Novel perineal approach for repair of a urethrorectal fistula in a bulldog

Abstract

A urethrorectal fistula was diagnosed in a 10-week-old, intact male bulldog, presented with a history of urine dribbling from his anus. The fistula was ligated using a novel perineal approach, resulting in resolution of clinical signs. The described procedure is simpler and less invasive than previously described repairs.

A 10-week-old, intact male English bulldog presented with a history of aberrant urination, with urine coming from the rectum as well as the urethra during micturition. There were no other abnormal clinical signs or findings on physical examination. A complete blood cell count and blood serum biochemical analysis did not reveal any abnormalities. Analysis of urine obtained by cystocentesis showed no indication of infection, but a culture of the urine did yield growth of Escherichia coli, Proteus mirabilis, and an Enterococcus sp. Digital rectal examination revealed a depressed region in the ventral surface of the rectum, approximately 1 cm cranial to the anus.

The penile urethra was catheterized with a #5 french red rubber catheter, and a contrast cystogram was obtained by injecting 11 mL/kg bodyweight (BW) iothalamate (Conray-Iothalamate meglumine injection U.S.P. 60%; Mallinkrodt, St Louis, Missouri, USA); it showed a very mild persistent urachal diverticulum but failed to reveal a urethrorectal fistula. An antegrade cytstourethrogram using fluoroscopy allowed confirmation of a fistula connecting the caudal pelvic urethra and the caudoventral rectum. The opening of the fistula into the rectum was located by using an ophthalmoscope, and a #5 french red rubber catheter was placed through it and into the bladder. There were now catheters entering the bladder from both the fistula and the penile urethra.

The dog was placed in sternal recumbency with its rear legs hanging over the edge of the table and prepared for surgery with both catheters in place. A 3-cm vertical incision was made on the midline, 0.5 cm below the anus. Blunt and sharp dissection was used to separate the external anal sphincter muscle and tissues along the midline just ventral to the rectum and dorsal to the pelvic urethra (Figure 1; normal anatomy). The dissection was continued until the catheter in the fistula was palpated. Blunt dissection and gelpi retractors were used to isolate the fistula, which was approximately 4 mm diameter, and 4 strands of 2-0 polydiaxonone (PDS Ethicon, Sommerville, New Jersey, USA) were passed around it. The catheter passing through the fistula was removed; the fistula was double ligated with the preplaced sutures and then transected. Closure was performed routinely; 3-0 polydiaxonone (PDS Ethicon) was used to close the muscular and subcutaneous layers in a simple continuous pattern, and 3-0 nylon (Ethibon; Ethicon) the skin. Total operating time was 50 min.

Figure 1. Normal anatomy of the canine male perineum. Illustration reproduced with permission from “Miller's Anatomy of the Dog” by Evans 1993.

The dog was discharged with instructions to administer amoxicillin-clavulanic acid (Clavamox tablets; Pfizer Animal Health, Exton, Pennsylvania, USA), 12.5 mg/kg BW, PO, q12h for 7 d, because of the contaminated nature of the surgery (perirectal) and the bacteria in the urine culture. He recovered well and had resolution of clinical signs immediately postoperatively and at reevaluation 6 mo later.

Urethrorectal fistulas have been reported as a congenital defect in dogs, cats, and horses (1,2,3,4,5). The defect is thought to be the result of incomplete division of the embryonic cloaca into the cranial ureterovesicular segment and caudal rectal segment by the urorectal fold (1,3,4,6). It is presumed to have a heritable component in bulldogs, but this has not been proven (1,3). The typical clinical signs described are dribbling or leakage of urine from the rectum, or urine passing from both the urethra and anus during micturition (3,6). Recurrent urinary tract infections, pollakiuria, and hemoturia have been reported, with several dogs presenting with struvite urolithiasis (3,7,8). Perianal dermatitis may also be present (1,4). Clinical signs are presumed to be present from birth but not recognized for a variable length of time. Diagnosis is typically made by observation of the urine dribbling from the anus; it can be confirmed by observation of the fistula with the use of positive contrast cystourethrography (3,6,7,8,9).

Of the 10 cases previously reported in dogs, 5 were in male bulldogs, 2 were in male miniature poodles, 1 was in a female miniature poodle, 1 was in a male Yorkshire terrier, and 1 was in a male Labrador retriever (1,3,4,6,7,8,9,10). In all 9 of the male dogs reported, the fistula was present in the pelvic urethra. Six of the 7 males in which the surgical technique was described had a fistulectomy performed through a ventral pubic symphysiotomy (1,3,4,10): 5 of the 6 had excellent results; 1 died 1 d post operatively from respiratory complications. Surgery was performed from a perineal approach in 1 dog, with a right curvilinear incision being made from the base of the tail to just ventral to the level of the pubis (8). The pudendal artery, vein, and nerve were then isolated and the fistula was located by using blunt dissection. The fistula was ligated and transected.

The dog described in this report had a small urachal diverticulum. This has been associated with persistent or recurrent urinary tract infections and could have been an indication for performing the standard ventral midline approach to examine the bladder as well as to repair the fistula. Several dogs with urethrorectal fistulas have had other concurrent congenital abnormalities, such as urethral duplication, pseudohermaphroditism, ectopic ureters, and vertebral malformation (4,6). Horses with this abnormality are reported to present commonly with rectal or anal atresia, although this has not been reported in dogs (1). It is not known whether these abnormalities are genetically linked to the formation of the urethrorectal fistula.

The technique described herein is less invasive than those previously described; it is technically easy and relatively fast to perform. The perineal approach that was previously described involved isolating the pudendal nerve to avoid injuring it. By making the approach on the perineal midline, this structure is avoided. The technique would be very difficult to perform if the rectal opening of the fistula were not visible and could not be catheterized, and thus may not be suitable for cases in which the fistulous opening is located more cranially, or is difficult to find.CVJ