Ureteral duplication – Ectopic ureter – Ureterocoele
Objectives: To identify the common ureteric anomalies Embryology of the ureter The ureter develops from the ureteric bud. The bud originates from the mesonephric duct above its entrance into the anterior half of the cloaca ( the future urinary bladder). The bud ascends to meet the metanephric blastema and divides to give rise to the ureter, renal pelvis, calyces and collecting ducts. The mesonephric duct above the origin of the ureteric duct will obliterate in the female, but in the male it will differentiate into the genital duct system (epididymis, vas deferens, seminal vesicle and ejaculatory duct).Below the origin of the ureteric bud, the mesonephric duct is termed the common excretory duct (carrying both future ureteric and genital duct systems). The common excretory duct is incorporated into the urogenital sinus to form the trigone of the urinary bladder. Further absorption of the ureteric bud and mesonephric duct into the developing bladder will create separate ureteric and genital duct orifices. The ureteric bud being lower will be absorbed earlier and is carried upwards and laterally to the corners of the trigone. The genital duct system being higher will be absorbed later and is carried downwards and medially into the posterior urethra (Fig. 1-2).
Figure (1): Development of the ureteric bud.
Figure (2): Incorporation of ureteric bud and genital duct into bladder and urethra.
Ureteral duplication 1) If two ureteric buds arise from the mesonephric duct, complete renal duplication will result. The lower bud (connected to the lower two thirds of the kidney) will migrate further up the trigone until the upper bud (connected to the upper one third of the kidney) reaches the bladder. Therefore, the ureter of the upper renal moiety will always open lower in the bladder than the ureter of the lower renal moiety (Fig. 3). 2) If one ureteric bud arises from the mesonephric duct, but bifurcates before it reaches the metanephric blastema, incomplete duplication of the ureter will
result. This will range from a bifid pelvis to a Y-shaped ureter with a common stem having a single opening into the bladder.
Gross appearance of double collecting system.
Figure (3): Complete renal duplication arising from 2 separate ureteric buds.
Ureteral duplication is often asymptomatic, complications may occur causing obstruction (hydronephrosis), vesicoureteric reflux, UTI, or incontinence if the ureter of the upper renal moiety opens in an excessively lower position below the bladder neck in females. Diagnosis depends on IVU visualization of the duplex system, ascending pyelography may be resorted to if the duplicated system is not visualized.
Treatment is tailored to the nature of the anomaly, ranging from just follow up to ureteric re-implantation of a refluxing system into the bladder, or heminephrectomy of a non-functioning renal moiety.
IVU showing double collecting system. Ectopic ureter An ectopic ureter results from failure of separation of the ureteric bud from the mesonephric duct as both are incorporated in the bladder. It may occur in a single system when the ureteric bud originates from a high point on the mesonephric duct so that it enters the bladder late and has no chance to migrate up the trigone (more common in boys). Or it may be a part of complete renal duplication , where the ureter of the upper renal moiety opens in an excessively lower position below the bladder neck (more common in girls). In boys the distal sphincteric mechanism is powerful, leading to ureteric obstruction and hydronephrosis. Whereas the distal sphincteric mechanism in girls is weak leading to urinary incontinence. If the connected renal segment is salvageable, the management is either by uretero-ureterostomy to the normally located ureter of a duplicated system, or by re-implantation of the ectopic ureter into the bladder above the bladder neck. If the connected renal system is not salvageable, the management is by nephrectomy of the single system or heminephrectomy of the involved system of a duplicated system. Ureterocoele A ureterocoele is a cystic dilatation of the lower end of the ureter. It may occur with a single system, or involves the ureter of one segment of a duplicated kidney. The ureterocoele may be located in the bladder, or it may open in an ectopic location below the bladder neck. Complications are related to vesicoureteric reflux
leading to UTI, obstruction leading to hydronephrosis, or voiding problems if the bulging ureterocoele interferes with competence of the bladder neck sphincteric mechanism. Management depends upon the condition of the connected renal unit. It ranges from transurethral incision of the ureterocoele, nephrectomy or heminephrectomy of the connected renal unit, or re-implantation of the ureter into the bladder above the bladder neck.
Bilateral single-system simple ureteroceles
Fig:IVU showing ureterocele.