Small Animal Surgical Emergencies. Группа авторов
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Ultrasound
Ultrasound has become widely used as a means of identifying foreign objects or GI obstruction in animals, with some suggesting ultrasound may be preferred over survey radiography [42, 43]. Availability of ultrasound in practice and ultrasonographer skill play key roles in determining whether radiography or ultrasound is the preferred imaging modality.
Ultrasonography has been shown to be an effective means of identifying GI foreign bodies and obstruction, even when radiographs are inconclusive. Sensitivity of ultrasound has been reported as high as 100% [42, 44] for identifying foreign bodies. Tyrell and Beck reported that 16 of 16 objects were identified by ultrasound in dogs and cats suspected of having GI foreign bodies, compared with only 9 of 14 detected by survey radiography [42]. In another study by Manczur et al., ultrasonography was reported to have a sensitivity of 85% and specificity of 94% for identifying intestinal obstruction based on findings of surgical or medical management, but results of radiographic findings were not compared [45]. In a veterinary study by Sharma et al., radiography definitively identified obstructed versus non‐obstructed dogs in 58 of 82 cases (70%), while ultrasonography produced a definitive result in 80 of 82 (97%) dogs [43]. In animals with suspected obstruction, ultrasound was able to rule out a small intestinal obstruction in 74% and correctly identify obstruction in 23% of cases, the majority of which were due to foreign bodies [46]. This yielded a sensitivity of 100%, specificity of 95.8%, and positive and negative predictive values of 87.5 and 100%, respectively [46]. In addition to successfully identifying objects and obstruction, ultrasonography may also provide additional information not identified on plain radiographs, including free abdominal fluid, evidence of perforation, free gas, GI wall thickening, loss of layering to the small intestine, and lymphadenomegaly [42, 44].
Ultrasonographic findings consistent with a foreign body include distal acoustic shadowing and surface reflection that vary with type of foreign body (Figure 5.3a) [42]. Intramural hematoma marked by septated, hypoechoic, mural expansion of the small intestine has also been reported [47]. Ultrasound may be especially helpful in identifying non‐radiopaque objects, such as wood. Ultrasonographically, wood appears as a linear, echogenic surface associated with uniform acoustic shadowing [48, 49]. Adjacent soft‐tissue swelling may also be present if the wood has migrated out of the stomach [48]. Small intestinal obstruction is suggested by identification of the actual obstruction, intestinal plication, or segmental dilation (Figure 5.3b). Sharma et al. suggested that finding a jejunal diameter greater than 1.5 cm should prompt a search for a small intestinal obstruction (Figure 5.3c) [43].
Figure 5.3 (a) Transverse sonogram of the duodenum at the level of the duodenal papilla. The lumen is filled with a foreign body (right of the image) and anechoic fluid (left of the image). The foreign body (cloth) is characterized by a convex hyperechoic interface in the near field and creates an acoustic shadow in the far field due to attenuation of the ultrasound beam. This is the most common appearance of gastrointestinal foreign bodies. (b) Sagittal sonogram of a plicated small intestinal segment. This image demonstrates the severe folding or pleating of the intestinal wall that occurs with linear foreign bodies. The linear hyperechoic foreign body is not seen as this image was obtained slightly off midline to the luminal center. (c) Transverse sonogram of the small intestine proximal (oral) to a foreign body. Note that the luminal diameter > 1.5 cm should prompt search for an obstruction.
Source: Dr. A. Sharma, University of Georgia, Athens, GA. Reproduced with permission of Dr. A. Sharma.
It may also be possible to identify GI perforation via ultrasonography. The most common ultrasonographic findings in dogs and cats with perforation include focal or regional hyperechoic fat, peritoneal effusion or pneumoperitoneum, fluid‐filled stomach or intestines, and thickening or loss of GI wall layering. Additional findings reported concurrently with foreign body perforation included corrugated or undulating intestine, regional lymphadenopathy, hypomotility, pancreatic changes, the presence of a mass or foreign object, gastroduodenal junction “crumpling,” and gastric wall mineralization [50, 51]. Ultrasonography has also been shown to be superior to computed tomography (CT) for the identification of hypoperfused lesions of the bowel [52].
Computed Tomography
CT is becoming a more commonly used modality because it is fast and easy to perform, and is more readily available. Contrast‐enhanced and non‐contrast CT have been shown to accurately identify GI foreign material and obstruction as well as to differentiate surgical from nonsurgical acute abdomen patients [52–54]. Additionally, while the diagnostic accuracy for surgical versus non‐surgical conditions is high for radiographs, ultrasound, and CT (94%, 94%, and 100%, respectively), median CT acquisition time was far faster than ultrasonography (2.5 and 26.0 minutes, respectively) [54].
Surgical Techniques
Removal of foreign material from the GI tract is primarily performed when the material has not yet reached or is unable to reach the colon. See Chapter 4 for the removal of foreign bodies from the esophagus.
Stomach
Foreign bodies within the stomach represent 16–50% of GI foreign bodies reported [2–4, 55]. Removal of foreign material from within the stomach is primarily achieved via either induced emesis, endoscopy, or gastrotomy. In two studies of dogs with gastric foreign bodies, administration of apomorphine resulted in successful gastric foreign body removal in 374/495, and 46/61 dogs. [56, 57] Only minor adverse effects were reported in four of the dogs. Recent ingestion, ingestion of fabric, leather or bathroom waste, and young age were associated with a successful emesis event. [56] In a study of endoscopic gastric foreign body retrieval, 10 of 36 gastric foreign bodies required surgical removal after attempts at endoscopic removal failed. The authors in that study pointed out that only foreign bodies with attempted endoscopic retrieval were included and that some types of foreign bodies would not be considered candidates for endoscopic retrieval [21].
When surgical intervention is required, it is important that the entire GI tract be evaluated via visualization and palpation, regardless of the specific location of the offending foreign body. Identification and removal of all foreign material is essential to prevent the possibility of a second obstruction. When the foreign material has been isolated to the stomach, the stomach must be packed off with saline‐moistened laparotomy sponges and stay sutures placed to minimize the risk of contamination of the abdominal cavity during foreign body retrieval (Figure 5.4). Following placement of stay sutures, an incision is made on the ventral surface of the stomach midway between the branches of the gastroepiploic and gastric vessels and along the greater curvature using a number 15 scalpel blade. In the majority of cases, the incision does not require excessive length; however, the length of the gastric incision may need to be extended with Metzenbaum scissors after the nature of the foreign material has been identified. For example, some wood glue compounds when ingested become a solid material that cannot be removed easily without an incision of adequate length of approximately the same size as the foreign body [8]. Maintenance of tension on the stay sutures is critical to prevent spillage of gastric contents. Following removal of a discrete foreign body, closure of the stomach may be achieved in any of the following ways: a simple continuous appositional pattern through all layers, a double layer, continuous pattern (gastric mucosa and submucosa in the first layer with the second layer being full thickness), a double layer, inverting pattern (the first suture line is full thickness and the second suture line incorporates only the seromuscular layers), or a simple continuous pattern in the