Ectopic Ureterocele in a Male Dog: A Case Report and Review of Surgical Management

Introduction

A ureterocele is defined as a cystic dilatation of the intravesicular submucosal segment of the distal ureter.¹ Ureteroceles have been commonly reported in humans.² In children, the incidence of ureterocele is as high as one in 500, although the incidence of clinically significant ureterocele in children is reported to be one in 5000 to 12,000.^2,3 Reports of ureteroceles in small animals are few. Twelve case reports in dogs and a single case report in a cat have been published between 1971 and 2002.^1,4–15 A further five cases have been documented in the veterinary literature.¹⁶

Although diagnosed infrequently, clinical signs associated with ureteroceles in dogs may include dysuria, stranguria, pollakiuria, and urinary incontinence.¹⁷ The presence of ureteroceles in male dogs has been described in three cases. Two dogs were Siberian huskies with intravesical ureteroceles, and the third was a Labrador retriever that developed an ectopic ureterocele secondary to surgical correction of a right ectopic ureter.^6,8,12 To the authors’ knowledge, there are no reported cases of congenital ectopic ureteroceles in male dogs.

Ureteronephrectomy, transurethral endoscopic incision, neoureterocystostomy, and ureterocelectomy are all previously reported surgical techniques used to manage ectopic ureteroceles in dogs.^{4,5,7–9,13,15,16} Omentalization is the surgical application of omental grafts, which utilize the immunogenic, angiogenic, adhesive, and lymphatic properties of the omentum to fill dead space, induce vascularization, enhance physiological drainage, provide support for grafted tissues, and adhere to and reinforce other organs during healing.^18,24,25 Although the use of omentum to treat ectopic ureteroceles in dogs has not previously been reported, its application for abdominal, urogenital, thoracic, and reconstructive surgery has been described.^18–26 This report describes the use of neoureterocystostomy and ureterocele omentalization for the surgical treatment of a young, male dog with urinary incontinence associated with a congenital ectopic ureterocele. Neoureterocystostomy and ureterocele omentalization failed to correct the urinary incontinence, and a second surgical procedure to perform partial ureterocelectomy was necessary before urinary incontinence resolved.

Case Report

A 16-week-old, male border terrier was presented for investigation and treatment of urinary incontinence that had been present from 6 weeks of age. The dog dribbled urine continuously, which was most noticeable when the dog was asleep. Voluntary urination was considered normal, and there was no stranguria, dysuria, or hematuria. On physical examination, penile glandular hypospadia was present, and persistent dribbling of urine was evident. A serum biochemical profile demonstrated normal blood urea nitrogen (14.6 mg/dL, reference range 4.8 to 21 mg/dL), creatinine (0.98 mg/dL, reference range 0.45 to 1.5 mg/dL), total protein (5.9 g/dL, reference range 5.8 to 7.3 g/dL), potassium (4.2 mEq/L, reference range 3.6 to 5.6 mEq/L), sodium (146 mEq/L, reference range 139 to 154 mEq/L), and phosphorus (3.0 mg/dL, reference range 2.7 to 6.2 mg/dL). Urine analysis was normal. Urine specific gravity was 1.022. No bacteria were cultured from a cystocentesis sample of urine.

Intravenous (IV) urography was performed under general anesthesia. Diuresis was maintained by administration of IV lactated Ringer’s solution^a at 10 mL/kg per hour. Initially a pneumocystogram was performed by inflating the bladder with 50 mL of carbon dioxide through a 6-French urinary catheter.^b This was followed by an IV injection (600 mg iodine/kg) of iothalamic acid.^c Ventrodorsal abdominal radiographs were taken at 2 and 5 minutes postinjection and were followed by right lateral and oblique abdominal radiographs at 10 and 15 minutes.

On pneumocystogram, the bladder appearance and location were normal. A radiolucent, spherical structure was evident immediately caudal to the bladder neck at the pelvic inlet. Intravenous urography demonstrated mild dilatation of the distal third portion of the right ureter. The right kidney, renal pelvis, and proximal ureter were radiographically normal. A well-circumscribed, spherical structure (approximately 20 × 25 mm in diameter) that filled with contrast material was present caudal to the bladder neck [Figure 1]. Fluoroscopy confirmed a direct communication of the spherical structure with both the distal part of the right ureter and proximal urethra. The left kidney, ureter, and ureterovesical junction were normal. These radiographic features were highly suggestive of a right extraluminal ectopic ureter and ectopic ureterocele.

