Therapeutics

Therapeutics can be divided into specific therapies to treat the associated underlying disease condition and supportive care to avoid regurgitation and aspiration pneumo­nia and ensuring adequate enteral nutrition.

Myasthenia gravis can be managed with pyridostigmine bromide (1-3mg∕kg, orally

Figure 15.1 Right lateral thoracic radiograph (Figure 15.1a) and transverse computed tomography at the level of the third intercostal space (Figure 15.1b), using a soft tissue window width with the dog in dorsal recumbency, of an 11-year-old, spayed female, Springer Spaniel diagnosed with myasthenia gravis. There is a demarcated, soft tissue opacity visible in the cranial mediastinum (asterisk). A tentative diagnosis of thymoma was made.

BID) (Shelton 2002). Acetyl choline receptor antibody concentration and clinical signs need to be monitored as spontaneous remis­sion can occur (Shelton 2002). Thymectomy is indicated in cats diagnosed with cranial mediastinal mass associated MG. Cats with MG are predominantly managed medically most commonly with a combination of pyri­dostigmine and steroids, only steroid or pyri­dostigmine or multiple immunosuppressive agents and pyridostigmine, but it is not pos­sible to make recommendations based on the outcome of these studies (Hague et al. 2015). Immune mediated diseases, including MG, and myostis can be managed with immuno­suppressive therapy such as glucocorticoids, cyclosporine, mycophenolate mofetil, and intravenous human immunoglobulin. Prokinetics such as metoclopramide and cisapride have been explored with little ben­efit, as they have no effect on the striated muscle of the canine esophagus (Washabau 2003). Bethanecol will stimulate propagating contractions of the esophagus in some dogs (Washabau 2003).

Surgical interventions are considered in thymomas causing MG, hiatal hernias, VRA, gastro-esophageal intussusception, and cau­dal esophageal neoplasia.

Calcium channel blockers, Botulinum toxin injections, pneumatic dilatation, esophagomyotomy, and fundic plication have been described in humans with achalasia (Boria et al. 2003).

Supportive care in this disease should focus on instituting nutritional support either in the form of postural feeding or enteral feeding devices. Dogs, of various breeds, with idiopathic congenital mega­esophagus provided strict postural feeding was implemented, consistently demonstrated improvement of esophageal motility over 6-9 months when monitored by means of manometry, indicative of delayed neuromus­cular junction maturity (Diamant, Szczepanski, and Mui 1974). Meals should be small volume and divided into several por­tions throughout the day with various con­sistencies trialed to tailor the diet for the dog (Johnson et al. 2008). Solids stimulate peri­stalsis with less risk of aspiration, liquids have a shorter transit time but higher risk of aspiration (Strombeck 1978). Postural feed­ing is achieved by using a “Bailey chair ”-like feeding platform and keeping the dog uprights for 15 to 20 minutes (bailey chairs 4 dogs n.d.). Appropriate feeding needs to address chronic complication like cachexia and hypoalbuminemia (Kang et al. 2013).

Oral feeding may not achieve caloric require­ments in all dogs in which case gastrostomy tubes are short-term solutions and low-pro­file gastrostomy tubes are long-term solu­tions. Gastrostomy tubes can be placed non-invasively by percutaneous endoscopic techniques (PEG). Anesthetic considerations and aspiration pneumonia are important during procedures.