Ectopic ureters

What are ectopic ureters?

Ectopic ureter is a birth defect in which the tubes leading from the kidney (the ureters) empty urine into a location other than the bladder. In females, one or both ureters may terminate in the vagina, urethra or uterus. In males, the ureter(s) will usually open in the urethra downstream of the prostate. Where the ureters terminate in the urethra, the ureter may pass intramurally/submucosally through the bladder, with the opening located at a more distant location than normal. At other times, the ureteral stoma may actually have formed in the normal location at the trigone of the bladder, but urine is diverted down the urethra due to partial persistence of a ‘tube-like’ structure (ureteral troughs etc).

How common are ectopic ureters?

One-sided (unilateral) is more common than a defect on both sides (bilateral), and only about 20-25% of cases are bilateral.

Ectopic ureters occur more commonly in females. There is a familial tendency for ectopic ureters in Siberian Huskies, with an increased incidence also reported in the Golden Retriever, miniature poodle, Labradors and some terriers. There are a few reported cases in cats, but bilateral ectopia is considered to be more common in this species. Ectopic ureters are often associated with other congenital anomalies or associated diseases such as megaureter due to urine reflux, decreased kidney size (due to congenital renal hypoplasia, or chronic pyelonephritis), and decreased bladder size. The effects of these other anomalies can impact significantly on the long-term prognosis despite correction of the ureteral ectopia.

What signs are seen in an animal with an ectopic ureter?

Animals with ectopic ureter are usually incontinent from birth. However, the condition should be suspected even in adult animals, especially if the duration of incontinence cannot be established from the history. Furthermore, ectopic ureter should not be discounted if the incontinence is only of an intermittent nature, and the animal still apparently voids normal volumes of urine at micturition, as animals can void normally if only one ureter is ectopic. Some males with ectopic ureter(s) may be continent because of the longer length of the male urethra.

Physical examination is frequently unremarkable. Urine staining of the perineum and perivulvar region, with secondary dermatological changes may be seen. Renal pain, or other palpable renal anomalies may be present if pyelonephritis or congenital deformities are present. The bladder is frequently small, or non-palpable.

How is an ectopic ureter diagnosed?

The diagnosis of ectopic ureter is confirmed by contrast radiography, which can performed with traditional radiographs or with CT. Intravenous excretory urography is essential as this will delineate the kidneys and ureters and will usually identify where the ureters are entering the lower urinary tract. The ectopic ureter is frequently dilated, but the absence of ureteral dilatation does not exclude the diagnosis. Poor peristaltic flow in the ectopic ureter can sometimes inhibit visualisation of the terminal junction. Retrograde vaginourethrography is very useful in identifying ectopic ureters and where they connect to the urethra or vagina, and may result in a better study than intravenous urography. The radiographs are also be closely assessed for other anomalies (e.g. renal disease, hypoplastic bladder, intrapelvic bladder, short uretheral length) within the urogenital tract which may influence treatment success and long-term outcome.

Ultrasound examination may be useful for evaluating renal morphology, and detecting the presence of pyelectasia, hydronephrosis or pyelonephritis. Ultrasound can also be used to detect the presence of normal ureteral jets as they empty into the bladder. Endoscopy can also be used to help identify the site of the ectopic ureteral opening.

When the clinical history and age of the dog makes a diagnosis very likely, some circumvention of the diagnostic pathway may occur. In these cases, a focused urinary tract ultrasound will be peformed to detect any concurrent upper urinary tract structural abnormalities such as renal dysplasia. The patient then moves to cystoscopy for confirmation of the ectopic ureter. This pathway can provide a considerable cost saving, because if ectopic ureters are confirmed during this diagnostic investigation, then cytoscopic laser ablation (CLA) can be performed at the time of cystoscopy.

What treatments are available for ectopic ureters?

Anatomical correction is the treatment of choice for ectopic ureter, with a new opening made at the correct location in the bladder. Correction should be performed as soon as possible to limit the potential for secondary abnormalities (e.g. hydroureter, hydronephrosis) to develop.

Traditional surgical re-implantation of ectopic ureters was associated with various complications (reports of around 25%) including but not limited to stricture formation and development of uroabdomen. The continence rate following surgical reimplantation was between 39-75%, although this success improved with additional medial management. 

Because the vast majority of cases (85-90% in some studies) are intramural meaning the ureter enters the bladder in a normal location before tunneling within the submucosa and opening in the urethra. This makes them very amenable to management by cytoscopic laser ablation (CLA). Cystoscopic laser ablation provides a minimally invasive alternative in both males and females (males being achieved via fluoroscopic guided perineal access). It allows simultaneous diagnosis and treatment on intra-mural ectopic ureters while avoiding the vast majority of complications associated with traditional coeliotomy. 

The procedure is performed on an outpatient basis and involves ablation of the medial wall of the ectopic ureter until it is at the same level as the normal ureter (in unilateral disease) or both are corrected to within the bladder (bilateral disease). At the same time as CLA, laser correction of any paramesonephric remnant that is present as this may contribute to ongoing incontinence or recurrent infections.

How successful is treatment?

A recent study of 30 dogs undergoing CLA showed that 70% of cases were continent immediately following the procedure but this decreased to 57% after six weeks. CLA therefore is associated with similar improvement in continence score when compared to surgical reimplantation. Following CLA if the patient is not 100% continent then medication for concurrent USMI, injectable urethral bulking agents and hydraulic occluders can be considered. 

Very rarely, nephrectomy may be necessary if chronic infection, or end-stage renal disease is present. Pre-operative assessment of renal function is essential to ensure that nephrectomy will not compromise the patient.

What care is required after surgery?

If urinary incontinence persists following surgery, enquiry should be made as to whether the nature of the ‘incontinence’ has changed. Appropriate investigations should be performed to identify a probable cause of the incontinence, with consideration for the differential diagnoses as outlined above. In dogs in which USMI has been identified, a variety of surgical techniques can be considered, but this is usually delayed until after the first oestral season. Pharmacologic management with a sympathomimetic agent may be necessary to improve sphincteric control in the interim.