Week 4 Flashcards
What are the two units of vomiting neural control?
Central neural regulation of vomiting is controlled by 2
separate units both in the medulla:
1) The Vomiting centre
2) The Chemoreceptor Trigger Zone, CTZ
List the types of drugs which may be used to modify the emetic response and gut motility
- Antihistamines
- Antimuscarinics
- Dopamine antagonists
- 5HT3 antagonists
- Neurokinin 1 receptor antagonists
- Synthetic cannabinoids
- Steroids
- Other neuroleptics
Vestibular labyrinth –> ______ ____ (____ ____) –> cerebellum –> ____ –> vomiting centre —> vomit
Vestibular labyrinth –> Vestibular nuclei (brain stem) —->cerebellum –> CTZ –> vomiting centre —> vomit
Vestibular labyrinth –> ______ ____ (____ ____) –> cerebellum –> ____ –> vomiting centre —> vomit
Vestibular labyrinth –> Vestibular nuclei (brain stem) —->cerebellum –> CTZ –> vomiting centre —> vomit
What is the difference between nausea, retching and vomiting?
Nausea: Feeling of wanting to vomit
- Associated with autonomic effects: salivation / pallor / sweating
- Often prodrome of vomiting
Retching: Strong involuntary effort to vomit, Unproductive
Vomiting: Expulsion of gastric contents through the mouth
Triggers for vomiting/nausea
- Stimulation of the sensory nerve endings in the stomach and duodenum.
- Stimulation of the vagal sensory endings in the pharynx.
- Drugs or endogenous emetic substances.
- Disturbances of the vestibular apparatus.
- Various stimuli of the sensory nerves of the heart and viscera.
- A rise in intracranial pressure.
- Nauseating smells, repulsive sights, emotional factors.
- Endocrine factors
- Migraine
3 types of vomiting and the difference between them?
- Projectile vomiting
Suggestive of gastric outlet or upper GI obstruction - Haematemesis
Vomiting fresh or altered blood (“coffee- grounds”) e.g. oesophageal varices, bleeding gastric ulcer - Early-morning
e. g. pregnancy, alcohol dependence, some metabolic disorders (uraemia)
How do antihistamines act as anti-emetics? Name 3 examples. Side effects?
• H1 histamine receptor antagonists
• Useful in numerous causes of N/V; including
motion sickness + vestibular disorders
• Side-effect profiles vary e.g. drowsiness and antimuscarinic effects
Examples:
- Cinnarizine
- Cyclizine
- Promethazine
How do antimuscarinics act as anti-emetics? Name an example. Side effects?
Muscarinic receptor antagonists
Mechanism: Blockade of muscarinic receptor-mediated impulses from the labyrinth and from visceral afferents
Example: Hyoscine hydrobromide
Side effects: Constipation, transient bradycardia, dry mouth
How do dopamine antagonists act as anti-emetics? Name 3 examples
Mechanism: Act centrally as dopamine antagonists on the CTZ. Active against CTZ-triggered vomiting but not stomach-induced vomiting. Examples: 1. Phenothiazines e.g. chloropromazine 2. Domperidone 3. Metoclopramide
How do 5HT3 antagonists act as anti-emetics? Name 4 examples
Block 5HT3 receptors in GIT and in the CNS. Particularly useful in managing N/V in patients receiving cytotoxic and postoperative N/V
Examples:
- Dolasetron
- Granisetron
- Ondansetron
- Palonosetron
How do neurokinin 1 receptor antagonists act as an anti-emetic? 2 examples?
Adjunct to dexamethasone and a 5HT3 antagonist in preventing N/V associated with chemotherapy
Examples: Aprepitant, fosaprepitant
How do synthetic cannabinoids act as anti-emetics? Name an example
Used for N/V caused by chemo unresponsive to conventional anti-emetics
Side effects: Drowsiness/ dizziness
Example: Nabilone
Use of steroids as anti-emetics? Example?
Used alone, to treat vomiting associated with cancer chemotherapy or in conjunction with other antiemetics
Example: Dexamethasone
Name 2 other neuroleptics used to treat emesis?
Haloperidol
Levomepromazine
Before prescribing laxatives, what 3 steps must be taken?
- Ensure the problem is constipation
- Check the patient’s “norm”
- Try to reverse the cause, including diet.lifestyle changes
What are the 5 types of laxatives?
- Bulk-forming laxatives
- Stimulant laxatives
- Faecal softeners
- Osmotic laxatives
- Peripheral opioid-receptor antagonists
How do laxatives work?
