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Gastrointestinal > GI 4 > Flashcards

GI 4 Flashcards

1
Q

What is a polyp?

A

A protrusion above the epithelium which is a type of tumour which can be benign or malignant

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2
Q

What are the three types of colorectal tumours?

A

1) Polyps
2) Adenomas
3) Adenocarcinomas

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3
Q

What are the differential diagnoses for a colonic polyp?

A
  • Adenoma (most polyps)
  • Serrated polyp
  • Polypoid carcinoma
  • Other
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4
Q

What is a colonic adenoma?

A

A benign tumour which is not invasive and does not metastasise. It must be removed as it is premalignant (precursor for colorectal carcinoma)

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5
Q

What is Dukes staging?

A

Predicts prognosis for carcinoma:

1) Dukes A: confined by muscular propria
2) Dukes B: through the muscular propria
3) Dukes C: metastatic to lymph nodes

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6
Q

Describe the distribution of colorectal carcinomas.

A
  • 75% are left-sided (rectum, sigmoid, descending)

- 25% are right-sided (caecum, ascending)

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7
Q

What is the pattern of spread for colorectal carcinoma?

A
  • Local invasion: mesorectum, peritoneum, other organs
  • Lymphatic spread: mesenteric nodes
  • Haematogenous: liver and distant sites
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8
Q

What are two inherited colorectal cancer syndromes?

A

1) Hereditary non-polyposis coli (HNPCC)

2) Familial adenomatous polyposis (FAP)

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9
Q

What is hereditary non-polyposis coli (HNPCC)?

A
  • Late onset, autosomal dominant
  • Defect in DNA mismatch repair
  • Right sided tumours
  • < 100 polyps
  • Mucinous tumours
  • Crohn’s like inflammatory response
  • Associated with gastric and endometrial carcinoma
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10
Q

What is familial adenomatous polyposis (FAP)?

A
  • Early onset, autosomal dominant
  • Defect in tumour suppression, mutation in FAP gene
  • Throughout the colon
  • > 100 polyps
  • No specific inflammatory response
  • Associated with desmoid tumours and thyroid carcinoma
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11
Q

What are diverticular diseases of the large intestine?

A

When sacs/bulges form in the all of the large intestine, which are related to a low fibre diet and high intraluminal pressure. Often asymptomatic unless complications occur.

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12
Q

What are some complications of diverticular disease in the large intestine?

A
  • Inflammation
  • Rupture
  • Abscess
  • Fistula
  • Massive bleeding
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13
Q

What are some of the causes of large bowel ischaemia?

A
  • CVD/CHD (atrial fibrillation)
  • Embolus
  • Shock
  • Vasculitis
  • Atherosclerosis of mesenteric vessels
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14
Q

What is the histopathology of ischameic colitis?

A
  • Withering of crypts
  • Pink smudgy lamina propria
  • Fewer chronic inflammatory cells
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15
Q

What are the complications of ischaemia of the large intestine?

A
  • Massive bleeding
  • Rupture
  • Stricture
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16
Q

What is antibiotic-induced “pseudomembranous” colitis?

A

In patients on broad-spectrum antibiotics, C diff is selected out and toxins A and B attacks the endothelium -> massive diarrhoea and bleeding.

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17
Q

What is collagenous colitis?

A

Thickened basement membrane associated with intra-epithelial inflammatory cells.

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18
Q

What is the histopathology of lymphocytic colitis?

A
  • No chronic architectural changes in crypts
  • Intraepithelial lymphocytes are raised
  • No thickening of the basal membrane
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19
Q

What is radiation colitis?

A
  • Chronic active or inactive colitis with Telangectasia
  • Bizarre stromal cells and vessels
  • May be other complications of immunosuppression if also on chemotherapy
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20
Q

What is acute infective colitis?

A

Infection, may be the onset of intestinal bowel disease

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21
Q

What is colonic angiodysplasia?

A
  • Submucosal lakes of blood
  • Obscure cause of rectal bleeding
  • Usually right side of the colon
  • Diagnosed with angiography or colonoscopy
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22
Q

What is signed volvulus?

