GI Flashcards
Duration of acute, persistent, chronic diarrhoea
<2w
2~4w
>1m
Equation for stool osmolar gap
290 - 2 ⨉ ([Na]s + [K]s)
Compare chronic secretory and osmotic diarrhoea
secretory: persist with fasting, ↓ stool osmolar gap
osmotic: cease with fasting, ↑ stool osmolar gap
Which test is used to differentiate inflammatory diarrhoea from others?
faecal calprotectin
Which test is used to test for exocrine pancreatic insufficiency?
faecal elastase
Indications of positive hydrogen breath test (2)
sugar malabsorption
small intestine bacterial overgrowth
What is coeliac disease?
autoimmune, inflammatory disorder triggered by gluten intake
Gene for cystic fibrosis
CFTR
Origins of ALP (5) (how to differentiate?)
liver, bone, placenta, small intestine, kidney
(isoenzyme electrophoresis)
Which liver enzyme is raised significantly in chronic alcoholism & anti-convulsant intake?
GGT (γ-glutamyl transpeptidase)
How does cirrhosis lead to ↑ globulin?
↓ liver function –> ↓ degradation of gut antigens –> ↑ monomeric / plasma IgA
RR for serum amylase
30~100
Which level of elevated serum amylase is sensitive for acute pancreatitis? Which is diagnostic?
300 (3 ⨉ ULN)
1000
FP for serum amylase
PPU, peritonitis, DKA, macroamylasemia
DDx for persistent elevation of serum amylase
pancreatic pseudocyst, macroamylasemia, (chronic pancreatitis)
Pathophysiology and diagnosis of macroamylasaemia
amylase bound to other macromolecules ==> macroamylase –> ↓ excretion
amylase clearance <1%
Usage of serum lipase
diagnosis of acute pancreatitis, esp. for delayed presentation
(longer half-life, normalise in 2w, compared with 3~5d for serum amylase)
Urea breath test procedure
- oral urea with carbon radioisotope
- urease from H. pylori will produce ammnonia & labelled CO2
- testing for labelled CO2 in patient’s breath
Tests for H. pylori
- Urea breath test
- Rapid urease test / CLO test
- Histology
Screening tests for CRC (2) (what is the regimen in HK? Interval, age indication)
- Guaiac-based faecal occult blood test
- Faecal immunochemical test [HK, Q2Y if -ve, 50~75]
Compare gFOBT and FIT mechanism
gFOBT: detect peroxidase reaction
FIT: detect Hb with anti-human Hb IgG
FP and FN for gFOBT
FP: red meat
FN: vitamin C