Bulk fibre provides increased volume and promotes peristalsis by distension
Some laxatives soften stool by coating and breaking up particles
Liquid mixes with stool to soften
Name examples of the following types of laxatives:
Bulk (2)
Stimulate (6)
Softener (2)
Osmotic (4)
Peripheral opioid receptor antagonist (1)
Bulk: Ispaghula husk, methylcellulose
Stimulant: bisacodyl, dantron, docusate sodium, glycerol, senna, sodium picosulfate
Softener: arachis oil, liquid paraffin
Osmotic: lactulose, macrogols, magnesium salts, rectal phosphates
Peripheral opioid receptor antagonist: methylnaltrexone bromide
What two properties of diarrhoea lead to loss of electrolytes?
Increase in the motility of the GIT
Decrease in the absorption of fluid
4 approaches to treating ACUTE diarrhoea?
- Maintenance of fluid and electrolyte balance e.g. oral rehydration preparation
- Antimotilty drugs
- Antispasmodics e..g. hyoscine hutylbromide (buscopan), mebeverine
- Antibacterial agent is indicated e.g. systemic bacterial infection, campylobacter enteritis, shigellosis and salmonellosis
What 3 agents are used to treat chronic diarrhoea?
Name at least 2 examples for each
Antimotility agents:
- Codeine
- Co-phenotrope
- Loperamide (Imodium)
- Morphine
Adsorbents:
- *Not for acute diarrhoea**
- Kaolin
- Light
Bulk forming drugs:
- Useful in controlling diarrhoea associated with diverticular disease
- Ispaghula
- Methycellulose
- Sterculia
5 components of bile?
Bile salts Bilirubin Cholesterol Lecithin Plasma electrolytes
Which hormone stimulates gallbladder emptying?
Cholecystokinin (CCK)
Treatment of gallstones?
- Lap Chole
2. Ursodeoxycholic acid to dissolve gallstones
Treatment of biliary colic and acute cholecystitis?
Biliary colic:
- V painful so may require morphine / pethidine (opioids) or diclofenac (NSAID) by suppository
- Parenteral/rectal route chosen as overcomes difficulties in absorption caused by vomiting
If pain continues for 24hrs+ or accompanied by fever = HOSPITAL ADMISSION
Bile acid sequestrates:
Main example?
Mechanism?
Uses?
Main example: Colestyramine (an anion-exchange resin)
Mechanism: Froms an insoluble complex with bile acids in the intestine
Uses:
- Relives pruritus associated with partial biliary obstruction and primary biliary cirrhosis
-Diarrhoea episodes e.g. Crohn’s disease cirrhosis
-Hypercholesterolaemia
What is Cholestyramine and it’s uses?
A bile acid sequestrant.
It works by helping the body remove bile acids, which can lower cholesterol levels in the blood. The medicine is also used to relieve itching that’s caused by a bile duct blockage.
What is the classification for benign and malignant tumours of the oesophagus
Benign:
- Mesenchymal e.g. Leiomyomas (Smooth muscle)
- Squamous papillomas
Malignant:
- Squamous cell carcinoma
- Adenocarcinoma
What is the classification of benign and malignant tumours of the stomach
Benign:
- Polyps: Non-neoplastic, adenomas
- Mesenchymal
Malignant:
- Carcinoma (epithelial cells)
- Lymphoma
- Carcinoid
- Mesenchymal
Sqaumous cell carcinoma: Incidence? Associated factors? Morphology? (Location, structure and patterns) Clinical features? Prognosis
SSC
Incidence:
->50
-More males
Associated factors:
- Diet: Vitamin deficiency, fungal contamination of foods, high content of nitrites/nitrosamines
- Lifestyle: Hot food/drinks, alcohol, tobacco
- Oesophageal disorders: Long standing oesophagitis and achalasia
- Genetic predisposition
Morphology:
- Location: Mainly in middle 1/3 of oesophagus
- Small, gray/white, plaque-like thickenings that become tumours masses
- Three patterns:
1. Protruded polypoid exophytic
2. Flat, diffuse, infiltrative,
3. Exacavated, ulcerated
Clinical features:
- Dysphagia
- Extreme weight loss
- Haemorrhage and sepsis
- Metastases to lymph nodes
- Cancerous TEF
Prognosis: 5% overall five-year survival
Adenocarcinoma: Where does it occur? Incidence? Associations? Morphology? Histology? Clinical features? Prognosis?
In lower 1/3 of oesophagus
Incidence: Age 40
Associations:
- Arise from Barrett Mucosa (intestinal metaplasia caused by gastric reflux)
- Tobacco and obesity
Morphology:
- Flat/ raised patches or nodular masses
- May be infiltrative or deeply ulcerative
Histology:
Mucin producing glandular tumours
Clinical features: • Dysphagia • Progressiveweightloss • Bleeding • Chestpain • Vomiting • Heartburn • Regurgitation
Prognosis: 20% overall five year survival
How is TNM staging of tumours broken down?
