Gastroenterology: Pathology - Small and large intestine Flashcards
What are the most common causes of bowel obstruction and what % of presentations do they account for? What accounts for the remainder?
Together account for 80%:
- Hernias
- Adhesions
- Intussusception
- Volvulus
10-15% caused by tumours and infarction
Three broad causes of pseudo-obstruction, with an example of each
- Paralytic ileus (e.g. postoperative)
- Vascular (e.g. bowel infarction)
- Myopathies and neuropathies (e.g. Hirschsprung’s)
Which three arteries supply the majority of the GIT?
Coeliac
Superior mesenteric
Inferior mesenteric
What three degrees of infarction are seen in ischaemic bowel disease? Which of these are often caused by acute or chronic hypoperfusion, and which are typically caused by acute vascular obstruction?
- Mucosal: no deeper than muscularis mucosa*
- Mural: mucosa and submucosa*
- Transmural: all three mucosal layers**
- often due to acute or chronic hypoperfusion
** typically due to acute vascular obstruction
Four causes of ischaemic bowel disease related to hypoperfusion
- Cardiac failure
- Shock
- Dehydration
- Vasoconstrictive drugs
Five causes of ischaemic bowel disease related to acute arterial obstruction
- Severe atherosclerosis
- Aortic aneurysm
- Hypercoagulable states
- OCP
- Embolisation of cardiac vegetations or aortic atheromas
Two other miscellaneous causes of ischaemic bowel disease
- Radiation injury
- Obstruction
Describe the pathogenesis of ischaemic bowel disease
Initial hypoxic injury followed by reperfusion injury
Watershed zones at end-arterial supplies are particularly susceptible (e.g. in setting of hypotension, hypoxaemia)
What is Coeliac disease?
Immune-mediated enteropathy triggered by gluten
Three morphological features of Coeliac disease
- Interepithelial lymphocytosis
- Crypt hyperplasia
- Villous atrophy
Three serological markers of Coeliac disease
- IgA antibodies to tissue transglutaminase
- IgA or IgG antibodies to deamidated gliadin
- HLA-DQ2 and -DQ8 association (strong negative predictive value but not specific)
There is increased risk of which two malignancies with Coeliac disease?
- Enteropathy-associated T-cell lymphoma
- Small intestinal adenocarcinoma
Malabsorption may be caused by disturbances in which four functions? Briefly explain each function and give an example of a condition that causes malabsorption by breakdown in its function
- Intraluminal digestion: proteins, carbohydrate, fats are broken down for absorption (e.g. chronic pancreatitis)
- Terminal digestion: hydrolysis of carbohydrates and peptides by brush border enzymes (e.g. disaccharidase deficiency)
- Transepithelial transport: nutrient, fluids and electrolytes transported across intestinal epithelium (e.g. abetalipoproteinaemia)
- Lymphatic transport: of absorbed lipids (e.g. Whipple disease)
What are the four types of diarrhoea? Describe each in brief (including the effect of fasting)
- Secretory: isotonic stool, persists during fasting
- Osmotic: excessive osmotic forces exerted by unabsorbed luminal solutes, diarrhoea fluid >50mOsm more concentrated that plasma, relieved by fasting
- Malabsorptive: due to generalised failures of nutrient absorption, characterised by steatorrhoea and relieved by fasting
- Exudative: due to inflammatory disease, characterised by purulent bloody stools that continue during fasting
