Week 8 GI and malabsorption Flashcards
H. Pylori and damaging lining
- Has urease enzyme, converts urea+water to ammonia + CO2.
- Ammonia neutralizes the acid environment.
- Gastric acid production is stimulated which can further damage lining.
characteristics of gastrinoma
elevated gastrin
gastrin producing tumours - normally stomach or pancreas.
stimulates excessive stomach acid.
characteristics of acute pancreatitis (exocrine disease)
- elevated levels of serum amylase.
- Raised inflammatory markers (CRP)
- Hypocalcaemia: release of lipase, which leads to saponification of calcium.
- acute abdominal pain
- associated with alcoholism and gall stones.
characteristics of chronic pancreatitis
deficient pancreatic activity.
- low enzyme level, malabsorption
- low levels of faecal elastase- pancreas specific enzyme
4 main absorption
- carbohydrate absorption
- fat absorption
- protein absorption
- bile acid absorption
carbohydrate absorption
- non-invasive test: testing the absorption of xylose a monosaccharide, and also disaccharides.
- small bowel biopsy: test to see the enzyme activity.
amino acid malabsorption
affect both intestinal and renal-epithelial transport.
hartnup disease: neutral amino acids (transport impaired)
cystinuria (di amino acid transport impaired)
bile salt absorption and function
BS is essential in the absorption of lipids and fat-soluble vitamins
bile salt malabsorption
bile salt is normally absorbed and stored in the gall bladder.
If malabsorption of BS, it will be passed onto the colon.
The accumulation of BS in the colon will convert it to toxic secondary BS.
toxic 2dary BS will lead stimulate the secretion of water and electrolytes.
secretory diarrhea.
hartnup disease
neutral amino acid
13C triglyceride breath test is for?
normal fat absorption will have high CO2 release.
fat malabsorption will have low CO2 release.
75Se-HCAT test
A low retention can indicate BS malabsorption.
- 75Se labelled bile acid given orally.
- If 75Se retention is low, BS malabsorption.
Serum cholestenone significance
Increases in bile acid malabsorption:
- cholestenone is an intermediate in BS synthesis pathway.
- cholestonone is increased in increased bile acid turnover due to excessive loss.
Coeliac disease
autoimmune disorder: triggered by gluten
antibodies against transglutaminase (tTGA).
LEADS TO small intestine cell damage.
villous atrophy and malabsorption
what is tissue transglutaminase’s abbreviation
tTGA
what are the 2 antibodies against tTGA?
IgA: high sensitivity and specificity
IgA deficiency:
test IgG
gold standard to diagnose coeliac disease
small bowel biopsy
Inflammatory Bowel Disease (IBD) is…
Group of chronic inflammatory diseases of large and small intestines.
2 main diseases of IBD are
Ulcerative Collitis
Crohn’s Disease
Inflammatory Bowel Disease symptoms
- Bloody stool
- Diarrhoea
- Frequent bowel movements
- weight loss
feature of ulcerative collitis
occur in large intestine and colon
feature of Crohn’s disease
patchy areas of inflammation
What is calprotectin used for?
Biomarker
inflammatory bowel disease will lead to release of calprotectin from neutrophils:
distinguishes IBD from non-inflammatory bowel disorders
(irritable bowel syndrome - IBS)
negative result of calprotectin
not likely to be IBD, reduce the need of endoscopy
elevated faecal osmotic gap appears in … diarrhoea
osmotic diarrhea:draws water into GI that leads to diarrhea.
- malabsored nutrients
- osmotic laxatives:
what is a VIPoma
- a pancreatic tumour that secretes excessive VIP
- 60-80% are malignant
effect of VIP (vasoactive intestinal polypeptide)
- secretion of water in bile and pancreatic juice.
- secretion of water and electrolytes in GI.
- inhibit intestinal absorption
which organ is VIPoma associated with
pancreas
where are carcinoid tumours located?
all GI tracts
what do carcinoid tumours secrete
serotonin
biomarker of carcinoid tumour/syndrome
metabolite of serotonin: 5-HIAA
Pathway of serotonin metabolism
tryptophan – serotonin – 5-HIAA
carcinoid tumour (biomarker changes): tryptophan, serotonin, 5-HIAA
- excessive tryptophan is used as a substrate
- there will be excessive serotonin and 5-HIAA, the metabolite of serotonin.
what is significant in diagnosis of malignancy (example with VIP)
stability of gut hormone, VIP is highly unstable
carcinoid tumour - symptoms
- diarrhea
- skin flushing, this is due to the secretion of vasoactive hormones and sertonin from the tumour
severe diarrhea will lead to … (biochemistry)
low potassium and chloride
secretory vs osmotic diarrhea
faecal osmotic gap:
- secretory diarrhea has electrolyte and water secreted into GI, thus normal osmotic gap.
- Osmotic diarrhea only has water drawn into the GI tract, thus higher osmotic gap in the faeces.
faecal osmotic gap
290 - faecal electrolyte (Sodium and Potassium) levels