Tis carcinoma in situ
T1 invasion of submucosa
T2 invasion of muscularis propria T3 invasion of adventitia
T4 invasion of adjacent structures
N0 no node spread
N1 regional node metastases
M0 no distant spread
M1 distant metastases
What is a polyp?
Module or mass that projects above the level of the surrounding mucosa, usually at the Antrum
What is the most common malignant tumour of the stomach?
Gastric carcinoma
What are the environmental, host and genetic factors of gastric carcinomas?
Environmental:
- Infection ny H pylori
- Diet
- Low socioeconomic status
- Cigarette smoking
Host:
- Chronic gastritis
- Gastric adenomas
- Barrett oesophagus
Genetic:
- Increased risk with blood group A
- Family history
- Hereditary non-polyposis
- Familial gastric carcinoma syndrome
Gastric carcinoma: Location? Classification? Macroscopic growth factors? Morphology? Clinical features? Prognosis?
Location:
-Pylorus and Antrum **
Classification on the basis of:
- Depth of invasion
- Macroscopic growth pattern
- Histological subtype
Macroscopic growth patterns:
- Exophytic
- Flat or depressed –> Linitis plastica
- Excavated
Morphology:
- All carcinomas eventually spread to regional and more distant lymph nodes.
- ->Supraclavicular node
- ->Local invasion to duodenum, pancreas and retroperitoneum
- Metastases to the liver and lungs are common
- Metastases to the liver and lungs
- Metastases to the ovaries called Krukenberg tumour
Clinical features: • Asymptomatic until late • Weight loss • Abdominal pain • Anorexia • Vomiting • Altered bowel habits • Dysphagia • Anaemic symptoms • Haemorrhage
Prognosis: 90-95% for early gastric cancer. Less than 15% for advanced
What is the histopathology of intestinal, diffuse and mixed type gastric adenocarcinomas?
[LAUREN CLASSIFICATION]
Intestinal type:
- Composed of neoplastic intestinal glands resembling those of colonic adenocarcinoma
- Cells often contain apical mucin vacuoles
Diffuse type:
- Composed of gastric-type mucous cells which permeate the mucosa and wall as scattered individual cells or small clusters in a n “infiltrative” growth pattern
- Mucin formation expands the malignant cells and pushes the nucleus to the periphery, creating a “signet ring”
Mixed type
Gastric lymphoma: What are they? Associations? Prognosis? Morphology?
What are they?
B cell lymphomas of mucosa-associated lymphoid tissue (MALT lymphomas)
Associations: Chronic gastritis and H. pylori infection
Prognosis: 50% five year survival
Morphology:
- Occurs in mucosa and superficial submucosa
- Lymphocytic infiltrate of the lamina propria surrounds gastric glands massively infiltrated with atypical lymphocytes and undergoing destruction
Functions of the liver?
METABOLIC: Breakdown down carbohydrates, hormones, lipids, drugs and proteins
STORAGE: Glycogen, vitamins, iron
PROTECTIVE: Detoxification and elimination of toxin compounds, kupffer cells ingest bacteria and other foreign material from blood
BILE: Produced and excreted. Formed in biliary canaliculi, emulsifies fats and provides route for waste removal
What two vessels supply the liver and what do they supply it with?
Hepatic artery= Oxygenated blood
Portal vein - Nutrient rick blood
What is the functional unit of the liver and where is it composed of?
Liver lobule:
- Hexagonal in shape
- Hepatocytes arranged in plates
- In contact with bloodstream one one side and bile canaliculi on the other
- Between the plates are vascular spaces (sinusoids) containing Kupffer cells (phagocytic macrophages)
Classifications of liver disease
VAN MIT
Infection- Viral, bacterial, parasitic
Toxic/drug induced
Autoimmune
Biliary tract obstruction- Tumours, gallstones
Vascular
Metabolic : Haemochromatosis, Wilson’s, hereditary hyperbilirubinaemias
Neoplastic
What is cholestasis?
Classifications?
What does it lead to?
Failure to produce or excrete bile
- Intrahepatic = Problems in secretion of bile by hepatocytes due to damage
- Extrahepatic = Problems with flow of bile out of the liver due to obstruction
Result:
- Accumulation of bilirubin in the blood leading to JAUNDICE.
- Urine darkens
- Stool becomes lighter
Other cause for jaundice apart from cholestasis?
Excessive haemolysis, so bilirubin is uncongutated and does not appear in urine
Difference between acute and chronic hepatic failure?
Acute: Development of severe hepatic dysfunction within 24wks of onset of disease
Chronic: Progressive decline in liver function with established disease
What are 3 causes of acute hepatitis?
