duplex collecting system

Infant with
urinary tract infection. 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. The diagnosis was acute pyelonephritis in a duplicated kidney with an ectopic ureterocele with hydroureteropyonephrosis throughout the upper pole of the right kidney and right upper pole ureter and ureterocele.
pediatricimaging.org • CC-by-nc-sa 4.0
Infant with a
diaper that is never dry. 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.The diagnosis was a left duplicated kidney with an ectopic insertion of the left ureter into the urethra and right Grade III vesicoureteral reflux.
pediatricimaging.org • CC-by-nc-sa 4.0
Newborn with
a cystic mass in the left kidney on prenatal US. 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.The diagnosis was duplicated kidney with a multicystic dysplastic kidney in the lower pole of the left kidney.
pediatricimaging.org • CC-by-nc-sa 4.0
Toddler with
urinary tract infection. 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.The diagnosis was bilateral duplicated kidneys with bilateral ectopic ureteroceles.
pediatricimaging.org • CC-by-nc-sa 4.0
Female infant
with a purple mass protruding from her vagina. 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).The diagnosis was prolapsed ectopic ureterocele from the upper pole of the left kidney in a patient with bilateral duplicated kidneys.
pediatricimaging.org • CC-by-nc-sa 4.0
Duplex
collecting system • Bilateral duplex kidneys with left-sided uterocoele - Ganzer Fall bei Radiopaedia
Babu V, Bilateral duplex kidneys with left-sided uterocoele. Case study, Radiopaedia.org (Accessed on 06 Jan 2023) https://doi.org/10.53347/rID-20811 • CC by-nc-sa 3.0 (modified)
Duplex
collecting system • Megaureters due to bilateral duplex kidneys (prenatal and neonatal imaging) - Ganzer Fall bei Radiopaedia
Ho F, Megaureters due to bilateral duplex kidneys (prenatal and neonatal imaging). Case study, Radiopaedia.org (Accessed on 06 Jan 2023) https://doi.org/10.53347/rID-59096 • CC by-nc-sa 3.0 (modified)
Duplex
collecting system • Pelviureteric junction obstruction and contralateral bifid ureter - Ganzer Fall bei Radiopaedia
Hacking C, Pelviureteric junction obstruction and contralateral bifid ureter. Case study, Radiopaedia.org (Accessed on 06 Jan 2023) https://doi.org/10.53347/rID-39524 • CC by-nc-sa 3.0 (modified)
Infant with
right hydronephrosis on prenatal US. 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.The diagnosis was a right ectopic ureterocele causing vesicoureteral reflux Grade V in a patient with a right duplicated kidney.
pediatricimaging.org • CC-by-nc-sa 4.0
Infant with a
urinary tract infection. 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.The diagnosis was a left duplicated kidney with an everting left ectopic ureterocele.
pediatricimaging.org • CC-by-nc-sa 4.0
Toddler with
respiratory distress and sepsis. 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.The diagnosis was left duplicated kidney with an extremely obstructed upper pole and an ectopic ureterocele.
pediatricimaging.org • CC-by-nc-sa 4.0
Radiopaedia • CC-by-nc-sa 3.0 • de

A duplex collecting system, or duplicated collecting system, is one of the most common congenital renal tract abnormalities. It is characterized by an incomplete fusion of upper and lower pole moieties resulting in a variety of complete or incomplete duplications of the collecting system. While considered an anatomical variant, duplex collecting systems may be complicated by vesicoureteric reflux, obstruction or ureterocele.

Epidemiology

Duplex collecting systems are seen in 0.7% of the healthy adult population and 2-4% of patients investigated for urinary tract symptoms .

Clinical presentation

Most duplicated systems are asymptomatic and diagnosed incidentally. However, where symptoms do occur (infection, reflux or obstruction), the patient is likely to have completely duplicated ureters. Occasionally, hydronephrosis can be severe enough to result in flank discomfort or even a palpable mass.

Pathology

Embryologically, duplication occurs when two separate ureteric buds arise from a single Wolffian duct. Interestingly, and explaining the Weigert-Meyer rule, the future lower pole ureter separates from Wolffian duct earlier and thus migrates superiorly and laterally as the urogenital sinus grows.

Duplication can be variable. At one end of the spectrum, there is merely a duplication of the renal pelvis, draining via a single ureter. At the other extreme, two separate collecting systems drain independently into the bladder or ectopically (see below).

Duplex systems may be unilateral or bilateral and can be associated with a variety of other congenital abnormalities of the urinary tract, e.g. ureterocele.

Associations
Classification

Duplex collecting system or duplex kidney anomalies can be classified into the following categories depending on the level or lack of fusion :

  • duplex kidney: two separate pelvicalyceal systems draining a single renal parenchyma
  • duplex collecting system: a duplex kidney draining into:
    • single ureter: i.e. duplex kidney's duplication pelvicalyceal systems uniting at the pelviureteric junction (PUJ)
    • bifid ureter (ureter fissus): two ureters that unite before emptying into the bladder
    • double ureter (complete duplication)
  • bifid collecting system: refers to a duplex kidney with the two separate pelvicalyceal collecting systems uniting at the PUJ or as bifid ureters
  • double/duplicated ureters (or collecting system): two ureters that drain separately into the bladder or genital tract

Radiographic features

As the abnormality is an anatomic alteration, all modalities able to image the renal tract may be able to visualize the typical features.

General features include:

  • duplicated ureters extending a variable distance down to the bladder
  • obstruction of the upper pole moiety down to the bladder, often with a ureterocele
  • vesicoureteric reflux into the lower pole moiety, often due to distortion in its insertion by the aforementioned ureterocele
  • ectopic insertion of the upper pole moiety e.g. into the prostatic urethra in males or vaginal vault in females

Additionally, if reflux is significant, evidence of reflux nephropathy may be evident.

Fluoroscopy
Excretory urography (IVP)

Although able to elegantly image both collecting systems, one should be aware that a poorly functioning system may not excrete contrast. In such a situation, the functioning lower pole moiety will be inferiorly displaced, taking on the so-called "drooping lily appearance" . The differential for such an appearance is that of an upper pole mass or cyst.

Ultrasound

Ultrasound, when no obstruction/hydronephrosis is present can be suboptimal in the detection of a duplicated system and will especially struggle to distinguish between partial and complete duplication. It is certainly able to detect ureteroceles, if present.

It provides excellent anatomic information but does not necessarily differentiate a bifid renal pelvis from a bifid ureter or two complete ureters.

CT

CT can delineate all abnormalities essentially, especially when performed during the excretory (IVP) phase (contrast outlining the collecting systems). CT reconstruction software can produce striking single images of the collecting systems. In an unobstructed system, the diagnosis can be difficult. A duplicated renal collecting system can be suspected by identifying the so-called faceless kidney.

Nuclear medicine

Renal scintigraphy is significantly impaired in its ability to identify non-obstructed systems, as the spatial resolution is poor. However, it is able to evaluate renal function and is particularly useful in planning corrective surgery.

Treatment and prognosis

A duplex kidney usually does not require any treatment per se, however, complications may necessitate intervention:

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu Doppelniere:
Vesikoureteraler
Reflux
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