PATHOLOGY - Vomiting Flashcards
Which four regions input information into the vomiting centre of the brain to trigger the vomiting reflex?
Chemoreceptor trigger zone
Gastrointestinal tract
Cerebral cortex
Vestibular system
What is the chemoreceptor trigger zone?
The chemoreceptor trigger zone detects emetic agents within the blood and relays this information to the vomiting centre to trigger emesis
Give three examples of emetic agents that are detected by the chemoreceptor trigger zone
Uraemic toxins
Ketones
Drugs (e.g. apomorphine, chemotherapy)
How does the gastrointestinal system relay information to the vomiting centre of the brain?
The gastrointestinal system relays information to the vomiting centre via the vagus nerve (CN X)
Give three examples of gastrointestinal changes that are relayed to the vomiting centre of the brain
Chemicals/irritants
Inflammation
Excessive stretch of the gastrointestinal tract
How does the vestibular system relay information to the vomiting centre of the brain?
The vestibular system relays information to the vomiting centre via the vestinbulocochlear nerve (CN VIII)
What is the difference between vomiting and regurgitation?
Regurgitation is the passive evacuation of food and/or fluid from the oesophagus due to oesophageal disease, whereas vomiting is the forceful evacuation of the stomach and/or duodenal contents
How do you differentiate between regurgitation and vomiting?
- Vomiting will usually be preceded by signs of nausea such as lip smacking and drooling
- Vomiting presents with retching/abdominal effort whereas regurgitation does not
- Vomiting may occur minutes to hours after eating whereas regurgitation is more likely to occur not long after eating
- Vomit is partially digested food or liquid and often contains bile, whereas regurgitation is typically undigested food
What are the differential diagnoses for acute vomiting?
Dietary indiscretion
Acute gastritis
Acute enteritis
Gastrointestinal foreign body
Mesenteric torsion
Intussusception (often presended by diarrhoea and hypermotility)
Gastric dilatation volvulus (GDV)
Acute pancreatitis
Acute hepatobiliary disease
Acute renal disease
Peritonitis
Pyrometra
Hypoadrenocorticism
Acute neurological insult
Toxin ingestion
Remember GDV is unproductive vomiting
Remember dietary indiscretion, foreign body (unless perforated) and intusussception usually don’t present as clinical unwell beyond maybe dehydration
How do you approach investigation of acute vomiting?
- Assess history, signalement and clinical signs
- Clinical examination
- Symptomatic management if mild clinical signs
- Symptomatic management and further investigation if severe vomiting and/or signs of systemic disease
Which differential diagnoses for acute vomiting would require surgical intervention?
Gastrointestinal foreign body
Mesenteric torsion
Intussusception
Gastric dilatation volvulus (GDV)
Peritonitis
Which history questions are useful to ask when investigating acute vomiting?
- Has there been any recent dietary changes?
- Is the patient a scavenger?
- How frequently is the patient vomiting?
- Is the vomiting productive or unproductive?
- Is the vomit undigested food, digested food, or partially digested food?
- Is there blood or ‘coffee grounds’ in the vomit?
- Has there been any recent weight loss?
- Are there any concurrent gastrointestinal signs?
- Is the patient on any medication?
- Is the patient systemically unwell?
- Appetite?
What are the two main aims of the clinical examination when investigating acute vomiting?
Determine if there are any clinical signs that can help discriminate the cause of the acute vomiting and determine the clinical status of the patient
What should you assess in detail during the clinical examination when investigating acute vomiting?
Signs of systemic disease
Pyrexia - indicates inflammation
Signs of hepatobiliary disease (jaundice)
Signs of kidney disease
Assess if the abdomen is painful
Palpate for any abdominal masses
Ascites
Assess for dehydration
Assess for hypovolaemia
Which diagnostic tests can be used when investigating acute vomiting?
Haematology
Biochemistry
Urinalysis
Diagnostic imaging
What are the aims of haematology and biochemistry when investigating acute vomiting?
Haematology and biochemistry can be used to identify primary disease as well as gather more information on the patient’s clinical status
Which systemic disease processes can be identified using haematology and biochemistry?
Acute pancreatitis
Acute hepatobiliary disease
Acute kidney disease
Hypoadrenocorticism
What is a distinctive feature of hypoadrenocorticism (Addison’s disease) on biochemistry?
Hyperkalaemia and Hyponatraemia
Which additional test can be done to diagnose acute vomiting secondary to hypoadrenocorticism (Addison’s disease)?
