Ureteral ectopia is a congenital abnormality in which one or both of the ureteral orifices terminate at a position other than the trigone of the urinary bladder. Entlebucher Mountain Dogs have recently been recognized to have a breed predisposition for ectopic ureters. A screening and breeding program has been established in Switzerland, Germany, Austria and the Netherlands. In a multicentric study, 529 Entlebucher Mountain Dogs were examined with ultrasound (n = 519), contrast CT scan (n = 37), cystoscopy (n = 9), or necroscopy (n = 2). Both ureteral openings at the normal anatomical position were found in 33%. At least one ureter terminated at an intravesical ectopic position (IVEU) in 46% and at an extravesical ectopic position (EVEU) in 21%. Of the Entlebuchers with EVEU 27% were incontinent compared to only 3% of IVEU. Of all animals examined 3% had hydronephrosis, one-third of which were clinically unapparent.

With these data a complex segregation analysis was performed in order to look at the mode of inheritance. For the analysis, data of 16 litters with all family members diagnosed were used. At the moment the Major Gene model explained the data better than all other models tested. The heritable base of ureteral ectopia was furthermore supported by the decline of the incidence after breeding restrictions applied in 2008.