Successful staged surgical management of atresia ani with urethrorectal fistula in a male kitten

Abstract

Case summary

A 2-month-old male British Shorthair cat was referred with suspected atresia ani. Physical examination revealed an imperforate anus and dribbling of faecal discharge through the penis. Radiographic findings, along with a retrograde urethrogram, confirmed the diagnosis of type II atresia ani with a urethrorectal fistula. Surgical anoplasty was performed and the patient recovered well. At 8 months of age, surgical treatment for the congenital urethrorectal fistula was carried out via a single perineal approach, including fistulectomy and castration through the same incision. Postoperative short-term outcomes were excellent, with normal defecation and urination.

Relevance and novel information

Atresia ani is a rare congenital anomaly, particularly in male cats. Despite advancements in surgical techniques, this case represents the first successful staged surgical management of urethrorectal fistula with type II atresia ani in a male kitten, potentially influencing future surgical approaches for similar congenital anomalies.

Case description

A 2-month-old male British Shorthair cat weighing 0.55 kg was referred for suspected atresia ani. The owner reported faecal contamination around an anus and abdominal distension. On examination, the kitten was alert, with a body condition score of 3/9. Physical findings included a completely absent anal opening, replaced by a bulging dimple, and watery faecal material dripping from the penile urethra (Figure 1). The patient did not exhibit any clinical signs of urinary tract infection (eg, dysuria, stranguria, pollakiuria). Abdominal palpation revealed a mildly distended colon. The anal reflex was present but indistinct. Complete blood count and serum biochemistry parameters were within normal limits. Urinalysis performed on a urine sample obtained via cystocentesis showed no evidence of haematuria, pyuria or bacteriuria. In addition, a urine culture was performed.

Abdominal radiographs showed a distended colon, with the rectum terminating 1 cm cranial to the anal region (Figure 1). A positive-contrast retrograde urethrogram was performed using a 24 G intravenous catheter (stylet removed), positioned a few millimetres into the penile urethra. A total of 4 ml contrast medium, consisting of 1 ml ioversol (Optiray 300; Mallinckrodt) diluted in 3 ml saline, was slowly administered. Serial radiographs confirmed a urethrorectal fistula (Figure 1). A diagnosis of type II atresia ani, characterised by the persistence of an anal membrane and a rectum terminating as a blind pouch cranial to it, along with a urethrorectal fistula, was confirmed. A staged approach was chosen. Anoplasty was performed initially to minimise surgical and anaesthetic risks in this very young cat.

Figure 1

Preoperative photograph and radiographs: (a) preoperative view showing an anal dimple with the absence of an anal opening, with faecal discharge visible at the tip of the penile urethra; (b) plain radiograph showing a distended colon filled with faeces and gas, with the rectum terminating as a blind pouch cranial to the anal region; and (c) positive-contrast urethrogram revealing a diverticulum-shaped fistula connecting the urethra and rectum

General anaesthesia was induced with propofol (6 mg/kg IV) and maintained after intubation with sevoflurane in a mixture of oxygen. Cephazolin (20 mg/kg IV) and morphine (0.1 mg/kg IM) were given preoperatively. During anaesthesia, intravenous fluids (lactated Ringer’s solution; B Braun) were continuously administered at a rate of 3–5 ml/kg/h. The patient was positioned in sternal recumbency with the perineum slightly elevated. A vertical elliptical incision was made over the anal dimple, medial to the anal gland sacs (Figure 2). The skin was dissected from the underlying tissue using tenotomy scissors, followed by careful separation of the subcutaneous tissue beneath the anal dimple. The external anal sphincter and anal gland sacs were preserved throughout the dissection, ensuring all manoeuvres remained medial to the sphincter muscle. The distal rectal pouch was identified based on radiographic findings indicating its location, while intraoperatively it was distinguished by its thickened wall and palpable faecal-like content.

Figure 2

Perioperative photographs: (a) a vertical elliptical incision (oval dotted line) was made over the anal dimple; (b) the rectal opening was sutured to the subcutaneous tissues and skin; and (c) the anoplasty was completed

A 4-0 polydioxanone (PDS, PDS II; Ethicon) stay suture was placed in the blind rectal pouch for manipulation. Blunt dissection was performed to separate the rectal pouch from the surrounding tissue, allowing for sufficient mobilisation as the rectal pouch was retracted caudally. The rectum was gradually advanced through the sphincter using stay sutures until the blind pouch could reach the perineal skin without tension. The rectal end was then incised to approximately 1 cm in diameter, the stay suture was removed and the rectal opening was sutured to the subcutaneous tissues and skin using a single layer of simple interrupted 4-0 PDS. Impacted faeces were removed before concluding the procedure.

