Ectopic Ureters-pathophysiology and Genetics

Definition
Congenital malformation of the uretero-vesical junction (UVJ) with termination of the ureter at a site other than the bladder trigone area

Embryology
Formation of the nephric duct is one of the earliest events in urinary tract formation, establishing a primary connection between the upper and lower urinary tract. The ureteric bud sprouts from the caudal nephric duct. While the proximal part of the ureteric bud differentiates into the collecting system, the distal part elongates and differentiates into the non-branched ureter. The ureter is brought into contact with the bladder epithelium by ureter maturation, a process which is depending on apoptotic elimination of the most caudal segment of the nephric duct. The caudal ureter undergoes apoptosis forming a new ureteral orifice in the bladder primordium. Subsequent expansion of the bladder moves the ureter orifice which is now fused with epithelium to its final position in the bladder (Literature review in Chia et al., 2011; Paces-Fessy et al., 2012). It is thought that a failure in ureteric sprouting and/or ureter maturation results in the most common ureteral abnormality in dogs, when the ureters terminate into the bladder neck or proximal urethra (Owen 1973).

Epidemiology
In 1984 data was published by Howard Hayes about 228 case records collected from 15 North American veterinary teaching hospitals over a 17 year period. Of these 228 cases of ectopic ureters diagnosed and treated only 11 were males. Among more than 32 affected breeds 6 breeds were represented significantly higher than expected by chance, these were Siberian Husky, Newfoundland, bulldog, West Highland white terrier, fox terrier and toy poodles. A study from the UK published in 2000 (Holt, Thrusfield and Moore) reported an increased prevalence also in Border terriers, Briards, Golden and Labrador Retrievers, Griffons and Skye terriers. It was also noted that many oft he affected cases were closely related to each other (Holt , Gibbs and Peason 1982).  [...]