Diagnostic Imaging of Ectopic Ureters: Contrast Radiography, CT or Ultrasound?

Introduction
Ureteral ectopia (UE) is a congenital anomaly of the urinary system where the ureteral orifice is inappropriately positioned (i.e. the bladder neck, urethra, vagina, vestibule or uterus). This is the most common cause of urinary incontinence in juvenile female dogs accounting for over 50% of cases in one study, compared to only 5% of incontinent adult dogs. Although ectopic ureters have been reported in male and female dogs, it seems to occur with greater frequency in female dogs (>20:1), as well as certain breeds (i.e. Siberian Huskies, Newfoundlands, Retrievers [Laborador or Golden], Terriers, and Poodles [miniature and toy]). The most common clinical finding in these dogs is constant or intermittent urinary leaking since birth or weaning, though many dogs present after a period of continence, and are only incontinent in certain positions. Ectopic ureters tunnel either intramurally or extramurally, with over 95% reported to be intramural in dogs. The typical intramural ectopic ureter(s) will enter the distal bladder neck in a relatively normal position but fail to open into the bladder lumen, traversing the urethra to the level of the prostate, vestibule or vagina in the submucosal tissue, where it terminates. Suspected concurrent bladder and/ or urethral functional anomalies, like urethral sphincter mechanism incompetence (USMI), has been reported in 75-89% of female dogs evaluated, though in one study there was no significant difference in outcome after surgery in dogs with or without USMI. Other associated urinary conditions such as urinary tract infections (64%), renal agenesis (5%), renal dysplasia, hydroureter (34-50%) or hydronephrosis (15-27%), short urethras (21%), persistent paramesonephric remnants (83%) and/or vaginal septum or dual vaginas (8%), hormonal imbalances, and ureteroceles have all been reported concurrently. The diagnostic method of choice for evaluating dogs for EU is now considered to be cystoscopy or CT.  [...]