Ectopic ureters in Dogs

Is a relatively common condition which primarily affects young dogs. Clinical signs arise from the positioning of the ureteral opening in an abnormal position. Normally, the ureters open into the trigone of the bladder. In these patients, the ureteral opening is distal to the sphincter mechanism resulting in incontinence. The ureter may travel within the wall of the bladder and urethra to its abnormal opening (intramural ectopic ureter) or outside the wall of the bladder and urethra (extramural ectopic ureter). The differentiation of the path that the ureter travels is important because it affects the treatment options.

Females are much more commonly affected than males, although it can still happen in either gender. Puppies are most commonly presented and diagnosis occurs at an average age of 9 months. Several breeds are predisposed, although we most frequently see it in Golden retrievers.

Patients usually present with chronic dribbling since birth. Often, bedding is found to be soaked with urine in the morning. Dogs may still void normal volumes of urine, either because of the presence of a normal ureter on one side emptying into the bladder or because of pooling of urine in the vagina. Incontinence can be exacerbated by urinary tract infection and this should always be screened-for and treated appropriately. In males with ectopic ureters, incontinence is much more intermittent and inconsistent in nature.

These patients often smell of urine and may have urine scalding around the vulva. Otherwise, they are often normal.

Urinalysis should be performed in any dog presenting for urinary incontinence to rule out a urinary tract infection. Routine haematology and serum biochemistry should be performed to rule out metabolic conditions which may be causing polyuria/polydypsia.

Definitive diagnostic testing involves an excretory urogram using either flat-film radiographs or computed tomography, with computed tomography being more sensitive. Iohexal (240 mg/ml) is used at a dose of 2-3 mls/Kg. If there is evidence of renal insufficiency, a reduced dose of 0.5 – 1.0 mls/Kg is used. Scans or radiographs are performed at regular intervals after injection of the contrast at time zero, 1 minute, 5 minutes, 10 minutes and 20 minutes.

If flat-film radiographs are being used, the patient should be fasted for 36 hours prior to the procedure to ensure that the bowels are evacuated and lateral and ventrodorsal views should be taken. If computed tomography is being used, these issues are not relevant.

The appearance and position of the ureteral openings are assessed noting that up to 70% of ectopic ureters can be bilateral. Many patients will have hydroureter or hydronephrosis of the affected side. Other conditions may also be present including ureterocoeles and bladder hypoplasia. The function of each kidney should be noted because a severely abnormal kidney with hydronephrosis and hydroureter may need to be removed rather than repositioning the ureteral opening.

Primary urethral sphincter incompetence can be present in about 50% of patients with ectopic ureters, so urethral pressure profilometry can be performed to assess the likelihood of success of repair of the ectopic ureter.

Cystourethroscopy is also very helpful on making a diagnosis. The ureteral opening can often be seen in its abnormal position.

Treatment of confirmed ectopic ureters is always surgical although presurgical management of urinary tract infections and renal dysfunction should be performed.

Surgical correction involves creating a new opening of the ureter in the correct position proximal to the sphincter mechanism.

Extramural ectopic ureters are ligated and transected at the entrance to the urethra. They are reimplanted in the urinary bladder.

Intramural ectopic ureters are treated by creating a new opening from the ureter into the bladder and ligating the distal continuation of the ureter.

Alternatively, the ureter can be identified using urethroscopy and the septum between the ureter and the urethra ablated using scissors or laser. This procedure has been highly successful in the management of ectopic ureters and is minimally invasive with patients suffering almost no morbidity associated with the procedure.

Around 50% of dogs having surgical correction of ectopic ureters are still incontinent due to primary urethral sphincter mechanism incompetence. Most of these can be effectively treated medically, but note that some dogs must be on medications (propalin or oestrogen) for life and incontinence may get worse after ovariectomy. There are also surgical procedures to address primary urethral sphincter incompetence including culposuspension and prosthetic urethral sphincter mechanisms.