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YEAR 5: Histopathology AS > Histo: Lower GI Disease > Flashcards

Histo: Lower GI Disease Flashcards

1
Q

List some congenital disorders of the GI tract.

A
  • Atresia/stenosis
  • Duplication
  • Imperforate anus
  • Hirschsprung disease (MOST COMMON)
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2
Q

What is Hirschsprung disease?

A
  • Caused by the absence of ganglion cells of the submucosal and myenteric plexus results in failure of dilatation of the distal colon
  • starts in rectum which fails to dilate
  • Presents with: constipation, abdominal distension, vomiting and overflow diarrhoea
  • 80% male
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3
Q

List some genetic associations of Hirschsprung disease.

A
  • Down syndrome
  • RET proto-oncogene Cr10
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4
Q

How is Hirschsprung disease diagnosed?

A
  • Clinical impression
  • Full thickness rectal biopsy
  • Shows hypertrophied nerve fibres but no ganglia
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5
Q

How is Hirschsprung disease treated?

A

Resection of affected (constricted) segment with frozen section to identify how far ganglion cells go

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6
Q

Mechanical disorders

A

obstruction
- adhesions
- herniation
- extrinsic mass
- volvulus

diverticular disease

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7
Q

What is a volvulus?

A

Twisting of a loop of bowel at the mesenteric base around a vascular pedicle

intestinal obstruction +/- infarction

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8
Q

Which part of the intestines tend to be affected by volvulus in children and the elderly?

A

Children - small bowel

Elderly - sigmoid colon

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9
Q

Describe the pathophysiology of diverticular disease.

A

High intraluminal pressure (e.g. due to low fibre diet) leads to herniation of the bowel mucosa through weak points in the bowel wall (usually sites of entry of nutrient vessels)

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10
Q

Most common place for diverticular disease

A

90% left bowel, sigmoid colon

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11
Q

complications of diverticular disease

A

pain
diverticulitis
gross perfoation
fistula: bowel, bladder, vagina
obstruction

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12
Q

List some causes of acute colitis.

A
  • Infection
  • Drugs/toxins: antibiotic
  • Chemotherapy
  • Radiotherapy
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13
Q

Chronic colitis causes

A

TB
IBD
Ischaemic

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14
Q

Infectious colitis causes

A

viral: CMV (immunosuppressed with IBD)
bacterial: salmonella
protozoal: entamoeba hystolytica
fungal: candida

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15
Q

List the effects of infection on the colon.

A
  • Secretory diarrhoea (due to toxin)
  • Exudative diarrhoea (due to invasion and mucosal damage)
  • Severe tissue damage and perforation
  • Systemic illness
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16
Q

What can cause pseudomembranous colitis?

A

Exotoxins by C. difficile

follows antibiotic therapy, acute colitis with pseudomembrane formaiton

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17
Q

How can C. difficile colitis be diagnosed?

A

Toxin stool assay

histology has characteristic features

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18
Q

How is pseudomembranous colitis treated?

A

Metronidazole or vancomycin

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19
Q

Where in the intestines does ischaemic colitis tend to occur?

A

Watershed zones (e.g. splenic flexure SMA and IMA, rectosigmoid IMA and internal iliac artery)

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20
Q

classification of ischaemic colitis

A

acute or chronic
mucosal, mural, transmural (perforation)

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21
Q

List some causes of ischaemic colitis.

A
  • Arterial occlusion (e.g. atheroma, thrombosis, embolism)
  • Venous occlusion (e.g. thrombus, hypercoagulable state)
  • Small vessel disease (e.g. diabetes mellitus, emboli, vasculitis)
  • Low flow states (e.g. CCF, hernia, shock)
  • Obstruction (e.g. hernia, intussusception, volvulus, adhesions)
22
Q

Chronic IBD aetiology

A

genetic predisposition: familial, aggregation, twin studies, HLA
infection: mycobacteria, measles
abnormal host immunoreactivity
microbiome

23
Q

List some characteristic features of Crohn’s disease.

A
  • Can occur anywhere from mouth to anus
  • Skip lesions
  • Transmural inflammation
  • Non-caseating granulomas
  • fissure/ sinus/ fistula formation
  • Mostly affects large bowel and terminal ileum
  • Thick rubber hose-like wall
  • Cobbelstone mucosa
  • Narrow lumen
24
Q

List some extra-intestinal features of inflammatory bowel disease.

