SURGERY: ADVANCING YOUR SKILLS IN THE FIELD AND CLINIC

How to Flush Guttural Pouches in the Field

Without the Use of an Endoscope

Mark T. Reilly, DVM, Diplomate ABVP (Equine)

Author’s address: South Shore Equine Clinic and Diagnostic Center, 151 Palmer Road, Plympton, MA 02367; e-mail: [email protected]. © 2012 AAEP.

1. Introduction

The guttural pouch is an anatomical structure unique to perissodactyls, including equids, tapirs, a South American forest mouse, and some species of rhinoceros, , and hyraxes.1 Unfortunately, it

has also become a medical issue for the horse be-

cause this blind-ended sac can hold fluid, infectious debris, and fungal growths. Access to the pouch has historically been difficult for a solo practitioner because it typically requires an endoscope and in- volves two or three assistants. The procedure often Fig. 1. Guttural pouch shown in red (provided by M. S. A. requires sedation for safe endoscopic examination Kumar, BVSc, MVSc, MS, PhD). because there are numerous delicate structures contained therein that could be damaged. This paper will outline a simple way to enter the gut- mainly on the and also covers and molds to tural pouches, without sedation in most cases, and the retropharyngeal lymph nodes and stylohyoid offer the opportunity to medicate the pouch bone, which presents a raised ridge within the gut- inexpensively. tural pouch and divides it into its lateral and medial

compartments. The left and right guttural pouches Anatomy are separated by a thin median septum. Its func-

The guttural pouch is an extension of the equine tion is unknown, although it has been hypothesized that connects the pharynx to the to be associated with pressure equilibration across middle ear. This pouch is located between the base the tympanic membrane, contribution to air warm- of the skull dorsally and the pharynx and esophagus ing, a resonating chamber for vocalization, a flota- F1 ventrally (Fig. 1). It is covered laterally by the tion device, and for cooling of the brain of the horse.1 pterygoid and digastricus muscles and the parotid Internal structures of the guttural pouch will be and mandibular salivary glands. The floor lies described in further detail below.

NOTES

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Fig. 2. Probe entering left guttural pouch through the pharyn- Fig. 3. Internal structures of right guttural pouch. geal orifice.

ment is further divided into medial and lateral Indications to Flush Guttural Pouches recesses. Structures that are associated with each Diseases involving the guttural pouch include fun- compartment and that should be identified on endo- gal empyema, Streptococcus equi subspecies equi in- scopic exam are described as one might see on en- fection, chondroid formation, and bacterial doscopic exam. On entering the guttural pouch, empyema. Contamination can occur from a pene- the dorsal aspect of the lateral recess of the medial trating exterior wound. Trauma can lead to a frac- compartment is encountered. The large stylohyoid tured stylohyoid bone. In addition, the guttural bone is usually readily noted. Clinically relevant pouch should be investigated in cases of head tilt, structures that can be seen in the medial and lateral 2 epistaxis, or cranial nerve dysfunction. compartments are as follows: atlanto-occipital ar- Diagnosis of a problem within the guttural pouch ticulation, glossopharyngeal nerve (c.n.IX), internal

