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302 review > GI > Flashcards

GI Flashcards

1
Q

what disease causes gene defect of UDP enzyme deficiency

A

crigler najjar - severe form from birth
gilbert syndrome - mild hyperbilirubinaemia

UGT1AT gene defect, causes UDP deficiency
so less bilirubin metabolism causing high UNconjugated bilirubin

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2
Q

what gene defect causes Dublin-johnson syndrome

A

MRP2 gene defect

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3
Q

what does INR measure

A

extrinsic coagulation
3+7 -> 10 -> 2 (thrombin) -> 1 (fibrin)

bilirubin/INR measure prognosis

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4
Q

what are time scales for acute, subacute, chronic liver diseases

A

acute <6wk, subacute 6-25wk, chronic 25+wk

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5
Q

what are the stages of progressive liver disease

A

normal -> steatohepatitis -> fibrosis ->
(IRREVERSIBLE) cirrhosis -> hepatocellular carcinoma

fibrosis is reversible, cirrhosis is not
cirrhosis is when liver architecture replaced by fibrotic nodules

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6
Q

how does cirrhosis appear on liver US

A

heterogenous irregular liver
splenomegaly, ascites

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7
Q

how is hepatic fibrosis assessed invasively + non

A

non:
ALT/AST levels
fibroscan for liver stiffness
FIB-4 scan
ELF test

invasive: biopsy (gold standard)

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8
Q

what are features of decompensated liver disease

A

jaundice
ascites
vatical bleed/haemorrhage
hepatic encephalopathy
coagulopathy INR >2

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9
Q

what is acute liver failure

A

jaundice -> encephalopathy within 4wk
no pre-existing liver disease

if pre-existing disease, acute on chronic liver failure instead

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10
Q

what is Budd chiari syndrome

A

portal vein thrombosis = main vessel to liver
triad - ascites, abdo pain, hepatomegaly

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11
Q

what is screened for in:
hepatitis serology
autoimmune hepatitis
ASH/NASH
PBC
alpha-1 antitrypsin deficiency
wilson disease
hereditary haemochromoatosis

A

hepatitis: hepA IgM, hepB sAg, hepC Ab, hepE IgM

autoimmune: ANA, anti-smooth muscle, LKM antibodies

ASH/NASH depends on ALT/AST ratio, if ALT high = fatty, if AST high = alcohol

PBC: anti-M2 (mitochondrial)

alpha-1: serum alpha-1 AT, phenotype

wilson: low serum Cu, low serum caeruloplasmin

HH: high serum ferritin

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12
Q

what is autoimmune hepatitis (what is it associated with) and how is it treated

A

usually affects women
associated with HLA DRB1/3

ANA, anti-smooth muscle, LMK Ab

treat with immunosuppression

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13
Q

what is PBC and how is it treated

A

usually affects women 40-50yr
causes granulomatous hepatitis affecting interlobular bile ducts

anti-M2
causes jaundice, pruritus/itch

treat with ursodeoxycholic acid (2nd line obtecholic acid)

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14
Q

what is PSC and how is it treated

A

associated with UC
triggered by bacteria and PAMP entering portal circulation via inflamed intestine
affects intra + extra hepatic bile ducts

biopsy shows concentric fibrosis of intra+extra-hepatic ducts

no effective treatment
increased risk of cholangiocarcinoma

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15
Q

what are congenital cholestatic syndromes

A

PFIC/PBIC

PFIC1 - ATP8 18q gene = reduced cholesterol secretion into bile

PFC2 - ATP11 2q gene = reduced bile acid secretion into bile, so hepatic BA accumulation and slowed hepatic BA flow

PFC3 - ACB4 7 q gene = less PL secretion, so bile more toxic

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16
Q

how do acute + chronic hepatitis differ

A

acute 1-3months = more florid
chronic 6month+ = abnormal LFT, positive serology

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17
Q

how many stages of hepatic fibrosis

A

6
s1-s3 = fibrosis of more portal areas
s4 = fibrosis bridging portal areas
s5 = probable cirrhosis
s6 = confirmed cirrhosis

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18
Q

summarise the different hepatitis viruses

A

A = acute infection, RNA picornavirus transmitted via faecal/oral route
investigate by checking HepA IgM

B (VACCINE) = acute->chronic, DNA virus transmitted via blood
most common cause globally
investigate with serology
if HepB sAg +ve, then treat (1st line: peginterferon a2, 2nd live: tenofovir/ectovir)

C = chronic, RNA virus transmitted via blood (body fluids - needles, sex OR vertical transmission)
usually IVDU
if HCV RNA +ve, then treat (sofosbuvir)

