CHAPTER 12 Spencer Barber, DVM, Diplomate ACVS Most wounds of the body and/or neck heal well; consequently, horses with a neck or body wound have an excellent prognosis for return to full function when the wound does not involve structures underlying the skin. Second‐intention healing is often the most appropriate method of managing wounds of the body and/or neck, but some wounds with a large skin flap or lacerated muscle heal faster and more cosmetically after they are completely or partially sutured. If the horse has extensive muscle loss, especially from the forearm or thigh, surgical reconstruction of the remaining muscle and skin may be required to minimize the amount of function lost. Some wounds, especially those in the axilla, thorax, or abdomen, have life‐threatening implications (e.g., pneumothorax and evisceration) that require immediate surgical intervention. Horses with wounds of the esophagus and trachea can be difficult to manage. The presence of foreign bodies in wounds of the body and neck can be a diagnostic challenge, and good surgical planning is required to find and remove them. A wide variety of wounds involving the neck and body are encountered in horses, and many of the factors contributing to the high incidence of these injuries are related to the nature and the use of the horse. As a “flight” animal, the horse often reacts to frightening circumstances by running into objects (e.g., a wooden post or fence, barbed wire). Additionally, horses housed on premises that are not properly maintained (e.g., protruding nails, broken boards, broken tin sheds) are at a greater risk of injury. Because the horse’s skin is relatively thin, impact with objects commonly leads to large skin wounds. Although most wounds of the neck and body are superficial, some wounds involve structures underlying the skin. It is therefore important for the attending veterinarian to be familiar with the anatomy of deeper structures, particular in the thoracic and abdominal regions. Moreover, understanding the biology of wound repair, as well as possessing a sound knowledge of the principles of wound management and the factors that affect healing, facilitates the management of wounds involving the neck and the body. Lacerations to the neck are especially common when horses are placed in pastures fenced with barbed wire. Injury occurs when the horse runs into the fence, causing a horizontal laceration that is usually located at the base of the neck. The skin edges retract as a result of the elastic fibers in skin, the normal skin tension lines,1 and the natural movement of the neck. Lacerations caused by wire often involve only the skin and subcutaneous tissue and are characterized by minimally retracted, relatively sharp edges, but if the laceration extends deeper, and especially deep into the brachiocephalicus, sternocephalicus, and sternothyrohyoideus muscles, the edges of skin and muscle retract a considerable distance. If the injury is caused by contact with a wooden object (e.g., a tree branch or fence), the wound edges are often ragged, irregular in depth, and highly contaminated. Treatment options include primary closure, delayed closure, and second‐intention healing. Many factors must be considered prior to selecting the most appropriate treatment, and these are discussed in Chapter 8 of this book. Horses with a wound of the neck are usually presented in a timely fashion, and the wound is often minimally contaminated and has sharp edges with viable tissue. Although the tension produced by closing the wound and that produced by movement of the head and neck may cause dehiscence of the suture line, primary closure is the ideal treatment in many cases, although suturing is not always required. A narrow wound (0.5–3 cm wound gap) can usually be closed successfully, in the standing horse, without creating excessive tension on the suture line. Lacerations of the neck caused by wire do not usually involve underlying muscle, but if they do, the muscle is often lacerated only superficially and does not require closure. The subcutaneous tissue and skin are closed in one or two layers using an interrupted suture pattern. In some cases, the number of small wounds is so great that primary closure would be impractical and cost‐prohibitive; such wounds usually heal uneventfully by second intention. With intermediate‐sized lacerations (10–15 cm wound gap), tension suture patterns (e.g., widely placed vertical or horizontal mattress or near–far–far–near), with or without the use of stents/supports, might be needed to counteract the tension created on the skin by closure (Figure 12.1). Stents/supports can cause skin necrosis if the sutures are applied too tightly or too close to the wound’s edges (more information on tension suture patterns can be found in Chapter 9 of this book). Wounds that are parallel to the long axis of the neck, especially those accompanied by a skin flap, are best managed by primary closure because skin tension is minimal and closure of the skin defect maintains the skin in position for rapid and cosmetic healing (Figure 12.2). Wounds that are several days old require more