requires endoscopic visualization. Entrance into carotid artery, and cranial cervical ganglion (c.n.X) the guttural pouch with the endoscope typically in- dorsal and medial to the ; volves utilizing an assistant to manipulate the en- other structures to note are the paracondylar (jugu- doscope and the use of a probe or stylet passed lar) process of the occipital bone, the occipitohyoid- through the endoscopic channel to lift the pharyn- eus muscle, and the rectus and longus capitus geal orifice of the Eustachian tube to gain entrance muscles. The floor of the medial compartment F2 to the guttural pouch (Fig. 2). Using a video cam- should be examined for enlargement and/or drain- era and screen makes the process easier because age of the medial retropharyngeal lymph nodes that both participants can visualize at the same time. lie just below the floor of the guttural pouch. The Without a video screen, communication between the chorda tympani (a branch of c.n.VII which joins veterinarian looking through the ocular end and the c.n.V) is seen at the proximal extent of the stylohy- assistant passing the endoscope is paramount to oid bone, coursing dorsally and laterally within the give directions to the assistant. lateral compartment of the guttural pouch. The Typically, the horse requires sedation to pass the large (c.n.VII) can also be seen in the probe and endoscope into the guttural pouch. The lateral compartment. The endoscope is passed in the ventral meatus until the is large, coursing laterally, and can be identified by pharyngeal orifice is visualized. At this point, the its pulsing motion; the caudal auricular artery can probe is passed through the scope channel and ad- often be identified as a branch of the external carotid vanced beneath the flap and forward into the gut- artery that courses dorsally and caudal to the facial tural pouch. The scope is then rotated clockwise to nerve. The maxillary vein can also be identified enter the left pouch and counterclockwise to enter passing behind and lateral to the external carotid the right pouch while advancing simultaneously. artery. Though not visualized directly, c.n.XI and Once the endoscope has entered the guttural pouch, c.n.XII are also closely related to the guttural pouch the probe is retracted back into the channel to avoid and may be affected by disease processes involving 1 inadvertent trauma to any of the structures. At the guttural pouch (Figs. 3 and 4). F4 this point, a complete exam of the guttural pouch Samples can be taken with an aspiration and relevant structures can be undertaken. The or cytology brush, utilizing instruments that could inside of the guttural pouch is lined with glistening pass through the endoscope channel. In addition, and should appear as such. There is not basket forceps can be used to remove chondroids, or normally any fluid, mucus, or muco-purulent or rat-tooth grabbing forceps can be used to remove plaque-like material associated with the lining of foreign bodies. the guttural pouch. The guttural pouch is divided Once a diagnosis is made, medication of the gut- into a large medial and smaller lateral compart- tural pouch may be indicated. Sedating on a daily ments by the stylohyoid bone. The medial compart- basis and repeating the above procedure can be cost-

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Fig. 4. Normal appearance of the floor of medial compartment of Fig. 6. Chambers catheter positioned over the location of the the right guttural pouch. guttural pouch.

prohibitive to many horse owners and is technically other nostril, and the process is repeated for the demanding. Placement and management of an in- contralateral guttural pouch. dwelling Bivona tube or large-bore catheter for daily Confirmation of the location of catheter can be accomplished by rotating the catheter in a circular lavage performed by the owner can also be expensive and requires skill and compliance of the owner. fashion. If the catheter is properly located inside

A less expensive, technically easy technique will the guttural pouch, the catheter will be unable to increase client compliance and make case manage- completely rotate because it will be obstructed by ment more successful. the lateral or medial wall. Additionally, when flu- ids are passed through the catheter, coughing will Method of Flushing Guttural Pouches Without an ensue if the catheter is not within the pouch as the Endoscope fluid enters the laryngeal area of the horse. Treatment without the use of an endoscope is easily Potential side effects or possible injuries can occur accomplished in the vast majority of horses and is when flushing guttural pouches. Trauma and/or typically performed without sedation. Equipment irritation to the mucosal lining or to the structures required includes a twitch and a Chambers cath- within the pouch are potential problems. Direct eter.a This catheter is stainless steel, 56 cm in contact from the catheter to any of the structures

length, slightly curved, with a finger rest and luer within the guttural pouch could lead to inflamma- F5 slip adapter (Fig. 5). It is typically used to infuse tion, carotid artery rupture, or neuritis; however, the uterus, but its length allows it to be used to flush trauma within the guttural pouch probably is not F6 the guttural pouch (Fig. 6). due to the restricted reach of the Chambers cathe- Once the animal is restrained with the twitch ter. More likely, trauma occurs in the ethmoid area positioned to open a nostril (ie, rope or chain twisted as the result of inappropriate restraint and/or dorsal away from the nostril), the catheter is passed slowly advancement of the catheter. Irritation within the up the ventral meatus. The catheter is rotated guttural pouches resulting in inflammation of the along the wall of the pharynx to open the entrance of mucosa or neuritis typically results from caustic the guttural pouch and then advanced into the gut- substances flushed into the pouches, such as strong F7 tural pouch (Fig. 7). The Chambers catheter is iodine solutions or hydrogen peroxide.1 then slowly backed out of the pouch and withdrawn The guttural pouch can hold a volume of approx- out of the nostril. The twitch is then released and imately 350 mL, but only 100 mL can be instilled in retightened in the opposite direction, opening the

Fig. 5. Chambers catheter. Fig. 7. Chambers catheter entering the left guttural pouch.

