Pathology of Colon Flashcards
What is the function of the small bowel?
Absorptive role
What are the functions of the large bowel?
Absorptive and secretory role
How long is the small bowel?
Approximately 6m long
How long is the duodenum?
25cm
What are the 3 parts of the small bowel?
Duodenum
Jejunum
Ileum
What are the different parts of the large bowel?
Caecum
Ascending colon
Transverse colon
Descending colon
Sigmoid colon
Rectum
How long is the rectum?
15cm
What are the different layers of the small bowel wall?
Mucosa
Submucosa
Muscularis propria
Subserosa
What are the layers of the mucosa in small bowel?
Epithelium
Lamina propria
Muscularis mucosa
What cell types are in the mucosa of the small bowel?
Goblet cells
Columnar absorptive cells
Endocrine cells
What is embedded within the mucosa of the small bowel?
Crypts that contain stem, goblet, endocrine and paneth cells
What are the projections from the epithelium of the small bowel?
Villi
What is the muscularis propria also known as?
Muscularis externa
How often is the wall of the small bowel renewed?
Every 4 to 6 days
What is different about the villi of the small bowel and the large bowel?
The large bowel does not contain any villi
What shape is the top of cells in the large bowel?
Flat, no villi
What shape are crypts in the large bowel?
Tubular
What is the difference between crypts in the small intestine and large intestine?
Crypts in the large intestine do not contain paneth cells
What is a consequence of the GI tract having a large surface area?
Large exposure to environment antigens so immune system must balance harmless ingested substances against active defect 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 from?
Meissener’s plexus (base of submucosa)
Auerbach plexus (between the inner circular and outer longitudinal layers of the muscularis propria)
Where is the Meissener’s plexus found?
Base of submucosa
Where is the Auerback plexus?
Between the inner circular and outer longitudinal layers of the muscularis propria
What are examples of pathologies of the lower GI tract?
Inflammatory bowel disease (IBS)
Large bowel neoplasia
What does IBD stand for?
Inflammatory bowel disease
What is inflammatory bowel diseases the pathological feature of?
Ulcerative colitis
Crohn’s disease
Ischaemic colitis
Radiation colitis
Appendicities
What is idiopathic inflammatory bowel disease?
Chronic inflammatory condition resulting from inappropriate and persistent activation of the mucosal immune system driven by the presence of normal intraluminal flora
What are the 2 main diseases of inflammatory bowel disease?
Crohn’s disease
Ulcerative colitis
What is the difference in where Crohn’s and ulcerative colitis can affect the GI tract?
Crohn’s can affect ny part of the GIT from mouth to the anus
Ulcerative colitis is limited to the colon
What is the pathogenesis of inflammatory bowel disease?
Strong immune response against normal flora with defects in the epithelial barrier function in genetically susceptible individuals
What percentage of people with IBD have an affected 1st degree relative?
15%
What gene mutation is associated with Crohn’s disease?
NOD2
What gene mutation is associated with ulcerative colitis?
HLA
What is the role of intetinal flora for IBD?
Specific microbe not yet identified
Defects in mucosal barrier could allow microbes access to mucosal lymphoid tissue triggering immune response
How is IBD diagnosed?
Requires clinical history, radiographic examination and pathological correlation
What is pANCA?
Perinuclear antineutrophilic cytoplasmic antibody
How does pANCA differ between Crohn’s and ulcerative colitis?
Postive in 75% of ulcerative colitis
Positive in 11% of Crohn’s disease
How does the incidence of ulcerative colitis change between males and females?
Affected equally
What age groups does ulcerative colitis peak?
20-30 years and 70-80 years
What is ulcerative colitis that is localised to the rectum called?
Proctitis
Where is ulcerative colitis more commonly spread?
Proximally
Can the appendix be involved in ulcerative colitis?
Yes
What is the pathology of ulcerative colitis?
Continuous pattern of inflammation
Pseudopolyps
Ulceration
Serosal surface has minimal or no inflammation
What are pseudopolyps?
Projecting masses of scar tissue that develop from granulation tissue during the healing phase in repeated cycles of ulceration
What does ulcerative colitis histology show?
Mucosa shows inflammation
Cryptitis
Crypts abscesses
Architectural disarray of crypts
Mucosal atrophy
Ulceration into submucosa
No granulomas
Where is inflammation due to ulcerative colitis limited to in the gut wall?
Mucosa and submucosa
Are granulomas present in ulcerative colitis?
No
What is a granuloma?
Mass of granulation tissue
What is granulation tissue?
New connective tissue and microscopic blood vessels that form during the healing process
What is a form of ulcerative colitis that affects the entire bowel?
Pancolitis
How does having pancolitis for more than 10 years change the risk for developing cancer?
20-30x normal
What are some complications of ulcerative colitis?
Hemorrhage
Perforation
Toxic dilation
Where in the GIT can Crohn’s disease affect?
Anywhere from the mouth to the anus
Is the incidence of Crohn’s disease increasing or decreasing?
Increasing
What is the pathology of Crohn’s disease?
Mesentery is thickened, oedematous and fibrotis
Narrowing of lumen
Shrp demarcation of disease segments from adjacent normal tissue “skip lesions”
Ulceration, cobblestone effect
What can be seen in Crohn’s disease histology?
