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Comments? Questions? Email: [email protected] Web: VetLearn.com • Fax: 800-556-3288 CE Article #5 (1.5 contact hours) Refereed Peer Review Diagnosing Guttural Pouch Disorders and Managing Guttural Pouch Empyema in Adult Horses KEY FACTS Cornell University I The guttural pouches contain Gillian A. Perkins, DVM, DACVIM many important neurovascular Anthony Pease, DVM structures that contribute to the Erin Crotty, DVM clinical signs of guttural pouch Susan L. Fubini, DVM, DACVS disorders.

I Bilateral or unilateral ABSTRACT: Clinical signs of guttural pouch disorders are associated with other structures in mucopurulent nasal discharge the area. Signs include cranial nerve dysfunction ( VII through XII), epistaxis can be seen with guttural pouch with mycosis of the internal and external carotid and maxillary arteries, and bilateral or unilat- empyema. eral mucopurulent nasal discharge. Guttural pouch empyema can be diagnosed by endoscopy and culture of the exudate. The most common bacterial species that result in guttural pouch empyema include Streptococcus zooepidemicus and Streptococcus equi. Treatment is often I Endoscopic examination frustrating because of the cost and duration of guttural pouch lavages, systemic antibiotics, provides the most diagnostic and antiinflammatories required to clear the exudate and infection. One-fifth of horses with information for guttural pouch guttural pouch empyema develop chondroids that may require more aggressive therapy. diseases, although radiography can be helpful. quine guttural pouches (auditory tube diverticula) are unique because of I The most common isolates their size—Equine guttural pouches are the largest of several species exam- from horses with guttural Eined in one study.1 The function of these pouches has been debated for pouch empyema are nearly two centuries, with hypotheses that they are a voice-resonating chamber, a Streptococcus zooepidemicus buoyancy device, or simply a space filler. A current hypothesis is that they play a and Streptococcus equi. role in cooling blood to the brain,2 although their purpose is still under debate.3 Although diseases of the guttural pouches are relatively rare, it is important to I Guttural pouch empyema can be be able to accurately diagnose and treat them to avoid sequelae, such as dyspha- frustrating to treat because gia or even fatal hemorrhage, as can occur with mycotic infections. This article repeated and possibly long-term reviews the anatomy and diagnostic imaging of the equine guttural pouch and guttural pouch lavage, discusses the clinical signs as well as diagnostics, treatments, and techniques used antiinflammatories, and in adult horses with guttural pouch empyema. systemic antibiotics are required and nearly 20% of horses with RELEVANT ANATOMY guttural pouch empyema have The equine guttural pouches are paired diverticula of the eustachian tubes, complications. each normally containing approximately 300 ml of air.4 Each guttural pouch is draped over the stylohyoid bone, forming medial and lateral pouches, with the

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medial pouch having twice the capacity of the lateral Endoscopy pouch. The is pseudostratified and ciliated Endoscopy is used most commonly and is an invalu- and contains goblet cells; mucous glands and lymph able tool for diagnosing upper airway and guttural nodules are also present.4 pouch disease. The fibrocartilage flap covering the pha- The guttural pouches are ventral to the cranium and ryngeal orifice of the guttural pouch must be adducted atlas and dorsolateral to the and extend ros- or elevated to advance the endoscope. The following trally to the level of the pharyngeal orifice of the steps generally require adequate restraint in stocks and caudally to the level of the and/or a nose or neck twitch. Sedation with detomidine atlantoaxial joint. They are partially separated by the hydrochloride (0.02 mg/kg IV) or a combination of rectus capitis ventralis and longus capitis muscles.4 xylazine hydrochloride (0.4 mg/kg IV) and butorphanol Below the longus capitis, the guttural pouches are in tartrate (0.01 to 0.02 mg/kg) is recommended. To per- direct contact with each other, separated only by a thin form this, a flexible biopsy instrument passed through