Primary distension of the guttural pouch lateral compartment secondary to empyema

Primary distension of the guttural pouch lateral compartment secondary to empyema Donald A. Smyth, Keith E. Baptiste, Antonio M. Cruz, Jonathan M. Naylor Abstract - A 6-year-old, 420-kg quarter horse gelding was presented with a 2-month history of difficulty swallowing and dyspnea. The horse was diagnosed with a right guttural pouch empyema with many large chondroids. Two surgeries were required to completely remove all the chondroids from what proved to be a primary distension of the guttural pouch lateral compartment.

Resume - Distention primaire de la poche gutturale suite a un empyeme. Un Quarter horse hongre de 5 ans pesant 420 kg a ete presente pour une histoire de difficulte de deglutition et de dyspnee qui durait depuis 2 mois. Un diagnostic d'empyeme de la poche gutturale droite accompagne de plusieurs gros chondroides a ete pose chez le cheval. Deux chirurgies ont ete necessaires pour extirper tous les chondroides de ce qui s'est revele etre une distention du compartiment lateral de la poche gutturale. (Traduit par docteur Andre Blouin) Can Vet J 1999; 40: 802-804

A6-year-old, 420-kg quarter horse gelding was referred to the Western College of Veterinary Medicine with a 2-month history of difficulty swallowing, episodes of dyspnea, and respiratory noise during exercise. Initially, the owner had noted a small amount of clear nasal discharge, which later became mucopurulent. One month following these initial signs, the horse was placed on a 4-day course of procaine penicillin (22 000 IU/kg body weight (BW), ql2h, IM). No improvement was noted. The horse had contracted strangles 2 y previously, but recovered after 5 d of mild illness. Physical examination revealed that the horse was bright, alert, and in good body condition. Temperature, pulse, and respiration were within normal limits. There was an audible inspiratory stridor and increased upper airway sounds on auscultation over the trachea. No external swellings were noted on the head. No other abnormalities were found at this time. Radiographs of the nasopharyngeal area revealed a large amount of opaque material dorsal to the nasopharynx and continuous with the right guttural pouch. Endoscopic examination of the upper respiratory tract showed that the nasopharyngeal area was compressed dorsally and laterally, rostral and caudal to the opening of the right guttural pouch (Figure 1). Attempts to enter the right guttural pouch were unsuccessful. Purulent material emanated from the pouch; Streptococcus equi was later cultured from an aspirate. Endoscopy of the left guttural pouch revealed 3 to 4 small chondroids within the medial compartment. These were removed with the Kipling Veterinary Clinic, Kipling, Saskatchewan SOG 2SO (Smyth); Department of Veterinary Internal Medicine (Baptiste, Naylor), Department of Veterinary Anesthesia, Radiology and Surgery (Cruz), Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5B4.

Address correspondence and reprint requests to Dr. Keith Baptiste.

802

Doral pharyngeal

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Guttural pou opening Figure 1. Endoscopic view of the nasopharynx. Note the swelling rostral to the opening of the right guttural pouch that almost totally occludes the airway.

aid of a basket forceps snare device passed through the biopsy channel of the endoscope. The horse was given procaine penicillin (22 000 IU/kg BW, ql2h, IM for 14 d). With endoscopic guidance, a balloon-tipped embryo-transfer catheter was inserted into each pouch and sutured to the nares. Through these catheters, the guttural pouches were flushed daily with 3 to 4 L of warmed saline for 3 d. Initial flushing expressed small amounts of mucopurulent material. Eventually, enough material was removed to allow endoscopic examination of the right guttural pouch. Large chondroids were found tightly packed within the medial compartment. The opening of the lateral compartment could not be seen at this time, presumably because of the inflammation and chondroids in the medial compartment. Given the size and number of these chondroids, surgical removal was recommended. Under general anesthesia, a modified Whitehouse approach was employed to access the floor of the medial compartment of the right guttural pouch (1). The endoscope was placed in the right pouch to aid dissection; Can Vet J Volume 40, November 1999

c:ompartment

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Stylohyol

Extemal carodd artery

Figure 2. Endoscopic view of the right guttural pouch after surgical removal of all chondroids. Note the distension of the lateral compartment and that the stylohyoid bone is pushed over into the medial compartment.

however, adequate visualization was difficult with the horse in the dorsal recumbency and the pouch filled with chondroids. A large amount of inspissated purulent material was removed manually from the medial compartment of the pouch. The mucous membrane of the medial compartment was grossly inflamed and edematous. The entrance to the lateral compartment was inflamed, thickened, and narrowed, such that it could not be easily explored with the endoscope or fingers. Given the substantial number of chondroids removed from the medial compartment, the problem was considered resolved and it was decided not to explore the lateral compartment. The horse recovered uneventfully and the incision was left to heal by second intention. Videoendoscopy was performed the following day. Dorsal and lateral compression of the nasopharynx was still present and unchanged. The mucosa of the medial compartment of the right guttural pouch was inflamed and thickened, but no chondroids were observed. The opening to the lateral compartment, observed for the first time since presentation, was filled with inspissated material and chondroids. An attempt to break the inspissated pus into small pieces, with a snare device advanced through the biopsy channel of the endoscope, was unsuccessful. A small-gauge catheter was passed down the biopsy channel. High pressure lavage, using a fluid pump to break down and remove the pus, was very tedious and only minimally productive. The horse was anesthetized for a second time and placed in left lateral recumbency. The right lateral compartment could not be adequately explored through the previous incision, even though the surgeon's hand could be passed into the medial compartment of the pouch. A second incision was made to approach the caudal aspect of the lateral compartment using a hyovertebrotomy technique (1). The endoscope was again placed in the pouch to assist surgery. An 18-mm (OD) tube was placed at the entrance to the lateral compartment through the modified Whitehouse incision as an aid to flushing out inspissated material. Access to the lateral compartment was achieved by blindly dissecting the soft tissue attachments to the stylohyoid bone. During this procedure, the external carotid artery was accidentally punctured, causing profuse bleeding. Attempts to achieve hemostasis by packing the area failed, and ligation of the common carotid artery was necessary to stop hemorrhage. Approximately 1 kg of inspissated pus and chondroids was

