Pathophysiology of Vomiting and Regurgitation Flashcards
contrast vomiting to regurgitation to expectoration
vomiting: active expulsion of material from stomach and/or intestine
regurgitation: passive expulsion of material from mouth, pharynx, esophagus
expectoration: active expulsion of material from respiratory tract; can happen at the same time as coughing (just air)
describe vomiting (8)
- common, nonspecific condition in small animals, pigs, and some exotic species
- rare in ferrets
- does NOT occur in:
-birds
-rodents
-rabbits
-because they lack neural emetic pathways - VERY RARE in large animals other than pigs
-horses have strong lower esophageal sphincter and poorly developed neural emetic pathways
-processes that cause vomiting in other species result in different clinical outcome - NOT associated with cervical esophageal distension
- associated with nausea, salivated, retching
- bile can be present, variable pH
- any amount of material or time after eating
describe the pathophysiology of vomiting
- coordinated effort of the GI, MSK, and NS
- emetic center: serotonin and alpha-2 adrenergic receptors
- other receptors are stimulated by humoral or neural pathways (5)
-nucleus tractus solitarii (NTS)- in the medulla
-chemoreceptor trigger zone (CRZ) in the medulla
-GI tract
-cerebral cortex/higher brain center
-oculovestibular system: visual cortex, cerebellum, pons, labryinth
describe the steps of vomiting (3)
- retroperistalsis: forces jejunal and duodenal contents into stomach
- retching: forceful contractions of abdominal muscles and diaphragm against closed glottis
-lower esophageal sphincter relaxes
-gastric contents pass into esophagus - expulsion of material to exterior
-glottis closed: prevent aspiration
-orifice between pharynx and nasopharynx closed
describe causes of vomiting (5)
- motion sickness
- ingestion or administration of emetogenic substances
- gastrointestinal obstruction
- GI tract or abdominal inflammation
- extra-GI tract disease
describe motion sickness
- in dogs, the oculovestibular system acts on CRZ via dopamine and serotonin
- in cats, the oculovestibular system can directly stimulate the emetic center
- challenges to the oculovestibular system can result in motion sickness:
-car rides
-otitis media/interna
-cerebellar diseases
describe emetogenic substances
- CRZ lacks blood-brain barrier so direct receptor binding is possible
-apomorphine (dopamine agonist; cats no have so use xylazine to induce vomiting in cats!) stimulates the CRZ
-xylazine, dexmedetomidine (alpha 2 agonist) can stimulate the CRZ or the emetic center - cisplatin stimulates GI tract serotonin receptors
- some substances (hydrogen peroxide, staphylococcal enterotoxins) can cause vomiting by direct gastric stimulation
- anti-emetics:
-maropitant inhibits substance P from binding to NK receptor
-metaclopramide is a dopamine antagonist
-ondansetron is a serotonin receptor antagonist
describe GI obstruction causing vomiting
- stimulates the vagal afferent fibers directly
-can also stimulate the enterochromaffin cells in gastric and duodenal mucosa - pythiosis
- foreign body
- neoplasia
describe pythium insidiosum
- aquatic oomycete
-fungus-like organism (does not respond to anti-fungal therapies though) - found in the stomach, small intestine, colon, rectum, rarely esophagus
- zoospores enter damaged skin and GI mucosa
- transmural pyoganulomatous and/or eosinophilic inflammation that leads to obstruction (and vomiting)
describe GI tract abdominal inflammation leading to vomiting
- stimulates the enterochromaffin cells in gastric and duodenal mucosa
-release serotonin and substance P which bind to receptors on the vagus nerve and stimulates the emetic center (NTS) - diet: complex mechanism of causing inflammation and emesis
- pancreatitis: lots of inflam, emesis possible
describe pancreatitis
- inflammation or in jury to the pancreas leads to premature activation of pancreatic enzymes
- inflammation stimulates the vagus nerve!!!
