An unusual case of urinary incontinence in an intersex West Highland white terrier

Abstract

A 5-year-old neutered female West Highland white terrier dog was presented with a history of congenital urinary incontinence that had become refractory to medical management. Complex urogenital anomalies including urethrovestibular and vestibuloperineal fistulae with low vulvar position along with a penoclitoris were present. Vaginectomy with perineal urethral reconstruction resolved the incontinence.

Disorders of sexual differentiation are uncommon in dogs, with only a small number of reviews having been published giving details of the variety of anatomical derangements of internal and external genitalia (1–3). Urinary incontinence occurs with failure of the normal voluntary control of urination and has been reported in dogs with complex congential urogenital malformations (1,2). Urinary incontinence also predisposes to the development of urinary tract infections and can lead to urine scalding of the animal and soiling of the environment. Frequently, owner frustration leads to premature euthanasia (4,5). Urinary incontinence as a consequence of intersexuality should also be considered and most frequently occurs due to urine refluxing into the vagina through an urethrovaginal fistula and subsequent passive leakage (2). One of the more common congenital anomalies in dogs is vestibulovaginal stenosis and vaginectomy has successfully been used to treat these dogs, which typically present for mating disorders or recurrent lower urinary tract infections (6).

Surgical management of urinary incontinence in intersex dogs with complex urogenital anatomy is rare, with only 5 cases reported in the English veterinary literature (7–10). This is the first case description of successful resolution of urinary incontinence using vaginectomy and urethral reconstruction in a dog with the specifically described urogenital anomalies.

Case description

A 5-year-old female neutered West Highland white terrier dog of 7.7 kg body weight (BW) was presented to the Calgary Animal Referral and Emergency Centre for assessment of congenital urinary incontinence which was noted by the owners soon after receiving the dog as an 8-week-old puppy. The dog dribbled urine constantly, but dribbling was worse after the dog rose from a lying position and while the dog slept. The owner reported that the dog had a couple of normal urine voids daily. On physical examination, it was noted that the vulva was positioned further ventrally from the anus (about 9 cm) than normal. There was moderate perineal and perivulvar dermatitis due to urine scald. The owner did not observe polyuria/polydipsia and neurological evaluation was unremarkable. The dog had a urinary tract infection at 4 mo of age and underwent an excretory urogram due to ongoing urinary incontinence at 7 mo of age, when it was neutered by the referring veterinarian. There was no evidence of ectopic ureters and the ovariohysterectomy was documented as routine; there was no histological evaluation of gonadal tissue. A tentative diagnosis of congenital urethral sphincter mechanism incompetence was made at that time and medical treatment was instigated. Phenylpropanolamine (Propalin; Vétoquinol, Lavaltrie, Quebec) was given at 1 mg/kg BW, q8h for the next 3 y and, although the urinary incontinence was not as pronounced during this time, the dog had become refractory to treatment over the few months prior to presentation. No further response to therapy was observed with the addition of diethylstilbestrol (Stilbestrol; Jaapharm, Woodbridge, Ontario), 0.5 mg/kg BW administered 3 times a week.

At initial presentation, serum chemistry and hematological evaluation were unremarkable. Analysis of urine taken by cystocentesis showed that the urine had a trace of red blood cells, which was attributed to the collection method, as there was no active sediment or bacteruria. Contrast retrograde vaginography was recommended, given the ongoing incontinence and the previous excretory urography having excluded ectopic ureters from the differential diagnoses. The dog was prepared with a warm water enema prior to the radiographic study. Premedication with acepromazine (Atravet; Ayerest, Guelph, Ontario), 0.02 mg/kg BW and hydromorphone (Sandoz, Boucherville, Quebec), 0.1 mg/kg BW was administered intravenously (IV), followed by thiopentone (Thiotal 2.5%; Vétoquinol), 10 mg/kg BW, IV for anesthetic induction, and the dog was maintained on isoflurane (AErrane; Baxter, Mississauga, Ontario) with oxygen after intubation.

On closer examination of the dog’s perineal region, a 1-mm diameter fistula was observed on the median raphe just 2 cm ventral to the anus. Examination of the dog’s lower reproductive tract demonstrated distally positioned vulva (low) and a penoclitoris with an external urethral orifice but no ossicle. The fistula was catheterized and 2 mL/kg BW of iodinated contrast material (Visapaque; GE Healthcare, Princeton, New Jersey, USA) was instilled. This demonstrated urethrovaginal and vestibuloperineal fistulae. The perineal urethra was narrow and long and this communicated with the vagina and pelvic urethra at a “cross-roads” with the vestibuloperineal fistula (Figure 1). There was also vestibulo-vaginal stenosis just proximal to this communication.