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SURGERY: ADVANCING YOUR SKILLS IN THE FIELD AND CLINIC a 500-kg horse before the fluid begins to flow back been shown to be ineffective when used to flush out the entrance while the catheter is still in place.3 guttural pouches because they can cause inflamma- Antibiotics, antifungal medications, acetylcysteine, tion within the guttural pouches.4 Antibiotic mix- anti-inflammatory solutions, and large volumes of tures based on culture and sensitivity results or isotonic fluids can be instilled through a Chambers other therapies can be based on cytology results. catheter by using syringes or hooking up an exten- Otherwise, a broad-spectrum flush solution can be sion set for large-volume flushing. The author typ- used for cases of pharyngitis or to flush the guttural ically uses 120 mL to flush the guttural pouches pouches at the conclusion of systemic antimicrobial after an initial high-volume flush of 250 to 400 mL. therapy. The authors have used this technique on hun- dreds of horses for numerous types of clinical cases, 2. Conclusion including strangles outbreaks, fungal infections, up- Using a Chambers catheter to flush guttural per respiratory infections, and traumatic injury with pouches is an inexpensive and technically simple contamination. A typical scenario for its use in a option for management of disease processes affect- case of strangles infection is as follows: a diagnosis ing the guttural pouches. Once an endoscopic diag- of strangles is made by positive polymerase chain nosis has been made, the guttural pouches can be reaction (PCR) on a nasopharyngeal flush and endo- flushed in less than a few minutes in the restrained scopic findings confirm enlarged retropharyngeal patient without the use of tranquilizers. Owner lymph nodes and/or purulent material within the compliance and treatment success are greatly in- guttural pouch. Antibiotic solutions can be flushed creased with the use of this technique because it into the guttural pouches and repository antibiotics minimizes cost, time, and management commit- made into gel formation can be left for extended treat- ments of the owner. The author recommends tran- ment. Other treatments that can benefit from this quilizing the first few horses until the “feel” of the technique include fungal empyema, foreign body catheter entering the guttural pouch is mastered. contamination from penetrating wounds, or inflam- Thereafter, in this author’s experience, horses rarely matory debris from upper respiratory disease. The require sedation for this procedure. author also commonly uses this technique with many horses at the conclusion of antibiotic therapy References and Footnote to remove any residual bacterial contamination in 1. Freeman DE, Hardy J. Guttural pouch. In: Auer JA, the guttural pouch. This technique can also be Stick JA, editors. Equine Surgery. 3rd Edition. St Louis, used to treat cases of pharyngitis and is particularly MO: Saunders Elsevier; 2006:591–608. 2. Lepage OM. Disorders of the guttural pouches. In: Lekeux useful in cases of dorsal displacement of the soft P, editor. Equine Respiratory Diseases. Ithaca, NY: In- palate caused by pharyngeal inflammation. ternational Veterinary Information Service; 2007. Balanced electrolyte solutions with acetylcys- 3. Barakzai S. Handbook of Equine Respiratory Endoscopy. teine, dimethyl sulfoxide (DMSO), or a combination St Louis, MO: Saunders Elsevier; 2007:49. 4. Brosnahan MM, Holbrook TC, Moll HD. Suitability of chlo- of antimicrobials can be used to flush the guttural rhexidene gluconate for equine guttural pouch lavage. In pouches. Dilute povidone-iodine solutions (1%) are Proceedings, Am Assoc Equine Pract 2007;53:81. also used; however, iodine can be neutralized by exudates.1 Dilute chlorhexidene solutions have a Jorgensen Laboratories, Loveland, CO 80538.

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