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
Gastroesophageal reflux under anesthesia preceded the development of esophageal strictures in what percent of cases?
46-65%
What anesthetic agents can cause a decreased in LES pressure, leading to GER?
Atropine, morphine, acepromazine, thiopental, xylazine, and isoflurane
Describe the pathogenesis of esophageal stricture formation
Damage to the muscularis layer of the esophagus leads to fibroblastic proliferation and contraction
Balloon dilation of an esophageal stricture provides what type of stretch while bougienage provides what type of stretch?
Balloon = radial dilation
Bougienage = longitudinal forces
Administration of what drug into the submucosa of a stricture site prior to dilation has been associated with reduced rate or re-stricture? What is the dose
Triamcinolone 2.5mg per quadrant, injected into all 4 quadrants
A persistent right aortic arch is hereditary in what breeds?
German Shepherd, Irish Setter
How is a persistent right aortic arch corrected?
Surgical resection of the persistent ligmentum arteriosum with balloon dilation of the esophagus
Surgical correction of a persistent right aortic arch results in improved esophageal motility in what percent of patients?
> 90%; some have persistent esophageal hypomotility
What parasite can cause esophageal granulomas in dogs?
Spirocirca lupi
Esophageal granulomas can undergo malignant transformation into what tumor types?
Fibrosarcoma or osteosarcoma
What is the treatment for esophageal granulomas secondary to Spirocirca lupi infection?
Doramectin - 3 subcutaneous injections given at 14 days intervals or oral administration once a day for 6-12 weeks
What are esophageal diverticula?
Circumscribed sacculations of the esophageal wall that affect motility
How do congenital esophageal diverticula form?
Abnormalities in embryologic development permit herniation of the esophageal mucosa through a defect in the muscularis
How do acquired pulsion diverticula form?
Develop from increased intraluminal pressure secondary to obstruction (stricture, etc) or altered motility
How to acquired traction diverticula form?
Result from peri-esophageal inflammation and fibrosis - adhesions to adjacent tissues distort the esophageal lumen and create sacculations. Grass awn migration is a common cause
What is the most common cause of regurgitation in dogs?
Megaesophagus
Congenital megaesophagus in cats is rare, but what breed may be predisposed?
Siamese
The pathogenesis of congenital megaesophagus is poorly understood, but what may be involved?
Defect in vagal afferent innervation of the esophagus
Myasthenia gravis accounts for what percent of acquired megaesophagus in dogs?
25-30%
Name 5 causes of acquired secondary megaesophagus in dogs?
Myasthenia gravis, hypoadrenocorticism, lupus myositis, polymyopathy, polyneuropathy, dysautonomia, lead poisoning, severe esophagitis
If the onset of megaesophagus is acute, and acetylcholine receptor antibody titers are in the “grey zone” (0.3-0.6), what should you do?
Repeat titers in 4-8 weeks
Name 3 common causes of GERD in dogs
Hiatal hernia, anesthesia, chronic vomiting leading to a weakened LES, gastric atony
Why are signs of GERD worse at night?
Transient relaxation of the LES occurs while sleeping, along with loss of the swallow reflex
Name 3 clinical signs of GERD in dogs
Lip smacking, hard swallowing, panting - often worse at night
What is a sialocele?
A collection of saliva that has leaked from a damaged salivary duct/gland and is surrounded by granulation tissue
How often do sialoceles recur after surgical removal of the gland/duct?
5-14%
Sialoceles that are refractory to surgical removal may respond to what therapy?
Radiation therapy - 16 or 20 Gray in 4 Gray fractions - achieved complete remission in 54% and partial response in 45%
Name two potential causes of esophageal varices
Portal hypertension (hepatic cirrhosis, etc), congenital or acquired arteriovenous communications, increased cranial vena cava resistance (thrombi, masses)
Name 2 potential clinical signs of esophageal varices in dogs
Ptyalism and hematemesis
Explain the difference between “downhill” and “uphill” esophageal varices
Downhill: extend downward or caudally, usually secondary to superior vena cava obstruction
Uphill: extend upward or cranially, commonly associated with portal hypertension
Unlike in humans, what clinical sign is rare in dogs with esophageal varices?
Hemorrhage - not seen in 25 dogs in Slead’s retrospective
In one study of dogs presenting for cough with no GI signs, what percent demonstrated swallowing abnormalities?
80.6%
The pharyngeal phase of swallowing is mediated by sensory afferents of what cranial nerves?
IX and X
What airway protective behaviors occur during vomiting? During regurgitation?
Vomiting: laryngeal adduction, soft palate elevation
Regurgitation: none
GER has been documented in what percent of healthy, asymptomatic dogs?