extensive debridement and often are more difficult to close because of loss of pliability of the skin edges. Because these intermediate‐sized wounds usually provide a cosmetically acceptable outcome when left to heal by second intention, many clients opt for this approach, over primary closure. Figure 12.1 This type of wound is expected to heal well by second intention but also could be treated successfully by primary closure. (a) This is a linear laceration parallel to the long axis of the neck. The wound was fresh, clean, and although the edges gaped moderately, they could be apposed without creating excessive tension on the skin. (b) After debridement and irrigation, the wound was closed in two layers: the skin closure consisted of simple interrupted sutures and near‐and‐far tension sutures. A Penrose drain was placed subcutaneously with one of its ends exiting ventral to the incision. The caudal portion of the incision was left open to enhance drainage. Figure 12.2 (a) This laceration, parallel to the long axis of the neck, resulted in a large skin flap based over the right jugular groove. The laceration was fresh and clean, and the edges could be apposed without creating excessive tension on the skin. (b) After debriding the wound, a Penrose drain was placed to encourage drainage of the dead space, with its exit point located ventral to the wound. The subcutaneous tissue was closed using interrupted segments of a simple continuous suture pattern. The skin was closed using several horizontal mattress tension sutures interspersed with interrupted segments of a simple continuous suture pattern. Fortunately, large wounds (wound gap greater than 15 cm), or those with complete transection of the brachiocephalicus or sternocephalicus muscles, are uncommon (Figure 12.3a,b). Horses with such wounds are usually treated by primary or delayed closure of the wound, if possible, because second‐intention healing is often protracted and labor intensive and because unsutured wounds can result in significant scarring and loss of function. If, in the standing horse, wound edges can be approximated without generating excessive tension, prognosis for primary‐intention healing is good as long as the horse is cooperative; horses that accept the use of a Martingale to limit head elevation are the best candidates for primary closure. Surgical repair of large wounds should be undertaken with the horse under general anesthesia to ensure optimal debridement and primary closure. Thorough, layered (excisional) debridement of the entire wound is important and is discussed in Chapters 4 and 8. Figure 12.3 (a) This foal was presented a few hours after sustaining an extensive laceration caused by barbed wire. The wound appeared clean and fresh, and the skin edges, which were sharply cut, could be easily apposed. (b) The foal was positioned in dorsal recumbency, under general anesthesia, for wound reconstruction. The exposed jugular vein was missing much of its perivascular tissue but was judged to be viable. The proximal ends of the transected muscles were retracted beneath the skin edge and the distal ends appeared dark (bottom left of wound). (c) Appearance of the wound after debridement in preparation for primary closure. (d) Two Penrose drains were placed into the depth of the wound, and their ends exited through slits in the skin proximad and distad to the wound. Care was taken to not place the drains in close proximity to the neurovascular structures. The transected muscles were apposed with a near–far–far–near suture pattern. The jugular vein was covered with viable tissue, and subcutaneous tissue and skin were closed separately using an interrupted suture pattern. Loops of umbilical tape were placed parallel to the skin closure in preparation for a stent bandage. If either the brachiocephalicus or sternocephalicus muscle is completely transected (Figure 12.3b,c), its ends should be approximated using a tension suture pattern, incorporating as much fascia as possible. The use of a drain is necessary because dead space is inevitable. Penrose drains are inexpensive, easy to place, and provide good passive drainage (Figure 12.3d). Most commonly, they are used as a single‐exit drain, whereby the proximal end is sutured within the depth of the wound and the distal end exits through a skin opening ventral to the wound. With a double‐exit technique, one end of the drain exits dorsal to the wound and the other, ventral to the wound. The advantage to the double‐exit technique in the ventral aspect of the neck is that drainage occurs regardless of whether the neck is flexed, extended, or in a neutral position. The Penrose drains are generally removed after 2–3 days, provided drainage is minimal, but can be retained for 5–7 days if drainage persists. Importantly, the longer the drains are left in place the greater is the risk of ascending infection; thus, sterility at the exit sites of drains should be maintained. More information on the use of drains in wound management can be found in Chapter 9 of this book. A stent bandage may be placed to protect the exit site(s) of the Penrose drain from contamination