An ectopic ureter terminates caudal to the normal position in the trigone. Although a ureter that terminates cranial to the normal position is clearly abnormal, and is often associated with vesicoureteral reﬂux (see Plate 2-21), the term “ectopic” is generally not applied.
In males, the most common sites of ureteral ectopia are the prostatic urethra and seminal glands (vesicles), whereas in females, the most common sites are the urethra and vagina. The incidence of ectopic ureter is not known with precision, although one series estimated it at 1 in 1900. The condition is at least twice as common in females than in males, for unknown reasons.
As described on page 30, the ureteric buds appear toward the caudal ends of the mesonephric ducts during the ﬁfth week of gestation. Each ureteric bud grows into the adjacent mass of metanephric mesenchyme, the precursor of the kidney, to form a ureter, a pyelocalyceal system, and collecting ducts.
During the sixth week, each mesonephric duct undergoes a process known as exstrophy, in which its most caudal end everts into the primitive bladder and draws in the attached ureter. After the ureters enter the bladder, they separate from the mesonephric duct and attach to the posterior bladder wall. At the end of this process, the ureters normally terminate at oriﬁces located at the superolateral corners of the trigone.
If, however, a ureteric bud is in a more cranial position on the mesonephric duct, the ureter is drawn farther than usual into the bladder during mesonephric duct exstrophy. As a result, the ureteric oriﬁce may appear in a more inferior and medial position, such as at the bladder neck or urethra. If the ureteric bud is even more cranial on the mesonephric duct, the ureter may not be drawn into the bladder at all, instead remaining attached to the mesonephric duct. In males, the ureter may consequently terminate in any of the mesonephric duct derivatives, which include the seminal glands (vesicles), vas deferens, or epididymis. In females, the ureter may end in vestigial mesonephric duct derivatives, such as the epoöphoron and paroöphoron, and then become incorporated into adjacent structures, such as the vagina, uterus, and uterine (fallopian) tubes. Ectopic ureters are usually seen as part of a duplicated collecting system (see Plate 2-23), in which the affected side has one ureter with a normally positioned oriﬁce and another with an ectopic oriﬁce. This association is logical because complete ureteral duplication occurs when a single mesonephric duct sprouts two ureteric buds, one of which must be in an abnormal position. Ectopic ureters are also frequently associated with renal hypoplasia or dysplasia because the abnormally positioned ureteric bud fails to induce normal differentiation of the metanephric mesenchyme.
Presentation And Diagnosis
Ectopic ureters may or may not be symptomatic. In males, the common sites of ectopia are all located proximal to the external urethral sphincter, and thus incontinence is not seen. An insertion into the prostatic urethra, however, may lead to urinary frequency and sensations of urgency. Reﬂux into the ectopic ureteric oriﬁce is often present, and thus upper tract infection may occur. Likewise, an insertion into the epididymis may cause epididymitis. In females, many of the common sites of ectopia are located distal to the external urethral sphincter. Thus many females have constant urine drib- bling despite otherwise normal voiding patterns. In both sexes, an ectopic ureter can become obstructed, causing ﬂank pain or even a palpable mass.
An ectopic ureter may initially be seen on ultrasound, either with or without associated renal (hypo)dysplasia. If there is ureteral obstruction, hydroureteronephrosis will be seen. If an ectopic ureter is suspected, high-resolution axial imaging or a VCUG can often provide additional information. With females, careful cystoscopy, vaginoscopy, and inspection of the urethrovaginal septum may even provide direct visualization of the ectopic ureteric oriﬁce. In males, careful cystoscopy and examination under anesthesia may also be diagnostic.
Once an ectopic ureter has been identiﬁed, a renal scan should be performed to assess the function of the associated renal parenchyma.
Because ectopic ureters are often associated with dysplastic kidneys, the treatment usually consists of nephroureterectomy or, in the case of a duplicated collecting system, heminephrectomy. If, in contrast, the renal parenchyma associated with the ectopic ureter appears to be functional, or if there are bilateral ectopic ureters, ureteropyelostomy or ureteral reimplantation can be performed instead.