After routine surgical preparation, a ventral midline celiotomy was performed. Cranial traction was applied to the bladder using stay sutures to improve exposure of the bladder neck and prostate. A combined ventral cystotomy and proximal urethrotomy was performed, extending caudally into the prostatic urethra. Multiple openings in the dorsal wall of the prostatic urethra were found to communicate directly with the ureterocele [Figure 2]. The right ectopic ureter was ligated at the level of the bladder neck with transfixing and circumferential 1.5 metric polypropylene^d sutures. A neoureterocystostomy was created midway between the trigone and apex of the bladder on the right side. The spatulated end of the ureter was sutured to the bladder mucosa using 1 metric poliglecaprone^e in a simple continuous suture pattern. The openings between the ureterocele and prostatic urethra were excised, and the edges of the urethral mucosa were apposed with 1 metric poliglecaprone in a simple continuous suture pattern. A stab incision through the wall of the ureterocele was made from the serosal surface and omentum packed into the cavity, similar to that described for prostatic omentalization.²⁵ The urethra and cystotomy were repaired with 1 metric poliglecaprone in a simple continuous suture pattern, and the abdomen was lavaged and closed routinely. A 6-French Foley^f urinary catheter was advanced through the urethra into the bladder at the end of surgery and was connected to a closed-collection system. Postoperative analgesia was provided by buprenorphine^g (15 μg/kg IV q 8 hours) and carprofen^h (2 mg/kg per os [PO] q 12 hours). The urinary catheter was removed 36 hours after surgery. At the time of discharge 5 days after surgery, the dog was urinating voluntarily and had no signs of incontinence or stranguria.

The owner reported no urinary incontinence for 3 weeks, but then the incontinence recurred. A retrograde positive-contrast urethrogram was performed under sedation with medetomidineⁱ (10 μg/kg IV) 6 weeks after the initial surgery. Iothalamic acid (10 mL) injected through a 6-French urinary catheter showed persistence of the ureterocele [Figure 3]. Ultrasonography of the bladder identified the reimplanted right ureter, and color-flow Doppler ultrasonography confirmed normal ejection of urine. On ultrasonography, the ureterocele was seen as a hypoechoic structure extending caudal to the bladder neck, with a narrow communication to the prostatic urethra.

A second ventral midline celiotomy was performed. The ectopic ureterocele was identified in the same position as before. Omentum was adhered to the outside surface of the ureterocele. A combined cystotomy and urethrotomy was performed as described previously. The previous surgical repair of the dorsal wall of the urethra had dehisced completely, and the ureterocele was in direct communication with the prostatic urethra. A small amount of omentum was still located within the lateral aspect of the ureterocele. The edges of the deficit in the dorsal wall of the urethra were excised. The dorsolateral wall of the ureterocele was brought through the opening and partially excised (ureterocelectomy). The deficit in the dorsal wall of the prostatic urethra was reconstructed with a flap created from the lateral ureterocele wall sutured to the axial border of the urethral opening with a full-thickness, 1 metric poliglecaprone simple continuous suture [Figure 4]. Complete excision of the dorsal portion of the ureterocele was not performed, in order to minimize iatrogenic damage to the neural and vascular structures dorsal to the prostate, including the pelvic and prostatic plexus, prostatic and urethral veins, and branches of the prostatic artery (caudal vesicular artery and artery of the ductus deferens).²⁷ The ureterocele remnant was omentalized using a technique similar to that described for partial resection and omentalization of prostatic retention cysts in dogs.²⁴ Urethral patency was checked by antegrade and retrograde urethral catheterization. Routine closure of the cystotomy, urethrotomy, and celiotomy was performed as described previously.

Postoperatively, the dog had signs of stranguria. To ensure patency of the proximal lumen of the urethra, an indwelling, silicone-coated latex, 6-French Foley urinary catheter attached to a closed-collection system was inserted into the bladder and maintained for 1 week. Daily cytology of urine sediment was performed to assess for iatrogenic urinary tract infection. The urinary catheter was removed 1 week after surgery, and by the 10th postoperative day the dog was continent and capable of passing continuous streams of urine.

