Criteria for Selection of Cases

Medical records of dogs examined at the University of London or the University of Pennsylvania between 1994 and 2004 because of intramural ureteral ectopia were reviewed. Cases were included in the study if ureteral ectopia had been treated surgically with the ligation or resection technique and follow-up information was available. However, cases were excluded if the dog had undergone additional simultaneous surgical procedures for the treatment of urinary incontinence or other urinary tract anomalies. In addition, cases were excluded if long-term follow-up information regarding outcome was not obtained.

Procedures

Data regarding signalment, duration of urinary incontinence prior to surgery, presence of urinary tract infection at the time of initial examination, type of ureteral ectopia (ie, unilateral vs bilateral), surgical technique, and complications were obtained from the medical records. Long-term follow-up information was obtained from the medical record or through use of a questionnaire administered to the owners by telephone. Information gathered included any long-term complications of surgery, the incidence and severity of urinary incontinence, the presence of recurrent urinary tract infections, whether medical treatment was used for urinary incontinence, and the owner's perception of the outcome of surgery.

Surgical procedures—In all dogs, a caudoventral midline laparotomy and ventral longitudinal cystotomy and urethrotomy were performed. For the ligation technique, the bladder mucosa and ectopic ureter were incised parallel to the longitudinal axis of the ureter in the area of the bladder trigone. Synthetic absorbable suture material was then used to suture the edges of the ureter to the bladder mucosa, creating a new ureteral stoma. The distal ureteral segment was catheterized in an antegrade fashion via the new ureteral stoma and double ligated with polydioxanone, polypropylene, or chromic gut suture material or some combination of these. These ligatures were tied either on the external surface of the bladder or submucosally, depending on the material used.

For the resection technique, the ectopic ureter was catheterized in a retrograde fashion, except that if the opening of the ectopic ureter was too far caudal to be seen, an incision was made through the urethral mucosa into the ectopic ureter as far caudally as possible, and the ectopic ureter was catheterized via this incision. The intramural portion of the ectopic ureter was dissected free from the surrounding submucosal tissues, beginning distally and continuing to the region of the bladder trigone. The resultant submucosal defect was closed with synthetic absorbable suture material. The distal ureteral segment was then transected, leaving sufficient tissue to allow creation of a new ureteral stoma. In some dogs, pubic symphysiotomy was performed to allow removal of the entire distal segment of the ectopic ureter. In other dogs in which the entire distal segment could not be examined without pubic symphysiotomy, the distal segment was excised to the level of the pubis. For both techniques, the cystotomy and urethrotomy were closed in a single layer with an appositional suture pattern of synthetic absorbable suture material. The laparotomy incision was closed routinely.

Statistical analysis—Data are given as mean ± SD. Plots of the continuous data were examined, and no major departures from normality were observed. The Student t test was used to compare values for continuous data between dogs that underwent ligation and dogs that underwent resection; the Fisher exact test or contingency table analysis was used to compare values for categorical data between groups. All analyses were conducted with standard software.^a Values of P < 0.05 were considered significant.

Results

Thirty-six dogs met the inclusion criteria. In 21, the resection technique had been used for correction of ureteral ectopia, and in 15, the ligation technique had been used. No significant differences were detected between surgical groups in regard to signalment parameters, clinical signs, or type of ectopia (ie, unilateral vs bilateral).

The 21 dogs in the resection group consisted of 12 sexually intact females, 5 neutered females, 1 sexually intact male, and 3 neutered males. There were 12 Labrador Retrievers, 4 Golden Retrievers, 2 Siberian Huskies, 2 Newfoundlands, and 1 Irish setter. Mean ± SD age was 16 ± 18 months (range, 2 to 64 months). Mean weight was 25.4 ± 13.3 kg (55.9 ± 29 lb; range, 6 to 63.5 kg [13.2 to 139.7 lb]). Mean duration of clinical signs of incontinence was 14 ± 18 months (range, 1 to 64 months). Thirteen of the 21 (62%) dogs had a urinary tract infection at the time of initial examination. Eleven (52%) had unilateral ectopia, and 10 (48%) had bilateral ectopia. In 3 dogs (5 to 8 months old at the time of surgery), pubic symphysiotomy was performed to facilitate removal of the distal portion of the ectopic ureter. In the 18 other dogs, pubic symphysiotomy was not necessary or not performed; it was unclear from the surgical reports how many of these dogs had a residual distal segment of the ectopic ureter that remained after surgery.