and the sutures from excessive tension (Figure 12.3d). For the stent bandage to effectively protect the skin closure sutures from tension, the lacing material (e.g., umbilical tape) must be pulled tightly enough to transfer tension on to the loops of suture securing the stent bandage to the surrounding skin; this will produce some discomfort for the conscious horse, thereby also discouraging head movement. The use of a Martingale is also advised. When the wound dressing requires changing, the stent bandage can be loosened and the dressing changed with the horse sedated. Anti‐inflammatory drugs may be used during the first postoperative week, although some tenderness at the wound site helps limit head extension. Moreover, a robust acute inflammatory response is essential to wound healing; consequently, unless the horse displays serious discomfort, it is best to avoid administering a NSAID in the first week following wounding. Wounds involving the crest of the neck are uncommon but occasionally result from impact when the neck is placed beneath a sharp object. A full‐thickness cutaneous laceration results in retraction of the skin edges and the formation of a gap between the hair follicles of the mane. The skin edges should be apposed to obtain the best cosmetic outcome for the mane (Figure 12.4). Figure 12.4 (a) This laceration resulted in complete transection of the skin on the dorsal surface of the neck and retraction of the skin edges, which contain the hair follicles for the mane. Fortunately there was no damage to the nuchal ligament. Primary closure of this wound is preferred as it would closely approximate the skin edges containing the hair follicles, whereas leaving the wound to heal by second intention would likely result in a scar devoid of hair follicles, which would produce a noticeable gap in the mane. (b) The wound, which was fresh and clean, was debrided, and a Penrose drain placed within its cavity. To relieve the tension resulting from primary closure, the soft tissues surrounding the wound were undermined, and a few tension‐relieving incisions were placed in the skin near the mane. Interrupted tension (vertical mattress) and simple interrupted suture patterns were used to close the skin. (c) Several months after repair, the wound had healed well, with no gap in hair growth noticed along the mane. Courtesy of Suzanne Mund. Wounds of the neck that are not sutured heal by second intention and, therefore, fill with granulation tissue, contract, and epithelialize (Figure 12.5, Figure 12.6). All wounds should be thoroughly debrided and cleansed/irrigated when initially seen by the veterinarian. With the aim to encourage filling of the defect with granulation tissue, the author often instructs the owner to spray the wound for 30 minutes with tap water from a garden hose (pressure unknown) once or twice daily. It is speculated that this “hydrotherapy” keeps the wound clean, moist and might stimulate granulation tissue formation through tissue massage or changes to tissue circulation. Although commonly prescribed, it is unclear whether this treatment is helpful or harmful. In fact, wounds in horses irrigated with isotonic saline solution or tap water administered by gentle pressure from a rubber hose showed increased collagen production, a blunted edge to the epithelium, and no enhancement of healing.2 Because tissue injury is known to cause the release of mediators that stimulate granulation tissue formation, the author advocates hydrotherapy with strong hose pressure, or scraping the surface of the granulation tissue lightly with the fingertips of a gloved hand or with a sterile gauze sponge, once or twice daily, to produce light surface bleeding. This treatment is continued until the surface of the granulation tissue is level with the surrounding skin. Although bandages have been shown to enhance the formation of granulation tissue, many body wounds, including those in the neck area, are difficult to bandage.3 A topical wound‐care product may be applied in the absence of a dressing to keep the wound surface moist (the reader is referred to Chapter 5 for more information on topical wound‐care products and the benefits of moist wound healing). The author stops all treatment when the surface of the granulation tissue filling the wound bed is level with the surrounding skin. Most horses with a laceration to the neck, except those with major muscle or skin loss, are expected to return to normal use with a minimal blemish. Figure 12.5 (a) A wound of the neck, presented a week after injury, healing by second intention. (b) The wound cavity should be encouraged to fill with granulation tissue for wound contraction to proceed rapidly and to a maximum extent, to produce cosmetic healing. Figure 12.6 This gelding was attacked by a stallion and suffered bilateral bite wounds to the dorsolateral aspect of the neck. Because of tissue loss, the wounds could not be closed without creating undue tension. A Penrose drain was placed within the wound cavity to ensure good ventral drainage from the dorsally located wound. The blemish, after healing, was minimal. Laceration to the cranial