Vomiting vs. Regurgitation

• Contrast vomiting and regurgitation, defining mechanisms and providing examples of diseases that cause each
• Recognize gross and histopathologic findings associated with mechanisms of vomiting and regurgitation

Introduction

• A complete patient history and a physical examination are necessary to distinguish between vomiting, regurgitation, and expectoration
• Vomiting is the active expulsion of material from the stomach and/or intestine
• Regurgitation is the passive expulsion of material from the mouth, pharynx, or esophagus
• Expectoration is the active expulsion of material from the respiratory tract
• Understanding the pathophysiology helps in guiding diagnostics and therapy

Vomiting

• Vomiting is defined as the active expulsion of material from the stomach and/or intestine
• The condition is common and nonspecific in small animals, pigs, and some exotic species
• Vomiting is a rare occurrence in ferrets and will not occur in birds, rodents, or rabbits
• Rodents and rabbits lack neural emetic pathways
• Vomiting is very rare in large animals other than pigs
• Horses possess a strong lower esophageal sphincter and poorly developed neural emetic pathways
• Processes that cause vomiting in other species result in a different clinical outcome
• Vomiting is not associated with cervical esophageal distention
• Vomiting is associated with nausea, salivation, and retching
• Bile can be present, and there is a variable pH
• Material can be thrown up any amount of time after eating

Pathophysiology of Vomiting

• Vomiting is a coordinated effort of the gastrointestinal, musculoskeletal, and nervous systems
• The emetic center has serotonin and alpha-2 adrenergic receptors
• Other receptors are stimulated by humoral or neural pathways
• Nucleus tractus solitarii [NTS] (medulla)
• Chemoreceptor trigger zone [CRZ] (medulla)
• Gastrointestinal tract
• Cerebral cortex (“higher brain center”)
• Oculovestibular system (visual cortex, cerebellum, pons, labyrinth)
• Cats have few to no dopamine receptors
• Retroperistalsis forces jejunal and duodenal contents into the stomach
• Retching involves forceful contractions of abdominal muscles and the diaphragm against a closed glottis
• The lower esophageal sphincter relaxes
• Gastric contents then pass into the esophagus
• During expulsion, the glottis closed, and the orifice between the pharynx and nasopharynx closes

Causes of Vomiting

• Motion sickness
• Ingestion or administration of emetogenic substances
• Gastrointestinal obstruction
• Gastrointestinal tract or abdominal inflammation
• Extra-gastrointestinal tract disease

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, or Cerebellar disease

Emetogenic Substances

• CRZ lacks a blood-brain barrier and allows direct receptor binding
• Apomorphine (dopamine agonist) simulates the CRZ
• Xylazine and dexmedetomidine (alpha2 agonist) can stimulate the CRZ or the emetic center
• Cisplatin stimulates gastrointestinal tract serotonin receptors
• Some substances (hydrogen peroxide, staphylococcal enterotoxins) can cause vomiting by direct gastric stimulation
• Anti-emetics include:
• Maropitant inhibits substance P from binding to NK receptor
• Metaclopramide is a dopamine antagonist
• Ondansetron is a serotonin receptor antagonist

Gastrointestinal Obstruction

• Stimulates the vagal afferent fibers directly
• Can also stimulate the enterochromaffin cells in gastric, duodenal mucosa
• Examples of gastrointestinal obstruction are:
• Pythiosis
• Foreign body
• Neoplasia

Pythium Insidiosum

• Aquatic oomycete that is a fungus-like organism
• Occurs in the stomach, small intestine, colon, rectum, and rarely esophagus
• Zoospores enter the damaged skin and gastrointestinal mucosa
• Transmural pyogranulomatous and/or eosinophilic inflammation leads to obstruction

Gastrointestinal Tract and Abdominal Inflammation

• The enterochromaffin cells in gastric, duodenal mucosa release serotonin and substance P, which binds to receptors on the vagus nerve
• Stimulates the emetic center, NTS
• Other causes are:
• Diet, and pancreatitis

Pancreatitis

• Inflammation or injury to the pancreas results in the premature activation of pancreatic enzymes
• Inflammation stimulates the vagus nerve
• Reflux into the pancreatic duct from chronic vomiting can exacerbate the disease

Extra-Gastrointestinal Disease

• Numerous pathways can induce vomiting
• Splanchnic nerves (visceral afferent fibers) can stimulate the NTS
• Causes of extra-gastrointestinal disease include:
• Uremia
• Feline hyperthyroidism
• Hypoadrenocorticism
• Hypercalcemia
• Hepatic disease or insufficiency
• Pyometra

Uremia

• Clinical syndrome of renal failure with azotemia
• Uremia likely induces vomiting in multiple ways
• Uremic toxins are suspected to stimulate the CRZ
• Gastritis stimulates enterochromaffin cells
• Abnormalities in gastric emptying stimulates vagal afferent fibers
• Metabolic disturbances

