Small Animal Surgical Emergencies. Группа авторов

sites for bulky (bone) foreign bodies.

Figure 4.2 Radiograph of an osseous foreign body within a dog's caudal thoracic (epiphrenic) esophagus. FB, foreign body.

Presentation

      A history of scavenging or being fed bones is typical. Signs are normally acute, and regurgitation of food, within minutes of swallowing, is readily noted by most owners. Water is usually retained and so animals may or may not be dehydrated. Gagging, inappetence, drooling of saliva, and listlessness are all common. Should esophageal perforation ensue, fulminant respiratory and cardiovascular deterioration occur as a result of a combination of pneumomediastinum, pneumothorax, mediastinitis, and pleuritis. Early signs of esophageal perforation may be mistakenly attributed to aspiration pneumonia, and hence thorough and continuing evaluation via imaging is important. Pyothorax, mediastinal abscessation, and either bronchoesophageal or tracheoesophageal fistulae are sequelae that may occur at a later stage following esophageal perforation. Fishhooks and needles may invoke similar clinical signs, although perforations of the esophagus seldom materialize.

Emergency Stabilization

A suspicion of an esophageal foreign body demands prompt intervention. Fluid and electrolyte imbalances are identified based on a thorough physical examination and bloodwork. Physical examination should assess mucous membrane moisture and color, capillary refill time, skin turgor, heart rate, pulse quality, body temperature, serial measurements of body weight and blood pressure. Bloodwork should evaluate for any electrolyte and acid–base abnormalities as well as the degree of dehydration based on packed cell volume and total solids. Even though animals with esophageal foreign bodies are seldom markedly hypovolemic, any imbalances should be corrected. Losses often relate to reduced water intake. An isotonic crystalloid, such as isotonic saline solution (0.9% NaCl), lactated Ringer's solution, Plasma‐Lyte 148, or Normosol‐R, can replace both vascular and interstitial volume deficits and maintain hydration. Because isotonic saline solution contains a higher concentration of sodium and chloride and may cause an increase in serum sodium and chloride, patient electrolytes should be monitored regularly and fluid therapy adjusted appropriately. Blood glucose concentration should be monitored and supplemented as needed. A constant rate infusion of 2.5–5% dextrose can be administered (appropriate amount of 50% dextrose can be added to the isotonic crystalloid therapy) until resolution of the hypoglycemia occurs. For patients that present in shock, shock fluid doses can be administered. If isotonic crystalloids are used, the total dose for dogs and cats is 80 and 50 ml/kg, respectively. Shock fluid therapy should be given in increments monitoring the patient's individual response. Synthetic colloids (hydroxyethyl starch, dextrans, and gelatins) can also be administered incrementally in dogs (10–20 ml/kg) and cats (5–10 ml/kg). Broad‐spectrum intravenous antibiotics (e.g., cefuroxime 10–15 mg/kg every 8–12 hours) should be considered, particularly if there is concern regarding esophageal perforation. In addition, pain medication such as an opioid analgesic (e.g., methadone: dogs 0.1–0.5 mg/kg every 4–6 hours intravenously, IV; cats 0.05–0.25 mg/kg IV every 4–6 hours) can be administered. If there is any suspicion of respiratory embarrassment secondary to pleural effusion or aspiration pneumonia, an arterial blood gas should be performed and thoracic radiographs taken once the patient is stabilized. If physical examination reveals muffled heart sounds and there is concern that pleural effusion is present, thoracocentesis should be performed before taking thoracic radiographs. If dyspneic, supplemental oxygen is administered via nasal prongs or oxygen mask. Gastric protectants such as omeprazole (0.5–1.5 mg/kg IV every 24 hours) help to limit the development of esophagitis. Ranitidine (2 mg/kg slow IV every 8–12 hours) is an alternative for dogs and is indicated for cats, for which omeprazole is not licensed for intravenous use.

Figure 4.3 Pathophysiology of esophageal injury.

Diagnostics

      Radiography

Survey cervical and thoracic radiographs identify most esophageal foreign bodies. Radiographic indicators of esophageal perforation include (Figure 4.4):

       Pneumomediastinum

       Pneumothorax

       Periesophageal fluid collection [6]. This sign may be subtle and even a careful search of the radiographic image may not disclose a perforation.

       Mediastinal widening. This sign is often evident on dorsoventral views (Figure 4.5).

Aqueous iodinated contrast media or barium may be introduced both to delineate radiolucent foreign bodies and to declare sites of esophageal perforation and leakage, although perforations plugged by the foreign body itself may not permit the contrast agent to issue extraluminally [7]. A stomach tube should be advanced along the esophagus toward the foreign body before infusing sufficient contrast agent to distend the esophagus.

Figure 4.4 Pneumomediastinum and pneumothorax following forceps retrieval of a bone foreign body from the esophagus. The trachea, esophagus, and great vessels are abnormally clearly delineated because of the pneumomediastinum. A thoracic drain has just been placed.

Figure 4.5 A markedly widened caudal mediastinum is seen here, due to the presence of an esophageal foreign body, on this dorsoventral radiographic projection.

      Computed Tomography

      Computed tomography imaging is seldom required to establish the presence of an esophageal foreign body, although it can be an invaluable modality for identifying both periesophageal fluid and extraluminal air, both of which are suggestive of esophageal perforation. Furthermore, the site of periesophageal fluid and air correlate well with the site of perforation, allowing accurate selection of the most suitable intercostal space for a subsequent surgical approach, which may not otherwise be evident in cases where the foreign body has been retrieved.

      Endoscopy

Endoscopic examination has a role in the assessment of these cases with two caveats. It is frequently impossible to fully evaluate the esophageal wall overlying the foreign body before the foreign body is retrieved and bleeding may impede visualization post retrieval (Figure 4.6). The clinician must be aware that insufflation of air via the endoscope may exacerbate a pneumomediastinum or pneumothorax in animals with esophageal perforation. Hence, careful anesthetic monitoring is critical in detecting any deterioration in oxygenation. In such an event, prompt thoracocentesis is indicated; ideally following survey radiography if the animal's conditions allow for this delay. Suction is invaluable in clearing frothy saliva to achieve an