region of the neck has the potential to damage important neurovascular structures, including the jugular vein, common carotid artery, recurrent laryngeal nerve, and vagosympathetic trunk (Figure 12.3b,c). Of these structures, the jugular vein is the most superficial. Fortunately, it is protected within the jugular groove formed by the sternocephalicus and brachiocephalicus muscles. The jugular vein may, however, be transected along with these muscles, resulting in severe hemorrhage. More commonly, perivascular tissue is stripped away from the intact vessel, which becomes ischemic, leading to delayed rupture. Deeper wounds may affect the carotid artery, whose complete laceration results in rapid exsanguination and death. If at all possible, viable soft tissue should be used to cover an exposed vessel to protect its wall from desiccation and further trauma. Horses can survive with a single jugular vein and a single carotid artery, so, if the integrity of one or both of these vessels is of concern, the vessel should be ligated prophylactically.4 The recurrent laryngeal nerve and vagosympathetic trunk are most likely to be injured in wounds of the lower cervical region, where they are no longer covered by the omohyoideus muscle and, consequently, are more superficial. Endoscopic examination of the larynx allows evaluation of arytenoid abduction, which depends on innervation by the recurrent laryngeal nerve. Numerous clinical signs accompany damage to the vagosympathetic trunk, including abnormal intestinal motility, colic, alteration in heart rate, abnormal esophageal function, sweating, and changes in skin temperature. If the carotid artery or jugular vein must be prophylactically ligated, as mentioned previously, care must be taken to prevent injury to these nerves when performing the procedure. The superficial location of the trachea predisposes it to various types of injury. It is located on the midline throughout the length of the ventral surface of the neck; the common carotid arteries, recurrent laryngeal nerves, and vagosympathetic trunks lie on its dorsolateral surfaces (Figure 12.7). The esophagus lies dorsal to the trachea in the proximal portion of the neck, to its left at the mid‐cervical region, and ventral to it at the base of the neck. The trachea is covered with musculature throughout the entire cervical region, and this musculature is especially thick in the caudal aspect of the neck. In the cranial cervical region, the trachea is more susceptible to injury because the left and right sternocephalicus muscles diverge in this region, leaving the trachea more exposed.5 The trachea is a flexible tube composed of cartilaginous rings that are incomplete dorsally where they are bridged by the dorsal tracheal ligament. Although the trachea may be lacerated, its rigid structure makes it more susceptible to damage by crushing, such as that caused by a kick, rope pressure, or impact with a solid object, or by puncture from internal or external forces (e.g., endotracheal tube). Figure 12.7 Drawing of the cross‐sectional anatomy of the proximal aspect of the cervical region of the horse, showing the location of the esophagus, trachea, overlying musculature, and neurovascular structures. Lacerations to the cranial aspect of the neck could cause injury to these structures. The tracheal mucosa, cartilaginous rings, dorsal tracheal ligament, and/or annular tracheal ligaments may be traumatized. The most common clinical signs of tracheal damage are subcutaneous emphysema and changes to the respiratory rate and sounds. External examination of the trachea through an open wound may be difficult if the wound is small, or if the site of injury is swollen or tender. A hole into the tracheal lumen allows air to escape from the trachea, possibly into the surrounding subcutaneous tissue. This may lead to extensive subcutaneous emphysema if the skin wound is small, but if the skin wound is large, emphysema may be minimal or absent. If cartilaginous rings or the dorsal tracheal ligament become invaginated into the tracheal lumen, increased inspiratory and expiratory noises are heard over the site of injury; marked obstruction causes an elevated heart rate and, occasionally, respiratory distress. If tracheal injury is suspected, the trachea should be examined radiographically. Radiographic examination may identify a narrowed lumen, intraluminal masses, peritracheal air, pneumomediastinum, or pneumothorax. Endoscopic examination of the trachea is useful to assess luminal integrity. Treatment depends on the structures involved and the severity of the injury. Full‐thickness tears of the tracheal wall, with only minimal or no accompanying subcutaneous emphysema, may heal without treatment. In this case, second‐intention healing can be assisted by confining the horse to a stall and by applying a pressure bandage over the injured area. If subcutaneous emphysema is extensive but the skin over the wounded trachea is intact, a horse with a tracheal wound may be treated in one of three ways: (1) the skin and soft tissue over the tracheal defect may be incised to release trapped air and prevent more