Postoperatively, the kitten was discharged on the same day with cephalexin (20 mg/kg PO q12h) for 7 days and was fed a wet diet. Urine culture results received 4 days postoperatively indicated no bacterial growth. Faecal impaction occurred three times within the first month at the distal rectum and anal canal, with firm to hard faeces. Manual evacuation with gentle perineal pressure was successful, and faecal consistency remained appropriate afterwards. In addition, occasional episodes of faecal incontinence were observed during the early postoperative period but gradually resolved within 1 month. After the first surgery, the kitten was monitored by the referring veterinarian for urinary tract infections based on clinical signs, and no signs were reported.

At 6 months postoperatively, the kitten weighed 2.2 kg. Both urinary and faecal continence were present; however, faecal discharge from the penile urethra persisted. Repeat contrast radiography confirmed the presence of a urethrorectal fistula (Figure 3). The owner opted for surgical repair without preoperative CT scanning because of concerns about prolonged anaesthetic time and risks.

Figure 3

Radiographic findings before and after the second surgery: (a) preoperative positive-contrast urethrogram (6 months after the first surgery), confirming a urethrorectal fistula; and (b) postoperative positive-contrast urethrogram demonstrating no urethral leakage or stenosis and the absence of a connecting tract between the urethra and rectum

The second surgery was conducted under general anaesthesia following the same protocol as the initial procedure. The rectum was manually evacuated and anal sacs compressed to reduce contamination. The patient was positioned in sternal recumbency, with a purse-string suture in the anal orifice, and a 3 French gauge urinary catheter was inserted for bladder drainage. After drainage, the catheter was plugged to prevent leakage. A midline perineal approach was made with a dorsoventral incision starting 1 cm ventral to the anus, preserving the external anal sphincter and extending to the scrotal–preputial junction (Figure 4). Castration was performed through the same incision. Dissection of the perineal tissue was carefully performed until the large, asymmetrical, diverticulum-shaped fistula was identified and isolated. The fistula was opened for direct exploration owing to incomplete radiographic delineation. A second urinary catheter was briefly inserted through the fistula to confirm the urethral connection and then removed, while the initial catheter remained in place. Blunt dissection was performed around the diverticulum to isolate the fistula from surrounding tissue. The ventral side of the fistula, connecting to the urethra, was excised. The catheter was reinserted to verify the position of the urethral defect, which was then closed with a simple interrupted pattern using 4-0 PDS. The dorsal side of the fistula, connecting to the distal rectum, was double ligated with 3-0 PDS and transected. The surgical site was lavaged with warm sterile saline, and gloves and instruments were changed before closure. The perineal incision was closed in layers: subcutaneous tissue with 3-0 PDS in a simple continuous pattern, and the intradermal layer with 4-0 PDS and the skin with 3-0 nylon (Dafilon; B Braun) in a simple interrupted pattern.

Figure 4

Perioperative views of the fistulectomy performed via a perineal approach: (a) a vertical incision was made along the midline of the perineum; (b) the fistula was incised, with a catheter inserted into the urethral opening (arrow); (c) excision of the fistula began at the ventral side, with the catheter reinserted into the urethra; and (d) a post-excision intraperineal view showing the area after fistula removal

The patient recovered uneventfully and was admitted for postoperative care, which involved close monitoring for complications. Morphine (0.1 mg/kg SC q6–8h) and robenacoxib (2 mg/kg SC q24h) were administered and discontinued after 2 days. Amoxicillin-clavulanic acid (15 mg/kg PO q12h) was prescribed for 10 days. The patient was discharged 5 days postoperatively without wound complications. Repeat contrast radiography on day 10 confirmed the absence of urine leakage (Figure 3). The cat exhibited normal urination and defecation. At a 1-year telephone follow-up, the cat was reported to have remained healthy with no abnormalities observed.