Cryptitis and crypt abscesses
Architectural distortion
Atrophy, crypt destruction
Deep ulceration
Transmural inflammation
Non-caseating granulomas
Fibrosis
Lymphangiectasia
Hypertrophy of mural nerves
Paneth cell metaplasia
What is inflammation of an intestinal crypt called?
Cryptitis
What are long term features of Crohn’s disease?
Small intestine malabsorption
Strictures
Fistulas and abscesses
Perforation
How does Crohn’s disease change the risk of developing cancer?
5x risk compared to matched population
What are the macroscopic differences between Crohn’s disease and ulcerative colitis?
What are the microscopic differences between Crohn’s disease and ulcerative colitis?
What is ischaemic enteritis?
Blood flow to part of the colon is reduced, usually due to narrowed or blocked arteries
What can ischaemic enteritis be caused by?
Anatomical occlusion of the mesenteric microvasculature or pathophysiologic vasospasm at the microscopic level
Where are ischaemic lesions found in ischaemic enteritis?
Either small or large intestine, or both depending on what vessel is affected
What does acute occlusion of one of the 3 major supply vessels lead to?
Infarction
What is infarction?
Obstruction of a blood vessel causing local death of a tissue
Is mesenteric venous or arterial occlusion more common?
Arterial occlusion
Why does gradual occlusion of intestinal blood supply have little effect?
Due to anastomotic circulation
What are some predisposing conditions for ischaemic enteritis?
Arterial thrombosis
Arterial embolism
Non-occlusive ischaemia
What can cause arterial thrombosis?
Severe atherosclerosis
Systemic vascultitis
Dissecting aneurysm
Hypercoagulable states
Oral contraceptives
What can cause arterial embolism?
Cardiac vegetations
Acute atheroembolism
Cholesterol embolism
What can cause non-occlusive ischaemia?
Cardiac failure
Shock/dehydration
Vasoconstrictive drugs such as propranolol
What part of the colon is most vulnerable to acute ischaemia?
Splenic flexure
What is the histology for acute ischaemia of the colon?
Oedema
Interstitial haemorrhages
Sloughing necrosis of mucosa-ghost outlines
Nuclei indistinct
Initial absence of inflammation
1-4 days bacteria gangrene and perforation
Vascular dilation
What does chronic ischaemia of the colon cause?
Mucosal inflammation
Ulceration
Submucosal inflammation
Fibrosis
Stricture
What is radiation colitis?
Inflammation of small or large bowel due to radiation from treatments
Radiation to what organs can cause radiation colitis?
Stomach
Sexual organs
Rectum
Radiation to where most commonly causes radiation colitis?
Rectum-pelvic radiotherapy
What does the damage of radiation colitis depend on?
Dose of radiation that caused it
What are the symptoms of radiation colitis?
Anorexia
Abdominal cramps
Diarrhoea
Malabsorption
What does the presentation of chronic radiation colitis mimic?
Inflammatory bowel disease
What is the histology of radiation colitis?
Bizarre cellular changes
Inflammation causes crypt absceses and eosinophils
Later on arterial stenosis occurs
Ulceration
Necrosis
Haemorrhage
Perforation
What is inflammation of the appendix called?
Appendicitis
What is the average size of the appendix?
6-7cm
What is the appendix?
Prominant lymphoid tissue
What happens to the appendix with age?
It regresses
What does appendicitis cause for the appendix?
Fibrous obliteration
What is appendicitis a form of?
Acute inflammation that is caused due to obstruction
How can appendicitis lead to ischaemia?
Causes increased intraluminal pressure
What is the histology of appendicities?
Fibrinopurulent exudate
Perforation
Abscess
Acute suppurative inflammation in wall and pus in lumen
Acute gangrenous, causing full thickness necrosis with or without perforation
What is a large bowel neoplasia?
Epithelial polyps
What are polyps?
Abnormal tissue growths
What is dysplasia?
Presence of cells of an abnormal type within a tissue
What are the 2 stages of large bowel neoplasia?
High grade
Low grade
What can be seen in high grade large bowel neoplasia?
Increased nuclear number
Increased nuclear size
Reduced mucin
What can be seen in low grade large bowel neoplasia?
Crowded
Very irregular
What can large bowel neoplasia lead to?
Colorectal cancer
What is the most common histological type of colorectal carcinoma?
Adenocarcinoma (98%)
What are risk factors for colorectal carcinoma?
Lifestyle
Family history
IBD
Genetics
What gene mutations are linked to colorectal carcinoma?
FAP
HNPCC
Peutz-Jeghers
What percentage of dysplasia in the colon are solitary?
50%
What is the clinical presentation of left sided colorectal adenocarcinoma?
Annular lesions (ring shaped)
Bleeding
Altered bowel habit
Obstruction
What are is the clinical presentation of right side colorectal adenocarcinoma?
Anaemia
Vague pain
Weakness
Obstruction
What does prognosis of colorectal carcinoma depend on?
Tumour grade
Tumour stage
Extramural venous invasion
Resection
What are the different systems for classifying colorectal carcinoma?
TNM
Dukes
What are the different aspects of TNM classification?
T 1-4
N 0-3
M 0-1
What does Dukes classification consider?
How far into the lumen wall the tumour is
What are the different grades for dukes classificaion?
A (inner lining or slightly growing into muscularis externa)
B (grown through muscularis externa)
C (spread to at least one lymph node close to bowel)
D (spead to another part of the body)