air from becoming trapped in the subcutaneous tissue; (2) a tracheotomy may be performed adjacent to the defect; or (3) the tracheal defect may be sutured if adequate tissue is available for primary closure. With the first two approaches, all the wounds are allowed to heal by second intention. An attempt should be made to close the tracheal defect if the dorsal tracheal ligament or extraluminal connective tissue has prolapsed into the tracheal lumen. Rarely is the trachea transected completely, and rarely is the tracheal defect large. A large defect or complete transection is an emergency because it causes severe respiratory compromise. Severed or nearly severed tracheas of horses have been repaired successfully by primary closure. Absorbable suture material (e.g., size 2 polydioxanone) rather than stainless steel suture (25–30 gauge) should be used, because steel sutures tend to cut through the cartilaginous rings and damage the soft tissues. Penetration of the tracheal mucosa with the suture material should be avoided. Broken tracheal rings may project into the tracheal lumen thereby obstructing airflow. If the trachea is not collapsing, the portions of the ring protruding into the lumen may be excised through the original wound or through an incision over the damaged tracheal rings, and the tracheal and skin wounds allowed to heal by second intention, or, if several tracheal rings are ruptured at the ventral aspect of the trachea, a permanent tracheostomy may be performed.6–8 Conversely, if the trachea is collapsing, each collapsing ring should be supported by suturing a polypropylene hoop to it. Horses with a severely damaged section of trachea have been treated successfully by resection of the damaged section followed by anastomosis.9 The site of anastomosis is subject to excessive tension if more than four or five tracheal rings are removed. Applying a Martingale to the horse decreases tension at the site of anastomosis. If resection and anastomosis are not performed as an emergency procedure, conditioning the horse before surgery to tolerate the Martingale is helpful.9 Overall, the vast majority of tracheal wounds heal uneventfully, by second‐intention healing, with proper treatment. The esophagus can suffer either intraluminal damage, when feed or a foreign body becomes impacted within its lumen, or extraluminal damage, from impact with a sharp or blunt object. This section focuses on the clinical signs, diagnostic procedures, and treatment options when the esophagus suffers damage from impact with a sharp or blunt object. The cervical portion of the esophagus, that portion most often traumatized, is well protected from external trauma proximally because of its location dorsal to the trachea. Its location lateral to the trachea in the mid‐cervical region and ventral to the trachea in the lower cervical region, however, leave it vulnerable to damage from blows or lacerations. Adjacent to the esophagus are the recurrent laryngeal nerves, vagosympathetic trunks, and common carotid arteries, which may also be injured (Figure 12.7). The esophagus is lined by abundant mucosa arranged in longitudinal folds that allow the esophagus to dilate. The mucosa and submucosa possess the greatest amount of collagen and, therefore, are the strongest layers for surgical closure. In the cervical portion of the esophagus there are two layers of striated muscle covered by a tunica adventitia.10 Clinical signs displayed by a horse with a damaged esophagus depend on the nature of the injury. Rupture of the esophageal musculature from blunt trauma produces a pulsion diverticulum, which may cause a discrete swelling, the size of which is dependent on the quantity of food and water residing within it. A full‐thickness rupture or laceration of the esophageal wall results in discharge of saliva, food, air, and bacteria into the peri‐esophageal fascial planes. If the skin is intact, a diffuse, hot, cervical swelling accompanied by subcutaneous emphysema may develop. Crepitus can be detected when the swelling is palpated, and palpation of the swelling may elicit signs of discomfort from the horse. If the skin is open, signs of infection may be less evident, but saliva and food material can be seen exiting the wound (Figure 12.8). In either case, cellulitis is present, and infection gravitates toward the thoracic inlet. Increased respiratory rate and abnormal respiratory sounds suggest that the horse has aspiration pneumonia or that infection has extended into the mediastinum or pleural cavity.11 Figure 12.8 Discharge of feed from a ruptured esophagus. Courtesy of Melissa Hines. Extension of the injury into the adjacent carotid artery could result in fatal hemorrhage, whereas damage to a recurrent laryngeal nerve causes ipsilateral laryngeal hemiplegia, while injury to the vagosympathetic trunk causes Horner’s syndrome. Lacerations of the esophagus lead to the loss of large volumes of saliva, and, without continued intake of food and water, hyponatremia, hypochloremia, metabolic alkalosis, and dehydration ensue.11 A wound located at a site where the esophagus could be involved in the injury should