GI Function and Tests Flashcards
What does the stomach do?
physical digestion - mechanical churning to make chyme
chemical digestion - gastric juice (acid and pepsin)
How are peptic ulcers formed?
H. pylori infection
weakens mucous coating of stomach and duodenum
stomach exposed to acid
How is H. pylori able to protect itself from stomach acid?
secretes urease which is alkaline
How do we diagnose peptic ulcers?
urea breath test (measure 13C labelled CO2 in breath - high concentration is positive)
serological tests for Ab to H-pylori
faecal antigen testing
How are peptic ulcers treated?
histamine antagonists
protein pump inhibitors
antibiotics to end infection
What is the Zollinger Ellison Syndrome?
gastrin producing tumours
–> gastric acid production –> ulceration
How is Zollinger Ellison syndrome diagnosed?
high gastrin
What are the 3 parts of the small intestine?
duodenum, jejunum, ileum
What are the common causes of acute pancreatitis?
alcoholism, gall stones
both cause interrupted blood flow to pancreas
How is acute pancreatitis confirmed clinically?
elevated serum amylase (5x ULN)
acute abdominal pain
low amylase =/= no pancreatitis
What are other causes of a high serum amylase?
peptic ulcer rupture, ectopic pregnancy, acute abdominal condition
What is acute pancreatitis?
acute inflammation of pancreas
What is chronic pancreatitis?
impaired secretion of pancreatic enzyme –> malabsorption
chronic inflammation
How do we test for chronic pancreatitis?
low faecal elastase (pancreas specific enzyme)
How do we treat chronic pancreatitis?
give pancreatic enzyme supplements
What is the function of bile salts?
digestion, absorption of lipids and fat-soluble vitamins
What is bile salt malabsorption and its causes?
impaired reabsorption of bile salts - excess delivery into colon
produces toxic bile salts
leads to water diarrhoea
many causes
How do we diagnose BSM using the 75-SeHCAT test?
75-SeHCAT bile acid is administered and retention is measured by gamma camera after 7 days
low retention is abnormal
How do we use serum cholestenone to diagnose BSM?
measure levels in blood
if high indicates BSM as it is a BS synthesis metabolite
What is malabsorption?
failure of the normal digestion and/or absorption of nutrients
What are the consequences of malabsorption?
weight loss, failure to thrive, abdominal distension (nutrients ferment in stomach –> bloating), anaemia, bone disease (vit D, calcium deficiencies), diarrhoea
How do we investigate malabsorption generally?
clinical history simple lab tests - LFTs, - iron/anaemia testing - calcium/mg test - CRP - TFTs (metabolic rate) - coeliac
What are the specific tests of malabsorption?
tissue transglutaminase Ab - coeliac faecal calportectin - IBD faecal elastase - pancreatic insufficiency laxative screen (abuse) urinary 5-HIAA - carcinoid and imaging
What is coeliac disease?
autoimmune disorder with sensitivity to gliadin component of gluten (wheat, barley, rye)
What is the mechanism of coeliac disease?
exposure to gluten cause T-cell mediated response against transglutaminase
causes small intestine cell damage (villous atrophy)
How do we diagnose coeliac disease?
presence of IgA tissue transglutaminase Ab in blood
definitive - endoscopy and intestinal sample examination
What is the treatment for coeliac disease?
no gluten in diet
What are 2 examples of inflammatory bowel disease?
Crohn’s and Ulcerative colitis
What is Crohn’s disease?
chronic inflammation of bowel
What is ulcerative colitis?
ulcers in small intestine
How do we test for inflammatory bowel disease?
calprotectin in faeces due to GI inflammation
distinguishes IBD and IBS
What is the mechanism of VIPoma/Verner Morrison Syndrome?
VIP (vasointestinal polypeptide) increases water/electrolyte secretion, increasing GI tract motility
(WDHA - watery diarrhoea, hypokalaemia, achlorhydria)
What is the cause of Verner Morrison?
pancreatic tumours secreting excess VIP
What is carcinoid syndrome?
tumours in GI tract, %-HT secretion,
lead to excretion of excess water/electrolytes, facial flushing (vasodilation)
How do test for carcinoid syndrome?
measure 5-HIAA in urine
5-HIAA is a serotonin (5-HT metabolite)
Why is more serotonin produced in carcinoid patients?
more tryptophan is metabolised through the 5-hydroxyindole pathway (increased serotonin and 5-HIAA production)
