Choanal atresia in a Himalayan cat – first reported case and successful treatment

A 2-year-old, female neutered Himalayan cat was presented to the referring veterinarian with a right-sided, seromucoid nasal discharge that had been present since the cat was acquired at 8 weeks of age. Stertor, exercise intolerance and open-mouthed breathing on exertion were reported. Further investigations were declined at that time. Sequential antibiotic treatment over a 6-month period using doxycycline, clindamycin, enrofloxacin then amoxycillin-clavulanate had no effect on clinical signs. Plain radiographs of the thorax and tympanic bullae taken 2 weeks prior to referral revealed no abnormalities. Visual examination of the nasopharynx by retracting the soft palate was reported to be normal.

On physical examination at referral the cat was of small stature with a body condition score of 3/5. Increased inspiratory effort, stertor and bilateral stenotic nares were identified. A small volume of seromucoid discharge was identified at the right nostril. Upper airway obstruction due to congenital and/or acquired defects was suspected. Brachycephalic airway obstruction syndrome, nasopharyngeal stenosis, nasopharyngeal polyp or foreign body were considered as the most likely aetiologies. No abnormalities were detected on serum biochemistry and the haematocrit was within the normal range. The cat was premedicated with subcutaneous acepromazine (0.02 mg/kg) and buprenorphine (0.02 mg/kg). General anaesthesia was induced with thiopentone (7 mg/kg) and propofol (2.5 mg/kg) given intravenously. The cat was intubated using a 3.5 mm cuffed endotracheal tube and was maintained on isoflurane in oxygen throughout the procedure. The nasopharynx was visualised using a retroflexed paediatric endoscope. The right choana was occluded by a sheet of mucous membrane which was continuous with the nasopharyngeal mucous membrane (Fig 1a). Complete occlusion was demonstrated by retrograde flushing of sterile saline via the right nostril which caused the membrane over the right choana to bulge. Flushing resulted in the expulsion of mucoid nasal discharge from the right nostril. Unilateral, membranous choanal atresia was diagnosed.

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Fig 1.

Endoscopic view of (a) unilateral (right) choanal atresia at diagnosis and (b) stenting of repaired choana with a feeding tube (10 Fr).

Transnasal surgical repair of the defect was performed. A 20 gauge×48 mm over the needle intravenous catheter, with the stylet removed, was passed via the right ventral meatus to the level of the persistent membrane. The catheter tip was seen through the membrane using endoscopic visualisation via the nasopharynx. The stylet was reintroduced through the catheter to puncture the membrane and then removed. A strand of suture material was passed through the catheter into the nasopharynx and then into the mouth. The catheter was removed and the suture material left in place. A Foley catheter (5Fr) was tied firmly to the distal end of the suture material. The latter was used to draw the Foley catheter rostrally through the punctured membrane. The balloon of the catheter was progressively dilated and the catheter pulled to and fro until a choanal opening was created. A stent was placed to prevent stenosis of the newly created right choana. A length of feeding tube (10 Fr) was passed through the right nostril so that it protruded 1 cm caudal to the choana in the nasopharynx (Fig 1b). The stent was sutured at the right nostril (Fig 2a). Prednisolone sodium succinate (Solu Delta Cortef; Pharmacia) (2 mg/kg) was given intravenously.

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Fig 2.

(a) The cat immediately postoperatively showing external suturing of stent. (b) Seven days postoperatively after stent removal.

The cat recovered uneventfully and was discharged the next day with amoxycillin clavulanic acid (Clavulox; Pfizer) (16 mg/kg per os q12 h for 14 days), prednisolone (Pred-X5 Apex Labs Pty) (0.8 mg/kg per os q24 h for 7 days) and an Elizabethan collar. The owner reported that the stent was well tolerated. At revisit 7 days later the stent was removed (Fig 2b). All clinical signs resolved. The cat continued to do well with no recurrence of signs at follow-up 15 months later.

The choanae are paired openings between the nasal cavity and the nasopharynx. Choanal atresia, a rare congenital anomaly where the choanae are imperforate, has been reported in humans, horses, sheep, llamas, alpacas and a single dog (Dennis 1975, Fenwick et al 1982, Aylor et al 1984, Coolman et al 1998, Daniel 2006). To the authors' knowledge, this is the first report of choanal atresia in a cat.

The incidence of choanal atresia in humans is 1 in 8000 (Daniel 2006). Unilateral disease is more common than bilateral with the right side most often affected and females being slightly overrepresented (Daniel 2006, Uslu et al 2006). The defect can be bony, membranous or mixed. Most human cases have some bony involvement (Brown et al 1996, Daniel 2006). In contrast, most cases of choanal atresia in animals are caused by membranous tissue (Coolman et al 1998).

The presenting signs depend on the extent of the lesion. Bilateral choanal atresia can result in severe neonatal respiratory distress and death. In contrast, cases of unilateral atresia typically present later as a persistent nasal discharge, as in the case reported here. As choanal atresia has now been documented in the cat and dog, it should be included in the differential diagnosis of neonatal respiratory distress and sudden death in these species. Choanal atresia in human infants is often associated with diverse concurrent defects including coloboma, developmental retardation, genitourinary abnormalities, heart and ear defects (Leclerc and Fearon 1987). Whether similar associations occur in animal species is currently unknown. The significance of the brachycephalic conformation and stenotic nares in both the case reported here and in that reported previously in a dog (Coolman et al 1998) is unclear.

Endoscopic examination of the nasopharynx was valuable in establishing the diagnosis in this case and should be included in the investigation of chronic nasal discharge and stertor. Axial computed tomography is routinely used to confirm the diagnosis in humans and has been used to diagnose choanal atresia in an alpaca (Nykamp et al 2003). Definitive treatment of choanal atresia requires surgery. The transnasal approach used here was minimally invasive and endoscopic-guidance provided an excellent view of the operative field. More invasive transseptal and transpalatal approaches have been described in humans where bony involvement is common (Forer et al 2001). Disadvantages of these approaches include poor visualisation, interference with nasal development, wound breakdown and oronasal fistula formation. These techniques have been largely superceded by endoscopic approaches using a microdebrider or contact-diode laser to puncture bony obstructions (Forer et al 2001, Saetti et al 2003). Repair of bilateral membranous choanal atresia in a dog via a ventral rhinotomy was complicated by postoperative nasopharyngeal stenosis. In the cat reported here, a minimally invasive technique, stenting and low-dose oral glucocorticoids were successful in preventing postoperative stenosis. Glucocorticoids should be used with care where bilateral defects have been repaired in neonates as these cases are at risk of aspiration during feeding. Topical administration of injectable triamcinolone was recently reported together with endoscopic repair of nasopharyngeal stenosis in the dog (Berent et al 2006). No reports were found of the use of triamcinolone in cats with nasopharyngeal stenosis. Topical application of Mitomycin C, an alkylating agent that inhibits DNA synthesis, cell division and proliferation of fibroblasts, was useful in preventing scar formation after transnasal choanal repair in humans (Markova and Kabelak 2003).