Regurgitation

• Passive expulsion of material from the mouth, pharynx, or esophagus
• Common, nonspecific condition in small animals and snakes
• Normal activity in ruminants (= rumination) and birds (i.e., owls)
• Rare in rabbits and rodents (i.e., chinchilla)
• Not reported in pigs and ferrets
• Esophageal regurgitation happens in horses
• Regurgitation from the stomach is very uncommon due to the strong lower esophageal sphincter
• Sometimes associated with cervical esophageal distension
• Not associated with nausea, salivation, or retching
• There is no bile and a pH ≥ 7
• Any amount of material at any time after eating

Pathophysiology of Regurgitation

• Interruption in normal swallowing results in regurgitation
• Mastication of food bolus
• Drinking water
• The upper sphincter relaxes to allow the bolus to pass
• Peristalsis moves bolus towards the stomach
• The lower esophageal sphincter relaxes to allow the bolus to pass
• Keep in mind the esophagus is striated muscle in the cat and horse
• In the cat, the distal 1/3 to 1/2 is smooth muscle
• In the horse, the distal 1/3 is smooth muscle

Causes of Regurgitation

• Inflammation or Irritation
• Obstruction
• Extraluminal
• Intraluminal
• Hypo-/dysmotility

Inflammation and Irritation

• Results in impaired peristalsis and sphincter function
• Esophagitis includes:
• Gastroesophageal reflux disease (GERD)
• Chronic vomiting
• Foreign body
• Chemical/thermal injury

Gastroesophageal Reflux Disease

• Also known as gastroesophageal reflux
• Believed to be lower esophageal sphincter (LES) incompetence
• Anesthetic drugs can decrease LES pressure
• An open LES allows gastric contents to reflux into the esophagus, causing esophagitis, also known as reflux esophagitis

Reflux Esophagitis

• HCl reduces esophageal pH, causing denaturation of protein in the mucosa
• Pepsinogen is converted to pepsin at low pH, which can lead to further proteolysis and tissue destruction
• Refluxed bile salts and pancreatic enzymes may also play a role
• Esophagitis disrupts normal esophageal contractile activity, causing delayed clearance of ingesta or regurgitated substances
• The LES can experience more incompetence, perpetuating further gastric reflux

Extraluminal Obstruction

• Inability for a bolus to pass
• Commonly at thoracic inlet, over the heart base, greater than the gastroesophageal junction
• Main examples are:
• Vascular ring anomaly (including persistent right aortic arch)
• Thymoma and other intrathoracic tumors
• Hilar lymphadenopathy

Vascular Ring Anomaly

• Aberrant artery causes a narrow esophageal lumen, which impedes bolus passage
• Persistent right (fourth) aortic arch is the most common
• Left ligamentum arteriosum (I), left subclavian artery (II), or both (III) are aberrant
• Aberrant right subclavian artery can also lead to ring anomaly

Intraluminal Obstruction

• The inability for a bolus to pass
• Common examples:
• Stricture
• Foreign body
• Impaction ("choke")
• Neoplasia
• Intussusception

Stricture

• Narrow esophageal lumen impedes bolus passage
• Often secondary to gastroesophageal reflux or a foreign body
• Common in horses with choke
• Other causes include:
• Doxycycline, clindamycin, and alendronate in cats
• Carcinomas and fibrosarcoma associated with Spirocerca lupi

Hypomotility

• Impaired peristalsis
• Dysmotility of the esophagus or GE sphincter
• Primary or secondary
• Megaesophagus

Megaesophagus

• Insufficient, absent, or uncoordinated peristalsis
• Common in dogs, rare in cats
• Can be congenital, such as in instances of an idiopathic, vascular ring anomaly
• Can be also be acquired:
• Idiopathic, myasthenia gravis, dysautonomia, esophagitis, polymyositis

Vomiting vs Regurgitation.

• A complete patient history and a physical examination are necessary to distinguish between vomiting and regurgitation

Large Animal Vomiting and Regurgitation

• Vomiting in:
• Pigs, similar to dogs
• Rare instances of vomiting in with ruminants who commonly present toxicities, such as cardiac glycosides
• Regurgitation:
• Ruminants/pseudoruminants
• Normal rumination/chewing cud
• Esophageal causes, such as ruminoreticular diseases
• Horses experience:
• Esophageal causes, mainly through the nose do to soft palate and larynx anatomy

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 active
• Ruminoreticular contents stay in rumen
• Gas accumulation or failure to eructate
• Ingesta fails to move to omasum/abomasum
• Need to use history, clinical signs, and diagnostic testing to localize

Horse Vomiting and Regurgitation Alternative

• Gastric reflux
• Most causes are discussed during LA acute abdomen section
• Color may provide a clue
• Yellow/Green indicates bile
• Orange/Red indicates inflammation/blood contribution

What is the esophagus?