ACTH stimulation test
Which factors should you assess to determine patient status based on haemoatology and biochemistry results?
Is the patient dehydrated?
Are there any electrolyte disturbances
Is there metabolic acidosis
Are there changes that are compatible with sepsis (neutropenia)?
Which imaging techniques can be used to investigate acute vomiting?
Radiography
Ultrasound
Which questions should you consider when assessing a radiograph when investigating acute vomiting?
Is there evidence of a gastric dilatation volvulus (GDV)?
Is there evidence of a gastrointestinal foreign body?
Is there evidence of gastrointestinal obstruction?
Is there evidence of a gastrointestinal perforation?
Is there evidence of peritonitis?
What are the key signs of a gastrointestinal perforation on radiography?
Loss of serosal detail due to free fluid
Gas bubbles in the abdomen
Bunching of the intestines
What are the benefits of using abdominal ultrasound when investigating acute vomiting?
Abdominal ultrasound allows for the assessment of the gastrointestinal tract, liver, pancreas and reproductive tract, as well as allows for ultrasound guided aspiration of free abdominal fluid
What are the aims of symptomatic management of acute vomiting?
- Address fluid and electrolyte imbalances caused by vomiting
- Decrease the frequency/stop the vomiting
- Reduce gastric acid production if there are suspicions of ulceration
- Increase gastric emptying
How do you carry out symptomatic management of acute vomiting?
- Intravenous fluids with appropriate electrolyte supplementation
- Antiemetics
- Gastroprotectants to reduce gastric acid production
- Prokinetic drugs to improve gastric emptying
- Starve for 24 hours and reintroduce a bland, low fat food with small frequent meals if appropriate
List three examples of antiemetic drugs
Maropitant
Metoclopramide
Ondansetron
What is the mechanism of action of maropitant?
Maropitant is a neurokinin 1 receptor antagonist which acts on the chemoreceptor trigger zone and the vomiting centre of the brain to inhibit emesis
(T/F) Maropitant is both an efficacious antiemetic and antinausea drug
FALSE. Maropitant is an efficatious antiemetic however it is not a very effective antinausea drug
What is the mechanism of action of metoclopramide?
Metoclopramide is an dopamine (D2) receptor and 5HT3 serotonin antagonist which acts on the chemoreceptor trigger zone and the gastrointestinal tract to inhibit emesis and have a prokinetic effect
Which method of administration is the most effective for metoclopramide?
Metaclopramide is most effective when administered as a continuous rate infusion (CRI)
What is the mechanism of action of ondansetron?
Ondansotron is a 5HT3 serotonin receptor antagonist which acts of the chemoreceptor trigger zone and the gastrointestinal tract to inhibit emesis
(T/F) Ondansetron is both an efficacious antiemetic and antinausea drug
TRUE.
Can be very useful but has to be used under the cascade
Which antiemetic drugs are liscenced in the UK?
Maropitant
Metaclopramide
Describe the physiology of gastric acid production
Distension of the stomach stimulates the neuroendocrine cells - G-cells and enterochromaffin-like cells - to release gastrin and histamine which act on receptors on the parietal cells to produce and release gastric acid (HCl)
List four classifications of gastroprotectants
Proton pump inhibitors
Histamine (H2) blockers
Sucralfate
Synthetic prostaglandins
Give an example of a proton pump inhibitor
Omeprazole
What is the mechanism of action of omeprazole?
Omeprazole inhibits the proton pumps within the parietal cells which are involved in gastric acid (HCl) production, resulting in decreased gastric acif (HCl) production
(T/F) Omeprazole is very efficacious at reducing gastric acid production
TRUE. Omeprazole is very efficacious at reducing gastric acid production as it directly targets the proton pumps in the parietal cells
What is the mechanism of action of histamine (H2) blockers?
Histamine (H2) inhibitors antagonise the H2 receptors on the parietal cells, inhibiting histamine binding which would usually trigger gastric acid secretion
Why are histamine (H2) blockers not as efficacious as omeprazole at reducing gastric acid?
Gastrin also stimulates the release of gastric acid from the parietal cells, making histamine (H2) blockers less efficacious than omeprazole which directly targets the proton pumps within the parietal cells
Give three examples of histamine (H2) blockers
Cimetidine
Ranitidine
Famotidine
What are the main limitations of cimetidine as a gastroprotectant?
Only available in an oral form in the UK
Not very potent
What is the most potent histamine (H2) blocker?