medial septum. Each guttural pouch communicates the biopsy channel of the endoscope or a Chamber’s with the pharynx via the pharyngeal orifice of the is necessary. The endoscope is passed nasally eustachian tube, covered by a thin plate of fibrocarti- (ventral and medial) and directed toward the dorsal lage. The pharyngeal orifice of the eustachian tube com- aspect of the ipsilateral guttural pouch; the flexible municates with the guttural pouch through a funnel- biopsy instrument is then advanced through the biopsy shaped vestibule, which is wider rostrally than caudally. channel and under the fibrocartilage flap until it is well A mucosal fold at the caudal aspect of the eustachian seated in the guttural pouch. tube, known as the plica salpingopharyngea, causes the Problems can be encountered when the biopsy instru- narrowing and forms a continuous ventral connection ment is too far ventral and does not pass fully into the between the medial lamina of the eustachian tube and pouch or when the instrument has entered the nasal the lateral wall of the pharynx.4 The plica salpingopha- cavity too dorsally and adjustment of the endoscope ryngea can sometimes be redundant and act as a one- should be necessary. Once the biopsy instrument is well way valve, trapping air within the guttural pouch and, seated, the endoscope is rotated counterclockwise for in turn, resulting in guttural pouch tympany.4,5 the right guttural pouch and clockwise for the left gut- Many important structures are anatomically related tural pouch and advanced slowly into the guttural to the guttural pouch and must be considered when pouch. Because the biopsy channel is eccentrically treating guttural pouch disease either medically or sur- located in the endoscope, the biopsy instrument actually gically. The , cranial cervical gan- rotates the flap away from the wall of the pharynx to glion, (i.e., cranial nerve X), glossopharyn- facilitate passage of the scope into the guttural pouch. geal nerve (i.e., cranial nerve IX), Once inside the guttural pouch, the biopsy instrument (i.e., cranial nerve XII), (i.e., cranial can be retracted into the biopsy channel. This process nerve XI), and sympathetic nerves all course through should be repeated in the opposite nasal passage to view the caudal lateral wall of the medial compartment.4 The the opposite guttural pouch. ventral wall of the medial compartment contains the Alternatively, a Chamber’s catheter can be placed pharyngeal branch of the vagus nerve, the cranial laryn- nasally, advanced into the nasopharynx, and viewed by geal nerve, and retropharyngeal lymph nodes. The ven- the endoscope, which is passed into the opposite nos- tral aspect of the lateral compartment contains the tril. The Chamber’s catheter is advanced into the gut- (which becomes the maxillary tural pouch opening that is on the same side in which artery), maxillary vein, chorda tympani nerve, and the endoscope has been passed (opposite to the side in (i.e., cranial nerve VII).4 The digastricus which the Chamber’s catheter was passed). The catheter muscle and the mandibular and parotid salivary glands is rotated to open the guttural pouch flap, allowing easy border the lateral wall of the lateral compartment. The passage of the endoscope. The guttural pouch is thor- jugular and linguofacial veins course ventral and lateral oughly examined by the clinician, who methodically to the pouches and just dorsolateral to the paired ster- looks at the medial and lateral compartments, dorsally nocephalicus and omohyoideus muscles, which lie ven- and ventrally, for evidence of mycosis, empyema, tem- tral to the guttural pouches. porohyoid osteopathy, and less common conditions, such as chondroids, cysts, and neoplasia.6 DIAGNOSTIC IMAGING A variety of diagnostic imaging techniques are avail- Radiography able for investigating cases of suspected guttural pouch Radiography can aid in diagnosing guttural pouch disease.6 diseases, especially when endoscopy is limited because of

