It is most common congenital anomaly of the upper urinary tract (4%).
Usually unilateral.
Common on the left side.
In 3% of cases, it is associated with duplication of ureter.
Upper renal pelvis is small, drains the upper calyces. Lower renal pelvis is larger, drains the middle and lower calyces.
Double ureter when associated, may be partial where two ureters join in lower third or complete where upper ureter opens into the bladder at a lower level and lower ureter opens into the bladder at the upper, normal ureteric orifice. This is called as “Weigert Meyer Law”.
In partial duplex, there is reno-renal reflux resulting in infection, stone formation and hydronephrosis.
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.
Ureteric meatotomy is done if there is narrowing of the orifice.
The co-existing complications are treated.
Often heminephrectomy including removal of corresponding ureter may be essential as treatment.
In females with complete duplication, lower ureteric orifice is ectopic, causing urinary incontinence which needs partial nephrectomy or ureteric reimplantation.