Famotidine
However not liscenced in the UK so has to be used under the cascade
What is the mechanism of action of sucralfate?
Sucralfate triggers a polymerisation reaction at a low pH, forming a viscous gel which binds to exposed proteins - such as ulcerated tissue
What is the mechanism of action of synthetic prostaglandins?
Synthetic prostaglandins trigger prostaglandins production within the gastrointestinal mucosa. Within the gastrointestinal tract, prostaglandins inhibit gastric secretion and cause vasodilation to increase blood flow to the stomach and increase mucus production to protect the gastric mucosa
When are synthetic prostaglandins particularly useful gastroprotectants?
Synthetic prostaglandins are particularly useful gastroprotectants when managing NSAID overdoses
Give an example of a synthetic prostaglandin
Misoprostol
Which gastroprotectants are licenced in the UK?
Cimetidine
Give two examples of prokinetic drugs
Metoclopramide
Ranitidine
Which prokinetic drug is liscenced in the UK?
Metoclopramide
What are the differential diagnoses for chronic vomiting?
Bilious vomiting syndrome
Chronic gastritis
Chronic gastrointestinal foreign body
Gastrointestinal neoplasia
Gastorintestinal ulceration
Pyloric outflow obstruction/pyloric stenosis
Motility disorder
Chronic idiopathic enteropathies
Extra-intestinal obstruction
Intussusception
Parasitism
Chronic pancreatic disease
Chronic hepatobiliary disease
Chronic kidney disease
Hypoadrenocortocism
Hyperthyroidism
Neurological disease
Chronic drug/toxin exposure
What is bilious vomiting syndrome?
Bilious vomiting syndrome is the vomiting of bile early in the morning
How do you approach investigation of chronic vomiting?
- Assess history, signalement and clinical signs
- Clinical examination
- Symptomatic management if mild clinical signs
- Symptomatic management and further investigation if increased frequency of vomiting, severe vomiting and/or signs of systemic disease
Which history questions are useful to ask when investigating chronic vomiting?
- How long after eating does the vomiting begin?
- Is there blood (haematemesis) in the vomit and/or meleana
- Is there concurrent diarrhoea? (indicates intestinal disease)
- Is the vomiting in the morning and is it always bile?
- Are there any concurrent signs of systemic disease (such as PUPD, jaundice, signs of endocrine disease, lethargic, etc.)
Which diagnostic tests can be used when investigating chronic vomiting?
Haematology
Biochemistry
Urinalysis
Diagnostic imaging
Which imaging techniques can be used to investigate chronic vomiting?
Radiography
Ultrasound
Endoscopy
Which questions should you consider when assessing a radiograph and ultrasound when investigating chronic vomiting?
Is there evidence of a gastrointestinal foreign body?
Is there evidence of a gastrointestinal neoplasia?
Is there evidence of pyloric ouflow obstruction/stenosis?
Is there evidence of chronic pancreatopathy? (has to be done on ultrasound)
What are the benefits of ultrasound when investigating chronic vomiting?
The main benefits of ultrasound when investigating chronic vomiting is the ability to assess the gastrointestinal lumen and wall for signs of neoplasia, obstruction, to assess the pancreas for pancreatopathy, and to determine if endoscopy is required for further diagnosis
Which components of the gastrointestinal tract can be evaluated using endoscopy?
Oesophagus
Stomach
duodenum
When is endoscopy indicated when investigating chronic vomiting?
If primary gastrointestinal disease is suspected (usually done after systemic disease is ruled out with haematology and biochemistry)
Investigate haematemesis
Endoscopic foreign body removal
Endoscopic mucosal biopsy
Why is it so important to investigate haematemesis with endoscopy?
Haematemesis can be indicative of neoplasia and ulceration
What is chronic gastritis?
Chronic gastritis is chronic inflammation of the gastric mucosa
What are the potential causes of chronic gastritis?
Dietary hypersensitivities
Gastrointestinal parasites
Fungal infection
Bacterial infection
Often the cause of chronic gastritis is not identified
Which gastrointestinal parasite can cause chronic gastritis in cats?
Ollunalanus tricuspis
Which fungal infection can cause chronic gastritis?
Pythiosis
Very rare
Which bacterial infection can cause chronic gastritis?
Helicobacter
How do you treat chronic gastritis?
Dietary modifications (e.g. hypoallergenic diets).
Immunosuppressive therapy in severe cases
Antiemetics
Treat the underlying cause
(T/F) Gastric neoplasia is very common
FALSE. Gastric neoplasia is very rare
What is the most common form of gastric neoplasia?