- reflux into pancreatic duct from chronic vomiting can exacerbate disease/vomiting
- grossly, can see fat necrosis due to early activation of enzymes
list 6 extra-GI diseases that can vomiting
- numerous pathways can induce vomiting
-splanchnic nerves (visceral afferent fibers) can stimulate NTS - uremia
- feline hyperthyroidism
- hypoadrenocorticism
-hypercalcemia - hepatic disease or insufficiency
- pyometra
describe uremia
- clinical syndrome of renal failure with azotemia
- uremia induces vomiting in multiple ways:
-uremic toxins suspected to stimulate the CRTZ
-gastritis stimulates enterochromaffin cells
-abnormalities in gastric emptying stimulates vagal afferent fibers
-metabolic disturbances
describe regurgitation (8)
- passive expulsion of material from mouth, pharynx, esophagus
- common, nonspecific condition in small animals, snakes
-normal activity in ruminants (rumination) and birds (owls)
-horses: esophageal regurgitation occurs normally but regurgitation from stomach VERY uncommon (due to their strong LES)
- rare in rabbits and rodents
- not reported in pigs or ferrets
- SOMETIMES associated with cervical esophageal distension
- NOT associated with nausea, salivation, retching
- no bile, pH at least or greater than 7
#basic - any amount of material or time after eating
describe the pathophysiology of regurgitation
- interruption in normal swallowing results in regurgitation
-normal is:
-mastication of food bolus or drinking of water
-upper sphincter relaxes to allow bolus to pass
-peristalsis moves bolus towards stomach
-lower esophageal sphincter relaxes to allow bolus to pass - keep in mind that the esophagus is striated muscle!
-cats: distal 1/3 to 1/2 is smooth
-horse: distal 1/3 is smooth
list causes of regurg (3)
- inflammation or irritation
- obstruction
-extra versus intraluminal - hypo/dysmotility
describe inflammation/irritation causing regurg
- impaired peristalsis, sphincter function
- esophagitis:
-GERD
-chronic vomiting
-foreign body
-chemical/thermal injury
describe GERD
gastroesophageal reflux disease
- believed to be LES incompetence
- anesthetic drugs can decrease LES pressure
- open LES allows gastric contents to reflux into esophagus leading to esophagitis
-also referred to as reflux esophagitis
describe reflux esophagitis
- HCl reduces esophageal pH, leading to denaturation of protein in mucosa
- pepsinogen converted to pepsin at low pH leading to further proteolysis and tissue destruction
- refluxed bile salts and pancreatic enzymes may also play a role
- esophagitis disrupts normal esophageal contractile activity: delayed clearance of ingesta or regurged substances
- LES can experience more incompetence, perpetuating gastruc reflux
describe extraluminal obstructions
- inability for bolus to pass
- more commonly at thoracic inlet, over heart base than at gastroesophageal junction
- vascular ring anomaly
- thymoma, other intrathoracic tumors
- hilar lymphadenopathy
describe vascular ring anomaly
- aberrant artery causes narrow esophageal lumen that impedes bolus passage
- persistent right (4th) aortic arch most common
-left ligamentum arteriosum, left subclavian artery, or both are aberrant
-aberrant right subclavian artery can also lead to ring abnormality
describe intraluminal obstructions (5)
inability for bolus to pass
- stricture
- FB
- impaction/choke
- neoplasia
- intussusception
describe stricture
- narrow esophageal lumen impedes bolus passage
- often secondary to gastroesophageal reflux or foreign body
-choke in horses - other causes:
-doxycycline, clindamycin, alendronate in cats
-carcinomas, fibrosarcomas associated with spirecerca lupi
describe hypomotility
- impaired peristalsis
- dysmotility:
-esophagus, GE sphincter
-primary or secondary - megaesophagus
describe megaesophagus
- insufficient, absent, or uncoordinated peristalsis
- common in dogs, rare in cats
- congenital:
-idiopathic
-vascular ring abnormality - acquired:
-idiopathic
-myasthenia gravis
-dysautonomia
-esophagitis
-polymyositis
how do you distinguish between vomiting and regurgitation?
complete history and physical exam!!!
describe large animal vomiting and regurg
vomiting:
1. pigs = dogs
2. rare, but can occur with ruminants: most commonly with toxicities (cardiac glycosides)
regurgitation:
1. ruminants/pseudoruminants:
-normal rumination/chewing cud
-esophageal causes
-sometimes with rumenoreticular diseases
- horses:
-esophageal causes
-through nose primarily (due to soft palate. larynx anatomy)
describe (pseudo)ruminant vomiting and regurgitation alternatives
- rather than getting back to the esophagus then nose/mouth, accumulates in the rumen
- abomasal/C3 contents
-reflux into rumen/C1 is referred to as internal vomiting, but is not an active process - rumenoreticular contents: stay in rumen
-gas accumulation (failure to eructate)
-ingesta fails to move to omasum/abomasum - need to use history, clinical signs, and dx testing to localize!
decsribe horse vomiting and regurgitation alternative
GASTRIC REFLUX
color:
-yellow/green: bile
-orange/red: inflammation/blood contribution