removed from the lateral compartment via the

Can Vet J Volume 40, November 1999

hyovertebrotomy incision site. The horse recovered and the incisions were left to heal by second intention. Videoendoscopy following the second surgery revealed a grossly distended lateral compartment of the right pouch, larger in size than the medial compartment (Figure 2). A small amount of inspissated material was found adherent to the dorsal aspect of the lateral compartment near the temporohyoid joint. Alligator forceps were passed through the modified Whitehouse incision, guided by an endoscope, to free the adhered material from the dorsolateral compartment. A gloved hand was then passed through the modified Whitehouse incision into the medial compartment, and the remaining chondroids were extracted. The guttural pouches were evaluated the following day and found to be clear of purulent material. Both pouches were lavaged with lactated Ringer's solution. Lavage samples from both guttural pouches were cultured and found to be negative for S. equi. The horse was kept in hospital for 5 more days while we looked for signs of complications from ligation of the common carotid artery, namely, unilateral blindness, laryngeal hemiplegia, and Homer's syndrome. He was eventually sent home without antibiotics. Through follow-up phone conversations over the next 12 mo, we ascertained that the horse had fully recovered without complications. Guttural pouch empyema commonly manifests as a caudoventral distention of the medial compartment of the guttural pouch into the area of Viborg's triangle, representing the pathway of least resistance. This case was unique, because there were no external head swellings and the guttural pouch distention occurred lateral and rostral to the opening of the right guttural pouch, leading to obstruction of the nasopharynx. This may be explained by the fact that the lateral compartment was primarily affected. Since the lateral compartment is mostly covered by the ramus of the mandible, distension of this compartment would probably occur in a medial direction into the nasopharynx, along the ramus of the mandible. To the authors' knowledge, this manifestation has not been described before. Several nonsurgical procedures have been reported in the successful management of guttural pouch empyema, such as acetylcysteine irrigation of the pouches (2), nonsurgical removal following endoscopically guided breakup of chondroids (3,4), as well as infusion of proteolytic dissolvents (5). Endoscopically guided breakup of the chondroids failed in this horse, as did their removal by vigorous lavage. Although general anesthesia and surgery carry some risks, surgical removal of chondroids from the guttural pouches and postsurgical lavage of the pouches proved to be the best option in this case. Due to the large quantity of inspissated material, the use of dissolvents would probably not have broken down all the material. Since the lateral compartment was later found to be so grossly distended and cavitated with chondroids, a second surgery was necessary. Passing instruments through the modified Whitehouse incision in the standing horse would probably have been tedious and would not have enabled us to adequately reach all aspects of the distended lateral compartment. Garm (6) found that a principal factor contributing to the chronicity and recurrence of guttural pouch empyema 803

of all inspissated material harboring the organism should eliminate this carrier site. This case demonstrates that prudence, persistence, and repeated endoscopic examinations are necessary to ensure that all chondroids are removed. A negative culture for S. equi from the guttural pouches upon discharge of the horse indicated successful resolution of the chronic infection. cvi

is that it is extremely difficult to completely remove all the exudate, especially from the lateral compartment. All recommended direct surgical approaches to the guttural pouches access only the medial compartment. Direct surgical access to the lateral compartment is considered too risky due to the many arteries that traverse the compartment. Instead, the modified Whitehouse or hyovertebrotomy approach to the medial compartment may allow digital exploration of the lateral compartment with the surgeon placing his or her entire hand through the incision. However, in this case, these approaches permitted only partial removal of the chondroids and a direct approach to the lateral compartment resulted in profuse bleeding of the external carotid artery. To avoid this problem, Garm (6) described a surgical approach to gain direct access to the rostral aspect of the lateral compartment through a caudodiagonal approach starting from a small incision made medial to the ramus of the mandible. This technique is not well known, but it was used successfully by Garm (6). The guttural pouches have been implicated as a possible source of chronic S. equi infection, creating an asymptomatic carrier state in some horses, with guttural pouch empyema following recovery from strangles (7). Of the carriers noted, all possessed chondroids within the guttural pouches (7). Thus, clearing the guttural pouches

References 1. Freeman DE. Guttural pouch. In: Auer JA, ed. Equine Surgery. Philadelphia: WB Saunders 1992: 480-488. 2. Bentz BG, Dowd AL, Freeman DE. Treatment of guttural pouch empyema with acetylcysteine irrigation. Equine Pract 1996; 18: 33-35. 3. Seahorn TL, Schumacher J. Nonsurgical removal of chondroid masses from the guttural pouches of two horses. J Am Vet Med Assoc 1991; 199: 368-369. 4. Adkins AR, Yovich JV, Colbourne CM. Nonsurgical treatment of chondroids of the guttural pouch in a horse. Aust Vet J 1997; 75: 332-333. 5. Misra SS, Angelo SJ. A modified technique for the management of empyema of guttural pouch (a report of two cases). Indian Vet J 1982; 59: 821-823. 6. Garm 0. Luftposeempyemer og deres behandling. Skand Vet Tidskr 1946; 26: 401-423. 7. Newton JR, Wood JLN, Dunn KA, DeBrauwere MN, Chanter N. Naturally occurring persistent and asymptomatic infection of the guttural pouches of horses with Streptococcus equi. Vet Rec 1997; 140: 84-90.

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