Management of the traumatic oronasal fistula in the cat with a conical silastic prosthetic device

Large defects of the hard and soft palate allow food and liquid to pass easily into the nasal cavity (Griffiths and Sullivan 2001). The result is a serous or mucopurulent nasal discharge, sneezing and possible aspiration pneumonia (Griffiths and Sullivan 2001). Acquired palatal defects may occur in cats for various reasons, including trauma (high-rise injuries, dog bites, electrical shock, gunshot wounds, foreign body penetration causing necrosis of the hard palate) or they can be a complication of surgery, radiation, or of hyperthermic treatment of oral lesions (Harvey 1987, Thacher 1993). Several techniques for the surgical repair of palatal defects have been described (Harvey 1987, Robertson and Dean 1987, Marretta et al 1991, Smith 2000). Many defects in the hard palate can be closed by some form of mucoperiosteal flap with a good blood supply and without tension (Marretta et al 1991). Large defects located in the caudal aspect of the palate can be frustrating to repair, and postoperative dehiscence is a common complication (Smith 2000). For these defects, alternative methods such as a permanent acrylic obturator, a prosthetic appliance, an implant of allograft auricular cartilage preserved in glycerin or a silastic nasal septal button can be used (Hale et al 1997, Smith 2000, Roehsig et al 2001, Souza et al 2002, Francisco et al 2003).

The present report describes the management of a traumatic oronasal fistula in a cat with a conical silastic prosthetic obturator.

A 7-year-old 5.3-kg male neutered domestic shorthair cat was referred to the Veterinary Teaching Hospital of the Universidade Federal Rural do Rio de Janeiro for evaluation of a chronic palatal defect. The owner reported that the oronasal fistula had originated from a fall from a height of three stories at the age of 1 year. One attempt by the referring veterinarian to repair the defect by suturing the fistula edges using a simple-interrupted pattern had been unsuccessful. From then on, the cat had been fed small pieces of raw meat.

Inspection of the oral cavity revealed a 1.2×1.8 cm oronasal fistula, including the caudal and cranial portion of the hard and soft palate, respectively. Putrified food in the mouth and nasal cavity, gingivitis and a serous bilateral nasal discharge were also observed. Complete blood count and a serum chemistry panel were within the reference range. The cat had negative results on testing for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV).

Surgery was planned for treatment of the lesion at the junction of the hard and soft palate. Premedication with acetylpromazine 0.05 mg/kg and butorphanol 0.3 mg/kg, given together intramuscularly, was followed after 15 min by induction with intravenous thiopental sodium 10 mg/kg and maintenance with an isoflurane/oxygen mixture using a Baraca Double T breathing circuit. Lactated Ringer's solution (10 ml/kg/h, IV) was administered during anaesthesia and surgery.

The patient was placed in dorsal recumbency and prepared for aseptic surgery. The defect was debrided and closed with an advancement flap. Two vertical incisions were made in the soft palate mucosa based on the palatal surface of the oronasal fistula. It was necessary for the elevation of the mucoperiosteum caudally to include part of the soft palate so that sufficient tissue could be pulled forward to prevent tension on the suture line. The flap was sutured using 4–0 polyglactin 910 (Vicryl, Ethicon) in a simple-interrupted pattern. An oesophagostomy tube was placed from the level of the mid-cervical region to the level of the seventh intercostal space. Postoperatively, the basal energy requirement (BER, in kcal/day) was calculated by multiplying cat's weight in kg by 30 and then adding to 70. The BER was then multiplied by a factor of 1.25 to get the maintenance energy requirement (MER, in kcal/day). The cat was given 220 ml (286 kcal) of a high quality commercial canned diet (Prescription diet Canine/Feline a/d, Hill's Pet Products) divided into four administrations per day via the oesophagostomy tube. Analgesia was provided for the first 24 h with butorphanol 0.3 mg/kg SC every 4 h and flunixin meglumine 0.25 mg/kg SC once. The patient recovered without complication and was discharged 1 day after surgery with an Elizabethan collar. Antimicrobial therapy consisted of clindamycin 10 mg/kg SC every 12 h for 7 days.

A telephone report 2 days following discharge indicated that the oesophagostomy tube had been removed by the cat's owner because the cat had partially expelled it by vomiting. The owner had felt that the cat was suffering and he did not know how to redirect the tube back down the oesophagus. A soft gruel diet was recommended for 4 weeks. The owner did not present the patient for a post-surgical examination as had been requested.

Twelve months after surgery, the patient was presented for evaluation of persistent mucopurulent nasal discharge and dysphagia. Oral examination revealed a fistula approximately 2.2×1.6 cm (covering almost one half of the width of the hard palate) (Fig 1a). The owner elected a non-surgical approach to manage the palatal defect.

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Fig 1.

Repair of the caudal hard acquired palatal defect in the cat with a conical silastic nasal septal button. 1A. Chronic 2.2×1.6 cm traumatic oronasal fistula in a 7-year-old cat. 1B. The device is shaped by trimming before insertion and placed in the oronasal fistula. 1C. One piece device is positioned on opposite sides of the oronasal fistula. 1D. Prosthodontic obturation.

