Case Report Laser Fenestrated Salpingopharyngeal Fistulas for Treatment of Bilateral Guttural Pouch Tympany in a Foal W
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EQUINE VETERINARY EDUCATION / AE / september 2007 419 Case Report Laser fenestrated salpingopharyngeal fistulas for treatment of bilateral guttural pouch tympany in a foal W. KREBS* AND W. B. SCHMOTZER Bend Equine Medical Center, 19121 Couch Market Road, Bend, Oregon 97701, USA. Keywords: horse; bilateral guttural pouch tympany; diode laser; bilateral salpingopharyngeal fistulae Introduction Clinical examination Guttural pouch tympany describes the condition in which one, On physical examination, the parotid area was bilaterally or both, guttural pouches become air-distended. Congenital enlarged, with the left side being slightly more prominent guttural pouch tympany manifests in neonatal foals, and can externally. No nasal discharge was evident. Thoracic be unilateral or bilateral, although unilateral presentation is auscultation was impaired due to referred noise from the more common (Tate et al. 1995). It is thought that in affected stertorous respiration. The foal was febrile (38.9ºC). Appetite foals, the mucosal flap that covers the opening to the guttural remained good and the foal was able to nurse vigorously. pouch acts as a one-way valve, allowing air to enter but not to Diagnostic tests exit. The cause is unknown, but theories include dysfunction of the mucosal fold itself, or malfunction of the pharyngeal The foal was sedated with xylazine (2 mg/kg bwt i.v. musculature (Ainsworth and Hackett 2004). administered twice during endoscopy) for standing Guttural pouch tympany may result in dyspnoea and/or videoendoscopic examination of the pharynx. The guttural dysphagia; affected foals frequently exhibit a degree of pouch distention resulted in ventral displacement of the roof aspiration pneumonia (Ainsworth and Hackett 2004). Females of the pharynx and severe nasopharyngeal narrowing, which are predisposed to guttural pouch tympany compared to allowed the soft palate to obstruct the larynx intermittently. males at a 2.92:1 ratio (Blazyczek et al. 2004a), and the No anatomical abnormalities of either guttural pouch opening heritability is estimated at 0.81 ± 0.16 (Blazyczek et al. 2003) were identifiable. A stylette passed through the biopsy port of with a theorised polygenic and a mixed monogenic-polygenic the endoscope was used to facilitate entrance of the mode of inheritance (Blazyczek et al. 2004b). The Paint horse endoscope into each of the guttural pouches sequentially. and Arabian breeds may be overrepresented (Blazyczek et al. Upon entrance of the endoscope into each individual guttural 2004a). pouch, each pouch respectively quickly deflated; however, the This article records the first published use of a right guttural pouch remained distended after the left was transendoscopic diode laser to create bilateral deflated, which was evidence of a bilateral disease. The salpingopharyngeal fistulae to treat congenital guttural interior of the guttural pouches was considered normal in pouch tympany in a neonate. appearance. The tracheal lumen contained moderate amounts of purulent material, which was aspirated transendoscopically Case details using sterile polyethylene tubing1. The sample was submitted for bacterial culture, and flora was subsequently characterised History as a moderate growth of Streptococcus zooepidemicus and a heavy growth of normal respiratory flora. Cytology of the A 2-week-old intact male American Paint Horse was referred tracheal aspirate revealed few white blood cells, rare epithelial cells, moderate numbers of Gram-negative rods and few for evaluation and treatment of bilateral guttural pouch Gram-positive paired cocci. A complete blood count and tympany. The tympanic guttural pouches were first observed serum chemistry were within normal limits. at 2 days of age. By Day 10, the tympany had progressed and had begun to cause stertorous breathing and dyspnoea. Diagnosis A diagnosis of congenital bilateral guttural pouch tympany *Author to whom correspondence should be addressed. with secondary aspiration pneumonia was made. 420 EQUINE VETERINARY EDUCATION / AE / september 2007 Treatments dorsocaudal to the guttural pouch ostium. The final size of the created fistula was approximately 1 cm (Fig 1). Size of the An over-the-wire i.v. catheter2 was placed in the left jugular fistula was determined by comparing to the diameter of the vein, and ceftiofur sodium administered i.v. at 6.6 mg/kg bwt. 9 mm endoscope, the tip of which could be inserted into the The foal was pretreated with 1 mg/kg bwt flunixin meglumine final fenestration. Total treatment time per fistulation was i.v. and with 0.04 mg/kg bwt dexamethasone i.v. to minimise approximately 60 s with total treatment energy of 970 J. post operative oedema formation. The foal was anaesthetised Smoke was evacuated using a smoke evacuator system5 with a combination of 0.02 mg/kg bwt detomidine i.v., placed at the contralateral nostril. Small amounts of 0.06 mg/kg bwt butorphanol i.v. and 2 mg/kg bwt ketamine haemorrhage were encountered, but