be examined visually and digitally to determine if the esophagus has been damaged, taking care to avoid injuring adjacent neurovascular structures. A nasogastric tube may be passed to assess the patency and integrity of the esophagus. The nasogastric tube may occasionally travel normally past a pulsion diverticulum or full‐thickness esophageal wound, while at other times the tip of the tube may lodge itself within the diverticulum or exit the lumen into the peri‐esophageal tissue. Endoscopic examination, using a flexible, 3‐m endoscope capable of irrigation and insufflation, is helpful in identifying an esophageal injury and evaluating its severity. Normal esophageal mucosa is white to light pink, and, except at the most proximal extent of the esophagus, it has longitudinal folds that flatten when the lumen is dilated with air. Saliva or feed present within the lumen should be removed by irrigation to allow a detailed inspection of the esophagus. A pulsion diverticulum appears as an outpouching of the esophageal wall, and a defect in the mucosa is seen if the wound in the esophageal wall is full thickness.11 Plain radiographic examination is important even though a normal esophagus is not radiographically visible. With a pulsion diverticulum, gas, food, and saliva mixed together proximal to the obstruction produce an irregular mottled gas shadow or a gas dilation of the proximal extent of the esophagus. Metallic foreign bodies or masses external to the esophagus (e.g., abscess), although rare, may also be identified radiographically. The presence of air outside the esophageal lumen when the skin is intact suggests that the esophageal wall has been ruptured. Conversely, when the skin has been penetrated, the presence of air in the depth of the wound is normal, and contrast radiography is necessary to demonstrate a concomitant luminal defect. A negative contrast radiograph, obtained by passing a cuffed nasogastric tube into the proximal extent of the esophagus and injecting air to dilate the esophagus, helps to identify foreign bodies, a diverticulum, or a full‐thickness perforation of the esophagus. A positive‐contrast radiograph, obtained by administering barium sulfate paste orally, coats the normal longitudinal folds of the esophagus. Contrast material collects within the lumen of a pulsion diverticulum and is disseminated into peri‐esophageal fascial planes if the esophagus is ruptured. A double‐contrast study is the method of choice to evaluate mucosal lesions and can be performed by injecting barium sulfate, followed by air, through a cuffed nasogastric tube. The air dilates the esophagus and the barium coats the longitudinal folds. Swallowing while the esophagus is distended may produce peristaltic waves that resemble a stricture; this can be prevented by premedicating with xylazine (Rompun, Bayer Inc.), which attenuates the swallowing reflex.11 Constant tension, motion, and dilation, as well as the presence of saliva, food, and bacteria, challenge healing of esophageal wounds. Tissue strength is also limited by the absence of a serosal layer and a scant blood supply, features of a normal intact esophagus. Furthermore, the healed esophagus must be dilatable to function properly. The most common complications during healing are dehiscence and stricture formation, and the long‐term rate of survival after esophageal injury is low.12 Injuries that cause only destruction of the mucosal epithelium heal without scar formation because of the epithelium’s excellent regenerative capabilities.13 Injury to the submucosal, muscular, or adventitial layers, however, leads to the formation of granulation tissue, which is followed by wound contraction and scar formation.13 Experimental studies in horses have shown that a linear esophagostomy can heal without causing a clinically significant stricture.14 This outcome is likely because the amount of damage produced by an experimentally created incision is minor compared to that accompanying a naturally occurring injury. Because wound contraction is a concern during esophageal healing, circumferential injuries are potentially more serious than linear incisions. Indeed, when 3‐cm long esophageal mucosal resections and anastomoses were performed experimentally, mucosal repairs dehisced, and all horses subsequently developed a stricture.15 Fortunately, the severity of strictures often decreases over time. For example, maximal reduction in luminal diameter was shown in seven horses with an esophageal injury to occur at approximately 30 days after wounding. The luminal diameter increased spontaneously to normal size in five of these horses by day 60.16 This increase in diameter was the result of scar remodeling and luminal dilation from eating. These results show that surgical correction of a stricture, unless severe to the point of hindering feeding, should be delayed until at least 60 days post injury since the stricture may resolve spontaneously. Sutured, experimentally created linear esophagotomies of horses healed faster than non‐sutured esophagotomies, and a traction diverticulum was less likely to develop at the site of esophagotomy. Horses