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Arjun's PM copy-Histopathology > Histo: Lower GI Disease > Flashcards

Histo: Lower GI Disease Flashcards

1
Q

What are the general effects of bowel pathology?

A
  • Disturbance of of normal function
  • Bleeding
  • Perforation / Fistula
  • Obstruction
  • Systemic illness
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2
Q

List some congenital disorders of the GI tract.

A
  • Atresia/stenosis
  • Duplication
  • Imperforate anus
  • Hirschsprung disease (MOST COMMON)
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3
Q

What is atresia?

A

Lack of connection between two parts of bowel

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4
Q

What is Hirschsprung disease?
How does it present?

A

The absence of ganglion cells of the myenteric plexus resulting in failure of dilatation of the distal colon

Presents with:

  • Delayed passage of meconium
  • Constipation
  • Abdominal distension
  • Vomiting
  • Overflow diarrhoea
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5
Q

List some genetic associations of Hirschsprung disease.

A
  • Down syndrome (2%)
  • RET proto-oncogene mutation (chr 10)
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6
Q

How is Hirschsprung disease diagnosed?

A

Clinical impression from history and examination

Full thickness rectal biopsy (gold standard)

  • Shows hypertrophied nerve fibres but no ganglia
  • if ganglion cells seen = not Hirschprungs
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7
Q

How is Hirschsprung disease treated?

A

Resection of affected (constricted) segment (anorectal pull-through precedure)

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8
Q

Causes of Mechanical obstruction

A
  • Adhesion
  • Herniation
  • Cancer
  • Volvulus
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9
Q

What is a volvulus? What complications does it cause

A

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

Causes bowel obtruction +/- infarction

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10
Q

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

A

Infant - small bowel

Elderly - sigmoid colon

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11
Q

Describe the pathophysiology of diverticular disease
Which part of bowel is most commonly affected?
What is a risk factor for developing diverticular disease?

A
  • High intraluminal pressure leads to herniation of the bowel mucosa through weak points in the bowel wall (usually sites of entry of nutrient vessels)
  • 90% in left colon (specifically sigmoid)
  • Associated with low-fibre diet
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12
Q

What are some 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 antibiotics)
  • Chemotherapy
  • Radiation
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14
Q

List some causes of chronic colitis

A
  • Crohn’s
  • Ulcerative colitis
  • TB
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15
Q

List some infectious causes of colitis

A
  • Viral e.g. CMV
  • Bacterial e.g. Salmonella
  • Protozoal e.g. Entamoeba histolytica
  • Fungal e.g. Candida
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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 is pseudomembranous colitis?

A

Antibiotic-associated colitis characterised by acute colitis with pseudomembrane formation

Caused by C. difficile exotoxins

pseudomembrane = membrane formed by inflammatory tissue

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18
Q

How can C. difficile colitis be diagnosed?

A
  • Lab - toxin stool assay
  • Histology - characteristic features on biopsy

Always considered in hospital - precipitated by ABx
(Clindamycin, Cephalosporins)

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19
Q

How is pseudomembranous colitis treated?

A

Vancomycin

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20
Q

What can causes both acute and chronic colitis?

A

Ischaemia
IBD

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21
Q

Where in the intestines does ischaemic colitis tend to occur? Give 2 examples.

A

Watershed zones - areas that receive dual blood supply from the most distal branches of two large arteries

  • Splenic flexure - SMA and IMA
  • Rectosigmoid - IMA and internal iliac
22
Q

How can ischaemic colitis be classified?

A
  • Mucosal
  • Mural
  • Transmural (perforation)
23
Q

List the potential causes of ischaemic colitis.

A
  • Arterial occlusion - atheroma, embolism
  • Venous occlusion - thrombus
  • Small vessel disease - diabetes mellitus, vasculitis
  • Low flow states - CHF, shock, haemorrhage
  • Obstruction - hernia, intussusception, volvulus, adhesions
24
Q

What are some clinical features of IBD?

A
  • Diarrhoea (bloody in UC)
  • Fever
  • Abdominal pain
  • Anaemia
  • Weight loss
  • Perforation
  • Extra-intestinal manifestations
25
Q

Describe the epidemiology of Crohn’s

A
  • Mainly affects white people
  • Onset typically late teens - 20s
  • Women
26
Q

List some characteristic features of Crohn’s disease.

A
  • Can affect whole GI tract (mouth to anus)
  • Skip lesions with cobblestone mucosa
  • Transmural inflammation
  • Non-caseating granulomas
  • Fissure/sinus/fistula formation
  • Bowel wall is thickened
  • Mostly affects large bowel and terminal ileum
27
Q

List some extra-intestinal features of Crohn’s.