A
  • When the bowel twists on mesentery and may become gangrenous
  • Diagnosed by plain X-ray abdominal or rectal contrast
  • Treated with flatulus tube or surgical resection
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23
Q

What is enterobacteriaceae?

A

A large family of Gram-negative bacteria which can cause a wide range of illnesses e.g. UTI and gastroenteritis; not all are truly pathogenic (some opportunistic).

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24
Q

Describe the microbiology of enterobacteriaceae.

A
  • 53 genera (26 cause infection)
  • Gram negative
  • Non-spore forming
  • Grow on a variety of solid media
  • Ferment sugars
  • Facultative anaerobes mostly
  • Increasing resistance
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25
Q

What is MALDI-TOF mass spectrometry?

A
  • Low cost machine which analyses protein composition of bacterial cell wall using a database
  • Discriminates between highly genetically similar organisms with identical 16s rRNA
  • Difficult to discriminate some species such as Salmonella vs E. coli
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26
Q

What is the normal flora of the GI tract?

A
  • Mouth: strep viridans, Neisseria sp, anaerobes, candida sp, staphylococci
  • Stomach/duodenum: usually sterile, few candida and staphylococci
  • Jejunum: few coliforms and anaerobes
  • Colon: large number of coliforms, anaerobes and Enterococcus faecalis
  • Bile ducts: sterile
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27
Q

What are the symptoms of C diff overgrowth?

A
  • Diarrhoea, sometimes bloody
  • Abdominal pain
  • In severe cases -> pseudomembranous colitis and bowel perforation
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28
Q

Describe the laboratory diagnosis for C diff infection.

A

1) Screening test for presence of organism (GDH)
2) If positive text for presence of toxin (A&B)
If 1 - = -; if 1 + and 2 + = +; if 1 + and 2- = indeterminate, repeat, if indeterminate again -> clinical decision

29
Q

What is rotavirus?

A
  • Commenest cause D&V in <3, mild in adults severe in immunocompromised children
  • Person-person spread (directly/indirectly)
  • Mild-severe diarrhoea, no blood
  • Self-limiting, lasts one week
  • Dehydration and post-infection malabsorption
  • Diagnosis by PCR test on faeces
  • Treat by oral rehydration
  • Oral vaccine at 2 & 3 months but not past 24 weeks
30
Q

What is norovirus?

A
  • D&V bug (2-4 days), affects all people all times
  • 5 billion viruses per gram of faeces
  • Faeceal-oral (droplet) or person-person
  • Survival on fomites for days/weeks
  • Short incubation <24 hrs
  • Diagnosed by faeces specimen/vomit swab for PCR test
  • Treatment with rehydration (esp kids and elderly)
  • Asymptomatic shedding up to 48 hrs post symptoms
31
Q

What are the standard infection control precautions for diarrhoea in hospital?

A
  • Side rooms with own toilets/commodes
  • Cohort nursing
  • Close wards to new admission
  • Regular cleaning and disinfection of the ward
32
Q

What is sepsis?

A

Life-threatening organ dysfunction caused by a dysregulated host response to infection

33
Q

What is septic shock?

A

A subset of sepsis with circulatory and cellular/metabolic dysfunction associated with a higher risk of mortality

34
Q

What are the local signs of intra-abdominal infection?

A

Pain, tenderness, guarding and blood PR in some

35
Q

What are the systemic signs of intra-abdominal infection?

A

Fever, chills/rigors, nausea/vomiting, constipation/diarrhoea, malaise, anorexia

36
Q

What is SIRS?

A

Systemic inflammatory response syndrome (SIRS) is an exaggerated defense response of the body to a noxious stressor to localize and then eliminate the endogenous or exogenous source of the insult; if presumed or confirmed infectious process = sepsis

37
Q

What are the four criteria for SIRS (>/=2 confirms SIRS)?

A

1) Body temperature >38 or <36
2) Heart rate >90bpm
3) RR >20 or PaCO2 <32mmHg
4) WCC > 12000 units/l or <4000 units/l

38
Q

What are the signs of septic shock?