A third attempt at closure of the defect was carried out using a permanent autopolymerizing acrylic resin implant (Roehsig et al 2001). The premedication and anaesthesia used was the same as previously described. The acrylic material used in the resin implant is based on the methylmethacrylate system (Jet Acrílico, Artigos Odontológicos Clássicos). Initially, the pink coloured powder is mixed together with liquid. The resulting thin liquid preparation increases in viscosity and sets hard within a few minutes (Coles and Underwood 1988). Due to the exothermic reaction during the polymerization of the resin, it was cooled in an isotonic solution (0.9% NaCl) in order to protect the tissues from thermal damage (Tholen and Hoyt 1990). Urinary catheters were passed through each nostril into the nasopharynx during the procedure for the maintenance of the nasal cavity (Roehsig et al 2001). The catheters prevented the Jet from slumping and flowing throughout the nasal passages while it was in the plastic state (Roehsig et al 2001). The mucoperiosteum around the fistula was partially elevated so that when the acrylic material obtained the optimal texture, a very thin sheet of the acrylic implant could be fixed at the edges of the palatine projection from the maxillary bone. Then, the urinary catheters were removed from the nasal cavity. Postoperatively, antimicrobial therapy consisted of ampicillin 20 mg/kg SC every 8 h for 10 days. Meloxicam 0.1 mg/kg PO every 24 h was administered for 4 days. The patient developed an ulcer on the anterior perimeter of the tongue; discomfort during feeding and signs of tissue reaction around the prosthesis were apparent. The acrylic implant was dislodged within 10 days. Feeding via oesophagostomy tube was required for 30 days. A fourth attempt at managing the defect was carried out using a 3 cm conical silastic nasal septal button (Hood nasal septal button with Ultra-smooth, Hood Laboratories) with a 7.0 mm diameter core (Souza et al 2002). The cat received premedication with acetylpromazine. Anaesthesia was induced by intravenous administration of thiopental sodium (10 mg/kg). The patient was placed in dorsal recumbency and the oral cavity was swabbed several times with a solution of 0.12% chorhexidine. The transparent device was shaped by trimming before insertion and placed in the oronasal fistula (Fig 1b). One piece of the double-sided device was positioned on each side of the oronasal fistula, providing obturation of the defect in 5 min (Fig 1c,d).

Oral intake, consisting of a soft, canned food diet was instituted on the first postoperative day. The patient was fed with soft food for 5 days, at which time it was offered dry food. An evaluation was performed 6 months after placement of the obturator. The silastic button was in place, providing obturation of the defect and there was no apparent need for removal or cleaning. There was no sign of any discomfort, tissue reaction around the prosthesis or functional problems associated with swallowing or breathing. The cat had gained 1.8 kg of body weight. There were no further problems reported for this case at 24 months after the placement of the prosthesis. After this period, the owner reported the cat had clinical signs related to rhinitis. On inspection of the oral cavity, there was mild tissue reaction around the silastic device. There was also a slight mucopurulent nasal discharge bilaterally. The button had partially deformed and had acquired a brown colour. The change of the conical shape had permitted saliva to enter the nasal cavity. The device was removed and a second one was put in its place as previously described. The patient was rechecked 2 weeks after the placement of the obturator. The silastic button was in place and no signs related to rhinitis and tissue reaction around the prosthesis were presented.

The hard palate consists of bone covered dorsally by nasal epithelium and ventrally by the thick, ridged oral palatal epithelium (Harvey 1987). The soft palate contains skeletal muscle between the epithelial surfaces; this muscle forms part of the nasopharyngeal sphincter that prevents food or fluid from entering the nasopharynx during swallowing (Harvey 1987). Large defects located in the caudal aspect of the palate can be associated with a high rate of surgical failure (Sager and Nefen 1998, Smith 2000). In this report, a postoperative suture line dehiscence resulting from tension at the surgical site was considered the reason for failure of the first attempt to repair the defect. Repeated attempts to repair palatal defects often result in chronic intractable dehiscence at the surgery site, especially, when the normal vascular supply is disrupted or abnormal (Smith 2000). The application of the split palatal U-flap or advancement flap techniques in the cat could be an option for repairing large caudal palatal defects which were unsuccessfully treated with alternative surgical techniques (Marretta et al 1991, Smith 2000). For extensive rostral hard palatal defects, a tongue flap may be another option (Robertson and Dean 1987).

Oral feeding should be prevented to avoid dehiscence or perforation of the flap separating the oral and nasal cavities postoperatively (Sager and Nefen 1998). Other reports recommend that soft food should be given for 2–3 weeks (Marretta et al 1991, Smith 2000).

A soft palate advancement flap was used to cover the oronasal defect in this case, but the oesophagostomy tube was removed early which might have been a contributing factor in the failure of the surgical repair. A prosthetic acrylic implant has been used in cats after an incomplete surgical repair of traumatic cleft hard palate resulted in an oronasal fistula similar in size and location to the lesion reported here (Roehsig et al 2001). The acrylic material is inexpensive, easy to use and appears to be well tolerated by the adjacent tissues (Coles and Underwood 1988). However, it was not a suitable material for the purpose in this case, as the patient exhibited glossitis and signs of discomfort during feeding and tissue reaction around the prosthesis. Another disadvantage was that the implant was easily dislodged.

A silastic nasal septal button may be used as a prosthetic appliance to provide obturation of an oronasal fistula in the cat (Smith and Rockhill 1996). This device should be considered after surgical treatment has failed to close the oronasal fistula (Smith 2000). The silastic nasal septal button is designed for humans with nasal septal perforations. It is fabricated of medical-grade silicone (soft, malleable and inert, and with thin, 1 mm edges). Besides the ultra-smooth property, silicone is resistant to biofilm germination and bacterial and fungal growth. The conical shape of the oral component of the appliance lies in close contact with the mucosa. This characteristic may have prevented clinical signs related to food entrapment. The patient tolerated the prosthetic appliance without apparent complications. The procedure of managing the traumatic fistula with the conical prosthetic device was fast, easy and efficient, when comparing with other prosthetic appliances. The device was removed and a second one was put in place after 2 years. This method would appear particularly useful in similar cases for obturation of large, recurrent oronasal fistulae and as an alternative treatment for debilitated cats that cannot undergo surgical repair.