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the severity of disease. Radiographic procedures are not technically challenging and can be performed by most x-ray machines. The caveat is that cassette holders and proper technique are required to optimize the safety of the patient while minimizing exposure to personnel. However, lesions identified on radiographs are rarely pathognomonic; therefore, further diagnostic tests (i.e., endoscopy or surgical exploration) are required. For imaging guttural pouches at the Cornell Univer- sity Hospital for Animals (CUHA), the horse is sedated while in standing stocks and placed in a halter made of gauze. A cassette holder is used to eliminate the need for a person near the primary x-ray beam. Using the machine at CUHA (Siemens Mobilette Plus, Siemens Medical Solutions, USA, Inc., Iselin, NJ), a technique using a 75 kilovolt peak (kVp) and 10 milliamp sec- onds (mAs) is usually adequate for an average-size horse. A fine screen is used without a grid to help mini- mize exposure time and dose while maximizing detail. If regular screens are used, the recommended exposure is a 66 kVp and 16 mAs. A routine examination includes opposite lateral radiographs (of the guttural Figure 1—Right lateral radiograph of the guttural pouch in a pouch region). CUHA has a smaller portable unit (HF clinically normal adult horse. Note the following features: the 80+, MinXray, Inc., Northbrook, Il) that can acquire body of C1 (1), the dens of C2 (2), the gas-filled guttural the images as described. The high frequency 80+ and pouches (3), the epiglottis (4), the left stylohyoid bone (5), other small portable units are able to generate a 50 to the right stylohyoid bone (6), the basisphenoid bone (7), and the external acoustic meatus (8). 80 kVp and up to 15 mAs. A lateral radiograph of the laryngeal region provides a clear outline of the guttural pouch (Figure 1). A ventrodorsal radiograph has been recom- mended to help differentiate unilateral from bilateral dis- ease.7,8 However, this view gener- ally requires general anesthesia, and thus the cost and risks out- weigh the benefits of the diag- nostic procedure. Portable radi- ograph machines can be used to obtain dorsoventral views with the use of heavy sedation to lower the horse’s head and pre- vent injury because the tube (located dorsally) cannot be moved away quickly if the horse raises its head abruptly. Radia- tion exposure is high, and expo- sure time may lead to motion artifact. Acquiring opposite lat- eral radiographs has been sug- Figure 2— Right and left lateral radiographs of the guttural pouch in a horse with left-sided gested to avoid general anesthe- guttural pouch empyema. Note: the fluid line (arrows) should appear sharper on the left lat- eral radiograph compared with that on the right. However, this may be difficult to assess. sia. In a unilateral infection, the fluid line has a sharper margin

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Figure 3—Lateral radiograph of the head of an adult horse showing chondroids in the guttural pouch. (Courtesy of the Section of Radiology, Cornell University)

when closest to the cassette9 (Figure 2). In the author’s experience (A. P.), right caudal–left cranial and left cau- dal–right cranial oblique radiographs allow enough sep- aration of the guttural pouches to differentiate bilateral from unilateral disease. Figure 4—Right lateral, positive-contrast angiogram of the left The main finding with radiography of the guttural side of the head in an adult horse with left-sided guttural pouch is the presence of soft tissue/fluid opacity in the pouch mycosis. A 14-gauge catheter was placed in the com- mon carotid artery. Iodinated, ionic contrast material (100 ml) usually gas-filled structure. The appearance of the soft was administered using a power injector set to administer a tissue/fluid opacity may vary with the disease process dose of 20 ml/sec with a 1-sec linear rise. The radiograph was (e.g., smoothly marginated, irregularly shaped masses obtained 3 sec after the injection was completed. No abnor- secondary to chronic guttural pouch mycoses [Figure 3]; malities were detected in the vascular structures of the head. fluid lines either unilateral or bilateral within the gut- tural pouches secondary to hemorrhage, emphysema, or diverticulitis). Also, the pharyngeal wall (i.e., ventral described,8 and the purposes of the procedure are to border of the guttural pouch) may appear thick or irreg- evaluate the size and margin as well as whether the ves- ularly shaped with pharyngeal lymphoid hyperplasia.7,8 sels are patent by using a positive-contrast medium. For common carotid