Diseases of the esophageal wall can be challenging to diagnose via noninvasive methods. The diagnostic approach for esophageal disease is currently limited to radiography, esophagoscopy, and, less commonly, CT or MRI. Esophagoscopy allows the possibility of a full examination of the esophageal mucosal surfaces and enables clinicians to detect strictures, diverticula, intraluminal masses, or lodged foreign bodies as well as to obtain biopsy specimens.1
Although CT and in some instances radiography may be useful in detection of extraluminal and intraluminal esophageal disease, none of these modalities are capable of allowing evaluation of the architecture of the esophageal wall in as great a detail as does the use of ultrasonography because of the greater spatial resolution for ultrasonographic examinations. Although EUS and especially radial EUS are not readily available in clinical settings, this technique may have great potential for use in veterinary medicine,2 particularly for the diagnosis and understanding of esophageal disease. In clinical settings, a radiographically visible, partially fluid-filled megaesophagus may hide esophageal masses and therefore be incorrectly interpreted as idiopathic megaesophagus.3,4 Esophageal masses such as leiomyoma can be mistaken radiographically with granulomatous disorders, such as infestation with Spirocerca lupi.5,6 Another beneficial aspect of EUS might be its use in staging of mural esophageal disease, which facilitates planning for resection of esophageal tumors.3,7 A better diagnostic imaging tool is needed to provide a more sensitive and specific description of diseases of the esophagus.
Endoscopic ultrasonography has been used in human medicine to overcome limitations (eg, superimposition of other organs on radiographs or inadequate soft tissue contrast on CT images) encountered with other imaging modalities as well as limitations (eg, narrow intercostal spaces, lung-air interference, and obesity) encountered with transcostal and transabdominal ultrasonography. Assessment of the esophageal wall via EUS in humans has been described, and EUS is routinely used for staging of neoplastic diseases (eg, esophageal and gastric carcinomas) because it has better sensitivity than other imaging techniques.8–11
Endoscopic ultrasonography has been used in small animals for evaluation of the gastric wall and other abdominal organs in situations requiring the need to overcome interference attributable to gas artifacts or extreme obesity.12,13 Furthermore, EUS has been used to investigate the mediastinum and selected intrathoracic lesions in dogs.14,15
Histologically, the canine esophagus is composed of the tunica adventitia, tunica muscularis (outer longitudinal and inner circular layer), submucosal glands, and mucosa; the mucosa is composed of 3 layers.16 The histologic appearance of the esophagus of dogs is similar to that of the esophagus in humans. Use of EUS in humans has revealed a 5-layer structure with alternating hyperechoic and hypoechoic layers, which is similar to the appearance of the intestinal wall of dogs.9 The tunica adventitia is evident as a thin hyperechoic layer, the tunica muscularis is evident as a hypoechoic layer, the submucosa is hyperechoic, and the mucosa is hypoechoic. The innermost layer, the mucosal surface, has been described as a thin hyperechoic line.
To the authors’ knowledge, the ultrasonographic appearance of the canine esophageal wall has not been described. Therefore, the objective of the study reported here was to assess the use of EUS for the evaluation of the esophageal wall architecture in healthy dogs and to compare the EUS results with histologic results.
Acepromacin, Fatro, Ozzano dell’ Emilia, Italy.
Temgesic, Reckitt Benckiser AG, Wallisellen, Switzerland.
Propofol 1%, Fresenius, Stans, Switzerland.
Iso Flo, Dr. E. Graeub AG, Bern, Switzerland.
Olympus UE-160 AL-5, Olympus Switzerland AG, Volketswil, Switzerland.
Aloka Prosound alpha 10, Hitachi Medical Systems Europe Holding AG, Zug, Switzerland.
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