• It is a big tube that carries food and water from the mouth/throat to the stomach
• There is a sphincter at the top and the bottom to keep things moving in the appropriate direction
• It is surrounded by muscle that contracts to propel a bolus forward – which is very important since companion animals are often horizontal to the ground

Problems With the Esophagus

• A problem with the sphincters
• Something gets stuck in the tube
• Something is in the way so things can't move down the tube
• The muscles don't contract or cant contract
• The inside of the tube gets inflamed and causes pain

Esophageal Phase of Swallowing and the Upper Esophageal Sphincter (UES)

• A swallowed bolus must pass from the back of the throat, activating a UES Opening
• The UES is composed of the the cricopharyngeal muscle However:
• A problem in this area means it doesn't open at all or it is diseased, causing and issue with cricopharyngeal achalasia or cricopharyngeal asynchrony.
• A symptom would be general dysphagia (trouble swallowing), dropping food or if food is sitting in the back of the mouth
• Note* - This is not considered to be general regurgitation

Esophageal Innervation

• Heavily involves CN X (Vagus nerve) – with 3 branches Pharyngeal - Glossopharyngeal - Recurrent laryngeal nerves
• Also includes Spinal nerves T1-T10 - Sympathetic trunk

Esophageal Phase Swallowing

• The esophagus includes an lower esophageal sphincter (LES)
• Esophageal distension → sensory feedback regulates contraction speed and intensity (peristaltic waves)
• There is Primary peristalsis: swallow induced that includes a Secondary peristalsis and subsequent distension
• The LES relaxes with esophageal distension, and the bolus enters the stomach and contacts then contracts to prevent reflux of contents

Regurgitate By Animals

• Small animal species highlight
• Dogs
• Cats
• Ferrets - Rodents - Lagamorphs

Regurgitation

• Refers to the passive movement of material that has entered into the esophagus and then comes back out the mouth..
• Is very differentiated from Vominiting: - Nauseau- vomitting occurs; regurg - doesn't occur - Retching and abodminal contraction - Vomiitng occurs; regurg doesn't occur - bile; vomitting occurs; regurg sometimes occurs - Time after eating; both vomiting and regurg can occur anytime -pH can become a factor but it is very difficult to ascertain

To Understand What Is Happening With Your Patient

• Need a proper history;
  • Owners are unable to discern the difference between it and can be difficult or confusing to explain - It is always best to clarify
• There are other factors: -If so determine their awareness and if they are nauseated or drooling, even moving to avoid the event - Is Is an actively happening event? what side is being focused more? and overall if there is Just something that is coming up

To Understand What Is Happening With Your Patient (Cont...)

• Assess the characteristics of the matter at play: what texture, amount, if it is digested and what the color seems to appear, - Take a Picture for best documentation What is the overall timeline of this event: -When did it all start and what is happening over the long run

To Understand What Is Happening With Your Patient- pt.3

• Take proper History
  • what is going on with the patient and any any additional ailments
  • what is their overall environment - Where does the pet live and reside what are the routine and everyday elements of it's life - What is going on with their eating habits

Physical Examination Is A Key Step

• Be very careful to examine what is going on in their oralpharnynx, check the gum line, teeth and overall symmetry
• Check for discomfort and asses the trachea and chest symmetry
• Check for muscle tone throughout the body Assess for:
• Diseases of the upper esophageal sphincter (UES) as these tend to be associated with Cricopharyngeal achalasia or asynchrony - -Diseases of the esophagus such as - Esophagitis, Esophageal stricture , Esophageal FB, Esophageal neoplasia, Esophageal diverticulum, Vascular ring anomaly, Megaesophagus
• -Diseases of the lower esophageal sphincter (LES) -Hiatal hernia and Gastroesophageal reflux

Esophageal Diseases

• Esophagitis - Acute and chronic inflammation that is caused by a caustic substance, chornic vommitting or esophageal foreign bodies Esophageal and lower gastro issues from the result of general anesthesia, and can causes subsequent relaxation of the LES

Diseases of the Esophagus and Clinical Signs -Esophahitis

• Very depending on it's overall severity - Overall mild - Mild-No Clinical signs - moderate to severe - anorexia, dysphagia even regurg in a high degree HISTORY, LABS , RADIOGRAPS all of which can need endoscopies during this part of the examination

Stricture

Diseases of Esophagus Narrowing of luminal passage; what has caused this: Esophageal reflux! Most caused is what the LES has done - this can be the cause or result

Clinical Signs- Esophageal Stricture

• Regurg, Painful, Salibatory

Additional info:

With the esphphagus; want to determine the over all cause of it and take a history exam if they haven't done something The thoracic region needs to be examined and and consider what is going into the tissue, which often can lead into more long term chronic illnesses such as cancer

Diseases of the Esophagus - Diverticulum Vs. Vascular Abnormalities (aka ring)

• diverticulum: The Sacculation of esphogoeal origin, with the occasional presence of forgin anomalies
• Vascular : a Vessel Outside and compression on the outside, which leads in external stricture
  • VASCULAR RING ANOMAY, - there is a very huge presence of the congenital abnormalitie

Abnormalities and What The Best Route Of Action Can Be

Overall signs need to have a regimented of once the affected area comes into contact and that there are a number of things happening

• Thoracic Radiographs are very common With Megaesophagus:
• there tends to be muscle pain, and gait problems
• can make the animal get sick and have bad reactions

Actional Considerations

TREATMANT - MEGAESOPHAGUS

• Small-frequent feedings

• Consistency that works for particular, meatballs are very very not recommended

• Bailey Chair feeding station

• TREAT ESOPHAGEAL SIGNS!

• Treat aspiration pneumonia if present.