The 15 dogs in the ligation group consisted of 12 sexually intact females, 1 neutered female, 1 sexually intact male, and 1 neutered male. There were 8 Labrador Retrievers, 3 Golden Retrievers, 3 purebred dogs of other breeds, and 1 mixed-breed dog. Mean ± SD age was 16 ± 22 months (range, 3 to 84 months). Mean weight was 21.4 ± 9 kg (47.1 ± 19.8 lb; range, 5.1 to 40.0 kg [11.2 to 88.0 lb]). Mean duration of clinical signs of incontinence was 9 ± 21 months (range, 0.5 to 84 months). Ten of 14 dogs in this group had a urinary tract infection at the time of initial examination; information regarding urinary tract infection at the time of initial examination was unavailable for the remaining dog. Ten (67%) dogs had unilateral ectopia, and 5 (33%) had bilateral ectopia.

Surgical complications occurred in 1 dog in the resection group and 1 dog in the ligation group. In both dogs, the cystotomy wound dehisced, requiring resuturing within 24 hours after the initial surgery. The dog in the resection group developed septic peritonitis. Both dogs recovered fully from these complications.

Long-term follow-up information was obtained through telephone conversations with owners of 18 dogs in the resection group and 14 dogs in the ligation group. For the remaining 4 dogs, long-term follow-up information was obtained from the medical records. Thus, for these 4 dogs, information on owner satisfaction was unavailable. In addition, for 2 dogs (1 in each group), information on postoperative urinary tract infections was unavailable.

Mean ± SD follow-up time was 51 ± 32 months (range, 5 to 118 months) for dogs in the resection group and 50 ± 26 months (range, 9 to 109 months) for dogs in the ligation group. Follow-up time was not significantly different between surgical groups. Only 1 dog (resection group) underwent additional surgery for treatment of urinary incontinence following surgery for correction of ureteral ectopia. This dog underwent colposuspension but remained incontinent.

At the time of final follow-up, 15 of 21 (71%) dogs in the resection group and 7 of 14 (50%) dogs in the ligation group reportedly had some degree of urinary incontinence following surgery. Thirteen of 21 (62%) dogs in the resection group and 4 of 14 (29%) dogs in the ligation group received medical treatment for urinary incontinence, including phenylpropanolamine, pseudoephedrine, and diethylstilboestrol, and urinary incontinence resolved with medical treatment in 6 dogs in the resection group and 1 dog in the ligation group. Thus, following combined medical and surgical treatment, 9 of 21 (43%) dogs in the resection group and 6 of 14 (43%) dogs in the ligation group had urinary incontinence. Proportions of dogs with urinary incontinence were not significantly different between surgical groups, regardless of whether results following medical treatment were or were not included. Proportions of dogs receiving medical treatment for incontinence after surgery was not significantly (P = 0.055) different between groups, although the P value was close to the cutoff for significance. All 3 dogs that underwent pubic symphysiotomy remained incontinent after surgery. All 3 were treated with phenylpropanolamine, which resolved the incontinence in 1 of the 3.

Three of 20 (15%) dogs in the resection group and 4 of 14 (29%) dogs in the ligation group reportedly had > 1 episode of urinary tract infection following surgery. These proportions were not significantly different.

The outcome of surgery was judged to be excellent by the owners of 10 of 18 (56%) dogs in the resection group and 9 of 14 (64%) dogs in the ligation group. Again, these proportions were not significantly different.

