Role of Urodynamic Investigation

The incidence of concurrent ectopic ureter(s) and urethral sphincter mechanism incompetence (USMI) is unknown.

Typically, dogs with USMI have a decreased urethral tone, characterized by a lower maximal urethral closure pressure (MUCP) and a shorter functional urethral length. Most of these dogs also show a pelvic bladder with a short and wide urethra.

Previous studies have suggested that dogs with ureteral ectopia may have concurrent USMI as low MUCP values were demonstrated on preoperative urethral pressure profiles (UPPs). Furthermore, pelvic bladders and short urethras have been reported in 27% to 47% of dogs affected with ectopic ureters.

Finally, in case of persistent postoperative incontinence after surgical correction of ectopic ureter(s), the use of drugs such as a-adrenergic agents may be beneficial, indicating that these animals likely have functional abnormalities of the bladder neck and urethra.

The question arises on whether or not USMI is present concurrently with ectopic ureters or if the intramural part of the ectopic ureter is interfering with normal urethral function, leading to low MUCP values. Indeed, references are missing of urodynamic data in dogs with ectopic ureters but without USMI.

Another question is whether or not the decreased bladder capacity demonstrated in some dogs preoperatively is a true finding of bladder dysfunction or if it is only the normal consequence of the presence of one or two ectopic ureters, leading to a suboptimal bladder filling volume. Lastly, most of the dogs with ectopic ureters are presented with urinary tract infections, which can lead to artifacts during urodynamic studies.  [...]