Poisoning e.g. from paracetamol
Infection (Hepatitis A-C)
Inadequate perfusion
3 potential outcomes for acute hepatitis?
Resolution
Progression to acute hepatic failure
Progression to chronic hepatic damage
3 common and uncommon causes for chronic liver disease?
Common:
- Alcoholic fatty liver
- Chronic active hepatitis
- Primary biliary cirrhosis
Unusual causes:
- Alpha-1 AT deficiency
- Wilson’s disease
- Haemochromatosis
6 consequences of chronic liver disease
- Cirrhosis
- Portal hypertension
- Ascites
- Renal failure
- Easy bruising due to lack of production of clotting factors
- Oedema as osmotic pressure is reduced
What is cirrhosis?
Irreversibile shrinkage of the liver and fibrosis
What is portal hypertension?
Consequences?
Increased blood pressure in the portal vein leading to:
- Haemorrhage of oesophageal / gastric varices
- Hepatic encephalopathy (detoxifying function bypassed)
- Hypersplenism
- Decreased resistance to infections
What is ascites as a consequence of chronic liver disease?
Accumulation of fluid in the peritoneal cavity
What are the features of liver failure?
Inadequate synthesis of albumin
Inadequate synthesis of clotting factors
Inability to eliminate bilirubin
Inability to eliminate nitrogenous waste
What is hepatic encephalopathy?
Name an example
Poorly defined neuro-psychiatric disorder that occurs when products normally metabolised by the liver accumulate in the systemic circulation.
Ammonia: Decreased liver capacity to synthesize urea and glutamine means the ammonia is no longer adequately metabolised and accumulates in the systemic circulation
What 4 Liver Function Tests are done to test if liver disease is present?
- Aminotransferases: ALT and AST for liver cell damage
- Bilirubin- For cholestasis (suggesting bile flow blockage)
- ALP and gamma-GT for biliary epithelial damage and obstruction
- Albumin for synthetic function
What is albumin?
What’s is its relevance in liver function tests?
Albumin is a main plasma protein
Used as an assessment of liver synthetic function but low albumin also found in the following:
- Post surgical/ITU patients due to redistribution
- Significant malnutrition
- Nephrotic syndrome
What is bilirubin?
Breakdown product of haemoglobin
What happens to unconjugated bilirubin?
Taken up by the liver and then conjugated. This can then be excreted in bile.
It is then attacked by bacteria in the colon and excreted in faeces.
Small amounts are reabsorbed and excreted in urine as urobilinogen
Name 4 of the liver enzymes that are used in Liver Function Tests?
AST and ALT
Bilirubin
ALP
gamma-GT
NOT EXCLUSIVELY FOUND IN LIVER TISSUE
What do AST and ALP levels suggest in Liver Function Tests?
These are non-specific markers of acute damage to hepatocytes
What does ALP levels suggest in Liver Function Tests?
Increase in liver disease due to increased synthesis in response to cholestasis
What does gamma-GT levels suggest in Liver Function Tests?
Raised in colestasis, also affected by ingestion of alcohol and drugs such as phenytoin
4 limits of biochemical tests?
- Lack of complete organ specificity
- Lack of disease specificity
- May be over sensitive
- “I have this abnormal result, what do I do with it?”
Bilirubin abnormal in asymptomatic patient, why?
Haemolysis
Gilbert’s syndrome
ALP abnormal in asymptomatic patient, why?
Physiological change e.g. pregnancy, adolescence
AST abnormal in asymptomatic patient, why?
Skeletal muscle disorders
MI
gamma-GT abnormal in asymptomatic patient, why?
Alcohol
Drugs
Pro’s and con’s of LFTs?
Pros:
- Cheap
- Widely available
- interpretable
- Direct subsequent investigation
Cons:
- Outdated by new diseases
- Little prognostic value in liver transplantation
- Little value for evaluating therapeutic success
- Do not assess liver function
What is the relation of the ribs to the spleen?
The spleen lies with ribs 9-11 to the left and posteriorly
How thick is the spleen? How long is it? How wide is it? Which ribs? How much does it weigh?
HINT: 1,3,5,7,9,11
1,3,5,7,9,11 The spleen is: 1 inch thick; 3 inches wide; 5 inches long; weighs 7oz (200g); lies between the 9th and11th ribs
Functions of the spleen?
- Mechanical filtration of red blood cells
- Active immune response through humeral and cell mediated pathways
- Haematopoesis until 5th month of gestation
What organs lie on/into the spleen?
Stomach in the gastric area
Left kidney in the renal area
Splenic flexure in the colic area
The spleen is surrounded by peritoneum that was derived from the dorsal mesentery of the ______
The spleen is surrounded by peritoneum that was derived from the dorsal mesentery of the stomach