Pathology of Colon Flashcards
What type of role does the small bowel play?
Absorptive
What 2 types of role does the large bowel play?
- Absorptive
- Secretory
What are the 3 sections of the small intestine?
- Duodenum
- Jejunum
- Ileum
What are the different sections of the large intestine?
- Caecum
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon (originates pelvic brim)
- Rectum
What is the mucosa of the small intestine made up of?
Innumerable villi
What are the 3 types of cells in the small intestine?
- Goblet cells
- Columnar absorptive cells
- Endocrine cells
How often are the cells in the small intestine renewed ?
4-6 days
What cells are found in the crypts of the large bowel?
- Goblet cells
- Endocrine cells
- Stem cells
What are the surface cells of the large bowel?
Columnar absorptive cells
Describe the structure of the large bowel,
- Flat: no villi
- Tubular crypts
What must the immune system balance in response to the large surface area of the GIT?
-Tolerance of harmless ingested substances against active defence reactions to potential microbial invaders
What does dysfunction of the intestinal immune system cause?
- Chronic disease
- Life threatening acute conditions
What is small and large bowel peristalsis mediated by?
Intrinsic (myenteric plexus) and extrinsic (autonomic innervation) neural control
What is the myenteric plexus formed of?
- Meissener’s plexus
- Auerbach plexus
Where is the Meissener’s plexus found?
Base of the submucosa
Where is the Auerbach plexus found?
Between the inner circular and outer longitudinal layers of the muscularis propria
Inflammatory bowel disease has pathological features of…
- Ulcerative colitis
- Crohn’s disease
- Ischaemic colitis
- Radiation colitis
- Appendicitis
Idiopathic Inflammatory Bowel Disease
Chronic inflammatory conditions resulting from inappropriate and persistent activation of the mucosal immune system driven by the presence of normal flora
What are the 2 main disease in idiopathic IBD?
- Crohn’s disease
- Ulcerative colitis
Where can Crohn’s disease affect?
Any part of the GIT from the mouth to the anus
Where is ulcerative colitis limited to?
Colon
What role does genetics play in CD and UC?
- 15% have affected 1st degree relatives
- NOD2 gene mutation associated with CD
- HLA associations with UC
What is the pathological cause of UC and CD?
- Strong (exaggerated) immune response against normal flora with defects in the epithelial barrier function in genetically susceptible individuals
- Defects in mucosal barrier could allow microbes access to mucosal lymphoid tissue triggering immune response
What is required for a diagnosis of IBD?
- Clinical history
- Radiographic examination
- Pathological correlation
pANCA
Perinuclear antineutrophilic cytoplasmic antibody
What is the prevalence of UC?
-M=F
When does UC peak?
- 20-30 years
- 70-80 years
What is the more common spread of UC?
Proximal
What other structure can also be involved in UC?
Appendix
What can occur with pancolitis?
Backwash ileitis
What is UC also associated with outside the colon?
Systemic manifestations
What is the pathology of UC?
- Large bowel only
- Continues pattern of inflammation
- Rectum to proximal
- Pseudo polyps
- Ulceration
- Serosal surface minimal or no inflammation
What is the histology of UC?
- Mucosa shows inflammation
- Cryptitis
- Cryps abscesses
- Architectural disarray of crypts
- Mucosal atrophy
- Ulceration into submucosa: pseudo polyps
- Limited mainly to mucosa and submucosa
- NO GRANULOMAS
- Sub mucosal fibrosis
How can dysplasia be graded?
High or low grade
How does flat epithelial atypia become an invasive cancer?
Undergoes an adenomatous change
Other than cancer what other complications are associated with UC?
- Haemorrhage
- Perforation
- Toxic dilatation
What is the prevalence of CD?
-F>M
When do the peaks in CD occur?
- 20-30 years
- 60-70 years
What is the pathology of CD?
- Granular serosa/ dull grey
- Wrapping mesenteric fat
- Mesentery thickened, oedematous and fibrotic
- Wall thick, oedematous
- Narrowing of lumen
- Sharp demarcation of disease segments from adjacent normal tissue (skip lesions)
- Ulcerations is like cobbles
What is the histology of CD?
- Cryptitis and crypt abscesses
- Architectural distortion
- Atrophy and crypt destruction
- Deep ulceration
- Transmural inflammation (chain of pearls)
- NON-CASEATING GRANULOMAS
- Fibrosis
- Lymphangiectasia
- Hypertrophy of mural nerves
- Paneth cell metaplasia
What are long term features of CD?