angiography, there are no special rec- Other Methods ommendations, although general anesthesia and fluo- Masses in or encroaching on the guttural pouch are roscopy are recommended. Any contrast medium can rare but include masses of the parotid or retropharyn- be used; however, because of the large volume (100 geal lymph nodes or primary cancer of the guttural ml), a pressure injector is recommended to achieve an pouch (i.e., usually squamous cell carcinoma or adequate bolus. The use of fluoroscopy and angiogra- melanoma).9 Masses arising from the skull have also phy provides a road map of the vasculature when using been described.7 Differentiating the masses from fluid arterial coil embolization for treating guttural pouch is difficult and is usually done by ultrasonography or mycosis. endoscopy. Because the parotid can Neither computed tomography (CT) nor magnetic sometimes cause guttural pouch lesions secondary to resonance imaging (MRI) has been reported as an aid occlusion of the auditory tube or erosion into the gut- in diagnosing guttural pouch disease in horses, except tural pouch, a sialogram can be performed.7 for cases of temporohyoid osteoarthropathy.10 This is Before surgery for guttural pouch mycosis, carotid most likely because most disorders of the guttural angiography has been recommended to help visualize pouch are diagnosed using endoscopy and radiography. the anatomy of the vasculature associated with the CT or MRI may help to more clearly define bony head7,9 (Figure 4). The technique has been thoroughly lesions that may cause secondary hemorrhage into the

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Differential Diagnosis Pharyngitis and upper or lower respiratory tract infec- tions can have a mucoid discharge present at the pha- ryngeal orifices when examined endoscopically. Guttural pouch tympany can have concurrent empyema. Diagnostic Evaluation Endoscopic findings include purulent exudate on the floor of the guttural pouch, mucosal hyperplasia, thicken- ing and discoloration of the cartilage flap at the pharyn- geal orifice,13 pharyngeal edema or narrowing, pharyngeal lymphoid hyperplasia, pharyngeal asymmetry, and chon- droids11 (Figure 5). Horses with strangles may have Figure 5—Chondroids removed from the guttural pouch. retropharyngeal lymph node enlargement noted on the (Courtesy of R. P. Hackett, Cornell University) floor of the guttural pouch (i.e., medial and/or lateral compartments, right and/or left guttural pouch), which can also result in dorsal collapse of the pharynx. Radio- guttural pouches, such as fracture of the stylohyoid graphs show unilateral or bilateral fluid lines and, in some bone. The limitations of CT and MRI include the cases, chondroids (Figure 3). Radiography is slightly less necessity for general anesthesia, the time required for sensitive than endoscopy in detecting chondroids.11 positioning and the procedure, and limited availability A sample taken directly from the guttural pouches of the technology for equine patients. endoscopically for aerobic and anaerobic culture and sensitivity is most representative of the infectious etiol- GUTTURAL POUCH EMPYEMA ogy of the guttural pouch empyema, although nasopha- Etiology and Clinical Signs ryngeal swabs can be obtained if the other is not feasi- Guttural pouch empyema is characterized by the uni- ble. The goals of culturing the affected guttural pouch lateral or bilateral accumulation of mucopurulent exu- are to confirm the presence of S. equi and obtain an date in the guttural pouches. It can occur as a sequela antimicrobial sensitivity pattern. Very little work has to upper respiratory tract infection, typically with β- been done to evaluate the normal flora of the equine hemolytic streptococci: Streptococcus equi subspecies guttural pouch, and it is assumed to be similar to that zooepidemicus or, of particular importance, Streptococcus of the rest of the equine upper respiratory tract. Nearly equi subspecies equi. Horses with suspect guttural pouch 60% of percutaneous guttural pouch lavages from 30 empyema should be handled with appropriate biosecu- clinically normal horses had positive cultures, and only rity precautions because it is frequently a sequela to a few were considered to be aerobic of recog- infection of the retropharyngeal lymph nodes with nized