in which the esophagotomy was sutured, however, had a higher incidence of complications, including death, because of dehiscence, fistula formation, and/or formation of an abscess at the esophagotomy site.17 Sutured esophagotomies are more likely to dehisce if a nasogastric tube is retained within the esophageal lumen following repair,15 and horses fed hay are more likely to experience dehiscence of the sutured esophageal wound than are horses fed a soft diet.17 Placement of an esophagostomy tube distal (aboral) to a sutured esophagotomy site allows better healing at the repair site, but complications, including thrombophlebitis, thoracic infection, and death, have been reported.15,18 Esophageal laceration or puncture is most likely when a wound is located in the lower half of the cervical region, where the esophagus lies more superficially. Ruptures, which can be caused by kicks or penetration with a foreign body, are commonly in the extent of the esophagus and result in the escape of food, saliva, and bacteria into the peri‐esophageal tissue (Figure 12.8).19 Important considerations in determining the best approach to wound management are the type and extent of damage to the esophageal wall, the age of the injury, the degree of contamination, and the presence of infection or necrosis of the peri‐esophageal tissue. Linear lacerations and acute ruptures with minimal esophageal trauma and contamination and with no signs of infection or necrosis may heal successfully following primary closure. If the esophagus is not visible through the skin wound, it should be exposed through an incision created over the jugular groove or on the ventral midline of the neck. The esophagus is best exposed with the horse anesthetized and in dorsal recumbency. The esophagus is more easily identified if a nasogastric tube has been placed within it. Debridement of esophageal tissue should be conservative in an effort to preserve as much tissue as possible for a subsequent tension‐free closure. The mucosa and submucosa are closed in a simple continuous pattern using 3‐0 suture material with the knots tied in the lumen, and the muscular layers are closed with an interrupted suture pattern using 2‐0 suture material.11 Because of contamination of the peri‐esophageal tissue, tissue superficial to the esophagus can be left to heal by second intention. Mucosal healing takes approximately 7 days,11 therefore feed should be withheld for several days after suturing, after which water‐soaked pellets are fed for a few days before transitioning to small amounts of softened roughage. Alternatively, an esophagostomy tube may be placed either through the esophageal rupture, if it was not sutured, or distal to the repair site. The esophagostomy tube is removed either after the sutured mucosa at the rupture or laceration site has healed or, in non‐sutured cases, after a granulation tissue stoma forms at the rupture and esophagostomy sites. These stomas are then left to heal by second intention.11 Closure of the esophageal wound should not be attempted if the esophageal wall is extensively damaged. If the skin is intact, feed, saliva, and bacteria become trapped within the fascial planes, resulting in marked cellulitis, which can cause the overlying skin to slough. If the skin does not slough, feed and bacteria dissect ventrally into the mediastinum or pleural cavity. Ventral drainage, therefore, should be established early, and the fascial planes debrided surgically, followed by wound irrigation. An esophagostomy tube placed either through the site of rupture or through an opening created surgically distal to the rupture can be used to provide nutritional support, thereby preventing contamination of peri‐esophageal tissue at the site of rupture from leakage of feed ingested orally.11,19 Loss of food, water, and saliva from the esophageal rupture site may also be prevented by placing a temporary patch of dental acrylic over the hole.19 Fluid therapy is used to correct hyponatremia, hypochloremia, and metabolic acidosis.20 Broad‐spectrum antibiotics (see Table 19.1), including those effective against anaerobic bacteria, must be administered and continued until the esophageal mucosa is healed or a stoma has formed, thereby preventing ingesta from draining into the subcutaneous tissue. Esophagostomies have been associated with the development of traction diverticulum, including a mucosal web obstruction from a traction diverticulum, and death.18,19 Despite the best efforts and care, the horse’s prognosis for survival after esophageal rupture remains guarded to poor.12 Rarely can injuries be successfully repaired. Simple injuries, with good drainage, may heal by second intention with minimal stricture formation, but horses with extensive cellulitis rarely survive.
Management of Wounds of the Neck and Body
Summary
Introduction
Wounds of the neck
Lacerations
Injuries of vessels and nerves
Injuries of the trachea
Injuries of the esophagus
Anatomic considerations
Clinical signs
Diagnostic considerations
Esophageal healing
Management of esophageal lacerations and ruptures
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