peptic ulcer disease Flashcards
1
Q
peptic ulcers
A
- sore that develop in the lining of the stomach/lower oesophagus/small intestine
- ulcers can penetrate the entire wall resulting in leakage of luminal content into abdominal cavity
- more common in men than women
2
Q
peritonitis
A
- when ulcer perforation allows bacteria that live in your stomach to infect the lining of the abdomen (peritoneum)
- infection can spread into blood (sepsis) reaching other areas causing organ failure if untreated
3
Q
peptic ulceration symptoms
A
- epigastric pain (relieved by antacids)
- nocturnal pain (spasms in leg muscles when sleeping)
- vomiting
4
Q
causes of peptic ulcer disease
A
- H. pylori
- NSAIDs/steroids
- pepsin
- smoking/alcohol
- bile acids
- stress
- genetics
5
Q
mucosa
A
- lined with goblet cells that secrete alkaline mucus that forms a layer over luminal surface
- protein content and alkalinity of mucus neutralises
H+ in the epithelium - mucus forms a chemical barrier between acidic contents of lumen and cell surface
6
Q
defence mechanisms from body to combat ulceration
A
- mucus
- bicarbonate
- mucosal blood flow
- prostaglandins
7
Q
duodenal mucosa
A
- forms gel layer which is impermeable to acid and pepsin
- other cells secrete bicarbonate which aids in buffering acid that lies near the mucosa
8
Q
prostaglandins
A
- type E (PGE)
- increases the production of bicarbonate and the mucous layer
9
Q
H. pylori
A
- infects lower part of stomach (antrum) causing inflammation of the gastric mucosa which leads to duodenal/gastric ulcer
- resides within gastric mucosa
- high activity of the enzyme urease which enables it to colonise the stomach
- stimulates increased gastrin release thereby increased acid secretion causing direct damage to mucosa
10
Q
NSAIDs
A
- impair mucosal resistance but do not alter acid secretion
- patients with an ulcer caused by NSAID discontinue the NSAID and be given a H2 antagonist
- if patient cannot stop NSAID then PPI should be given to heal ulcer
11
Q
H. pylori mechanism of action
A
- using its flagella to burrow into mucus lining of stomach to reach epithelial cells where pH is neutral
- it adheres to the cells by producing adhesions that bind to lipids and carbohydrates in the membrane
- uses chemotaxis to avoid areas of low pH and neutralises the acid in its environment by producing large amounts of urease
- urease breaks down the urea present in the stomach to carbon dioxide and ammonia
12
Q
urea breath test
A
patients swallow capsule containing urea made from an isotope of carbon and CO2 exhaled by patients is measured for the isotope and if detected the patient is H. pylori positive
13
Q
stool antigen test (SAT)
A
enzyme immunoassay (EIA) designed to detect H. pylori in faecal specimens by measuring H. pylori antigen released from organisms lining the stomach wall as the antigen is only detected if H. pylori is present
14
Q
fundus
A
- thin walled upper portion of stomach
- secretes mucus, pepsinogen, HCl
15
Q
antrum
A
- lower part of the stomach
- thicker layer of smooth muscle responsible for mixing and grinding stomach contents
- contain endocrine cells that secrete hormone gastrin
16
Q
parietal cells
A
secrete acid and intrinsic factor
17
Q
chief cells
A
secrete pepsinogen
18
Q
gastric glands in antrum
A
- contain enterochromaffin-like cells which release paracrine agent histamine and endocrine cells called D cells which release the peptide somatostatin
- histamine binds to the H2 receptor on the parietal cell resulting in the activation of adenylyl cyclase which increases cAMP and activates protein kinase that stimulates acid secretion from the H+/K+ ATPase
19
Q
acid secretion in the stomach
A
- when parietal cells are activated by ACh/gastrin there is an increase in the intracellular Ca2+ which stimulates acid secretion from the H+/K+ ATPase (proton pump) on the canalicular surface
20
Q
chemistry of acid secretion
A
- carbonic anhydrase produces HCO3- and H+
- HCO3- is exchanged for Cl-
