Anatomical Variations of Ureteral Ectopia in Dogs

Although ectopic ureters (EU) is considered relatively rare in dogs with a reported incidence of .016-.045%, it is the most common cause of urinary incontinence in young female dogs. EU is also recognized as the most common anatomical abnormality associated with urinary incontinence in female dogs of any age group. Clinical symptoms of urinary incontinence associated with EU are variable ranging from mild and intermittent to continuous and severe. Incontinence is often reported to be more severe in recumbent positions, with increased activity and increased water consumption due to swimming, eating snow, drug therapy i.e. steroid administration, etc. Despite many “urban legends,” the severity of urinary incontinence does not dictate whether EU are intramural or extramural, unilateral or bilateral, specific location of the ectopic ureteral orifice(s) nor has it been correlated to treatment outcomes. EU has also been diagnosed as an incidental finding in both male and female dogs with no clinical signs of incontinence or symptoms which are delayed until an advanced age. Canine patients diagnosed with EU are most often juvenile, less than 1 year of age at the time clinical signs of urinary incontinence are recognized. However, studies have shown that time to presentation for diagnosis and treatment may be delayed for various reasons until well after the juvenile period. Delayed-onset urinary incontinence has been reported in 5 of 22 female dogs diagnosed with congenital EU. It is likely that that urinary sphincter mechanism incompetence (USMI) may play a contributing role in some female dogs presenting with delayed-onset urinary incontinence. Female dogs tend to present at a younger age than males. Female dogs are diagnosed with EU at a significantly increased rate compared to males with the exception of a 2012 study describing almost equal distribution. EU may be more common in males than historically appreciated as male dogs may be less likely to have symptoms of incontinence as a consequence of the length of urethra distal to the displaced ureteral orifice. Though EU is often viewed as a simple plumbing “bypass” problem, it is far more complex due to concurrent anatomical anomalies contributing to the embryologic development of the trigone and proximal urethra. EU can be associated with a number of additional structural and functional anomalies which may impact continence including short urethra, low urethral closure pressure, and poorly described abnormalities in the formation of the urethravesicular junction. Abnormalities in the development of the upper urinary tract (single agenesis, renal dysplasia and hypoplasia) are encountered in some dogs as well as the finding of hydronephrosis, hydroureter and ureteral tortuosity. [...]