Urinary Incontinence in a Dog With an Ectopic Ureterocele

Introduction

Urinary incontinence in dogs may be the result of urge incontinence (e.g., secondary to urinary tract infection, urolithiasis); trauma causing loss of innervation of the bladder, urethra, or urethral sphincter; congenital anomalies of the urogenital tract; or estrogen-responsive incontinence in spayed females.¹ Congenital anomalies are among the most common causes of urinary incontinence in young dogs. Diagnosis of the etiology of urinary incontinence is based on historical observations (e.g., constant urine dribbling as opposed to nocturia or urge incontinence), physical examination findings (e.g., distended or small bladder, observation of micturition, obvious pelvic trauma, neurological deficits), urinalysis, imaging of the urinary system, and urethral pressure profilometry. Definitive determination of the cause(s) of urinary incontinence in young dogs usually entails diagnostic imaging of the urinary tract, which may include ultrasonography, excretory urography, positive-contrast vaginography, retrograde urethrography, or a combination of the above.¹

Ectopic ureter is a relatively common cause of urinary incontinence in young dogs. A ureterocele is a congenital abnormality that is defined as a focal dilatation of the distal ureter, usually that portion of the ureter which lies within the bladder wall.² Ureteroceles may form in ureters that open into the bladder at the normal location within the trigone (orthotopic ureterocele), or they may occur in conjunction with ectopic ureter (ectopic ureterocele).² The presence of a ureterocele in conjunction with ectopic ureter has been described previously in four dogs,^3–6 and orthotopic ureterocele has been reported in three other dogs.^7–9 All dogs with ectopic ureterocele exhibited urinary incontinence, and most dogs with ureteroceles also develop chronic urinary tract infection.^3–8 Ureteral transposition⁴ or marsupialization of the ectopic ureterocele into the bladder in conjunction with ligation of the distal continuation of the ureter⁶ have been reported to successfully correct urinary incontinence associated with ectopic ureterocele in dogs.

This report describes the treatment of a young dog with urinary incontinence associated with right-sided ectopic ureterocele, hydroureter, and renal hypoplasia. Removal of the right kidney and ureter failed to correct urinary incontinence in this dog; however, continence was restored after ureterocelectomy.

Case Report

A 7-month-old, female intact English cocker spaniel was examined at the University of Wisconsin Veterinary Medical Teaching Hospital for evaluation of urinary incontinence present since birth. Urinalysis prior to referral had revealed pyuria, bacteruria, and granular casts. The dog was treated with cephalexin. Urinary incontinence persisted despite treatment, and the referring veterinarian suspected a congenital anomaly of the urinary tract.

Physical examination of the perineal area of the dog revealed urine dribbling from the vulva. The bladder was small on abdominal palpation. No other physical abnormalities were noted. Blood and urine were collected for laboratory analysis. Differential blood count and serum biochemistry values were unremarkable. Microscopic hematuria was observed in the urine sediment. General anesthesia was induced, and an excretory urogram was performed. Radiographs made during the excretory urogram revealed hypoplasia of the right kidney, enlargement of the right ureter, and a right ectopic ureterocele that appeared to open into the pelvic urethra [Figure 1]. The bladder neck appeared to be located within the pelvic canal, and compensatory hypertrophy of the left kidney was also apparent on radiographs.

Right ureteronephrectomy was performed in conjunction with ovariohysterectomy. The right ureter was dissected to the level of the bladder, and a ventral cystotomy was performed. The left ureter was catheterized and found to be normal. The right ureter was transected at the point of contact with the bladder, leaving the intramural and ectopic portions of the ureter and the ureterocele intact.

The right ureter and kidney were submitted for histopathology. Approximately one-third of the renal parenchyma was normal, and two-thirds of the renal parenchyma had interstitial fibrosis and lymphocytic infiltration. The ureter was severely dilated and thickened, and histopathological evaluation demonstrated the presence of an outer, fibrous capsule; infiltration of the submucosa by lymphocytes, plasma cells, and neutrophils; and hyperplasia of the urothelium.