Figure 1.

Contrast fistulogram made during injection with a catheter positioned within the vestibuloperineal fistula (VP). Note the vestibulovaginal stenosis (VVS), the long, narrow penile urethra (PU) with contrast leaking distally from the penoclitoral opening. Contrast filling the vagina (V) and urethrovestibular fistula (UV) complete the abnormal anatomy.

The presence of the vestibuloperineal fistula was considered to be the possible cause of the urinary incontinence by allowing passive flow following normal voiding. Local excision of the vestibuloperineal fistula was performed under the same general anesthetic. The deep perineal tissue was closed in 2 layers with 3/0 polydioxanone suture (PDS; Ethicon, Somerville, New Jersey, USA). The skin was closed with a subcuticular pattern of 3/0 polyligacaprone (3/0 Monocryl; Ethicon). No attempt at reconstruction of the urethrovaginal fistula was made. The dog showed immediate improvement with no evidence of urinary incontinence for the next 5 mo. On telephone consultation at 6 mo after the surgery, however, the owner commented that the dog had became incontinent again. A urinalysis performed at that time was normal. Reinstatement of the phenylpropanolamine at the previously stated dose was recommended, and although a slight improvement was initially noted, the dog did not regain full voluntary urinary control.

At 1 y following the initial surgery, the dog was readmitted for further evaluation. The dog would void normally and then dribble small amounts predominantly after normal voiding, suggesting urine pooling. There was also marked perivulvar dermatitis. Another retrograde contrast urethrogram was performed as previously described. This demonstrated the urethrovestibular communication with poor filling of the pelvic urethra, and the blind-ending remnant of the repaired vestibuloperineal fistula. Vaginectomy with reconstruction of the urethra to remove the urethrovestibular fistula was recommended with the aim of creating a more “male-like” anatomy (personal communication, Professor Peter Holt, University of Bristol).

Premedication with acepromazine at 0.02 mg/kg BW and hydromorphone at 0.1 mg/kg BW was administered intravenously followed by thiopentone at 10 mg/kg BW, IV for anesthetic induction; the dog was maintained on isoflurane with oxygen after intubation.

An epidural injection of bupivicaine (Marcaine 0.5%; Hospira Healthcare, Montreal, Quebec) and morphine (Sandoz, Boucherville, Quebec) at 0.1 mg/kg BW was administered. A 5 French urinary catheter was placed in the distal urethra. A midline approach to the perineum was made with excision of the vestibuloperineal remnant. The vagina was dissected with a combination of sharp and blunt dissection from the surrounding tissue, staying close to the vaginal wall. A small tear in the rectum occurred during dissection and was immediately repaired with 3/0 PDS in a simple interrupted pattern. The vestibule was then incised on the midline to aid in passage of the urinary catheter proximally into the pelvic urethra. The vagina continued to be isolated from its peritoneal reflection with ligation of the vaginal branch of the urogenital artery and vein bilaterally. Careful dissection continued close to the vaginal wall cranial to the internal pelvic brim; a transfixing ligature was placed and the vagina was excised by transection just dorsal to the urethrovestibular communication. The potential space was closed with interrupted appositional sutures of 3/0 PDS. The urethra was then reconstructed by partially resecting the wall of the urethra longitudinally and reducing its diameter around the previously placed 5 French urinary catheter with simple interrupted sutures of 4/0 PDS. The perineum and skin were closed in a layered fashion using 4/0 monocryl. A postoperative contrast urethrogram showed the reconstructed urethra (Figure 2). The urinary catheter was immediately removed and a 7-day course of antibiotics (Cephalexin, Novo-lexin; Novopharm, Toronto, Ontario), 250 mg q12h and meloxicam (Metacam; Boehringer Ingelheim, Burlington, Ontario), 0.1 mg/kg BW, q24h was administered with the patient discharged from the hospital on the first postoperative day. Karyotyping of the dog performed at the University of Calgary revealed that the dog had an XX genotype. The dog continues to be continent almost 4 y since the urethral reconstruction procedure and has not been receiving any medication.

Figure 2.

Retrograde urethrogram made at mid-injection immediately following the second surgery, showing good contrast filling of the penile and pelvic urethra (PU) after resection of the vagina and vestibuloperineal fistula remnant. Note the irregular filling defects at site of the reconstructed urethra, probably from post-surgical swelling.

