of Duplicated Kidney With Ectopic Insertion of Ureter Into Urethra

VCUG of ectopic ureter inserting into the urethra — Sagittal US of the right kidney (above left) is normal while sagittal US of the left kidney (above right) shows a parenchymal bar between the upper and lower pole collecting systems. AP image of the bladder (below left) obtained during filling of the bladder during a voiding cystourethrogram (VCUG) shows right-sided vesicoureteral reflux into a dilated collecting system with the right ureter inserting normally into the base of the bladder. AP image of the bladder (below right) obtained during the voiding phase of the VCUG shows new left-sided grade I vesicoureteral reflux with the left ureter inserting into the urethra.

Radiology Cases of Duplicated Kidney With Prolapsed Ectopic Ureterocele

US and IVP of prolapsed ectopic ureterocele — Sagittal US of the vaginal mass (above left) shows it to be cystic in nature. Sagittal US of the right kidney (middle left) shows moderate hydronephrosis of the upper and lower poles of a duplicated renal collecting system. Sagittal US of the left kidney (below left) shows marked hydronephrosis of the upper pole and moderate hydronephrosis of the lower pole of a duplicated renal collecting system. Excretory phase of a vintage intravenous pyelogram (right) shows on the right a moderately hydronephrotic duplicated renal collecting system and on the left an obstructed nonopacified nonfunctional upper pole collecting system which displaces the opacified functional moderately hydronephrotic lower pole collecting system inferolaterally (drooping lily sign).

Radiology Cases of Duplicated Kidney With Spinning Top Urethra

CT of spinning top urethra — Coronal MIP simulating an intravenous pyelogram (above left), coronal (above right) and axial (below) CT urogram with contrast shows the right kidney to be duplicated. There were normal ureteral insertions bilaterally into the bladder (not pictured). There was an oval structure inferior to the bladder that appeared to be the posterior urethra.