Discussion

Results of the present study suggest that although most owners of dogs that undergo surgery for treatment of ureteral ectopia consider the outcome of surgery to be excellent, substantial proportions of dogs will continue to have urinary incontinence and recurrent urinary tract infections after surgery. In addition, we did not identify any significant differences in regard to prevalence of surgical complications, proportions of dogs with urinary incontinence or recurrent urinary tract infections after surgery, or owner satisfaction rate between dogs in which the resection technique was used and dogs in which the ligation technique was used. Therefore, our findings do not provide any evidence to support the hypothesis that the resection technique is superior to the ligation technique for management of dogs with intramural ureteral ectopia.

That said, findings of the present study must be interpreted with caution, as there were several limitations to the study. In particular, low case numbers were included in each group, mainly because of the infrequent nature of this disease and the inability to obtain long-term follow-up information in some cases. For this reason, it is possible that true differences between groups went undetected (ie, type II error). In addition, cases included in the present study involved dogs examined over a long period at 2 institutions. Surgical procedures were performed by a variety of surgeons and neither surgical technique was standardized, which could have led to variations in outcome. Inconsistencies in diagnostic testing meant that in many cases, the location and nature of the ureteral openings were not always known. Finally, individual cases were not randomly assigned to surgical groups, leading to potential bias that could have caused variability in outcome between treatment groups, masking any differences between surgical techniques.

In the present study, although the proportion of dogs in the resection group that received medical treatment for urinary incontinence after surgery (13/21 [62%]) was not significantly different from the proportion of dogs in the ligation group that did (4/14 [29%]), the P value was close to the cutoff for significance (P = 0.055). However, even if a significant difference had been found, it would not be clear whether this would have reflected a higher rate of postoperative urinary incontinence among dogs in the resection group or a greater response rate to medical treatment for dogs in this group. Concerns have been raised that resection of the distal segment of an ectopic ureter may result in damage to the urethral sphincter mechanism as a result of edema, inflammation, or secondary fibrosis, negating any potential benefits on urethral sphincter function associated with removing mechanical interference caused by the distal segment of the ectopic ureter. Prospective studies involving follow-up cystoscopy and histologic examination of the urethral sphincter would help to clarify this point. It has been proposed that removal of the distal segment results in a more anatomic relationship of the circular bands of smooth muscle in the internal urethral sphincter.^7,8 If this were the case, it could be hypothesized that following such reconstruction, the sphincter may be more likely to respond to medical management. However, additional studies involving pre- and postoperative urodynamic measurements are needed to assess the effect of resection of the distal ureteral segment on function of the urethral sphincter mechanism in dogs with ureteral ectopia.

The proportion of dogs with recurrent urinary tract infections following surgery was not significantly different between surgery groups in the present study. This suggests that retention of the distal segment of the ectopic ureter, as occurs with the ligation technique, does not significantly increase the incidence of postoperative urinary tract infections. It has been suggested that recurrent urinary tract infections may occur following use of the ligation technique because the retained distal segment of the ectopic ureter remains as a blind-ending sac in the urethral wall. However, our data do not support this hypothesis.

In the present study, urinary incontinence persisted in 22 of 35 (63%) dogs following surgical correction of ureteral ectopia, regardless of the surgical technique used. This is comparable to results of previous studies,^2–4,11,12 which have reported postoperative incontinence rates of 42% to 78%. Proposed causes of persistent urinary incontinence include concurrent urethral sphincter mechanism incompetence, hypoplasia of the urinary bladder, vesicoureteral reflux, hormonal imbalances, neurogenic abnormalities, persistent urinary tract infection, and inadequate surgery.^1,3,7,8,12 Seven of 17 dogs in the present study in which medical treatment was administered after surgery because of urinary incontinence responded, which was similar to response rates reported previously.^4,12,13