After surgery, urinary incontinence persisted. Although urinary incontinence was not constantly present, the owners noted that the perineum was persistently damp; incontinence was particularly noted at night, when the dog lay down, and when the dog was jumping or playing. Treatment with phenylpropanolamine (0.25 mg/kg body weight, q 12 hours per os [PO]) provided slight improvement, but 15 months after surgery, the dog was examined because incontinence was unresponsive to increasing doses of phenylpropanolamine (0.5 to 2.0 mg/kg body weight, q 12 hours PO). Pollakiuria of 6-weeks’ duration and persistent Escherichia coli (E. coli) bacteruria, despite treatment with ampicillin followed by chloramphenicol, were also reported. Analysis of urine sediment revealed mild hematuria, moderate pyuria, and marked bacteruria. Urine culture yielded E. coli and an ∞-hemolytic streptococcus. The E. coli isolate was resistant to ampicillin, piperacillin, and trimethoprim sulfamethoxazole. Both organisms were sensitive to enrofloxacin, and treatment with this antibiotic^a (5 mg/kg body weight, q 12 hours PO) for 8 days was prescribed.

One week later, the dog was anesthetized, and a positive-contrast vaginourethrogram was performed. A remnant of the ureterocele that communicated with the pelvic urethra was observed [Figure 2]. The persistence of this structure was assumed to contribute to continued urinary incontinence and bacterial cystitis. The dog was discharged with owner instructions to continue enrofloxacin^a administration (5 mg/kg body weight, q 12 hours PO) for 5 weeks.

Four months after initiation of antibiotic therapy, urinary incontinence persisted, but urine culture indicated that the urinary tract infection was no longer present. No abnormalities were noted in laboratory tests (i.e., packed cell volume, total solids, blood urea nitrogen, serum creatinine) performed at this time. The dog was prepared for abdominal surgery, and a midline celiotomy was performed. A ventral cystotomy incision was made extending into the ventral aspect of the pelvic urethra. The communication between the urethra and ureterocele was identified. Samples were obtained from within the ureterocele for microbial culture. An elliptical incision was made around the opening of the ureterocele within the dorsal wall of the urethra, and the remnant of the ureterocele was resected. The defect in the urethral wall was closed with 5-0 monofilament polyglyconate^b in a simple continuous pattern. Cefazolin^c (20 mg/kg body weight) was administered intravenously during surgery, and treatment with amoxicillin/clavulanate^d (18 mg/kg body weight, q 12 hours PO) was initiated after recovery from surgery.

Treatment with phenylpropanolamine was discontinued prior to surgery, and urinary incontinence resolved 2 weeks after surgery. Pseudomonas aeruginosa and an ∞-hemolytic streptococcus were isolated from cultures taken from the lining of the ureterocele. Both were susceptible to gentamicin, and the Pseudomonas isolate was susceptible to ciprofloxacin. The ∞-hemolytic streptococcal isolate was susceptible to amoxicillin/clavulanate. Treatment with enrofloxacin (5 mg/kg body weight, q 8 hours PO) and amoxicillin/clavulanate (20 mg/kg body weight, q 8 hours PO) was continued for 4 weeks.

Ten months later, the dog was examined to evaluate the acute onset of straining to urinate and the observation of the presence of blood and stones in the urine. Blood work was within reference ranges. Under general anesthesia, abdominal radiographs, an excretory urogram, and vaginourethrogram were performed. A small diverticulum appeared to be present within the pelvic urethra at the previous location of the ureterocele [Figure 3], and multiple cystic calculi were evident within the urinary bladder. Urine culture indicated the presence of E. coli sensitive to amoxicillin/clavulanate. The calculi were removed by hydropulsion, and stones were submitted for analysis. The dog was discharged on amoxicillin/clavulanate (20 mg/kg body weight, q 8 hours PO) for 3 days. The uroliths were determined to be struvite by laboratory analysis, and a calculolytic diet^e was prescribed.

