9.5.1: Approach to vomiting, regurgitation, and dysphagia Flashcards
Vomiting is an active reflex mediated via the emetic centre. Describe the various pathways by which this can be stimulated.
The emetic centre can be stimulated via the:
* Chemoreceptor trigger zone (CRTZ)
* GI tract
* Cerebral cortex
* Vestibular system
This means that in vomiting, there are several systems to consider as possible causes.
What does the chemoreceptor trigger zone monitor and how does it achieve this?
- CRTZ is full of various receptors
- Samples the blood for endogenous substances e.g. azotaemia (renal system), ammonia (hepatic system), and inflammatory mediators.
- Samples the bloood for exogenous substances e.g. drugs/toxins
What are the likely broad causes of acute vomiting?
Acute vomiting is most likely to be:
* Toxic
* Obstructive
* Inflammatory
* Infectious
What are the likely broad causes of chronic vomiting?
Chronic vomiting is most likely to be:
* Chronic inflammatory
* Chronic infectious
* Metabolic
* Endocrine
* Neoplastic
Dysphagia
a failure to prehend/bite and initially swallow. This involves the mouth and pharynx.
What are some possible causes of dysphagia?
- Pain e.g. dental disease, retrobulbar abscess, jaw fracture
- Failure of neuromuscular control e.g. masticatory myositis, botulism, cranial nerve disease (V, VII, IX, X, XII)
- Obstruction e.g. FB, abscessation, neoplasia, lymphadenopathy
Regurgitation
Failure to pass food down the oesophagus
What are some possible causes of regurgitation?
- Dilatation e.g. megaoesophagus
- Obstruction
- Neuromuscular disease e.g,. botulism, tetanus, dysautonomia, Addison’s, peripheral neuropathy
Describe the types of oesophageal obstruction and provide an example cause for each
- Obstructions may intraluminal (internal), mural (wall), extramural (external)
- Intraluminal e.g. FB, stricture secondary to oesophagitis
- Mural e.g. neoplasia, inflammation
- Extramural e.g. vascular ring anomaly, hiatal hernia, SOL (neoplasia)
SOL = space-occupying lesion
What are some neuromuscular disorders that may cause regurgitation?
- Addison’s
- Botulism
- Distemper
- Dysautonomia
- Hypothyroidism
- Myasthenia gravis
- Peripheral neuropathy (may be autoimmune)
- Tetanus
Vomiting may be caused by events in the GIT, cerebral cortex, vestibular system, or CRTZ. List some possible GIT causes of acute vomiting.
- Obstructive: FB, neoplasia, parasitic constipation, intussuception, volvulus
- Inflammatory: gastritis, gastroenteritis, colitis
- Mucosal insult: dietary indiscretion, intolerance, sudden changes in diet, toxins
- Infectious: bacterial/viral/parasitic cause
- Gastric stretch (overeating)
Vomiting may be caused by events in the GIT, cerebral cortex, vestibular system, or CRTZ. List some possible causes of acute vomiting that originate in the cerebral cortex.
- Head trauma
- Sudden changes in intracranial pressure (ICP)
Vomiting may be caused by events in the GIT, cerebral cortex, vestibular system, or CRTZ. List some possible causes of acute vomiting that originate in the vestibular system.
- Motion sickness
- Idiopathic vestibular disease
- Otitis interna
Vomiting may be caused by events in the GIT, cerebral cortex, vestibular system, or CRTZ. List some possible causes of acute vomiting that originate in the CRTZ.
- Endogenous causes: any systemic metabolic or endocrine disease resulting in acute changes that will be picked up in the CRTZ e.g. DKA, Addison’s, AKI, pancreatitis, acute hepatitis, peritonitis, prostatitis, pyometra
- Exogenous: toxins/drugs
Vomiting may be caused by events in the GIT, cerebral cortex, vestibular system, or CRTZ. List some possible causes of chronic vomiting that originate in the GIT.
- Obstructive: pyloric FB, neoplasia, parasitic obstruction, constipation
- Chronic inflammatory: gastritis, gastroenteritis, colitis, chronic enteropathy
- Mucosal insult: dietary intolerance
- Infectious: chronic bacterial/viral/protozoal infection
Vomiting may be caused by events in the GIT, cerebral cortex, vestibular system, or CRTZ. List some possible causes of chronic vomiting that originate in the cerebral cortex.
- Neoplasia/SOL
- CNS disease
SOL: space occupying lesion
Vomiting may be caused by events in the GIT, cerebral cortex, vestibular system, or CRTZ. List some possible causes of chronic vomiting that originate in the vestibular system.
- Chronic vestibular damage
- Otitis interna
- Neoplasia
- Cerebellar disease
Vomiting may be caused by events in the GIT, cerebral cortex, vestibular system, or CRTZ. List some possible causes of chronic vomiting that originate in the CRTZ.
- Endogenous causes: any systemic metabolic or endocrine disease resulting in acute changes that will be picked up in the CRTZ e.g. DKA, Addison’s, AKI, chronic renal failure, chronic pancreatitis, electrolyte disturbances, acid-base disturbances, hyperthyroidism (cats)
- Exogenous causes: drugs and toxins are less likely when vomiting is chronic rather than acute
Which tetracycline can cause oesophagitis in cats?
Doxycycline
Describe your approach to a case of vomiting
- Differentiate vomiting (active) from regurgitation/dysphagia (passive)
- History (e.g. recent medications)
- Signalment clues
- Physical exam –> other clinical signs may be suggestive of a cause
How could you differentiate vomiting from dysphagia/regurgitation?
- Vomiting is active, dysphagia/regurgitation is passive
- Vomiting usually associated with retching, abdominal effort, and noise
- Regurgitation is associated with less noise and no retching
- Timing after food for each can be variable so don’t rely on this.