A

Sepsis plus signs of at least one acute organ dysfunction e.g. renal, respiratory, hepatic, haematological, CNS, unexplained metabolic acidosis or hypotension

39
Q

What is the protocol for gentamicin prescription?

A
  • Concerns regarding nephrotoxicity (limit use and monitor renal function daily)
  • Correct dosing for overweight patients, max of 600mg
  • Follow clear exclusion criteria
  • Prescribe in once-only section and let the ward pharmacist know
40
Q

What steps should be completed within 3 hours of a patient surviving sepsis?

A

1) Measure lactate level
2) Obtain blood culture prior to antibiotics
3) Administer broad spectrum antibiotics
4) Administer 30ml/kg crystalloid for hypotension or lactate levels >/= 4mmol/l

41
Q

What steps should be completed within 6 hours of a patient surviving sepsis?

A

5) Apply vasopressors for hypotension that does not respond initial fluid resuscitation to maintain MAP >/= 65
6) If persistent arterial hypotension despite volume resuscitation or initial lactate >/4 mmol/l: measure CVP and SCVO2
7) Remeasure lactate if initial lactate was elevated

42
Q

What are the risk factors for GI infections?

A
  • Malnutrition (micronutrient) deficiency
  • Closed/semi-closed communities
  • Exposure to contaminated food/water/travel
  • Winter congregating/summer floods
  • Age <5, not breast feeding
  • Older age
  • Acid suppression/immunosuppression/microbiome/genetics
43
Q

What bacterial factors are a risk for GI infections?

A
  • Adherence/attachment to the GI mucosa
  • Cellular invasion
  • Production of exotoxins
  • Changes in epithelial cell physiology
  • Loss of brush border enzymes and/or cell death
  • Increased intestinal motility, net fluid secretion, influx of inflammatory cells, and/or intestinal haemorrhage
44
Q

What is dysentry?

A
  • Inflammation of the intestine, particularly the colon, causing diarrhea associated with blood and mucus;
  • e.g. shigella and campylobacter
  • Generally associated with fever, abdominal pain, and rectal tenesmus (sense of incomplete defaecation).
45
Q

What is gastroenteritis?

A
  • An illness caused by eating food contaminated with micro-organisms, toxins, poisons etc
  • Bacteria, viruses, parasites
  • Usually have gastrointestinal symptoms (diarrhoea, abdominal pain, vomiting)
46
Q

What GI infections have the shortest incubation periods (1-6 hours)?

A

1) Bacillus cereus - starchy foods, heat resistant spores, profuse vomiting, gram positive bacillus
2) Staphylococcus aureus - gram positive coccus, in room temperature food, acts on vomiting centre in brain, abdominal pain

47
Q

What physical examinations should you conduct on a returned traveller?

A
  • Fever
  • Rash
  • Hepatosplenomegaly/lymphadenopathy
  • Insect bites
  • Wounds
48
Q

What might a fever in a returned traveller indicate?

A
  • Respiratory tract infections (pneumonia/influenza)
  • Traveller’s diarrhoea
  • Malaria
  • Enteric fever (typhoid/paratyphoid fever)
  • Arboviruses - dengue/zika/chikungunya
49
Q

What is acute traveller’s diarrhoea?

A
  • 3 loose stools in 24 hours
  • Associated with self reported fever in 30%
  • Typically enterotoxigenic E. coli (maybe campylobacter, salmonella, shigella or amoebic diarrhoea)
  • Cruise ships - norovirus and rotavirus
  • 50% of cases no pathogen identified
50
Q

What are the two types of acute traveller’s diarrhoea?

A

1) Bloody diarrhoea (dysentery) – Bacterial causes including E.coli 0157, plus Amoebic colitis
2) Profuse watery diarrhoea – Cholera – toxin mediated disease often associated with outbreaks – refugee camps

51
Q

What are the investigations for acute traveller’s diarrhoea?

