Pathology of The Colon Flashcards
Which portion of the rectum is extraperitoneal?
The distal 7 cm
What are the three types of cell in the small intestine?
Goblet cells
Columnar absorptive cells
Endocrine cells
What is within the crypts of the small intestine?
Cells: stem, goblet, endocrine and Paneth
Paneth cells are responsible for the production of antimicrobial peptides
What is contained within the crypts of the large intestine?
Crypts-goblet cells, endocrine cells, stem cells turnover 3-8 days
What does the intestinal immune system balance up?
The tolerance for harmless ingested substances and potential microbial invaders
What is the neuromusclular control of the bowel (large and small)
Peristalsis is mediated by intrinsic (myenteric plexus) and extrinsic (autonomic innervation) neural control
What does the myenteric plexus consist of?
Meissener’s plexus: base of the submucosa
Auerbach plexus: between the inner circular and outer longitudinal layers of the muscularis propria
In what conditions might inflammatory bowel disease be seen?
Ulcerative colitis
Crohn’s disease
Ischaemic colitis
Radiation colitis
Appendicitis
What is idiopathic IBD?
Chronic inflammatory conditions resulting from inappropriate and persistent activation of the mucosal immune system driven by the presence of normal intraluminal flora
(Basically when the gut responds to harmless bacteria over a long period of time)
What are the two main causes of inflammatory bowel disease?
Ulcerative collitis
Crohn’s disease
Where do both:
- Crohn’s disease
- Ulcerative colitis
Affect the GI tract
CD can affect any part of the GIT from the mouth to the anus
UC limited to colon
Why is IBD linked genetically?
Possible genetic defects in epithelial barrier function
15% have affected 1st degree relatives
NOD2 gene mutation is seen in association with CD
HLA associations in UC
How can intestinal flora access the mucosal lymphoid tissue?
As a result of a defect in the mucosal barrier, allowing microbes access to mucosal lymphoid tissue triggering immune response
What is the diagnosis of IBD?
Requires clinical history, radiographic examination and pathological correlation
pANCA( perinuclear antineutrophilic cytoplasmic antibody)
- positive in 75% of UC patients
- BUT only 11% of CD patients.
Where does ulcerative collitis normally invest itself?
Can be localised to the rectum (proctitis)
More commonly spreads proximally
Associated with systemic manifestations
How does inflammations affect the colon?
Pseudopolyps (Pseudopolyps are projecting masses of scar tissue that develop from granulation tissue during the healing phase in repeated cycle of ulceration)
Ulceration
Serosal surface minimal or no inflammation
What are the histological findings in ulceratve collitis?
Mucosa – inflamamtion and atrophy
Crypts: Cryptitis, Crypt abscesses, Architectural dissarray of crypts
Submucosa: Fibrosis and ulceration (Pseudopolyps)
Limited mainly to mucosa and submucosa
NO granulomas
What might happen as a result of flat epithelial atypia in UC?
Atypia: structural abnormality in a cell
Adenomatous change and consequent invasive cancer
What is the risk of developing cancer if you have pancolitis?
20-30 x higher risk of developing cancer.
What are other complications of UC?
Haemorrhage
Perforation
Toxic dilatation
Who is more affected by Crohn’s?
Females > males
Any age including childhood
Peaks 20-30 years and also 60-70 years
More common in Caucasians 2-5x
3-5x more common in the Jewish population
Which part of the intestine does Crohn’s disease normally manifest?
40% SI, 30% SI and LI , 30% Colon
What is the serosa like in Crohn’s disease?
Granular / dull grey
What is the mesentry like in crohn’s disease?
Thickened, oedematous and fibrotic
What is the lumen like in Crohn’s disease?
Narrow
Cobblestone appearance as a result of deep ulceration and thickening of the intestinal wall
What are the histological findings for Crohn’s disease?
Crypts: Cryptitis, abscesses, architectural distortion, atrophy - crypt destruciton
Deep ulceration
Inflammatino: Transmural
Non-caseating granulomas
Fibrosis
Lymphangiectasia (pathologic dilation of lymph vessels)
Hypertrophy of mural nerves
Paneth cell metaplasia
What are long term features of chrohn’s disease?
