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 . The guttural ; affected foals frequently exhibit a degree of pouch distention resulted in ventral displacement of the roof (Ainsworth and Hackett 2004). Females of the pharynx and severe nasopharyngeal narrowing, which are predisposed to guttural pouch tympany compared to allowed the 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 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). The ceftiofur administration was and moderate neutropenia (1.69 x 109/l). Sulphamethoxazole discontinued, and administration of sulphamethoxazole trimethoprim (15 mg/kg bwt per os q. 12 h) was begun. On Day 23, the foal began to exhibit signs of right-sided guttural pouch tympany and concurrent stertorous breathing.

Fig 6: Appearance of the right side fistula on Day 23. A web of tissue is visible deep to the fistula, and was presumed to be responsible for recurrence of tympany. The tissues were re- lasered and thus removed and the pharyngeal opening was also enlarged. Fig 4: Placement of the Foley catheter into the right side fistula.

Fig 7: Appearance of both fistulae on Day 31. Both fistulae are Fig 5: Appearance of both fistulae on Day 14. patent. 422 EQUINE VETERINARY EDUCATION / AE / september 2007

trimethoprim administration was discontinued, and a second tympany is confirmed when the right guttural pouch remains course of ceftiofur sodium (6.6 mg/kg bwt i.v. q. 12 h) was distended after the left is deflated (or vice versa). initiated for 10 days, to be followed with an additional 14 days This case report describes minimally invasive of sulphamethoxazole trimethoprim (15 mg/kg bwt per os q. transendoscopic creation of bilateral salpingopharyngeal 12 h). The foal was discharged to the owner’s care with fistulae with a diode laser to treat congenital bilateral guttural instructions to lavage the right guttural pouch through the pouch tympany in a 2-week-old foal. Lasers have been used Foley catheter the next day with 180 ml of sterile saline for several different applications in the equine guttural containing 200 mg ceftiofur sodium. Thereafter, the owner pouch, including fenestration of the medial septum to treat was instructed to lavage the pouch with 180 ml of sterile unilateral tympany (Tetens et al. 1994; Tate et al. 1995), saline once per day for 7 days. fistulation of the pharyngeal orifice to treat chronic guttural On Day 31, a final endoscopic recheck was performed. The pouch empyema (Hawkins et al. 2001), creation of a left fistula had decreased in size to approximately 30% of the unilateral salpingopharyngeal fistula (Tate et al. 1995) and length of the salpingopharyngeal opening, and was fenestration of the medial septum to facilitate removal of completely surrounded by a ring of normal-appearing mucosa. guttural pouch chondroids via the contralateral The right fistula retained a small peripheral ring of pale, salpingopharyngeal ostium (Gehlen et al. 2005). To our presumably devitalised tissue, and was approximately 50% of knowledge, creation of bilateral salpingopharyngeal fistulae the length of the salpingopharyngeal opening (Fig 7). The foal with a laser has not been reported, although its use has been did not exhibit any signs of upper or lower respiratory suggested (Tate et al. 1995). infection at that time. The foal responded well to treatment with this surgical technique, with no evidence of side effects. The Foley catheter Long-term follow-up on the left side was left in place for a shorter period (5 days) than recommended in previous publications (7–10 days [Tate The foal was normal in external appearance at a 60 day et al. 1995]) or 14 days (Tate 2004), but did not reseal; recheck examination. The owner reported that the foal conversely, the right side, in which the catheter was left in remained free of any signs of tympany or abnormal respiratory place for what is considered a more appropriate period noise 9 months post operatively. (8 days), did have recurrence of tympany 9 days after catheter removal. Granulation tissue appeared to have obstructed air- Discussion flow through the fistula, although the mucosa had not resealed. A longer duration of catheterisation or a larger area The condition of congenital guttural pouch tympany has been of laser cauterisation of the tissues may have prevented this successfully treated with several surgical procedures. These development. This finding suggests that 14 days may be a include surgical fenestration of the median septum via an more appropriate duration of catheterisation. approach through Viborg’s triangle (McCue et al. 1989), Use of the diode laser in contact mode eliminated the transendoscopic electrocautery of the median septum (Sullins need for a backstop behind the target tissues, decreasing the 1990, 1991), transendoscopic fenestration of the median technical difficulty of the procedure. Additionally, diode lasers septum with a Nd:YAG laser (Tetens et al. 1994; Tate et al. are smaller, lighter and more economical than Nd:YAG lasers. 1995), partial resection of the pharyngeal openings to the In this case, the procedure was performed under a short guttural pouch (McCue et al. 1989; Tetens et al. 1994), i.v. general anaesthesia, with the foal supported in a sternal creation of a salpingopharyngeal fistula with electrocautery position. It could alternatively be performed with standing and a trocar (Cook 1971), and transendoscopic creation of a sedation, if adequate restraint was possible. However, the unilateral salpingopharyngeal fistula with a Nd:YAG laser (Tate demeanour of the foal and excessive movement did not allow et al. 1995, 2004). sufficient accuracy with sedation alone in this instance. In foals If the guttural pouch tympany is unilateral, it may be with significant respiratory compromise, general anaesthesia possible to effectively treat the condition by creating either a would be best avoided. fenestration of the median septum by one of the above A plastic artificial insemination pipette was used to methods, or by creating an ipsilateral salpingopharyngeal manipulate the salpinyx in this case, rather than the previously fistula. Fenestration of the median septum allows release of air reported metal Chamber’s catheter (Tate et al. 1995). The through the opening of the opposite, unaffected guttural plastic pipette was selected to reduce the risk of reflected laser pouch. Ipsilateral salpingopharyngeal fistulation allows air to beam from the metal of a Chamber’s catheter. Use of the escape directly through the fistula in the pharynx on the plastic pipette could potentially result in melting plastic or affected side. flaring, although this did not occur in this case. Optimally the In cases where the condition is bilateral, it is necessary to salpinyx would be manipulated with an instrument perform 2 procedures, e.g. either fenestration of the median constructed of nonreflective, nonflammable materials, such as septum combined with a unilateral salpingopharyngeal fistula a ceramic or a matte-finished metal. (Tate et al. 1995), fenestration of the medial septum with Proper placement of the fistulae is important. A ventrally resection/revision of the salpinyx (Tetens et al. 1994), or creation located guttural pouch fistula has been associated with food of bilateral salpingopharyngeal fistula. Bilateral guttural pouch impaction of the fistula (Cook 1968). Additionally, EQUINE VETERINARY EDUCATION / AE / september 2007 423