A

1) Stool culture

2) Stool wet prep on recently passed stool for amoebic trophozoites

52
Q

What is enteric fever?

A
  • Typhoid or paratyphoid fever
  • Most common in those returning from Indian subcontinent and SE Asia
  • Often in people visiting family or friends
  • Incubation period 7-18 days (though occasionally up to 60 days)
53
Q

What are the symptoms of enteric fever?

A

Fever, headache, constipation/diarrhoea, dry cough

54
Q

What are the complications of enteric fever?

A
  • GI bleeding
  • GI perforation
  • Encephalopathy
  • Bone and joint infection
55
Q

What causes pre-hepatic (haemolytic) jaundice and fever?

A
  • Malaria
  • HUS as a complication of diarrhoeal illness
  • Sickle cell crisis triggered by infection
56
Q

What causes hepatic jaundice and fever?

A
  • Hepatitis A and E – acute (occasionally Hepatitis B)
  • Leptospirosis – Weils diseases (Icteric, haemorrhagic and renal failure)
  • Malaria
  • Enteric fever
  • Rickettsia (scrub typhus, Rocky Mountain spotted fever etc)
  • Viral haemorrhagic fever
57
Q

What causes post-hepatic jaundice and fever?

A
  • Ascending cholangitis

- Helminths

58
Q

What investigations should be completed for a traveller with fever/jaundice?

A
  • Malaria blood film and rapid antigen
  • Blood film for red cell fragmentation
  • FBC/UE/LFT/coagulation
  • Blood cultures
  • USS abdomen
  • Serological testing for viruses
59
Q

What is amoebiasis?

A
  • Entamoeba histolytica, a protozoa
  • Faecal-oral spread, strong association with poor sanitation
  • Asymptomatic carriage (chronic cyst shed in stool)
  • Symptoms: abdominal dysentery
60
Q

What are the symptoms of amoebiasis?

A
  • Abdominal dysentery
  • Abdominal pain
  • Fever
  • Bloody diarrhoea / colitis (can perforate)
  • Toxic and unwell, abdominal tenderness, peritonism
61
Q

What are the investigations for amoebiasis?

A
  • Stool microscopy for trophozoites or cysts (distinguish between E. histolytica and E. dispar)
  • AXR - ?toxic megacolon
  • Endoscopy for biopsy (not if evidence of toxic dilatation)
62
Q

What is an amoebic liver abscess?

A
  • Entamoeba histolytica
  • Incubation period 8-20 weeks
  • More common in men
  • Subacute presentation over 2-4 weeks; fever, sweats, abdominal pain
63
Q

What are the symptoms of an amoebic liver abscess?

A
  • Fever, sweats
  • Upper abdominal pain
  • Sometimes history of GI upset (dysentery)
  • Hepatomegaly
  • Point tenderness over right lower ribs
64
Q

What are the investigations for an amoebic liver abscess?

A
  • Abnormal LFTs
  • CXR – raised right hemi-diaphragm
  • USS/CT scan
  • Serology
  • Stool microscopy - often negative (E. histolytica looks similar to E.dispar)
65
Q

What is giardiasis?

A
  • Giardia intestinalis (lamblia), flagellated protozoa
  • Invades duodenum and proximal jejunum
  • Faecal-oral spread (contaminated water most commonly)
  • Incubation usually around 7 days
66
Q

What is the typical presentation for giardiasis?

A
  • Watery, malodorous diarrhoea
  • Bloating, flatulence
  • Abdominal cramps
  • Weight loss
67
Q

What are the investigations for giardiasis?

A
  • Stool microscopy for cysts (often difficult), in developed world PCR tests
  • OGD for duodenal biopsy (rarely necessary)
68
Q

What are helminth infections?

A
  • Occur in gut/tissue
  • Often associated with eosinophilia
  • Often diagnosed by the adult worm passed or the eggs in stool
69
Q

What are some common helminths?

A
  • Cestodes (tapeworms)
  • Nematodes (roundworms)
  • Trematodes (flukes)

Gastrointestinal (8 decks)

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