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YEAR 5: HISTOPATH > Histo: Lower GI Disease > Flashcards

Histo: Lower GI Disease Flashcards

1
Q

List some congenital disorders of the GI tract.

A
  • Atresia/stenosis - failure of normal bowel to develop
  • Duplication - cyst can form
  • 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 in the submucosa and myenteric plexus results in failure of dilatation of the distal colon
  • Starts in the rectum –> spreads proximally
  • Presents with: constipation, abdominal distension, vomiting and overflow diarrhoea
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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

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6
Q

Causes of mechanical bowel obstruction

A

adhesions
herniation
extrinsic mass
volvulus

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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

Obstruction –> ischaemia –> 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 (congenital - long mesentery)

Elderly - sigmoid colon

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9
Q

Describe the pathophysiology of diverticular disease.

A

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

low fibre diet

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10
Q

Where does diverticular disease occur

A

sigmoid
(left colon)

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11
Q

What layer does the colon herniate in diverticular disease

A

muscularis externa

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12
Q

Complications of diverticular disease

A

Pain
Diverticulitis
Perforation
Fistula
Obstruction

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13
Q

List some causes of acute colitis.

A
  • Infection
  • Drugs/toxins - especially Abx
  • Chemotherapy
  • Radiotherapy
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14
Q

Causes of infectious colitis

A

CMV
Salmonella
Enteromoeba
Candida

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15
Q

Causes of chronic colitis

A

Crohn’s
UC
TB

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16
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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17
Q

What can cause pseudomembranous colitis?

A

Exotoxins by C. difficile

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18
Q

How can C. difficile colitis be diagnosed?

A

Toxin stool assay

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19
Q

What is pseudomembranous colitis

A

Inflammatory slough overlying bowel mucosa - forms pseudomembrane

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20
Q

Diagnosis of pseudomembranous colitis

A

Pseudomembrane on mucosa characteristic on biopsy and endoscopy

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21
Q

How is pseudomembranous colitis treated?

A

Metronidazole or vancomycin

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22
Q

Where in the intestines does ischaemic colitis tend to occur?

A

Watershed zones
splenic flexure - SMA and IMA
rectosigmoid - IMA and internal Iliac

23
Q

When does ischaemia risk perforation

A

WHen the ischaemia becomes transmural –> infarcted

Previously moves from mucosal to mural

24
Q

List some causes of ischaemic colitis.

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

If mesentery twists –> vein will twist + occlude before artery

25
Q

What part of bowel is affected earliest in ischaemic colitis

A

Part furthest from blood supply –> mucosa first

26
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
27
Q

List some extra-intestinal features of inflammatory bowel disease.

A
  • Arthritis
  • Uveitis
  • Stomatitis/cheilitis
  • Skin lesions (pyoderma gangrenosum, erythema multiforme, erythema nodosum)
  • Primary sclerosing cholangitis
28
Q

List some characteristic features of ulcerative colitis.

A
  • Continuous inflmmation from rectum to colon
  • May see backwash ileitis (involvement of the terminal ileum) in patients with pan colitis
  • Inflammation is confined to the mucosa
  • Bowel wall is normal thickness
  • Shallow ulcers
29
Q

List some complications of ulcerative colitis.

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

Which liver condition is associated with UC?

A

Primary sclerosing cholangitis

New diagnosis PSC get colonscopy, New IBD have liver examined

31
Q

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

A
  • Adenoma
  • Adenocarcinoma
  • Neuro-endocrine tumours
32
Q

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

A
  • Stromal tumours
  • Lipoma
  • Sarcoma
  • Other: lymphoma
33
Q

What does presence of crypt abscesses signify in IBD

A

active disease

likely indication for steroids

34
Q
A
35
Q

List three types of non-neoplastic polyp.

A
  • Hyperplastic (not neoplastic as not clonal) and Sessile serrated lesions
  • Inflammatory (pseudopolyp)
  • Haemartomatous (juvenile, Peutz-Jeghers) - abnormal organistation of tissue
36
Q

Sessile serrated lesion vs hyperplastic polyp

A

Sessile serated are hyperplastic polyps + architectural changes
might show dysplasia - carry same risk of cancer adenoma

No risk of cancer of celullar abormality in hyperplastic polyp

37
Q

List three types of neoplastic polyp.

A
  • Tubular adenoma
  • Tubulovillous adenoma
  • Villous adenoma
38
Q
A

Pedunculated adenoma - sits on a stalk –> easier to remove

Sessile - is smooth and flat on bowel

39
Q

What is a polyp

A

tissue projecting into lumen

40
Q

What is an adenoma?

A
  • Excess epithelial proliferation with dysplasia
  • NOTE: there are three types - tubular, tubulovillous and villous
41
Q

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

A
  • Size of polyp (>4cm = 45%) - bigger is worse
  • Proportion of villous component - more villous is worse
  • Degree of dysplastic change within a polyp (high vs low grade)

villous > tubulovillous > tubular

42
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
43
Q

List some familial syndromes that are characterised by intestinal polyps.

A
  • Peutz-Jegher’s dynrome
  • Familial Adenomatous Polyposis (Gardner’s, Turcot)
  • Hereditary non polyposis colon cancer
44
Q

What is the inheritance pattern of FAP?

A

Autosomal dominant

develop by age 25

45
Q

Which gene is mutated in FAP?

A

APC gene - chromosome 5q21

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

46
Q

Features of FAP

A

Minimum 100, average 1000s of colorectal polyps (polyposis)

virtual 100% will develop cancer in 10-15 years

colon and duodenum polyps

47
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

48
Q

What is the inheritance pattern of HNPCC?

A

Autosomal dominant

49
Q

Which gene mutation is associated with HNPCC?

A

1 of 4 DNA mismatch repair genes is mutated

50
Q
A

May have a few polyps

Numerous DNA replication errors:
Colorectal cancer at early age
Extracolonic, multiple cancers - prostate, breast, stomach, endometrial cancer

51
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.

52
Q

Outline Dukes’ staging of colorectal cancer.

A

A - confined to bowel wall

B - through the bowel wall

C - lymph node metastases

D - distant metastases

53
Q

What is colon cancer staging dependent on

A

the projection of the tumour through the bowel wall

YEAR 5: HISTOPATH (20 decks)

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