GI disease: oral, pharyngeal, esophagus Flashcards
What is juvenile hyperplastic gingivitis?
Enlarged, inflamed gingiva in young cats, usually around the cheek teeth
What oral medication has been shown to reduce gingival hyperplasia in dogs?
Azithromycin containing dentifrice (8.5%)
What two drugs can cause gingival hyperplasia?
Cyclosporine, amlodipine
What 4 muscles are affected in masticatory muscle myositis?
Temporal, masseter, medial and lateral pterygoid muscles
What signalment is more commonly affected with masticatory muscle myositis?
Young adult to middle age, large breed dogs
What are the clinical signs in the acute phase of masticatory muscle myositis?
Painful muscle swelling, lethargy, reluctance to eat, pain on opening the jaw, fever, regional lymphadenopathy, exophthalmus, inability to open the mouth fully
What are the clinical signs in the chronic phase of masticatory muscle myositis?
Progressive atrophy of the muscles (can be symmetric or asymmetric), enophthalmus, inability to open the mouth fully
What is the pathogenesis of masticatory muscle myositis? Why does it only occur in these muscles and not other skeletal muscle?
Autoimmune destruction of the 2M muscle fibers, which are only found in the masticatory muscles (other skeletal muscles have 2C fibers)
What pathogenic mechanism is thought to contribute to sialadenosis and necrotizing sialometaplasia? What treatment is sometimes successful?
Abnormalities of the vagus nerve - some cases respond to phenobarbital
What is craniomandibular osteopathy?
Woven, irregular bone proliferation at the body of the mandible, TMJ, and tympanic bulla - occurs in small breed dogs
What is calvarial hyperosteosis? What breed does it occur in?
Irregular, progressive, bony proliferation and thickening of the cortical bone of the calvarium. Occurs in young Bullmastiffs
In dogs, the esophagus in comprised of what type of muscle? In cats?
Dogs: entirely striated muscle
Cats: 2/3 striated, 1/3 smooth muscle
What is the esophageal mucosa comprised of?
Keratinized, stratified squamous epithelium
Name the 4 phases of swallowing
Oral preparatory phase, oral phase, pharyngeal phase, esophageal phase
Describe the oral preparatory phase of swallowing
Mastication and lubrication of food or liquid. The bolus is modified and prepared for swallowing
What are potential causes of abnormalities in the oral preparatory phase of swallowing?
Dental disease, xerostomia (dry mouth), weakness of the lips, tongue, and cheeks
What cranial nerves innervate the lips?
V and VII
What cranial nerve innervates the tongue?
XII
Describe the oral phase of swallowing
Muscular events responsible for moving the bolus from the tongue to the pharynx. Facilitated by movement of the tongue, jaw, and hyoid muscles
When does the pharyngeal phase of swallowing begin?
When the bolus reaches the tonsils
What occurs first in the pharyngeal phase of swallowing?
Protection of airways: elevation of the soft palate to prevent the bolus from entering the nasopharynx; elevation and forward movement of the larynx and hyoid, retroflexion of the epiglottis, and closure of the vocal folds to protect the trachea
After protection of the airway, what occurs in the pharyngeal phase of swallowing?
Synchronized contraction of the middle and inferior constrictor muscles of the pharynx with relaxation of the UES to allow passage of the bolus into the esophagus
What muscle makes up the majority of the upper esophageal sphincter?
Cricopharyngeus muscle
Abnormalities of bolus transfer during the pharyngeal phase of swallowing can be divided into 3 categories. Name them and give examples
1) Oropharyngeal pump failure: pharyngeal weakness
2) Oropharyngeal and UES asynchrony: neuropathies
3) Pharyngeal outflow obstruction: cricopharyngeal achalasia, tumors, foreign bodies
Primary esophageal peristalsis is induced by what?
Swallowing
Secondary esophageal peristalsis is induced by what?
Distention of the esophageal lumen by the bolus that has failed to be propelled into the stomach by primary peristalsis
Muscular dystrophy is more common in what two dog breeds?
Bouvier des Flandres, Cavalier King Charles
Cricopharyngeal dysphagia is more common in what dog breeds?
Cocker and Springer Spaniels, Golden Retrievers (achalasia)
Pharyngeal weakness as the only sign of myasthenia gravis has been described in what percent of affected dogs?
1%
What laboratory test should be performed in all dogs with dysphagia?
Acetylcholine receptor antibody test
On fluoroscopy, timing of the swallow can be measure from when the epiglottis closes over the larynx to when it opens. How many frames does this take in a healthy dog?
5-6 frames (each frame 1/30 of a second)
Name 6 potential causes of pharyngeal weakness
Myasthenia gravis, muscular dystrophy, polymyositis, hypothyroidism, cranial nerve neuropathy, infection, neoplasia, trauma
Cricopharyngeal dysphagia can be characterized into two disorders. What are they?
Cricopharyngeal achalasia - failure of the UES to relax
Cricopharyngeal asynchrony - lack of coordination between UES relaxation and pharyngeal contraction
What is the cause of cricopharyngeal asynchrony?
Weak pharyngeal muscles are unable to propel the bolus through the UES in a timely manner
What form of bolus do patients with cricopharyngeal dysphagia display more trouble swallowing?
Liquids
When does cricopharyngeal dysphagia typically present?
At the time of or shortly after weaning
Most patients with cricopharyngeal achalasia display what structural change on imaging?
Prominent thickening of the cricopharyngeus muscle (cricopharyngeal “bar”)
What is the definitive treatment for cricopharyngeal achalasia?
Surgical myotomy or myectomy of the cricopharyngeus muscle
What does cricopharyngeal myotomy involve?
Incision of the cricopharyngeus muscle to the level of the pharyngeal mucosa (can be performed transcervically or endoscopically)
What procedure can be performed for temporary treatment of cricopharyngeal achalasia? How long does it last?
Injection of botulinum toxin into the circopharyngeus muscle - lasts 3-4 months
What is the mechanism of action of botulinum toxin A?
Acts at the presynaptic cholinergic nerve terminal to block the release of acetylcholine - weakens contraction of the muscle in a dose-dependent manner
What is the most common cause of high grade esophagitis and stricture in dogs?
Gastroesophageal reflux under anesthesia