Gastric adenocarcinoma
Which dog breeds are predisposed to gastric adenocarcinoma?
Belgian Shepherds
Collies
Staffordshire Bull Terriers
What are the clinical signs of gastric adenocarcinoma?
Chronic vomiting
Haematemesis
Meleana
Hypersalivation
Weight loss
Anorexia
Lethargy
How do you diagnose gastric neoplasia?
Gastric neoplasia is usually diagnosed based on ultrasound scanning which can show thickening and a loss of layering of the stomach wall, and evidence of gastric ulceration on endoscopy. Endoscopic mucosal biopsies are very important for definitive diagnosis
What is the prognosis for gastric neoplasia?
Very poor prognosis
What are the potential causes of gastrointestinal ulceration?
Gastritis
Gastric neoplasia
NSAID associated ulceration
Addison’s
Renal disease
Liver disease
Portal hypertension
Acute pancreatitis
Mast cell disease
Gastrinoma
Which forms of gastric neoplasia can cause gastric ulceration?
Adenocarcinoma
Lymphoma
Leiomyosarcoma
Leiomyoma
Which endocrine disease can cause gastrointestinal ulceration?
Hypoadrenocorticism (Addison’s disease)
How can mast cell disease can gastrointestinal ulceration?
Mast cell disease causes excess histamine release which will act on H2 receptors on the parietal cells to produce excess gastric acid (HCl) which can cause gastrointestinal ulceration
What is a gastrinoma?
Gastrinomas are neuroendocrine tumours which produce excessive gastrin which will act on parietal cells to produce excessive gastric acid (HCl) which can cause gastrointestinal ulceration
Gastrinomas are very rare
What are key clinical signs of gastrointestinal ulceration?
Haematemesis
Meleana
How do you treat gastrointestinal ulceration?
Antiemetics
Gastroprotectants
Small frequent meals
Treat the underlying cause
Which gastroprotectants are typically used in combination for the treatment of gastrointestinal ulcers?
Omeprazole
Histamine (H2) blockers
Sucralfate
How long should you administer gastroprotectants if the ulceration is caused by NSAIDs or gastritis?
Administer gastroprotectants for 6 - 7 weeks to allow the ulcers to heal
What is delayed gastric emptying?
Delayed gastric emptying is where the food has been in the stomach for more than 8 hours post ingestion
What are some of the potential causes of delayed gastric emptying?
Hypothyroidism
Post anaesthetic complication
Extramural compression of the stomach
Gastrointestinal foreign body (pyloric outflow obstruction)
Pyloric stenosis
What is pyloric stenosis?
Pyloric stenosis the muscular and/or mucosal thickening of the pyloric sphincter which obstructs pyloric outflow
(T/F) Pyloric stenosis can only be congenital
FALSE. Pyloric stenosis can be congenital or acquired
What is the key anatomical difference between congenital and acquired pyloric stenosis?
Congenital pyloric stenosis only involves muscular thickening whereas acquired pyloric stenosis involves muscular and mucosal thickening
What are some of the key clinical signs of pyloric stenosis?
Projectile vomiting large volumes of fluid and food
Vomiting over 8 hours after ingestion
Intermittent regurgitation
Clinical signs are representative of delayed gastric emptying
When do the clinical signs of congenital pyloric stenosis tend to arise?
The clinical signs of congenital pyloric stenosis tend to arise just after weaning where the patient is converted from liquid to solid food
Which dog breeds are predisposed to congenital pyloric stenosis?
Boxers
Boston Terriers
Which signalement is predisposed to acquired pyloric stenosis?
Small breed dogs
How do you diagnose acquired pyloric stenosis?
Assess clinical signs
Radiography
Ultrasound
How does pyloric stenosis appear on radiography?
Dilated stomach filled with fluid/soft tissue opacity (note the displacement of the gastric axis)
How does pyloric stenosis appear on ultrasound?
Dilated, fluid filled stomach
‘Donut’ appearance of the pylorus due to muscular and/or mucosal thickening
How do you treat pyloric stenosis?
Pyloromyotomy
Pyloroplasty
What is a pyloromyotomy?
A pyloromyotomy is where a portion of the muscular pyloric sphincter is cut
What is a pyloroplasty?
A pyloroplasty is a surgical procedure performed to widen the opening at the pylorus
What is the prognosis for pyloric stenosis?
Good prognosis
