Duplex renal collecting system

The most common ureteric anomaly is that of ureter number, such as a duplex renal collecting system.

The The renal parenchyma may be divided into upper and lower components by a septum of Bertin, which is associated with a bifid collecting system and two renal pelvicesservices. The upper renal pelvic moiety will drain the upper renal calyces, while the lower moiety will drain the lower calyces.

The double ureters may join proximal or distal to the ureteropelvic junction, doing so in the latter case with a 'Y-configuration'. In this scenario, urine may reflux from one ureter up the other (ureteroureteric reflux) which is also known as 'yo-yo reflux'.

In In complete duplication, the upper moiety ureter has a tendancytendency to insert lower (i.e ectopically medially and below) the normal ureteric orifice. The lower moiety inserts orthopically, but tends to reflux.

In duplication systems, a commonly dilated upper pole ureter can impinge and displace the lower pole ureter.

A voiding cystourethrogram (VCUG) or CT intravenous urogram/ pyelogram (CT IVU/IVP) will adequately visualize these systems, their anatomical relations, and any complications such as focal or diffuse hydronephrosis, urine reflux, distal ureteric stricturing and ureterocele formation.

Coronal contrast enhanced-enhanced CT images in the arterial phase which demonstrate features consistent with a left sided-sided duplex renal collecting system, with two renal pelvicespelvises an upper and a lower ureteric moiety. 

The left sided-sided ureteric moieties crossover at a level coinciding with the junction of the upper third and middle third parts of the ureters.

The distal attachments/ anatomy of the two left sided-sided ureteric moieties is unclear, as a delayed (nephrogenic(excretory) phase was not performed.

The right kidney and collecting system is normal in appearance, with no duplex system seen on this side.