SI – malabsorption
Strictures
Fistulas and abscesses
Perforation
Increased risk of cancer - 5x increased risk over the same age matched population.
Crohn’s vs Ulcerative Collitis
Where in the intestine can ischaemic enteritis affect?
Ischaemic lesions can be restricted to either the SI or LI or they can affect both depending on vessel affected
When can infarction offucur?
Acute occlusion of 1 of the 3 major supply vessels leads to infarction (Coeliac, Inferior and Superior mesenteric arteries)
Why might gradual occlusion of the major supply vessels not be a problem?
Anastomotic circulation
What thickness of infarcation is associated with ischaemic enteritis?
Transmural injury
What might predispose a patient to arterial thrombosis?
severe atherosclerosis
systemic vasculitis eg PAN,HSP,WG
dissecting aneurysm
hypercoagulable states
oral contraceptives
What might cause someone to be more susceptible to arterial embolisms?
cardiac vegetations
acute atheroembolism
cholesterol embolism
What might pre-dispose someone to non-occlusive ischaemia?
cardiac failure
shock /dehydration
vasoconstricive drugs eg propanolol
Which part of the GI tract is vulnerable to acute ischaemia?
Splenic flexure
What are the histological features of acute ischaemia?
Oedema
Interstitial haemorrhages
Sloughing necrosis of mucosa-ghost outlines
Nuclei indistinct
Initial absence of inflammation
1-4 days –bacteria-gangrene and perforation
Vascular dilatation
What is the result of chronic ischaemia?
Mucosal inflammation
Ulceration
Submucosal inflammation
Fibrosis
Stricture
What is radiation collitis?
Iflammation of the intestines that occurs after radiationtherapy
Impairs the normal proliferative activity of the small and large bowel epithelium
Usually rectum- pelvic radiotherapy
Damage depends on dose
Targets actively dividing cells esp. blood vessels
and crypt epithelium
What are symptoms of radiation collitis?
Anorexia; abdominal cramps; diarrhoea and malabsorption
What are the histological findings of radiation collitis?
Bizarre cellular changes
Inflammation-crypt abscesses and eosinophils
Later-arterial stenosis
Ulceration
Necrosis
Haemorrhage
perforation
What causes acute inflammation of the appendicitis?
Obstruction: ne.g. feocolith or Enterobius vermicularis
Feocolith: A hard stony mass of feces in the intestinal tract.
Increased intraluminal pressure: Ischaemia
What are the histological findings for appendicitis?
Macro- fibrinopurulent exudate, perforation, abscess
Micro-
Acute suppurative inflammation in wall and pus in lumen
Acute gangrenous-full thickness necrosis +/- perforation
What is the name given to large bowel malignant neoplasia?
Colorectal carcinoma
What form does dysplasia take in the colon?
Adenoma: polyps
What are the features of low grade dysplasia?
Increased nuclear nos.
Increased nuclear size
Reduced mucin
What are the features of high grade dysplasia?
Carcinoma in situ
Crowded
Very irregular
Not yet invasive
Carcinoma in situ (a group of abnormal cells) - controversy over whether or not they should be classified as cancer
Cells are still sitting on a basement membrane so are not quite yet invasive
What makes up 98% of colorectal cancers?
98% are adenocarcinomas
What are the risk factors for colorectal cancer?
Many risk factors
Lifestyle
Family history
IBD (UC & Crohn’s disease)
Genetics:
FAP
HNPCC
Peutz-Jeghers
What are the features of right sided colorectal cancer?
Exophytic/Polypoid
Anaemia
Altered blood PR
Vague pain
Weakness
Obstruction
Exophytic: Tending to grow outward beyond the surface epithelium from which it originates
Polypoid: Resembling or in the form of a polyp
What are the symptoms of left sided colorectal cancer?
Annular: Napkin ring lesion (a tumor that encircles a tubular structure of the body)
Bleeding
Fresh/altered blood PR
Altered bowel habit
Obstruction