pathogenicity, such as Pseudomonas aeruginosa. strangles. In a recent study, 30% of horses with guttural No fungal organisms were isolated.14 Therefore, inter- pouch empyema tested positive for strangles,11 and preting culture results may be difficult; a clinician must asymptomatic horses can carry S. equi in their guttural determine whether an isolated organism is the offend- pouches for extended periods of time.12 Other isolates ing agent or normal flora. from horses with guttural pouch empyema include A guttural pouch wash can be obtained by using ster- Escherichia coli, Klebsiella spp, Corynebacterium spp, ile technique and advancing a sterile polyethylene tube Bordetella spp, and Salmonella spp.11 through the biopsy channel of a previously sterilized The most common clinical signs of empyema are per- endoscope into the guttural pouch. Before passing the sistent mucopurulent nasal discharge (either unilateral tubing into the endoscope, a 14- or 16-gauge needle or bilateral; it can be bilateral with unilateral empyema) (that has had the sharp end sawed off) is placed in one and retropharyngeal swelling that is painful on palpa- end of the tubing to facilitate attachment of a syringe for tion. Other clinical signs usually include cough, fever, aspiration. To maintain sterility, an injection cap can be anorexia, respiratory noise, depression, dyspnea, and placed on the end of the needle until the syringe is used. .11 Occasionally, cases of empyema are compli- Once in the guttural pouch, the tubing is advanced, and cated by the presence of chondroids (oval masses formed up to 50 ml of sterile saline can be instilled into the gut- by inspissated pus), which can prevent complete resolu- tural pouch and subsequently aspirated using the endo- tion of empyema until removed. Their presence can be scope to visualize the fluid. The fluid is then submitted confirmed endoscopically or radiographically. for culture as already described.12 These samples could

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also be submitted for S. equi PCR15 for diagnosis or fol- nia. A Chamber’s catheter can be passed blindly and low-up evaluation of the previously infected guttural nasally into the nasopharynx and advanced into the pouch to declare it free of S. equi. guttural pouch by advancing the curved end beneath the flap of the medial lamina of the ipsilateral pouch. Treatment The Chamber’s catheter, when properly advanced to Guttural pouch empyema, when diagnosed early and complete depth into the guttural pouch, has a very treated appropriately, generally resolves uneventfully. characteristic feel, without any resistance; otherwise, at Treatment requires lavaging the pouch on a daily basis this depth, resistance would be felt at the caudal aspect for 5 to 10 days. Guttural pouch lavage and establish- of the pharynx, and the horse would begin to swallow. ment of drainage are the most helpful factors in suc- If difficulty is encountered and/or to ensure proper cessfully treating guttural pouch empyema, and this is placement, the endoscope can be passed in the opposite often accompanied by antiinflammatories and systemic nasal passage to view the placement of the Chamber’s antimicrobials. This can be costly to a client because catheter. We advise against blind placement of the lavaging the guttural pouches requires hospitalization Chamber’s catheter and recommend that placement be (mean hospitalization time for horses was 8 days in one confirmed by endoscopic visualization. Once the study, although the range was 1 to 176 days)11 or Chamber’s catheter is confirmed to be in the guttural repeated visits to the farm. Also, a horse may require pouch, a fluid administration line can be secured to the irrigation of the guttural pouches for an extended end of the catheter and a substantial volume (up to 3 to period of time beyond what was initially estimated. 