D = chronic, RNA virus that only infects if HepB also present, so spread via blood
treat with pegylated interferon-a (low success rate)

E = acute, ssRNA spread via faecal-oral route
if pregnant, risk of fulminant hepatitis

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19
Q

how does HBV replicate

A

DNA virus
via reverse transcription of RNA intermediate

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20
Q

how does immune system down regulate HBV viral replication and protein synthesis

A

TLR3 recognises HBV’s PAMP with RIG-I signalling
IFN NF-kB activates interferon stimulating genes
these form IFN a/B that reduce viral replication + protein synthesis

also promote adaptive immunity via MHC-class1 expression on APC
causing cell death via perforins

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21
Q

what antibody provides lifelong immunity against HBV

A

HepB sAb - neutralising Ab against HBsAg that prevents uptake by uninfected hepatocytes

early priming of CD4+ and CD8+ intrehepatically

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22
Q

how does HBV persist to cause chronic infection

A

HBX protein protects cccDNA, preventing antigen presentation/processing
T-reg express more FoxP3, suppressing CD4/CD8
CD28 upregulated causes apoptosis of HBV specific T cell
IFN-a/y inhibited

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23
Q

what does HBV DNA correlate to

A

risk of fibrosis + HCC

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24
Q

why does HDV rely on HBV

A

HDV is an incomplete RNA virus, enclosed in shell of HBsAg

HDV is a satellite virus, so can not make its own viral proteins or replicate independently