did not interfere with i.v. for transendoscopic laser fenestration of the left guttural laser firing or visualisation. Patency of the fistula was pouch. The foal was positioned in sternal recumbency, and confirmed by directing the bent tip of the artificial supported on either side by assistants. A plastic artificial insemination pipette retrograde through the defect until the insemination pipette3 was moulded using application of heat tip could be visualised. An 18 French Foley catheter was then to create a mildly angled (approximately 20º) distal 5 cm tip. guided antegrade through the fistula with the help of a The customised pipette was passed through the ipsilateral custom metal stylette, and seated within the guttural pouch nostril and nasal passage and passed through the opening of (Fig 2). The balloon cuff was distended to prevent the guttural pouch. The tip was then angled axially in order to dislodgement. The rostral end of the Foley catheter was elevate and tense the pharyngeal tissues for laser treatment. A sutured into the false nostril. 50 watt diode laser4 and 600 micron fibre was used The foal was discharged following surgery to the owner’s transendoscopically through the biopsy channel of the care with instructions for continued administration of ceftiofur endoscope at 20 watts power in continuous (80:20), contact sodium at 6.6 mg/kg bwt i.v. q. 12 h for 14 days, 1 mg/kg bwt mode through the contralateral nostril to create a full- flunixin meglumine i.v. once the next day, and 0.04 mg/kg bwt thickness salpingopharyngeal fistula approximately 1 cm dexamethasone i.v. once the next day to minimise post operative pharyngeal oedema. The owner was instructed to leave the Foley catheter in place for 10 days to allow time for epithelialisation of the edges of the fistula to prevent premature closure. The foal was returned for re-evaluation on post operative Day 5 because it had prematurely dislodged the Foley catheter. The foal did not exhibit any external signs of guttural pouch tympany or excessive respiratory noise. On endoscopic examination, the fistula was patent, and appeared to have enlarged slightly from its original size, presumably via thermal necrosis around its periphery (Fig 3) and wound retraction. The fistula was considered unlikely to close prematurely due to its large size, and it was concluded that the fistulation of the right side could be carried out the same day. The same preoperative analgesic/anti-inflammatory drug Fig 1: Endoscopic photo showing the newly created fistula in therapy was repeated, the foal was anaesthetised with the left side of the pharynx. xylazine (2 mg/kg bwt i.v. administered twice during the anaesthetic period) and ketamine (2.6 mg/kg bwt i.v. Fig 2: Antegrade insertion of a Foley catheter through the fistula and into the guttural pouch. Fig 3: Appearance of the left side fistula 5 days after its creation. EQUINE VETERINARY EDUCATION / AE / september 2007 421 administered 3 times) and a matching fistula was created in Endoscopic examination showed that both fistulae remained the right pharyngeal wall (Fig 4). The 600 micron laser fibre patent, and the ring of necrosis had been almost completely used in the first procedure was exchanged for a 1000 micron replaced with healing mucosal tissue. The right side fistula fibre to decrease the time necessary for fistula formation; appeared to have an adequately-sized external pharyngeal settings were the same. Total treatment time was opening, but the inner lumen was partially obstructed with approximately 50 s, with total energy of 793 joules. An webs of tissue (Fig 6). The fistula was retreated with the diode 18 French Foley catheter was placed through the newly laser and 1000 micron fibre at 20 watts power to remove the created fistula; the Foley catheter was not replaced in the left obstructive tissue; approximately 560 joules were used. The salpingopharyngeal fistula because of concern that bilateral interior of the guttural pouches were re-examined and catheterisation might compromise nasal air flow. showed accumulations of purulent material in the ventral No changes were made to the antimicrobial therapy, and aspect; a repeat tracheal wash was performed, and the the foal was discharged to the owner’s care on the same tracheal aspirate was submitted for bacterial culture. previous plan for post operative analgesia/anti-inflammatory Subsequent bacterial culture results from the tracheal aspirate therapy. showed a light growth of Streptococcus zooepidemicus, The foal was re-examined endoscopically on Day 14 for a which was sensitive to ceftiofur sodium. A Foley catheter was scheduled recheck. The Foley catheter was removed from the replaced within the fenestration and 250 ml of 0.9% sterile right salpingopharyngeal fistula following confirmation of a saline solution containing 2 mg/ml ceftiofur sodium were large, patent fenestration. The fistula was similar in appearance injected via the Foley catheter to lavage the guttural pouch. to the left, with a clearly patent opening and a periphery of A complete blood count showed mild leucopenia (5.16 x 109/l) pale mucosal tissue (Fig 5).