gastrointestinal pathology Flashcards
What is the junction between the oesophagus and the stomach?
Surrounded by diaphragm which acts as valve to prevent reflux
Oesophagus lined with squamous epithelium
Stomach lined with glandular epithelium w layer of mucin
What is Barretts oesophagus?
Columnar lined lower oesophagus (CELLO)
Looks red in endoscopy as opposed to white
Metaplasia- change in differentiation of cell
If acid refluxes, it becomes a low pH environment so the squamous epithelium die (ulceration-heart burn), if persistent, the glandular epithelium replaces and mucin protects
Due to obesity (ab fat increases intra abdominal pressure)
The new epithelium is unstable and predisposes adenocarcinoma (metaplastic—>dysplastic—>neoplastic)
What does the prevalence of oesophageal cancer look like?
More men than women
Risk factors- obesity and reflux cause adenocarcinoma, smoking and drinking spirits causes SCC
V low survival rates- presents late, v close to important structures
What does oesophageal cancer look like?
Tumour- advanced, late presentation
Trouble swallowing
Can also be an ulcer
What is Helicobacter gastritis?
Helicobacter pylori- flagella, live in mucin layer, produces chemicals that attract neutrophil polymorphs- causes acute inflam and ulceration
Tx= proton pump inhibitor + metronidazole/amoxicillin + clrithromycin
What is gastric cancer?
Going down in prevalence
May be due to smoked/pickled food diet, H. pylori, pernicious anaemia
Genetic mutations cause-
Intestinal metaplasia—>dysplasia—>intramucosal carcinoma—>invasive carcinoma
Late presentation
Low survival rates esp older pts
What does gastric cancer look like?
Tumour lump
Shallow section- early
Linitus plastica- thickened wall
What is coeliac disease?
Gluten sensitive enteropathy
Villous atrophy and crypt hyperplasia in duodenum
Large no of lymphocytes in epithelium
Immune response to gliadin protein in gluten from HLADQ2, produces T cells which release toxins that kill epithelial cells
What is inflammatory bowel disease?
Chronic idiopathic- crohns, ulcerative colitis
There are also others that cause bowel inflam
What is Crohn’s disease?
Patchy discontinuous inflammation anywhere from mouth to anus
White aphthous ulcers can be seen in mouth
Can get subsequent fibrosis in bowel (looks like cobble stone)
Can affect all layers (mucosa, submucosa, muscularis propria, fat)
Can also cause granulomas (epitheliod macrophages surrounded by lymphocytes)
What is ulcerative colitis?
Continuous inflam starts at rectum and extends further up
Only affects colon mucosa
Distinct interface between normal/inflamed
What is diverticular disease?
Outpatches of mucosa in sigmoid colon
Due to raised pressure in bowel (lack of fibre), this pushes mucosa to the holes in the wall (weakened areas for blood vessels) to produce outpatches
Can get inflamed/clogged w faeces and rupture- faecal peritonitis (emergency)
What is colorectal cancer?
Mainly older people
Polyps (adenomas) can predispose- dysplastic epithelium-colorectal adenocarcinoma
What is familial adenomatous polyposis?
Genetic- autosomal dominant
Late teens/early 20s- thousands of adenomas
1. apc gene produces GSK forming complex which binds to beta catenin, takes it away and breaks it down
2. Mutation of apc so it can’t bind to beta catenin so high lvls bind to DNA causing epithelial proliferation
What is hereditary nonpolyposis colorectal cancer HNPCC?
Lots of DNA repair protein genes usually
Sometimes none produced due to congenital/mutations
Tumours develop
What is gastroenteritis?
Syndrome characterised by GI symptoms inc. N&V, diarrhoea and abdominal pain
What is diarrhoea?
Abnormal faecal discharge- frequent +/- fluid stool
Associated w increased fluid and electrolyte loss
Often disease of small intestine
What is dysentery?
Abnormal inflam of GI tract- often blood and pus in faeces, pain, fever and abdominal cramps
Often disease of large intestine
What is enterocolitis?
Inflam of mucosa of small and large intestine
How does the GI tract defend against pathogens?