fenestration theoretically increases the risk of contamination Blazyczek, I., Hamman, H., Ohnesorge, B., Deegen, E. and Distl, O. of the guttural pouches and subsequent infection, but this has (2003) Guttural pouch tympany in German Warmblood foals: not been reported as a complication to date, and was not a influences of sex, inbreeding and blood proportions of founding breeds as well as estimation of heritability. Berl. Munch. problem in this case. Tierarztl. Wochenschr. 116, 346-351. This case indicates that bilateral salpingopharyngeal Blazyczek, I., Hamann, H., Ohnesorge, B., Deegen, E. and Distl, O. fistulation with a diode laser is a feasible treatment for bilateral (2004b) Inheritance of guttural pouch tympany in the Arabian guttural pouch tympany in the neonate. The technique used horse. J. Hered. 95, 195-199. was technically simple, minimally invasive and avoided the Cook, W.R. (1968) The clinical features of guttural pouch mycosis in more severe complications sometimes seen with the the horse. Vet. Rec. 83, 336-345. fenestration of the median septum, such as iatrogenic damage Cook, W.R. (1971) Diseases of the ear, nose, and throat in the horse. to the or blood vessels of the guttural pouch. It Part 1. Vet. Ann. 12, 12-43. also allowed treatment of the foal on an outpatient basis. Gehlen, H. and Ohnesorge, B. (2005). Laser fenestration of the mesial In summary, creation of bilateral salpingopharyngeal septum for treatment of guttural pouch chondroids in a pony. fistulae with a diode laser is a viable treatment choice for foals Vet. Surg. 34, 383-386. with bilateral guttural pouch tympany, is relatively technically Hawkins, J., Frank, N., Sojka, J. and Levy, M. (2001). Fistulation of the auditory tube diverticulum (guttural pouch) with a easy to perform, and should be considered along with other neodymium:yttrium-aluminum-garnet laser for treatment of chronic more established techniques when treating bilateral guttural empyema in two horses. J. Am. vet. med. Ass. 218, 405-407. pouch tympany. McCue, P.M., Freeman, D.E. and Donawick, W.J. (1989) Guttural pouch tympany: 15 cases (1977-1986). J. Am. vet. med. Ass. Manufacturers’ addresses 194, 1761-1763. Sullins, K.E. (1990) Endoscopic application of cutting current for upper 1Les Wilkins, Seattle, Washington, USA. respiratory surgery in the standing horse. Proc. Am. Ass. equine 2 Mila International, Florence, Kentucky, USA. Practnrs. 36, 439. 3Vedco, St. Josephs, Missouri, USA. 4Lumenis, Santa Clara, California, USA. Sullins, K.E. (1991) Standing endoscopic electrosurgery. Vet. Clin. N. 5Buffalo Filter, Buffalo, New York, USA. Am.: Equine Pract. 7, 571-581. Tate, L.P. (2004) Why lasers in the airway. Proc. Am. Coll. Vet. Surg. References 39, 116-119. Tate, L.P., Blikslager, A.T. and Little, E.D.E. (1995) Transendoscopic laser Ainsworth, D.M. and Hackett, R.P. (2004) Disorders of the respiratory treatment of guttural pouch tympanites in eight foals. Vet. Surg. system. In: Equine Internal Medicine, 2nd edn., W.B. Saunders, St. 24, 367-372. Louis, Missouri. p 300. Tetens, J., Tulleners, E.P., Ross, M.W., Orsini, P.G. and Martin, B. (1994) Blazyczek, I., Hamman, H., Deegen, E., Distl, O. and Ohnesorge, B. Transendoscopic contact neodymium:yttrium aluminum garnet (2004a) Retrospective analysis of 50 cases of guttural pouch laser treatment of tympany of the auditory tube diverticulum in tympany in foals. Vet. Rec. 154, 261-264. two foals. J. Am. vet. med. Ass. 204, 1927.