A
  • Arthritis
  • Uveitis
  • Stomatitis/cheilitis
  • Skin lesions - pyoderma gangrenosum, erythema multiforme, erythema nodosum
28
Q

Describe the epidemiology of UC

A
  • Slightly more common that Crohn’s
  • Mainly affects white people
  • Onset typically 20-25 years
29
Q

List some characteristic features of ulcerative colitis.

A
  • Involves rectum and colon in a continuous fashion (starts at rectum)
  • May see backwash ileitis (involvement of the terminal ileum)
  • Inflammation is confined to the mucosa
  • Shallow ulceration
  • Bowel wall is normal thickness
30
Q

List some complications of ulcerative colitis.

A
  • Severe haemorrhage
  • Toxic megacolon
  • Adenocarcinoma (20-30x increased risk)
31
Q

List some extra-intestinal manifestation of UC

A
  • Arthritis
  • Myositis
  • Uveitis/iritis
  • Skin lesion - erythema nodosum, pyoderma gangrenosum
  • Primary sclerosing cholangitis
32
Q

Which hepatobiliary condition is associated with UC?

A

Primary sclerosing cholangitis

NOTE: PSC is big risk factor for cholangiocarcinoma

33
Q

List some types of tumour affecting the of colon and rectum

A

Non-neoplastic polyps

Neoplastic Epithelial Tumours

  • Adenoma
  • Adenocarcinoma
  • Neuro-endocrine tumours - carcinoid (mainly affects small bowel)

Mesenchymal lesions

  • Lipoma
  • Leiomyoma

Lymphoma

34
Q

What is a polyp?

A

A growth that protrudes into the lumen of an organ

35
Q

List some non-neoplastic and neoplastic polyps of the colon and rectum

A

Non-neoplastic

  • Hyperplastic and sessile serrated lesions
  • Inflammatory pseudopolyps seen in UC
  • Hamartomatous polyps (Peutz-Jeghers)

Neoplastic

  • Adenoma
  • Adenocarcinoma
36
Q

What are sessile serrated lesions?

A

Type of hyperplastic polyp with architectual abnormalities that may be premalignant and show dyplasia

37
Q

What are adenomas? What are the types of adenoma?

A

Benign tumours that characterised by excessive epithelial proliferation and may be dysplastic

  • Tubular
  • Tubulovillous
  • Villous (highest risk of carcinoma)
38
Q

What are the risk factors for cancer in an individual adenoma polyp?

A
  • Size (>4cm = 45%)
  • Proportion of villous component (finger-like projections)
  • Degree of dysplasia
39
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
40
Q

What are some genetic causes of colon cancer?

A

Familial adenomatous polyposis

  • Gardner’s
  • Turcot

Hereditary non-polyposis colon cancer (Lynch syndrome)

All are autosomal dominant

41
Q

What is Lynch syndrome (HNPCC)?

A
  • Autosomal dominant condition
  • Affects DNA mismatch repair genes - MSH2 most commonly affected
  • Associated with increased risk of colorectal, endometrial, gastric, and ovarian cancers
42
Q

What is familial adenomatous polyposis?

A
  • Autosomal dominant condition
  • Caused by mutation in APC tumour supressor gene (chr 5)
  • Characterised by numerous (average 1000) colorectal polyps
  • Virtually 100% will develop colorectal cancer within 10-15 years
43
Q

What is Gardner’s syndrome?

A

FAP plus extra-intestinal manifestations e.g.

  • Cranial osteomas
  • Desmoid tumours
  • Epidermoid cysts
44
Q

Where does colon cancer typically arise in HNPCC?

A

Colon cancer typically arises proximal to splenic flexture (proximal colon) and is typically poorly differentiated

45
Q

Describe the epidemiology of colorectal cancer?

A
  • 98% are adenocarcinoma
  • Average age affected is 60-79
  • If <50 years consider familial syndrome
  • Primarily affects western population
46
Q

List some risk factors for colorectal cancer

A
  • Familial
  • Diet (low fibre, high fat)
  • Lack of exercise
  • Obesity
47
Q

List some prediposing conditions to colorectal cancer

A
  • Adenomas
  • IBD
48
Q

What are the symptoms of Colorectal Cancer?

A
  • Change in bowel habit
  • Blood in stool
  • Anaemia
  • Weight loss
  • Pain
49
Q

Describe the grading and staging of CRC?

A
  • Grade - degree of differentiation
  • Staging - TMN
50
Q

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

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

Arjun's PM copy-Histopathology (20 decks)

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