One month after the second surgery, the dog had no signs of urinary incontinence, stranguria, or dysuria. Follow-up ultrasonography showed resolution of the ureterocele. The penile glandular hypospadia was surgically corrected by preputial reconstruction when the dog was 7 months old, at which stage the dog remained clinically normal.²⁸

Discussion

Ureteroceles are defined as cystic dilatations of the intravesicular, submucosal segment of the distal ureter.¹ Dysembryogenesis of the ureteral bud is most likely involved in the etiology, but no single hypothesis has yet been formulated that completely explains all aspects of ureterocele formation.^29–31 The classification of ureteroceles in both human and veterinary literature is unclear. Ureteroceles have been categorized in a variety of ways, based on location, morphology, and the presence of other associated anatomical abnormalities.^1,14,32 In humans, ureteroceles are most commonly associated with a duplex kidney (i.e., a kidney that can be divided into upper and lower poles, each drained by a separate renal pelvis and associated ureter).³³ None of the reported cases of ureteroceles in dogs described the presence of a duplex kidney, and there was no gross evidence of renal duplication in the current case.^1,4–16 Single-system ureteroceles (i.e., ureteroceles associated with a kidney having only one renal pelvis and ureter) appear to predominate in animals; in humans, single-system ureteroceles are rare.³⁴

The Committee on Terminology, Nomenclature, and Classification of the Section of Urology of the American Academy of Pediatrics introduced standardized terms to classify human ureteroceles as either intravesical or ectopic.³⁵ Intravesical ureteroceles are defined as cystic dilatations of the ureter in the submucosa of the bladder wall, which are contained entirely within the bladder, and have an orifice opening into the bladder in the region of the trigone.³⁵ If any portion of the ureterocele is situated permanently at the bladder neck or urethra, regardless of the position of the orifice, the ureterocele is termed ectopic.³⁵ This classification system was used to define the ureterocele in the case reported here, and it has also been used previously to classify ureteroceles in dogs.¹⁷ Other classification systems adapted from humans have been described in the veterinary literature and include abnormalities that may be seen concurrently with ureteroceles, such as hydroureter, hydronephrosis, and chronic renal disease.^14,32 Application of this classification system to previously reported cases of canine ureteroceles suggests that it might also be predictive of response to surgical intervention, with outcome being related to the severity of concurrent abnormalities.¹⁴ The ureterocele presented in this report was associated with an ectopic, right ureter that opened into the prostatic urethra, and therefore was classified as an ectopic ureterocele. This report describes the management of a congenital ectopic ureterocele in a male dog.

Of the previously reported cases in dogs, ureteroceles appear to occur most frequently in females (ratio 3.5:1).^1,4–16 Thirteen were classified as ectopic, and six were intravesical.^{1,4–10,12–16} Ectopic ureteroceles associated with duplex kidneys have not been reported in dogs, and as such, the upper-pole heminephrectomy commonly used to manage human ectopic ureteroceles is not indicated.³⁶ Previously reported surgical techniques used in dogs to manage ectopic ureteroceles include transurethral endoscopic incision, ureteronephrectomy, ureterocelectomy, and neoureterocystostomy.^{4,5,7–9,13,15,16}

Following neoureterocystostomy in the dog reported here, the orifice of the ureterocele was identified, and primary closure of the urethral mucosa was performed. The ureterocele was then omentalized through a stab incision made from the serosal surface of the ureterocele, similar to that described for prostatic omentalization.²⁵ The rationale for ureterocele omentalization was based on its ability to obliterate dead space within cavitated lesions, provide physiological drainage, enhance vascularization, and promote adhesion formation that would provide a seal and help contribute to the strength of the mucosal repair.^18,24,25 Although the use of omentum has not been described for the treatment of ureteroceles in dogs, it has successfully been used in the reinforcement of gastrointestinal anastomosis; reconstruction of chronic, nonhealing wounds; treatment of pancreatic, prostatic, uterine stump, and lymph node cysts and abscess; and as a physiological drain for the treatment of idiopathic chylothorax.^18–26

Ureterocelectomy was not performed during the initial surgery, as complete resection would have required extensive dissection dorsal to the prostate, potentially resulting in iatrogenic damage to the neural and vascular structures in this region.²⁷ The prostatic plexus forms the middle portion of the pelvic plexus, derived from the pelvic and hypogastric nerves, and penetrates the dorsolateral capsule of the gland.²⁷ Sympathetic innervation is supplied to the detrusor muscle and smooth muscle of the urethra.³⁷ Stimulation of alpha-adrenergic fibers results in contraction of the smooth muscle in the trigone and proximal urethra and the formation of a functional internal urethral sphincter.³⁷ Compromise to these neural structures caused by extensive surgery could potentially induce or exacerbate postoperative urinary incontinence.²⁴ Ureterocele omentalization was therefore considered a novel alternative to complete ureterocelectomy, as it required less surgical exposure of the ureterocele, thus minimizing trauma to the surrounding tissues.