Discussion

The urogenital anomalies seen in this case are similar to those reported in other case reports (7–10). With a normal female karotype, this dog is a female pseudohermaphrodite. The anomalies in this dog involved structures derived from the urogenital sinus, genital tubercle, and genital swellings. Early in its development, the urogenital sinus consists of a pelvic portion associated with the bladder and a distal phallic portion associated with the genital tubercle. In the normal female, the 2 portions merge creating the vestibule where the urethra is not associated with the genital tubercle. In the male, the pelvic portion extends from the bladder to the ischial arch and the phallic portion extends throughout the length of the developing genital tubercle creating the penis and penile urethra (11). In the present case, there had been failure of differentiation and the vestibuloperineal fistula probably represented the remains of the pelvic urogenital sinus with the penoclitoris and probably resulted from abnormal development of the phallic portion of the urogenital sinus and the genital tubercle (10).

The initial improvement following closure of the vestibuloperineal fistula may have been related to the new anatomic arrangement apparently allowing more normal urination down the narrow penile urethra. We hypothesized that with time, reflux of urine into the vagina caused pooling and this eventually presented as ongoing dribbling.

The vaginectomy procedure in the present case varies greatly from those in the previously published cases. In the most recent case description, Gregory and Trower (10) created a single vestibular tube of sufficient width to allow the passage of urine with no outflow resistance. This was done in 2 intact female dogs without concomitant neutering. In essence, they attempted to recreate normal female anatomy by amputating the penis; however, because the reconstructed urethra was not long enough to be anastomosed to the vulva, a large perineal stoma with communication with the vagina and urethra and a blind ending vulva were created. Although their immediate follow-up indicated a successful resolution of incontinence, there was no long-term follow-up after ovariohysterectomy (performed over a year later in both dogs).

Urinary incontinence attributed to urethral sphincter mechanism incompetence (USMI) occurred in another dog following ovariohysterectomy (9). The dog in our case report was neutered at 7 mo of age and the urinary incontinence was noted to have improved (for over 3 y) with phenylpropanolamine, which suggested that congenital USMI may also have been a contributing factor in our case. Urinary incontinence is more common in female than male dogs, which has been attributed to the anatomical difference between the sexes (5,11–13). It is our opinion that recreating a more male-like anatomy had several benefits in this case. Urethral narrowing and lengthening has been successful in pediatric human patients with intractable urinary incontinence (14). The procedure described in these children creates a longer, narrower urethra, which offers increased resistance to urine flow following Poiseuille’s law. This physical law states that the resistance to flow of liquid is proportional to the length of the tube and inversely proportional to the radius to the fourth power (14). Thus, a reduction in urethral diameter of 50% would hypothetically lead to a 16-fold increase in resistance. In this case, urethral reconstruction also created a longer, narrower urethra, although urodynamic studies would be required to confirm increases in physiological urethral resistance. Thus, if USMI is indeed a contributing component, particularly with the loss of hormonal stimulation following ovariohysterectomy, urethral narrowing and lengthening should prove beneficial. Acquired USMI occurs mainly in female dogs when there is a reduction in urethral tone combined with a short urethra and an intrapelvic bladder (12,15). It is likely, therefore, that lengthening the functional urethra would increase resistance to urine flow and potentially be advantageous in preventing further urinary incontinence.

Another potential advantage to reconstruction to a more male-like anatomy would be reduced incidence of recurrent urinary tract infection (UTI). In the described procedure, normal urethral length and the external urethral orifice are preserved; therefore, the risk of ascending UTI should be minimized (13). It is our opinion that the large perineal stoma present with the procedure described by Gregory and Trower (10) would likely increase the risk of ascending UTI as seen following perineal urethrostomy in cats (13); however, this was not reported by the authors. Any surgical procedure on the urethra had the potential to disrupt the normal protective mechanisms of the uroepithelium against infection; however, a large stoma in the perineum would likely increase the risk of ascending bacterial infection.

Vestibulo-vaginal stenosis was present in this case, but its contribution to urinary incontinence is questionable. Holt et al (15) did not find any increase in urinary incontinence in dogs with vestibulo-vaginal stenosis and concluded that it is not a primary cause of incontinence but can contribute by causing vaginitis.

One caveat regarding the reconstruction of a narrow urethra is stricture formation (16); however, with attention to precise urethral mucosa apposition during suturing, the risk should be minimized. Vaginectomy also has some potential complications; if strict adherence to careful dissection of the vagina is compromised, interruption of the neurovascular supply to the bladder and urethra can ensue (6). Vaginectomy with subsequent urethral reconstruction gave a successful long-term outcome in this patient with unusual urogenital anomalies and it provides a viable alternative to the previously described surgical management strategies for this complex problem. CVJ