5 L) of isotonic balanced electrolyte solutions can be Twenty percent of horses with guttural pouch flushed through the system using a pump, manual pres- empyema have complications and may require more sure, or a fluid pressure bag. This entire procedure may sophisticated and invasive procedures.11 take 30 to 60 minutes. The efficacy of systemically administered antimicro- Addition of antimicrobials or antiseptics to the lavage bials for treating guttural pouch empyema may be solution is controversial, although 47 of 91 (52%) decreased by poor drug penetration into the guttural horses with guttural pouch empyema had either pouch and into the interior of the exudate. It is impor- antimicrobials (unspecified) or iodine solutions diluted tant to remember that lavage and establishment of to various concentrations added to the lavage solu- drainage are mainstays of successful management of tion.11 There were no discernible differences between guttural pouch empyema and that systemic antimicro- horses treated with additives in the lavage fluid versus bials are an adjunct to therapy. Indications for systemic those treated solely with isotonic fluids. In fact, both antimicrobials in guttural pouch empyema include pro- the authors of this retrospective study11 and an experi- tection of the lower airways from contaminated mental study in which 1% povidone-iodine and 3% drainage from the pouch, especially during lavage; pre- hydrogen peroxide solution were infused into the gut- vention and treatment of ; and tural pouch of horses on three to four occasions, caus- treatment of lymph node abscesses. The nasal discharge ing inflammation and exudate production,16 advise often persists with antimicrobial treatment alone. against using these substances in the guttural pouch. When treating with antimicrobials, the antibiotic of The mechanical action of the flushing most likely pro- choice should be based on susceptibility patterns of the vides the most benefit in these horses. Therefore, we bacterial organism isolated. The drug of choice for the recommend lavaging the guttural pouches with isotonic most commonly isolated organisms, S. equi and S. balanced electrolyte solutions and discourage the instil- zooepidemicus, is penicillin; because the treatment is fre- lation of noxious agents (e.g., betadine, acetylcysteine, quently prolonged, IV penicillin is preferred to avoid hydrogen peroxide) into the guttural pouch because of repeated high-volume IM injections (sodium or peni- harmful and serious adverse effects (e.g., dysphagia). cillin G potassium at 22,000 IU q6h). If the cost of IV A Chamber’s catheter can be passed on a daily basis to penicillin is prohibitive, penicillin G procaine (22,000 irrigate the guttural pouches. Alternatively, a retention IU IM q12h) or sodium ceftiofur (2 mg/kg IV or IM catheter can be made using an 8- or 10-Fr polypropylene q12h) can be used. Seventy-five percent of isolates in male dog urinary catheter17 or polyethylene tubing18 one study were resistant to potentiated sulfonamides, (Figure 6), or a commercially available guttural pouch making them a less favorable treatment option.11 catheter can be used. These retention are some- Irrigating the guttural pouch requires sedation of the times difficult to place, can only facilitate small amounts horse to maintain restraint and keep the head low to of fluid for irrigation, and are frequently sneezed or encourage drainage of the contaminated guttural pouch blown out by the horse. In addition, the problems with fluid from the nostrils and prevent aspiration pneumo- retention catheters must be weighed against the trauma

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down the mucoprotein and allow subsequent drainage of the guttural pouch. This was successful in one horse, without any adverse complications.20 Nonsurgical en- doscopic removal of chondroids using a snare can be attempted in standing horses or under general anesthe- sia.21 Removal of chondroids was successful in 7 of 16 (44%) horses using lavage and/or endoscopic snare technique11 and is therefore worth attempting. Fre- quently, these procedures are long and involved, requir- ing hours and innovative instrumentation. Should the procedure be unsuccessful, the surgical approach is the last viable option. Figure 6—Retention catheter for daily treatment of guttural For chronic and/or recurrent empyema or abnormali- pouch empyema. ties of the opening of the pharyngeal orifice of the guttural pouch, creating a fistula using a neodymium: yttrium–aluminum–garnet laser has been described by to the pharynx induced by passage of a firm metal Hawkins et al.22 The procedure is performed in stand- Chamber’s catheter on a daily basis. Alternatively, ing, well-sedated horses. The mucous membranes sur- indwelling