- Cl- diffuses into lumen
- H+ is pumped into lumen by H+/K+ ATPase
21
Q
gastric HCl
A
activates pepsinogen which breaks down peptide bonds in a process called proteolysis
22
Q
canaliculus
A
- found on gastric parietal cells
- a deep folding/channel which increases surface area for secretion
23
Q
H+/K+ ATPase (proton pump)
A
- located within cytoplasmic membrane of resting parietal cells
- translocated to the canalicular membrane and begins to pump cytoplasmic H+ into the canalicular space in exchange for extracellular K+ ions
24
Q
antacids
A
- weak alkalis
- partly neutralise free acids in stomach
- can stimulate mucosal repair mechanisms around ulcers by stimulating prostaglandin release
- used for symptomatic relief of peptic ulcer disease/GORD and non-ulcer dyspepsia
25
Q
antisecretory agents
A
- inhibit gastric acid secretion
- more effective in treating peptic ulcer disease
26
Q
histamine receptor antagonists (H2)
A
- cimetidine, ranitidine, famotidine, nizatidine
- competitive antagonists for histamine at H2 receptor on parietal cells
- reduce acid secretion by parietal cells especially at night/fasting state
- less effective at reducing food-stimulated acid secretion
- treat duodenal ulcers faster than gastric ulcers
27
Q
H2 antagonists mechanism of action
A
- histamine release from enterochromaffin-like (ECL) cells by gastrin or vagal stimulation is blocked by the binding of H2 antagonists to parietal cell H2 receptor
- inhibiting histamine from binding to H2 receptor thus decreasing gastric acid production
28
Q
adverse effects of H2 antagonists
A
- diarrhoea
- headache/dizziness
- confusion in elderly
- erythema-multiforme
- hepatitis (inflammation of liver)
- gynaecomastia (man boobs) with cimetidine
29
Q
H2 antagonist interactions
A
- cimetidine inhibits CYP450
- cimetidine increases blood concentration of erythromycin
- famotidine/ranitidine reduce plasma concentration of atazanavir
30
Q
proton pump inhibitors (PPIs)
A
- omeprazole, lansoprazole, pantoprazole, esomeprazole
- irreversible inhibitors of the H+/K+ ATPase pump
- bind covalently via disulphate bond
- most effective when taken around meal times as they only bind to active pumps
- acid production is inhibited 90% for 24 hrs by a single dose
31
Q
adverse effects of PPIs
A
- epigastric discomfort
- nausea
- vomiting
- diarrhoea
- headache
- skin rashes
- arthralgia/paraesthesia
- gynaecomastia
- gastric atrophy (thinning of inner lining of stomach)
32
Q
PPI interactions
A
- omeprazole has stimulatory/inhibitory effects on CYP450 enzyme system in liver
- omeprazole also inhibits the hepatic metabolism of diazepam/phenytoin/warfarin
- esomeprazole/omeprazole decreases antiplatelet effect of clopidogrel
- pantoprazole may increase anticoagulant effect of warfarin
33
Q
patients with peptic ulcer disease and tested positive for H. pylori triple therapy:
A
- PPI
- amoxicillin
- clarithromycin or metronidazole
patients with penicillin allergy: - PPI
- clarithromycin
- metronidazole
34
Q
misoprostol
A
- synthetic prostaglandin E analogue
- inhibitory effect on acid secretion
- enhances secretion of bicarbonate
- can be used to heal ulcers but used prophylactically to prevent NSAID induced ulceration
- avoid in pregnancy as induces abortion
35
Q
zollinger-ellison syndrome
A
- rare disorder that causes gastric/duodenal ulcers (usually multiple) as well as jejunum
- due to gastrin secreting tumour in the pancreas/duodenum that stimulates acid secretion in stomach
36
Q
gastro-oesophageal reflux disease (GORD)
A
- lower oesophageal sphincter relaxes inappropriately at times other than during swallowing which allows an excessive reflux of gastric contents into oesophagus
- symptoms: retrosternal burning (heartburn)
37
Q
barretts oesophagus
A
- commonly diagnosed in patients with long term GORD
- replacement of normal stratified squamous epithelium lining of the oesophagus by columnar epithelium with goblet cells
- can lead to oesophageal adenocarcinoma (cancer)