The proportion of dogs in the present study with urinary incontinence after surgery that responded to medical treatment suggests that in at least some dogs, urethral sphincter mechanism incompetence was present as a preexisting condition or as a result of surgery.¹³ Similarly, previous studies^3,13,14 have suggested that dogs with ureteral ectopia may have concurrent urethral sphincter mechanism incompetence. In 1 study,³ for instance, 47 of 174 (27%) dogs with ureteral ectopia had radiographic evidence of an intrapelvic bladder and short urethra prior to surgery. Such findings are considered to be consistent with urethral sphincter mechanism incompetence, although the presence of these radiographic findings was not significantly associated with postoperative urinary incontinence in that study.³ Moreover, the incidence of postoperative incontinence in that study³ (42%) was substantially higher than the percentage of dogs with preoperative radiographic findings consistent with urethral sphincter mechanism incompetence (27%), suggesting that there are other causes for urinary incontinence in dogs with ureteral ectopia.

Urethral pressure profilometry has the potential to provide information on urethral sphincter function, and a previous study¹² found that 6 of 9 dogs with ureteral ectopia had abnormal urethral pressure profiles, consistent with urethral sphincter mechanism incompetence. Dogs that remained incontinent after surgical correction of ureteral ectopia had significantly lower maximal urethral pressures, maximal urethral closure pressures, and functional profile areas than did those that became continent after surgery. Unfortunately, results of urethral pressure profilometry cannot be used to predict which dogs with ureteral ectopia will remain incontinent following surgery.¹⁵ Thus, the clinical utility of urethral pressure profilometry is still unclear.

It has previously been suggested that in dogs with ureteral ectopia, removal of the distal ureteral segment and reconstruction of the urethra and trigone can result in resolution of urinary incontinence.^7,8 Results of the present study, however, do not support this claim. It is possible that resection of the distal ureteral segment is simply not effective in increasing resting urethral tone such that urethral pressure is greater than intravesicular pressure and continence is achieved. Alternatively, it is also possible that we did not detect an effect because, in some dogs, the entire distal ureteral segment was not removed. Unfortunately, whether the entire distal ureteral segment was removed in dogs treated with the resection technique was not consistently recorded in the medical records. Therefore, we were unable to compare outcomes for dogs with partial versus complete resection. However, 3 dogs in the present study underwent pubic symphysiotomy, which was performed to allow removal of the entire distal ureteral segment, and all 3 remained incontinent following surgery.

In female dogs, smooth muscle is thought to provide the greatest contribution to resting urethral tone,¹⁶ and a detailed anatomic study¹⁷ showed that most of the urethral smooth muscle in healthy female dogs is located in the trigone and proximal portion of the urethra. This coincides with the observation that static urethral pressure is maximal in the proximal portion of the urethra in clinically normal dogs.¹⁸ We believe, therefore, that in dogs with ureteral ectopia, the portion of distal ureteral segment that lies within the internal urethral sphincter is resectable without recourse to pelvic splitting techniques and that inadequate resection is an unlikely explanation for continued urinary incontinence after surgery.

A potential advantage of the resection technique is that recanalization of the distal ureteral segment, which potentially can occur following use of the ligation technique, is prevented. Diagnostic imaging was inconsistently performed in dogs in the present study that remained incontinent after surgery. Thus, it was not possible to determine how frequently recanalization occurred. However, recanalization has been reported previously as a rare complication in dogs undergoing ligation of the distal ureteral segment.³

Future studies of dogs with ureteral ectopia should seek to gain more detailed knowledge of the anatomic and histologic appearance of the genitourinary tract in affected dogs. There is recent evidence to suggest that cystoscopy and contrast-enhanced computed tomography may provide more information regarding the anatomic variations of the genitourinary tract in dogs with ureteral ectopia than do more traditional diagnostic techniques, such as contrast radiography, ultrasonography, and surgical exploration.^19,20 However, there is little, if any, information regarding the histologic appearance of the urogenital tract in dogs with ureteral ectopia. More detailed knowledge of the anatomic and histologic appearance of the genitourinary tract in dogs with ureteral ectopia may provide us with a greater understanding of the functional mechanisms underlying urinary incontinence in these dogs and, thus, allow us to formulate improved techniques, both medical and surgical, for managing these cases.