GI

Question 1

Duration of acute, persistent, chronic diarrhoea

Answer 1

<2w
2~4w
>1m

Question 2

Equation for stool osmolar gap

Answer 2

290 - 2 ⨉ ([Na]s + [K]s)

Question 3

Compare chronic secretory and osmotic diarrhoea

Answer 3

secretory: persist with fasting, ↓ stool osmolar gap
osmotic: cease with fasting, ↑ stool osmolar gap

Question 4

Which test is used to differentiate inflammatory diarrhoea from others?

Answer 4

faecal calprotectin

Question 5

Which test is used to test for exocrine pancreatic insufficiency?

Answer 5

faecal elastase

Question 6

Indications of positive hydrogen breath test (2)

Answer 6

sugar malabsorption
small intestine bacterial overgrowth

Question 7

What is coeliac disease?

Answer 7

autoimmune, inflammatory disorder triggered by gluten intake

Question 8

Gene for cystic fibrosis

Answer 8

CFTR

Question 9

Origins of ALP (5) (how to differentiate?)

Answer 9

liver, bone, placenta, small intestine, kidney
(isoenzyme electrophoresis)

Question 10

Which liver enzyme is raised significantly in chronic alcoholism & anti-convulsant intake?

Answer 10

GGT (γ-glutamyl transpeptidase)

Question 11

How does cirrhosis lead to ↑ globulin?

Answer 11

↓ liver function –> ↓ degradation of gut antigens –> ↑ monomeric / plasma IgA

Question 12

RR for serum amylase

Answer 12

30~100

Question 13

Which level of elevated serum amylase is sensitive for acute pancreatitis? Which is diagnostic?

Answer 13

300 (3 ⨉ ULN)
1000

Question 14

FP for serum amylase

Answer 14

PPU, peritonitis, DKA, macroamylasemia

Question 15

DDx for persistent elevation of serum amylase

Answer 15

pancreatic pseudocyst, macroamylasemia, (chronic pancreatitis)

Question 16

Pathophysiology and diagnosis of macroamylasaemia

Answer 16

amylase bound to other macromolecules ==> macroamylase –> ↓ excretion

amylase clearance <1%

Question 17

Usage of serum lipase

Answer 17

diagnosis of acute pancreatitis, esp. for delayed presentation

(longer half-life, normalise in 2w, compared with 3~5d for serum amylase)

Question 18

Urea breath test procedure

Answer 18

• oral urea with carbon radioisotope
• urease from H. pylori will produce ammnonia & labelled CO2
• testing for labelled CO2 in patient’s breath

Question 19

Tests for H. pylori

Answer 19

1. Urea breath test
2. Rapid urease test / CLO test
3. Histology

Question 20

Screening tests for CRC (2) (what is the regimen in HK? Interval, age indication)

Answer 20

1. Guaiac-based faecal occult blood test
2. Faecal immunochemical test [HK, Q2Y if -ve, 50~75]

Question 21

Compare gFOBT and FIT mechanism

Answer 21

gFOBT: detect peroxidase reaction
FIT: detect Hb with anti-human Hb IgG

Question 22

FP and FN for gFOBT

Answer 22

FP: red meat
FN: vitamin C