Foley catheters can be placed easily with the rounding the pharyngeal orifice of the guttural pouch help of a Chamber’s catheter or stylet and visualized with are topically anesthetized, and a Chamber’s catheter is the endoscope in the opposite nasal passage. Once the inserted into the guttural pouch and then withdrawn Foley is completely within the guttural pouch, the bal- until its distal end remains just inside the guttural loon is distended with saline and the stylet or Chamber’s pouch and can be observed tensing the pharyngeal catheter removed. Distention of the balloon within the mucosa dorsal to the pharyngeal opening.22 The funnel of the pharyngeal opening could cause pressure neodymium:yttrium–aluminum–garnet laser is used to necrosis.19 Foley catheters can stay in place without incise the portion of the cartilage directly over the suturing to the nares. Unfortunately, standard Foley Chamber’s catheter. To prevent premature closure of catheters may not be long enough to reach the guttural the new opening, a 22- to 30-Fr Foley catheter is pouch in large horses.19 Indwelling Foley catheters are inserted through the fistula and into the guttural pouch superior for intermittent lavage of the guttural pouches and maintained up to 14 days postoperatively.22 This because large volumes of fluid can be administered and procedure provides a large opening into the pharynx they are easier to pass and maintain. Others have men- and improves drainage from the guttural pouches when tioned daily flushing with a larger bore tube, such as an the horse lowers its head to drink water or eat. equine stomach tube, guided into the guttural pouch by Complications from this procedure were not noted in the endoscope and Chamber’s catheter. the two horses. This procedure can be done in standing Most horses (up to 80%) with uncomplicated gut- horses, avoids complications such as dysphagia and tural pouch empyema are successfully managed with iatrogenic trauma to the cranial nerves associated with daily irrigation of the guttural pouches for 5 to 10 open surgical exposure of the guttural pouch, and could days.11,17 If the horse is continuing to improve at the be used in place of traditional surgical techniques to end of this time frame, it is justified to continue treat- establish drainage from the guttural pouch in horses ing the horse medically with irrigation. In one study, with chronic guttural pouch empyema and chon- 20% of horses with guttural pouch empyema11 showed droids.21 For example, a horse with chronic guttural no improvement with repeated flushing and had inspis- pouch empyema with inspissated, purulent material sated purulent material, chondroids, or abnormalities improved 90% through a modified Whitehouse surgical of the pharyngeal openings of the guttural pouch; approach. Then a fistula was made, more of the inspis- therefore, more aggressive procedures were necessary. sated material could be removed, the rest of the exudate Management decisions can be difficult to make because eventually drained, and the horse was cured.a On a of the risks involved with performing surgery in this recheck examination several months later, the fistula had area and the financial burden to the client. More inva- healed over.a Further studies investigating the pros and sive nonsurgical treatments for chondroids include cons of this procedure in the horse are warranted. using acetyl cysteine (i.e., 60 ml of a 20% solution aParente E: Personal communication, New Bolton Center, infused into the pouch using polyethylene tubing School of Veterinary Medicine, University of Pennsylvania, through the biopsy channel of the endoscope) to break Kennett Square, Pennsylvania, 2003.