- Small intestine malabsorption
- Strictures
- Fistulas and abscesses
- Perforation
- Increased risk of cancer
Where can ischaemic lesions be restricted to?
- Small intestine
- Large intestine
- Both
Acute occlusion of which vessels can lead to infarction?
- Celiac artery
- Inferior mesenteric artery
- Superior mesenteric artery
Why may gradual occlusion of major supply vessels have little effect?
Anastomotic circulation
What does occlusion od small end arteries lead to?
Lesions which are small and focal
What conditions predispose for ischaemia?
- Arterial thrombosis
- Arterial embolism
- Non-occlusive ischaemia
What can cause arterial thrombosis ?
- Severe atherosclerosis
- Systemic vasculitis
- Dissecting aneurysm
- Hypercoaguable states
- Oral contraceptives
What can cause arterial embolisms?
- Cardiac vegetations
- Acute atheroembolism
- Cholesterol ischaemia
What can cause non-occlusive ischaemia?
- Cardiac failure
- Shock/dehydration
- Vaso-constrictive drugs
What is vulnerable to acute ischaemia?
Splenic flexure
How does early intense congestion appear?
- Dusky/purple/blue
- Lumen: sanguinous mucin
What does arterial acute ischaemia look like?
There is sharp demarcation
What does venous acute ischaemia look like?
Venous fade gradual
What is the histology of acute ischaemia?
- Oedema
- Intestinal haemorrhages
- Sloughing necrosis of mucosa-ghost outlines
- Nuclei indistinct
- Initial absence of inflammation
- 1-4 days- bacteria- gangrene and perforation
- Vascular dilatation
What are the characteristics of chronic ischaemia?
- Mucosal inflammation
- Ulceration
- Sub mucosal inflammation
- Fibrosis
- Stricture
How does radiation colitis occur?
- Abdominal irradiation can impair the normal proliferative activity of the small and large bowel epithelium
- Usually rectum-pelvic radiotherapy
What does the damage by radiation depend on?
Dose
What does radiation target?
Actively dividing cells especially blood vessels and crypt epithelium
What are the symptoms of radiation colitis?
- Anorexia
- Abdominal cramps
- Diarrhoea
- Malabsorption
What does radiation colitis mimic?
IBD
What is the histology of radiation colitis?
- Bizarre cellular changes
- Inflammation: crypt abscesses and eosinophils
- Later arterial stenosis
- Ulceration
- Necrosis
- Haemorrhage
- Perforation
What is the appendix essentially?
- Bowel remnant which is a prominent lymphoid tissue that regresses with age
- Undergoes fibrous obliteration
How big is the appendix?
Approx 6-7cm
Appendicitis
Acute inflammation of the appendix
What causes appendicitis?
Obstruction eg. feocolith or enterobius vermicularis
What does the increased intraluminal pressure associated with appendicitis lead to?
Ischaemia
What is the histology of appendicitis?
- Fibrinopurulent exudate
- Perforation
- Abscess
- Acute suppurative inflammation in wall and pus in lumen
- Acute gangrenous full thickness necrosis +/- perforation
What is low grade dysplasia reasonably like?
Normal
What is high grade dysplasia reasonably like?
Cancer
What are the 3 different formations of adenomas (polyps) ?
- Tubular
- Villous
- Tubulovillous
Describe the histology of low grade dysplasia.
- Increased nuclear no
- Increased nuclear size
- Reduced mucin
Describe the histology of high grade dysplasia.
- Carcinoma in situ
- Crowded
- Very irregular
- Not yet invasive
What are the risk factors for colorectal carcinomas such as adenocarcinomas?
- Lifestyle
- Family history
- IBD
- Genetics
What genes can predispose you to CRC?
- FAP
- HNPCC
- Peutz-Jeghers
Describe right sided colorectal adenocarcinoma.
- Exophytic/polypoid
- Anaemia (altered blood PR)
- Vague pain
- Weakness
- obstruction
Describe left sided colorectal adenocarcinoma.
- Annular (napkin ring lesion)
- Bleeding (fresh/altered blood PR)
- Altered bowel habit
- Obstruction
What determines the prognosis of CRC?
- Tumour grade
- TNM staging
- Extramural venous invasion
- Can it be resected?