Discussion

Atresia ani is a rare, potentially life-threatening congenital defect of anorectal development, more frequently reported in dogs than cats, especially in females.^{1 –3} The rarity of atresia ani in male kittens is well documented, with only a handful of cases reported worldwide,^{4 –6} including one male pseudohermaphrodite. ⁷ Congenital anorectal malformations often involve abnormal cloacal development,^2,3,8,9 with most female cases linked to rectovaginal fistulas.^{3,9 –16} However, atresia ani with a congenital urethrorectal fistula, where the rectum connects to the urethral lumen, in a male kitten is exceptionally rare, requiring surgical management. To date, no successful surgical outcomes have been reported for this condition.

Surgical intervention for atresia ani is intended to re-establish anorectal continuity, preserve colonic motility and protect the external anal sphincter to maintain voluntary defecation. ¹ Timely surgical intervention is critical to prevent life-threatening complications, such as megacolon, chronic abdominal distension, bowel atony and stasis, particularly in cases where defecation is impossible.^13,17 In the present case, the surgery was performed promptly upon presentation to avoid delays and minimise the risk of these complications. Anoplasty was chosen to treat type II atresia ani. Unlike type I, in which an anal opening is present but stenotic and may respond to bougienage or balloon dilation, type II requires surgery to create a functional anus.^1,3

Faecal incontinence is a common postoperative complication; however, many cases with preoperative inducible anal tone have demonstrated controllable defecation after surgery.^12,15 Careful dissection is essential to preserve the innervation and structural integrity of the external anal sphincter. ³ Alternative techniques to the fistula flap method have been recommended to bridge the distal rectum to the anus,^7,12 aiming to preserve the internal anal sphincter and reduce postoperative complications.^12,18 In this case, such techniques were not used because of the need for separate surgeries to minimise anaesthetic risks and the limitations of the perineal access during the initial surgery. However, several previous cases without the flap technique have shown favourable outcomes without faecal incontinence over variable time periods.^3,9,13,15 In the present case, positive preoperative anal tone and preservation of the external anal sphincter contributed to postoperative faecal continence.

The first documented case of congenital urethrorectal fistula with type II atresia ani in a male kitten was reported in 1988 and resulted in euthanasia. ⁴ More recently, a juvenile cat with urethrorectal fistula was successfully treated using a pelvic osteotomy approach, ¹⁹ a technique previously common in dogs. ²⁰ In contrast, the perineal approach used in the present case offers advantages, including reduced surgical time, less pain and a lower nerve injury risk compared with more invasive methods.^{20 –24} However, this approach in a young kitten posed challenges due to limited surgical access, requiring delayed intervention until the patient was more mature, which had to be balanced against the risks of faecal contamination and urinary infections.

Urinary tract infections have been frequently reported in dogs with urethrorectal fistulas, possibly due to delayed surgical correction; however, some dogs exhibited only aberrant urination through the anus, without infection.^{20 –24} In contrast, cats with rectovaginal fistulas have rarely developed infections,^{3,7,9,12,14,15} likely because of early surgical correction alongside atresia ani repair, reducing prolonged faecal contamination. Although no urinary tract infection occurred in this case, close monitoring remained essential, especially given the delayed repair. Early diagnosis and treatment are necessary if an infection is suspected. Wound dehiscence and infection have been frequently reported in female kittens undergoing anoplasty with rectovaginal fistula correction,^10,12,15 and may be associated with faecal contamination. ¹⁰ A staged surgical approach, with anoplasty performed before fistulectomy, along with preoperative preparation and perioperative and postoperative therapy, further minimised contamination risks, leading to successful wound healing.

A recently introduced rectal mucosal approach for urethrorectal fistula correction in dogs preserves critical structures by avoiding nerve and muscle damage. ²⁵ This technique involves blunt dissection of the fistula through the rectal mucosa, followed by ligation and closure of the fistula opening with sutures. In the present case, this technique was not chosen because of the limited accessibility and a large diverticulum, necessitating transection for complete resolution. The perineal approach effectively separated the rectal and urethral tracts while preserving the external anal sphincter, restoring normal urination and defecation. It is recommended for caudally located fistulas as a result of its minimally invasive nature and successful outcomes.

Conclusions

This is the first documented case of successful staged surgical management of type II atresia ani with a congenital urethrorectal fistula in a male kitten. Anoplasty was followed by fistulectomy via a perineal approach, prioritising structural preservation and resulting in an excellent clinical outcome, advancing veterinary care for similar cases.