Abdominal radiographs made 1 month later demonstrated the absence of cystic calculi, and urine culture indicated that infection was no longer present. However, the owner complained that the dog experienced frequent urination and recurrent incontinence. The diet was changed.^f Six weeks later, the owner reported resolution of urinary incontinence. A double-contrast cystogram was performed under general anesthesia, and no cystic calculi were seen.

Four years after resection of the remnant of the ureterocele, the owners reported that the dog has not had recurrent incontinence, although occasional urinary tract infections occurred. A positive-contrast urethrocystogram demonstrated that the small diverticulum at the site of the ureterocelectomy was no longer present. Examination of the dog revealed the presence of a recessed vulva and vulvar fold pyoderma, which may have predisposed the dog to intermittent urinary tract infection. Episioplasty was performed to correct this problem, and repeated urinary cultures have confirmed the absence of urinary tract infection 6 months after episioplasty.

Discussion

Three potential causes of urinary incontinence were identified in this dog: ectopic ureter, ureterocele, and pelvic displacement of the bladder neck. It appears that incontinence was primarily the result of ectopic ureter and the presence of the ureterocele, because surgical correction of these abnormalities controlled urinary incontinence. It is assumed that retention of contaminated urine within the ureterocele was the cause of urinary tract infection prior to removal of the ureterocele.

Ureteral ectopia is a congenital anatomic anomaly of the urinary tract, resulting from failure of normal differentiation of the mesonephric and metanephric ducts. This results in termination of one or both ureters at a site other than the trigone of the bladder.¹⁰¹¹ The vagina and urethra are the most common sites of termination of the ectopic ureter in bitches.¹² In this particular case, the right ureter terminated in the urethra. Additionally, right renal hypoplasia and hydroureter were present, necessitating ureteronephrectomy. Prognosis for resolution of urinary incontinence after surgical treatment of ureteral ectopia, in which the ureter terminates in the urethra, is guarded (44% to 69%) in dogs, since function of the urethral sphincter mechanism is often compromised by developmental changes or the presence of the ectopic ureter(s).¹³¹⁴ The cause of the right renal hypoplasia and hydroureter was not definitively determined in this case. While these abnormalities have been associated with ectopic ureter in dogs, in view of this dog’s age and the presence of a urinary tract infection, other potential causes would include congenital, ureteral obstruction, and ascending infection.

The embryological derivation of ureteroceles remains unknown. Clinical signs may include incontinence, dysuria, or both; in human infants, the most common presenting problem is urinary tract infection,¹¹¹⁵ and it is interesting to note that urinary tract infection has been a consistent observation in dogs with ureterocele.⁷ Ureteroceles may also result in deterioration of renal function, either as a result of ureteral obstruction or chronic vesicoureteral reflux of contaminated urine.²¹⁵¹⁶

Treatment of ureteroceles in children must be tailored to address the array of congenital and developmental abnormalities present in individual patients.^215–17 Marsupialization of ectopic ureteroceles by creating a direct communication of the ureterocele into the bladder and eliminating any potentially obstructing tissue has been recommended in children,¹⁷ and this has been performed in at least one dog.⁶ However, the presence of multiple defects may necessitate ureteral transposition, ureteronephrectomy, ureteroplasty, reconstruction of the bladder neck, or a combination of the above in humans.¹⁵¹⁶

Treatment of ectopic ureteroceles in dogs must similarly be individualized. Failure to remove the ureterocele during the first surgery may have resulted in persistent urinary tract infection and could have interfered with function of the urethral sphincter mechanism in this dog. Although marsupialization of ectopic ureterocele in a dog resulted in improved continence,⁶ it is unlikely that marsupialization of the ureterocele would have restored urinary continence in the dog described in the current report because of the persistent defect in the dorsal wall of the urethra. It is interesting to note that recurrent urinary tract infections were observed subsequent to marsupialization of the ectopic ureterocele in a dog despite improved urinary continence.⁶ The results of this and other reports indicate that ectopic ureterocele is associated with urinary incontinence and urinary tract infections in dogs and that surgical treatment should be directed toward correction of both the ectopic ureter and the ureterocele.