GI Diseases Clinical Flashcards
Explain why upper GI conditions occur?
Due to acid:
-wrong location eg through oesophagus reflux/ overflow into duodenum
-overproduction
-faults with protective mechanisms- Lower Oesophageal Sphincter (LOS) and pyloric sphincter- if not working acid can pass through, protective lining (gastric cytoprotection is faulty)
What is dyspepsia?
A broad term for a range of symptoms in upper GI tract:
upper abdominal pain, gastric reflux, heart burn, nausea and vomiting, wind
What is the epidemiology of upper GI conditions?
Prevalence varies from 20-40%
Quarter of which will have peptic ulcer disease
90% of patients self medicate, this can make potentially serious problems
What is the epidemiology of gastric cancer?
UK incidence-10/10000
4400 deaths from stomach cancer
17th most common cancer cause death
54% are preventable
Describe the aetiology of gastric cancer:
More common in smokers and drinkers (decrease in protective mechanisms)
Salt intake
Related to H Pylori infection
Less common in vegetarians
More common in 45 years + and x2 prevalence in men
Name common upper GI conditions:
Gastro-oesophageal reflux disease (GORD) 10-20%
Duodenal stomach ulcer disease (PUD) 10-25%
Gastritis 30%
Functional dyspepsia 30%
Oesophageal and gastric cancer 2%
What is the function of HCl and parietal cells?
Parietal cells secrete HCl and intrinsic factor- secreted from fundus
They activate pepsinogen and kills bacteria
Intrinsic factor aids absorption of vitamin B12
Name the 4 phases of controlling acid secretion via parietal cells:
Cephalic phase
Gastric phase
Intestinal phase
Basal state
What occurs in the cephalic phase?
Nervous control, parasympathetic
Thought, smell, taste or sight of food
What occurs in the gastric phase?
Local control, parasympathetic
Distention of stomach and chemical makeup
What occurs in the intestinal phase?
Hormonal control
Food in the duodenum (chyme) causes secretion of somatostatin which inhibits acid production (-ve feedback, enterogastric reflex)
What occurs in the basal state?
Occurs in time between meals, level of acid secretion during these times are regulated by body weight, nº parietal cells and time of day
What is gastrin and how is it produced?
Produced in response to vagal stimuli, a rise in pH (decrease in acidic conditions) and ingested protein and calcium
Stimulates growth of gastric mucosa- protective function
Describe how Ach has an affect on H2:
Vagal stimulation causes Ach to have a direct effect on parietal cell (minor)
Major effect is Ach release onto enterochromaffin like cells
Gastrin has same effect
Describe how somatostatin has an affect on acid production:
PGE2 receptor on parietal cells, somatostatin binds here as its a PG, it stops acid production, negative feedback due to contents of duodenum
Describe what gastric cytoprotection is:
Auto digestion of the stomach is prevented by a thin layer (500microns) above the mucosa surface (neutral)
Complex matrix of bicarbonate and mucus- unstirred layer
How can a stress ulcer be formed in shocked/ critically ill patients?
H+ is normally taken away by submucosal blood flow
In shocked pts, there is a decrease in blood flow, so necrosis in mucosa by increase in H+ conc and decrease in O2
How does somatostatin offer gastric cytoprotection?
Increase mucus secretion
Increase bicarbonate
Increase blood flow
Decrease in acid
How does the Lower Oesophageal Spincter (LOS) have a role in oesophageal protection?
Permanent state of contraction, relaxes to allow food
Reflux can be caused this way
What is gastritis?
Inflammation of the gastric mucosa
What is the pathophysiology of gastritis?
It is a precursor for ulceration
80% of cases due to H pylori-> chronic gastritis-> PUD-> gastric cancer
What are the symptoms of gastritis?
For many they can be asymptomatic
Symptoms include indigestion, sickness, burning
What other health issues can gastritis cause?
40x increased risk of PUD
6x increased risk of gastric cancer
How does Helicopactor Pylori survive in the stomach?
Adapted to survive in acidic conditions
They protect themselves by hydrolysing urea to produce ammonia, which causes a buffer H+ions
Have flagella to burrow into mucosa in the antrum