Diagnosis
Regurgitation is the hallmark clinical sign of mega-esophagus and esophageal dysmotil- ity and needs to be distinguished from vomiting. Ideally, visualizing the primary complaint by feeding the dog is the most helpful in defining the clinical problem.
However, regurgitation will not necessarily regularly occur in less than 30 minutes postprandial. Survey thoracic radiographs are the first diagnostic procedure that should be performed (Figure 15.1). Megaesophagus, whether it is segmental or global is easily diagnosed without contrast studies and the added benefit of diagnosing an underlying etiology in the case of thymomas and MG. In the absence of megaesophagus, esophageal dysmotility needs to be distinguished from pharyngeal or cricopharyngeal dysphagia, by fluoroscopic studies using barium contrast in both dogs and cats (Boria et al. 2003; Levine, Pollard, and Marks 2014; German et al. 2005). In diagnosing VRA, in addition to segmental mega-esophagus, focal leftward tracheal curvature at the region of the heart on dorsoventral or ventrodorsal view and moderate to marked focal narrowing of the trachea is visible in 100% and 74% of thoracic radiographs respectively (Buchanan, 2004).Physical examination should include a complete neurological examination and evaluation for signs of muscle atrophy that could indicate peripheral neuropathies and myositis respectively. Minimum database should include screening and testing for endo- crinopathies associated with lower motor neuron disease including hypothyroidism, typical and atypical hypoadrenocorticism. If these endocrinopathies are diagnosed; response to treatment should be monitored, as they may be a coincidental finding. Myasthenia gravis can be screened for by acetylcholine receptor antibodies or rapid response to parenteral cholinesterases (Tensilon test), in the case of the generalized form (Shelton and Comparative Neuromuscular Laboratory 2015).
Inflammatory myositis should be considered in a dog with dysphagia, weakness and muscle atrophy. Clinical pathology may have elevated creatinine kinase, aspartate transaminase, and alanine transaminase activities (Evans, Levesque, and Shelton 2004). Electromyography has characteristic positive sharp waves. If myositis is suspected; serology for infectious diseases should be conducted, in addition antibodies to 2 M masticatory muscle fibers, followed by muscle biopsy (Evans et al. 2004). Esophagitis with or without stricture should be expected within approximately three weeks of surgery, or in any dog or cat with vomiting and postpilling of acidic drugs. Esophagoscopy is diagnostic. Diagnosis of caudal esophageal neoplasia requires survey and contrast thoracic radiographs, computed tomography, esophagoscopy, and biopsy for a definitive diagnosis by histopathology.The gold standard for diagnosing achalasia and dysmotility is high-resolution manometry (Kempf et al. 2014). Cricopharyngeal dysphagia has been described by videofluoroscopy as a significant delay in opening and closing of the cranioesophageal sphincter (Pollard et al. 2000).