- Look at the food - does it look partially digested?
What are some history questions/clinical exam findings that might help you in a case of vomiting?
- Recent medication e.g. doxycycline
- GI disease: dietary changes/scavenging, FB risk? Access to toxins? Worming regime? Concurrent diarrhoea/constipation?
- Neuro abnormalities: any behavioural changes/ataxia/cranial nerve deficits?
- Pain
- BCS and musculature especially masticatory muscles - helps ascertain if acute/chronic cause
- Signs of systemic disease e.g. PUPD, jaundice
One of these dogs walks in. It is a puppy. The owner reports has been struggling to keep food down. What are you suspicious of and what might be your next step?
- Breeds pictured: Lab, Newfoundland, Shar Pei
- These breeds are at higher risk of congenital megaoesophagus
- Possible next step: more thorough history taking to ascertain what the owner means by “struggling to keep food down” i.e. is this true vomiting or instead regurgitation?
Which dog breeds are at higher risk of congenital and acquired megaoesophagus?
Great Danes, GSDs, Irish Setters
The following breeds are all more likely to have which anatomical abnormalities that could lead to regurgitation?
Breeds pictured: Great Dane, GSD, Irish Setter
At increased risk of:
* congenital and acquired megaoeophagus
* vascular ring anomaly e.g. PRAA
PRAA: persistent right aortic arch. This wraps around the oeosphagus, leading to regurgitation.
Which species are most at risk of doxycycline-induced oesophagitis?
Cats
Which of the following are most likely to present with an intusseception?
a) older animals
b) younger animals
c) middle-aged animals
b) younger animals
A labrador puppy presents with an acute history of vomiting. The most likely cause is:
a) intestinal neoplasia
b) gastric/intestinal foreign body
c) vascular ring anomaly
d) congenital megaoesophagus
b) gastric/intestinal foreign body
* Remember that labradors are idiots and eat everything.
* Labs are more at risk for congenital megaoesophagus, but we might expect a more chronic presentation, and this would be associated with regurgitation rather than vomiting.
You suspect a puppy has an intusseception. What information from the history might make you even more suspicious of this?
Recent history of diarrhoea
Radiography will be best utilised to detect which causes of vomiting?
a) inflammatory disease
b) obstructive disease
c) metabolic disease
b) obstructive disease
You suspect a systemic disease/metabolic cause of your canine patient’s vomiting. What specific blood tests could you do and what would each test for?
- cPLI - Pancreatitis
- AChR - Myasthenia gravis
- Basal cortisol - Addison’s
- T4/TSH - Hypothyroidism
Management and prognosis of megaoesophagus
- Feed from height over 5-10 mins
- Feed small balls of food rather than large amounts
- Consider placing a feeding tube
- Treat any concurrent/underlying disease e.g. hypoT, PRAA
- Prognosis is often poor for chronic regurgitation
Management of oesophagitis
- Provide pain relief
- Place a feeding tube that bypasses the oesophagus e.g. a PEG tube
Management of oesophageal FB
- Could attempt removal via endoscopy
- If very challenging -> consider referral because if you rupture the oesophagus the animal will need a thoracotomy
True/false: it is appropriate to give any anti-emetic to the acutely vomiting patient, and instruct the owners to return the following day if the vomiting has not stopped.
False although this does happen in practice.
* If an animal has a FB, for example, giving an anti-emetic may mask this (animals with FBs cannot be relied upon to vomit “through” the anti-emetic).
* Some anti-emetics e.g. metoclopramide have prokinetic effects which could lead to GI rupture if a FB is present.
* Sometimes anti-emetics may be appropriate but this should be decided on based on history, case presentation and understanding of the risks.
Name some anti-emetics available in small animal practice
- Maropitant
- Metoclopramide
- Ondansetron
Mode of action of maropitant
- NK1 antagonist
- Helps with centrally mediated nausea (e.g. of metabolic cause/related to CRTZ or vestibular system)
Mode of action of metoclopramide
- D2 receptor antagonist and 5-HT3 receptor antagonist
- Dual effect on CRTZ and lower oesophageal sphincter
- Has a prokinetic effect so if FB is present, could lead to GI rupture❗️
Mode of action of ondansetron
- 5-HT3 receptor antagonist
- Effective against centrally mediated nausea (acts on CRTZ)
What gastroprotectants are available in small animal practice?
- Omeprazole
- Misoprostol
- H2 receptor antagonists e.g. cimetidine
- Sucralfate
Mode of action and uses of omeprazole
- Proton pump inhibitor -> leads to reduced H⁺ secretion
- Useful for gastric ulceration
- (Also reduces CSF production so can be used in syringomyelia)
- Long term use leads to dysbiosis in 3-4 weeks❗️
Mode of action, uses and contraindications of misoprostol
- Prostaglandin analogue -> increased mucosal blood flow and therefore healing (e.g. of ulcers)
- Primarily used in NSAID toxicity
- Do not use in pregnancy❗️
Mode of action and uses of H2 receptor antagonists such as cimetidine
- Reduces acid secretion
- Questionable efficacy - not much research in small animal
Mode of action and uses of sucralfate
- Polyionic surfactant (anion) binds to damaged mucosa (where the positively charged proteins are exposed)
- There is weak evidence for its use in oesophagitis
- Probably not that helpful in gastric ulceration
- Use the liquid rather than tablet form
In a case with chronic vomiting, what might influence your decision to put in a feeding tube? What should you consider?
- BCS loss -> good idea to consider feeding tube
- Try to use this to bypass the problem if you can: NO/NG tube vs O tube vs PEG tube