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More aggressive surgical treatment strategies may be pouch catheter: Production and placement. Proc AAEP needed for cases that are refractory to medical manage- 43:158–159, 1997. ment. A modified Whitehouse approach with the horse 19. Hardy J, Leveille R: Diseases of the guttural pouches. Vet Clin North Am Equine Pract 19:123–158, 2003. in dorsal recumbency or a Viborg’s triangle approach 20. Bentz BG, Dowd AL: Treatment of guttural pouch empyema can be used in standing horses, and these approaches with acetylcysteine irrigation. Equine Pract 18(9):33–35, 1996. 6 are discussed elsewhere. 21. Seahorn TL, Schumacher J: Nonsurgical removal of chondroid masses from the guttural pouches of two horses. JAVMA 199(3): REFERENCES 368–369, 1991. 1. Baptiste KE: Functional anatomy observations of the pharyngeal 22. 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Butler JA, Colles CM, Dyson SJ, et al: Pharynx, larynx, and sopharyngeal nerve (IX), vagus nerve (X) eustachian tube diverticulum, in Butler JA, Colles CM, Dyson SJ, et al (eds): Clinical Radiology of the Horse, ed 2. London, d. trigeminal nerve (V), vagus nerve (X), accessory Blackwell Science, 2000, pp 384–393. nerve (XI), hypoglossal nerve (XII) 10. Walker AM, Sellon DD, Cornelisse CJ, et al: Temporohyoid e. facial nerve (VII), glossopharyngeal nerve (IX), osteoarthropathy in 33 horses (1993–2000). J Vet Intern Med vagus nerve (X), accessory nerve (XI), hypoglossal 16:697–703, 2002. nerve (XII) 11. Judy CE, Dhaffin MK, Cohen ND: Empyema of the guttural pouch (auditory tube diverticulum) in horses: 91 cases 2. What diagnostic modality assists the most in diagnos- (1977–1997). JAVMA 215(11):1666–1670, 1999. ing guttural pouch disorders? 12. Newton JR, Verheyen K, Talbot NC, et al: Control of strangles a. ventral dorsal radiographs of the guttural pouch outbreaks by isolation of guttural pouch carriers identified using b. nuclear scintigraphy PCR and culture of Streptococcus equi. Equine Vet J c. endoscopy of the pharynx and guttural pouches 32(6):515–526, 2000. d. lateral radiographs of the guttural pouch 13. Barber SM: Diseases of the guttural pouches, in Colahan PT, e. MRI Merritt AM, Moore JN, Mayhew IG (eds): Equine Medicine and Surgery. St. Louis, Mosby, 1999, pp 501–512. 3. Horses with guttural pouch empyema should be han- 14. Chiesa OA, Vidal D, Domingo M, Cuenca R: Cytological and bacteriological findings in guttural pouch lavages of clinically dled with appropriate biosecurity measures because normal horses. Vet Record 144:346–349, 1999. ___% have tested positive for S. equi subspecies equi. 15. Timoney JF, Artiushin SC: Detection of Streptococcus equi in a. 10 d. 75 equine nasal swabs and washes by DNA amplification. Vet b. 30 e. 90 Record 141:446–447, 1997. c. 50 16. Wilson J: Effects of indwelling catheters and povidone iodine flushes on the guttural pouches of the horse. Equine Vet J 4. What is a common sequela to guttural pouch 17(3):242–244, 1985. empyema? 17. White SL, Williamson L: How to make a retention catheter to a. chondroids d. guttural pouch mycosis treat guttural pouch empyema. Vet Med 82(1):76–82, 1987. b. bastard strangles e. dysphagia 18. Gelbmann LM, Vrotsos PD, MacLeay JM, Wilson JH: Guttural c. purpura hemorrhagica (continues on p. 983)

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Guttural Pouch Disorders (continued from p. 973)

5. To confirm the agent causing guttural pouch mycosis, 8. Patients with guttural pouch empyema that do not aerobic and anaerobic cultures can be conducted on a respond to repeated guttural pouch lavage frequently a. transtracheal wash. have b. nasopharyngeal swab. a. S. equi subspecies zooepidemicus. c. blood culture. b. chondroids. d. guttural pouch wash. c. abnormalities of the pharyngeal opening of the gut- e. bronchoalveolar lavage. tural pouch. d. guttural pouch mycosis. 6. Initial treatment of guttural pouch empyema consists of e. guttural pouch tympany. a. surgical removal of the purulent material. b. daily guttural pouch lavages, antibiotics, and anti- 9. Lavage and/or endoscopic snaring of chondroids is inflammatories. successful ___% of the time and should be attempted c. systemic antibiotics. before surgical removal. d. administering procaine penicillin into the guttural a. 15 pouch. b.44 e. ligation of the internal carotid artery. c. 60 d. 80 7. When lavaging the guttural pouch, it is advised to use e. 100 a. physiologic solutions. b. physiologic solutions with 0.5% povidone–iodine 10. The current theory on the purpose of the equine gut- solution. tural pouch is that it c. water and 1% povidone–iodine solution. a. is a buoyancy device. d. physiologic solutions with potassium penicillin b. cools blood traveling to the brain. added. c. serves no purpose. e. physiologic solutions and 1% iodine and 3% d. assists voice resonance. hydrogen peroxide. e. aids digestion.

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