Mouth- liquid flow, saliva, lysozyme, normal flora
Oesophagus- liquid flow, peristalsis
Stomach- acidic pH
Small intestine- gut content flow, peristalsis, mucus/bile, secretory IgA, lymphoid tissue, epithelium replacement, normal flora
Large intestine- normal flora, peristalsis, epithelium replacement, mucus
What is food poisoning?
Staphylococcus aureus
-mainly dairy, cooked meats, prepacked sandwiches
-50% strains produce heat stable enterotoxins + resistant to acid and digestive enzymes
-3-6hrs severe vomiting, self limiting, complete recovery
BOTULISM (infant most common)
Clostridium botulinum
-heat stable toxin- flaccid paralysis and death
Bacillus cereus
-spores and vegetative cells (aka fried rice syndrome), gram +ve
-self limiting
How does Helicobacter pylori work?
Infects antrum of stomach
Produces urease which turns urea into ammonia and CO2
Ammonia has pH 7
Protective cloud during transit to gastric mucin layer
Causes inflammation of mucosa- may lead to duodenal/gastric ulcer
Linked to gastric cancer
What is the tx for diarrhoea?
Fluid and electrolyte replacement
Antibiotic tx may worsen- wipes out competing organisms/stimulates toxin production (C. diff)
What is E. coli?
Gram -ve motile rod, genetically diverse
Major cause of diarrhoeal disease and gastroenteritis
Complications- HUS
Some strains in normal flora
Others infect urinary tract- meningitis
Diarrhoea- food ingest/fecal-oral
How does the lab detect E. coli?
Lactose fermentation on Hektoen enteric agar
MacConkey agar
PCR/antigen tests for serotypes
What are the different strains of E. coli?
EPEC- bundle forming pili, type III secretion injects proteins into host, translocated intimin receptor (Tir), attaches and effaces lesion- watery diarrhoea
ETEC- adhesive pili, heat stable and labile enterotoxins- cholera like diarrhoea
EHEC- actin pedestals, vero-toxin (STx) has receptor on kidney cells- damages directly- bloody diarrhoea
UPEC- cause of Genito-urinary infections
What is haemolytic urinary syndrome HUS?
15% lead to kidney failure
O157:H7 strain most well known
What is Shigella?
Fecal-oral, often water contamination
Shigella dysenteriae
- bloody stool, bacillary dysentery
Shigella sonnei and flexneri
- milder, low infectious dose
- non lactose fermenters
What is salmonella?
Mainly chicken, dairy, person-person
Invade M-cells then spread to surrounding epithelium
Severe, self limiting diarrhoea and enterocolitis
Salmonella enterica (subsp. Typhimurium and enteriditis)
How is salmonella detected?
MacConkey agar
Non lactose fermenter
H2S deposits on Hektoen enteric agar
What is typhoid?
Salmonella typhi
Initiate in intestine
Spreads systemically via macrophages
Seed many organs
2 week increasing fever, GI symptoms
Complications- GI lesions and haemorrhage, toxaemia-endocarditis, meningitis
Gi antigen vaccine
What is Campylobacter spp.?
No 1 cause of food poisoning Uk
Gram -ve micro aerophiles
C. jejuni most common
Food ingestion, major reservoir in chickens
Jejunum ulceration, diarrhoea
Complications- Guillame Barre and reactive arthritis
What is cholera?
Motile gram -ve comma shaped bacterium
OI aero type most important historically
Classical and El Tor (modern)
Vibrio cholerae ingested large nos
Colonise small intestine (depends on motility and production of mucinase attachment to receptors), produces toxins
Increased secretion of chloride ions
Prevents influx of Na ions into cells
Rapid loss of water from tissue (1-2l/hr)
-rice water stool- extreme dehydration- death
What are rotaviruses?
Wheel like viral particle
Diarrhoea- tissue damage in small intestine
V low infectious dose, v contagious
Dehydration main risk
What is norovirus?
Winter vomiting virus
Chills, headache, fever, N&V
V low infectious dose
24-48hr recovery
Common in hospitals