Persistence of urinary incontinence postoperatively was attributed to failure of the urethral mucosal repair and persistence of the ureterocele cavity. Dehiscence was thought to arise from failure to incorporate all layers of the urethral wall within the sutured repair. The submucosa has been well documented as the supporting layer of the gastrointestinal tract and is considered to be the only layer that supplies significant mechanical strength following intestinal anastomosis.^38,39 The submucosa is therefore surgically important as a key structure to be sutured.³⁸ By definition, a ureterocele is a dilatation of the submucosal portion of the distal ureter. Although histopathology of the resected tissue was not performed in this case, it was hypothesized that the submucosa of the urethral repair may have been absent or poorly developed, resulting in a mechanically weak repair. Omentalization of the ureterocele was ineffective at providing a seal and reinforcing the outer layer of the urethral mucosal repair. Adhesion formation was poor, and only a small amount of omentum was observed within the ureterocele at the second surgery. Failure to suture the omentum directly to the serosal layer of the mucosal repair and inadequate packing of the ureterocele with omentum may have contributed to failure of ureterocele omentalization, and omentalization may be an ineffective method of obliterating ureteroceles. Disruption of the urethral sphincter by the distended ureterocele may also have been a contributing factor to the recurrence of incontinence following surgery.

A second surgery was necessary to reconstruct the prostatic urethra and perform partial ureterocelectomy. Complete resection of the ureterocele was again not performed because of the risk of neural or vascular compromise, as previously discussed. Partial resection of the ureterocele was therefore considered preferable to complete ureterocelectomy. A full-thickness flap created from the wall of the ureterocele was used to reconstruct the deficit of the dorsal urethral wall, and full-thickness sutures were placed to ensure incorporation of the submucosa in order to maximize mechanical strength of the repair. Omentum was again used to support the repair and provide continued physiological drainage, similar to that described for partial resection and omentalization of prostatic retention cysts in dogs.²⁴ The greater exposure achieved by partial resection of the ureterocele allowed 1) the placement of sutures to secure the omentum to the outer layer of the urethral repair and 2) remnants of the ureterocele in order to enhance adhesion formation.

In five previously reported cases of ectopic ureteroceles in dogs, in which neoureterocystostomy was performed without ureterocelectomy, urinary incontinence failed to resolve in two dogs.^5,16 Similarly, urinary incontinence and recurrent urinary tract infections have been reported in one dog following ureteronephrectomy for the treatment of an ectopic ureterocele.¹⁵ Dogs with ectopic ureters and transplanted ureters do not have normal flap valves at the junction of the ureter with the bladder, and are at increased risk for urinary tract infections. The persistent urinary incontinence in the case reported here was attributed to failure to resect the ureterocele, and it resolved following a second surgery to perform ureterocelectomy. Two previously reported cases of dogs that had neoureterocystostomy combined with ureterocelectomy (either at the time of the initial surgery or during a second procedure) had resolution of urinary incontinence postoperatively.^9,13 These findings and the findings from the case reported here suggest that there is a greater risk of recurrence of clinical signs following neoureterocystostomy or ureteronephrectomy for the surgical management of ectopic ureteroceles in dogs when ureterocelectomy is not performed or fails.^{4,5,7–9,13,15,16}

Conclusion

Neoureterocystostomy and omentalization of a ureterocele in a male dog failed to resolve the dog’s urinary incontinence. Partial resection of the ureterocele and reconstruction of the proximal urethra resolved the clinical signs. Ureterocele omentalization cannot be recommended as an alternative to ureterocelectomy, but it may be a useful adjunctive technique when only partial resection of the ureterocele is possible.

Acknowledgments

The authors thank Kathryn Pratschke for her help with the follow-up evaluations.