A
  • Arthritis
  • Uveitis
  • Stomatitis/cheilitis (CD)
  • Skin lesions (pyoderma gangrenosum, erythema multiforme, erythema nodosum)
  • PSC (UC)
  • myositis (UC)
25
Q

List some characteristic features of ulcerative colitis.

A
  • Involves rectum and colon in a continuous fashion
  • May see backwash ileitis (involvement of the terminal ileum) and appendiceal involvement but small bowel and proximal GIT not included
  • Inflammation is confined to the mucosa
  • Bowel wall is normal thickness
  • shallow ulcers
26
Q

List some complications of ulcerative colitis.

A
  • Severe haemorrhage
  • Toxic megacolon
  • Adenocarcinoma (20-30x increased risk)
27
Q

Which liver condition is associated with UC?

A

Primary sclerosing cholangitis

28
Q

what cancer is primary sclerosing cholangitis associated with

A

cholangiocholangitis

29
Q

List some types of neoplastic epithelial lesions that occur in the GI tract.

A
  • Adenoma
  • Adenocarcinoma
  • Neuroendocrine tumour
30
Q

List some types of other lesions that occur in the GI tract.

A
  • Stromal tumours (GIST)
  • mesenchymal: Lipoma, Sarcoma
  • Other: lymphoma
31
Q

List three types of non-neoplastic polyp.

A
  • Hyperplastic and sessile serrated lesions
  • Inflammatory (pseudopolyp)
  • Haemartomatous (juvenile, Peutz-Jeghers)
32
Q

Hyperplastic polyps

A

small polyps of little significance, saw tooth serrations, overgrowths

33
Q

Sessile serrated lesion

A

darker glands at base showing dysplasia
architectural abnormalities

34
Q

List three types of neoplastic polyp.

A
  • Tubular adenoma
  • Tubulovillous adenoma
  • Villous adenoma
35
Q

What is an adenoma?

A
  • Excess epithelial proliferation with dysplasia
  • NOTE: there are three types - tubular, tubulovillous and villous

20-30% prev before age 40
40-50% prev after age 60

36
Q

List some features of an adenoma that are associated with increased risk of becoming a carcinoma.

A
  • Size of polyp (>4cm = 45%)
  • Proportion of villous component
  • Degree of dysplastic change within a polyp
37
Q

List some observations that have given rise to adenoma-carcinoma sequence theory.

A
  • Areas with a high prevalence of adenomas have a high prevalence of carcinoma
  • Adenomas tend to appear 10 years before a carcinoma
  • Risk of cancer is proportional to the number of adenomas
  • near sigmoid colon to rectum- sigmoidoscopy screening
38
Q

adenoma symptoms

A

usually none
bleeding/ anaemia

39
Q

List some familial syndromes that are characterised by intestinal polyps.

A
  • Peutz-Jegher’s syndrome
  • FAP (Gardner’s, Turcot)
  • HNPCC
40
Q

What is the inheritance pattern of FAP?

A

Autosomal dominant
avg onset 25 years

41
Q

Cancer risk in FAP + type of cancer

A

average 1,000 polyps (min 100)
100% cancer risk in 10-15 years
colectomy= 5% ampullary Ca risk (duodenal monitoring)

42
Q

Which gene is mutated in FAP?

A

APC TS gene - chromosome 5q21

NOTE: almost 100% will develop cancer in 10-15 years

43
Q

What is Gardner’s syndrome?

A

Same features of FAP but with extra-intestinal manifestations: multiple osteomas of the skull and mandible, epidermoid cysts, desmoid tumours and supernumerary teeth

44
Q

What is Turcot tumours?

A

FAP + brain tumours

45
Q

What is the inheritance pattern of HNPCC?

A

Autosomal dominant
3-5% all colorectal cancers

46
Q

Which gene mutation is associated with HNPCC?

A

1 of 4 DNA mismatch repair genes is mutated
numerous DNA replication errors

47
Q

Where do carcinomas in HNPCC tend to occur?

A

Proximal to the splenic flexure

NOTE: poorly differentiated and mucinous cancers are more common. Polyps do not necessarily precede the cancer.

Multiple synchronous cancers

presence of extracolonic ca: endometrial, prostate, breast, stomach

48
Q

Most common type of colorectal cancer

A

98% adenocarcinoma
consider familial syndrome <50

49
Q

Outline Dukes’ staging of colorectal cancer. (outdated)

A

A - confined to bowel wall

B - through the bowel wall

C - lymph node metastases

D - distant metastases

50
Q

classification of ischaemic colitis

A

acute or chronic
mucosal, mural, transmural (perforation)

YEAR 5: Histopathology AS (20 decks)

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