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25
how is chronic HBV + HCV treated
HBV - pegylated interferon-a2, tenofovir, ectovir (if HBsAg +ve) HBV vaccine available HCV - sofosbuvir (if HCV RNA +ve) no vaccine for HepC
26
how does HCV cause chronic infection
RNA virus with rapid replication rate, so high viral load many mutants (quasi-species that escape immune system) form as high error rate of RNA-polymerase HCV non-structural viral proteins disrupt RIG-I signalling, inhibiting innate immunity neutralising Ab develop too slowly and don't last long
27
why does HCV re-infection occur
neutralising AB develop too slowly and don't last long enough
28
where does HCV replication occur
in cytoplasm only
29
what are the symptoms of inflammatory diarrhoea
constant diarrhoea worse when eating
30
how does inflammation cause diarrhoea
inflammation -> ulcer -> necrosis disrupts mucosal immunity so mucous, serum and blood are lost into stool
31
what are effects of thickened mucosa from inflammation, on absorption
SB - malabsorption of nutrients LB - poor water reabsorption
32
what causes inflammatory diarrhoea
bacteria - campylobacter, shigella, salmonella, c.doff, e.coli parasite - giardiasis ischaemia - vasculitis
33
how do Crohn + UC differ
crohn - anywhere in GIT (mouth to anus - perianal disease) skip lesions with transmural inflammation crypt hyperplasia goblet cell hyperplasia granulomas, lymphoid hyperplasia strictures, fistulas UC - only LI, starts distally in rectum then spreads proximally continuous mucosa/submucosa inflammation crypt abscess/distortion goblet cell depletion
34
on colonoscopy, how do UC + crohn look
UC - pseudopolyp crohn - cobblestone appearance
35
what is impact of smoking on IBD
worsens crohn protective for UC
36
what is osmotic diarrhoea
osmotic solutes (lactose, bile salts) not absorbed into lumen so salt/water reabsorption inhibited MOA for osmotic laxatives - macragol, lactulose, Mg
37
how to stop osmotic diarrhoea
not eat
38
what disease causes osmotic diarrhoea
coeliac disease malabsorption of bile salts prevents salt/water reabsorption
39
what is coeliac disease
intolerance to dietary gluten associated with HLA-DQ2/8 damages SI - mainly proximal in jejunum, then extends distally to ileum
40
how is coeliac disease diagnosed + what is seen on biopsy
initial investigation - TTG IgA Ab, anti-endomysial, anti-gliadin definitive - endoscopy + jejunal biopsy shows: crypt hyperplasia, villous atrophy, intra-epithelial lymphocytes, lamina propria inflammation
41
what is secretory diarrhoea
increased gut secretions - toxin, hormone, stimulant laxative, rectal cancer
42
does fasting help with secretory diarrhoea
NO
43
when is an erect CXR + AXR done
erect CXR = free gas, airspace disease (lower lobe pneumonia) AXR = obstruction, perforation, IBD, calcification
44
how do SBO + LBO differ on AXR
SBO = centrally dilated loops >3cm, valvulae conniventes - extend full width LBO = peripherally dilated loops >6cm, haustra (+associated SBO)
45
what is triad for gallstone ileus
rigler triad - SBO, pneumobilia (air in bile duct), ectopic gallstone
46
what is sigmoid volvulus
coffee bean sign summation line - large bowel gas upstream
47
what is toxic megacolon
medical emergency - complication of UC dilated transverse colon mural oedema, creating thumb-printing
48
what contrast studies are done for UGI LGI small bowel
UGI - OGD LGI - colonoscopy, CT colonography, flexi-sigmoidoscopy if volvulus small bowel - MR enterography
49
why is a barium swallow done
post-OGD test for functional disease - benign (achalasia) or malignant
50
what are the different types of colorectal cancer
colon cancer = laparoscopic surgery, if node -ve then chemotherapy as well rectal cancer = MRI staging, neo-adjuvant chemo/RT, anterior resection oligo-metastatic disease = MRI/PET, metastatectomy widespread metastatic disease = palliative chemo + support
51
what is histology of colorectal cancer
adenocarcinoma
52
what is progression of colorectal cancer
progression from normal mucosa -> polyps -> cancer normal mucosa APC gene forms initial adenoma k-RAS gene forms intermediate adenoma DCC gene causes loss of long-arm of chr18 causes late adenoma TP53 gene causes loss of short-arm of chr17 causes cancer
53
what genes are involved in colorectal cancer
APC gene forms initial adenoma (from normal mucosa) k-RAS gene forms intermediate adenoma DCC gene causes loss of long-arm of chr18 causes late adenoma TP53 gene causes loss of short-arm of chr17 causes cancer
54
what are 6 hallmarks of cancer
1 - sustain proliferative signalling 2 - evade growth suppressors 3 - activate invasion + metastasis 4 - enable replicative immortality 5 - induce angiogenesis 6 - resist apoptosis
55
what are emerging hallmarks + enabling characteristics of cancer
emerging hallmark: dysregulate cellular energetics, avoid immune destruction enabling characteristic: tumour-promoting inflammation, genetic instability/mutation
56
what causes point mutations
accidental silencing (epigenetic loss) of mismatch repair genes causing point mutations
57
which 2 hereditary syndromes linked to colorectal cancer
all with AD inheritance FAP - inherited loss of APC so multiple polyps form during teens, driving further mutation to cause cancer virtually guaranteed colorectal Ca in 20s so need prophylactic pan-proctocolectomy Lynch/HNPCC - inherited mutation of MLH1/MSH2 in mismatch repair genes, causes multiple point mutations increasing risk of cancer colorectal, endometrial, small bowel, pancreatic (also juvenile polyposis, peutz-jegher syndrome - STK11 mutation)
58
what cancers affected in Lynch/HNPCC
colorectal, endometrial, small bowel, pancreatic
59
what are management options for FAP/Lynch
direct referral for genetic testing (1st degree relative 2-4x risk) FAP - consider prophylactic pan-colectomy at 40yr HNPCC - regular screening colonoscopy, preventative treatment with 600mg aspirin daily
60
where does colorectal cancer metastasise
liver - via portal circulation lung - via venous circulation resection/ablation of lung/liver may be curative
61
what cellular dysfunction occurs in colorectal cancer
activating mutations in k-RAS esp in polyp -> cancer progression + left-sided or rectal cancers if right-sided MMR tumour, usually BRAF mutation
62
how is colorectal cancer classified
with Duke + TNM staging from Duke C or TNM stage 3, adjuvant chemo needed as lymph node involvement Duke A - not beyond muscularis B - beyond msucularis C - regional lymph nodes involved D - distant metastasis
63
what is colorectal cancer screening
FIT every 2yr for anyone aged 60-74yr if +ve referred for colonoscopy if histology +ve, CT TAP to stage if rectal cancer = MRI/endorectal US to identify local invading disease
64
what is urgent 2WW for colorectal cancer
>40yr with weight loss + abdo pain >50yr with unexplained rectal bleeding >60yr with Fe-deficient anaemia OR changed bowel habit red-flag: rectal bleeding + abdo pain, changed bowel habit, weight loss OR Fe-deficient anaemia
65
how are colon + rectal cancers managed
if stage 1-3 = surgical resection if stage 3 = surgery + post-op chemotherapy (as lymph nodes involved) same for rectal cancer if tumour >8cm from anal canal or in proximal 2/3 of rectum = anterior resection if tumour <8cm from anal canal or in distal 1/3 rectum = abdomino-perineal resection

302 review (14 decks)

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