41%
What is the most common form of hiatal hernia in dogs and cats?
Type I = sliding hiatal hernia
In cats with hiatal hernias, what percent had evidence of upper airway disease/obstruction?
29%
What is the median survival time for cats with hiatal hernias? Did cats treated surgically or medically survive longer?
Overall MST 959 days
Medically - 2559 days
Surgically - 771 days
What risk factors increase the odds of GER post-anesthesia?
Male (OR 9.2), overweight BCS (12.3), gastrointestinal surgery (30.5) and requirement for a dexmedetomidine CRI after surgery (9.6)
Does prophylactic administration of maropitant and metoclopramide decrease the incidence of GER post-anesthesia?
Not in the 2019 JAVMA paper
What risk factors increase the odds of regurgitation and vomiting post-operatively?
Gastrointestinal surgery (OR 11.5), premedication with acepromazine (5.4), hx of vomiting/regurgitation (5.1), emergency surgery (4), neurologic surgery (3.2), sevoflurane (2.3)
When evaluating GER in healthy dogs by nuclear scintigraphy, what percent of healthy dogs experienced reflux?
All of them. In 5/12, it refluxed all the way to the pharynx
Name 4 potential treatment options for lower esophageal sphincter achalasia in dogs
Sildenafil, mechanical dilation, botulism toxin A injection, surgical myotomy and fundoplication
Mechanical dilation and botulism injection improved clinical signs in how many dogs with lower esophageal sphincter achalasia? How long did the improvement last?
100% of dogs improved by 21 days - BW increased 20%, regurgitation decreased by 80%
Lasted 40 days
Balloon dilation resulted in resolution of esophageal strictures in what percent of cases?
59% (not all had triamcinolone injected, only done twice)
Placement of a balloon dilatation esophagostomy tube (B tube) resulted in improved modified dysphagia scores in what percent of animals?
97%
What is the goal of a B tube?
Placed after initial dilation of the stricture under anesthesia. Goal is to cause microtrauma to the previously dilated stricture, preventing fibrosis and contraction
How long are B tubes kept in place?
6 weeks, dilated twice daily
What features on video fluoroscopy can be used to identify lower esophageal sphincter achalasia?
Bird beak sign 63%, esophageal fluid line 68%, megaesophagus 73%, failure of the LES to open during pharyngeal swallowing (100%)
Of dogs/cats undergoing esophageal surgery, what is the complication rate and what complications occur?
54% overall - persistent regurgitation, esophageal stricture formation
What risk factors are associated with increased complications after esophageal surgery?
- Type of surgery - partial esophagectomy with R&A
- Mass lesion, larger lesion size
Following esophageal surgery, what are negative prognostic indicators for survival to discharge?
Pneumomediastinum, leukopenia
In a review of 222 dogs with esophageal foreign bodies, what was the most common foreign material and where was it?
Osseous material (81%), distal esophagus (50%)
What percent of esophageal foreign bodies are able to be removed endoscopically?
91.8% (222 dog study 2017); 83.6% (224 dog study 2018)
In a review of 222 dogs, what was the fatality rate for esophageal foreign bodies? What was associated with mortality?
5% mortality - associated with need for surgical intervention, esophageal perforation (OR 65), post procedure esophageal hemorrhage (OR 11.8)
What percent of dogs develop esophageal strictures post-foreign body removal?
2.1% (2017 study); 11.2% (2018 study)
In a study of 52 cats with foreign bodies, what percent were successfully retrieved endoscopically? How often did radiographs identify foreign material?
94% retrieval rate, 48% identified on rads
In a study of 52 cats with foreign bodies, what percent of cats had major complications?
15% overall - higher in cats with esophageal foreign bodies than gastric
Esophageal perforation is more common with what type of foreign body?
Fish hook
In a JVIM study evaluating 114 dogs with esophageal foreign bodies, what was associated with severe esophagitis and major complications?
Foreign body present for >24 hours
What percent of brachycephalic dogs present with gastrointestinal signs prior to airway surgery?
Overall 56%, but it was 93% in Frenchies, 58% in bulldogs, and only 16% in pugs
What surgical technique can be used to prevent regurgitation in brachycephalic dogs?
Circumferential esophageal hiatal rim reconstruction and esophagopexy
Brachycephaly is associated with what abnormalities on fluoroscopic swallowing studies?
Esophageal dysmotility characterized by prolonged esophageal transit time, GER, and hiatal hernia
Pre-treatment with maropitant and famotidine as well as the reduced use of opioids reduced post-operative regurgitation in brachycephalics by what percent?
From 35% to 9%
