Theme 11 L2: Lower GI Pathology Flashcards
What is diverticulosis of the colon?
protrusions of mucosa and submucosa through the bowel sall
Which part of the colon does diverticulosis usually occur?
sigmoid colon - located between the mesenteric and anti-mesenteric taenia coli
What are the two types of diverticula of the large bowel?
- True “congenital” diverticulum
2. Acquired / “false”/ “pseudo” diverticulum
What food group in the diet are diverticula associated with?
fibre content
What is the pathogenesis of diverticula of the large bowel?
- increased intra-luminal pressure
- irregular, unco-ordinated peristalsis
- over lapping (valve like) semi circular arcs of bowel wall - Points of relative weakness in the bowel wall
What are the clinical features of diverticular disease?
- asymptomatic in 90%
- cramping abdo pain
- alternating constipation and diarrhiea
What are the acute complications of diverticular disease?
- diverticulitis/ peri diverticular abscess
- perforation
- haemorrhage
How does diverticulitis or a peridiverticular abscess arise?
- faeces get stuck in diverticulum
- bacteria accumulates
- causes inflammation or an abscess
What are the chronic complications of diverticular disease?
- intestinal obstruction
- fistula
- diverticular colitis
- polypoid prolapsing mucosal folds
What is colitis?
- inflammation of the colon
- usually mucosal inflammation
- occasionally transmural e.g Chron’s
What are the types of acute colitis?
- Acute infective colitis e.g campylobacter, salmonella
- antibiotic associated colitis
- Drug induced colitis
- Acute ischaemic colitis (transient or gangrenous)
What are the two types of chronic colitis?
- Chronic idiopathic inflammatory bowel disease
2. Ischaemic colitis
What are the 3 types of idiopathic inflammatory bowel disease?
- ulcerative colitis
- crohn’s disease
- unclassified and indeterminate colitis
What are the risk factors for the different IBD?
- CD is more common in females, UC has equal incidence
- Cigarette smoking is a risk factor for CD, but a protective factor from UC
- Oral contraceptive
What is the clinical presentation of a patient with Ulcerative colitis?
- diarrhoea with urgency/ tenesmus
- rectal bleeding
- abdominal pain
- anorexia
- weight loss
- anaemia
What are the complications of ulcerative colitis?
- toxic megacolon and perforation
- haemorrhage
- stricture
- carcinoma
What is the clinical presentation of Crohn’s disease?
- chronic relapsing disease
- affects all levels of GIT from mouth to anus
- bloody diarrhoea
- abdominal pain/ mass
- weight loss/ failure to thrive
- anorexia
- fever
- oral ulcers
- peri-anal disease
- anaemia
What are the top 3 sites that Crohn’s disease occurs?
- Ileocolic
- Small bowel
- Colonic
What is a characteristic feature of Crohn’s disease?
skip lesions - unequal distribution around the GI tract
What are the complications of Crohn’s?
- toxic megacolon (colonic distension)
- perforation
- fistula
- stricture
- haemorrhage
- carcinoma
- short bowel syndrome (repeated resection)
What are some extra intestinal manifestations of IBD?
- Hepatic
- fatty change and granulomas
- PSC and bile duct carcinoma - Osteo-articular
- polyarthritis
- sacro-ileitis & ankylosing spondylitis - Muco-cutaenous
- oral ulcers
- pyoderma gangrenosum & erythema nodosum - Ocular
- uveitis and retinitis - Systemic
- amyloidosis
- thrombo-embolic disease
What are the risk factors of ColoRectal Cancer in UC?
- early age of onset
- duration of disease > 10 years
- total or extensive colitis
- PSC
- family history of CRC
- severity of inflammation
- presence of dysplasia
Explain the development of UC to colorectal cancer?
- inflammed mucosa
- low grade dysplasia
- high grade dysplasia
- colorectal cancer
What is ischaemic colitis?
- colonic injury secondary to a acute, intermittent or chronic reduction in flow
- may be occlusive or non-occlusive
What are the 3 clinical forms of ischaemic colitis?
- Transient - acute onset cramping abdominal pains; urge to defaecate; bloody diarrhoea
- Chronic segmental ulcerating (ischaemic stricture)
- Acute fulminant and gangrenous
What are the 3 causes of mesenteric ischaemia?
- Arterial embolism
- Arterial thrombosis
- Non-occlusive mesenteric ischaemia
What is a colorectal polyp?
- a ‘mucosal protrusion’
- solitary or multiple (polyposis)
- pedunculated, sessile or “flat”
How are colorectal polyps classified?
- neoplastic
- hamartomatous
- inflammatory
- reactive
What are the commonest non-neoplastic polyp in the colo-rectum?
hyperplastic polyps
Where are hyperplastic polyps located?
in the rectum and the sigmoid colon
Why is a small, distal hyperplastic polyp safer than a large hyperplastic polyp?
-small, distal HPs have no malignant potential
What are the two types of hamartomatous polyps?
- Juvenile polyps
2. Peutz-Jeghers poylps
What is the classical appearance of a juvenile polyp?
-often spherical and pedunculated
What is the most common type of polyp in children?
juvenile polyp
Where do juvenile polyps typically occur?
rectum and distal colon
Do juvenile polyps have malignant potential?
- sporadic polyps do not have malignant potential
- juvenile polyps associated with increased risk of gastric and colorectal cancer
What is Peutz-Jeghers syndrome?
- autosomal dominant condition
- mutation in STK11 gene on chromosome 19
- very rare
How does Peutz-Jeghers syndrome present?
- in teens/20s
- with abdo pain, GI bleeding, anaemia, increased risk of cancer
- multiple GIT polyps (predominanatly small bowel)
- muco-cutaneous pigmentation
Which benign epithelial tumour a precursor of colorectal cancer in at least 80% of cases?
adenomas
What features of an adenoma are associated with a higher risk of malignant change?
- “flat” adenomas
- > size
- villous and tubule-villous
- severe (high grade) dysplasia
- lynch syndrome associated adenomas
What are the risk factors for colorectal cancer?
- diet
- dietary fibre, fat, red meat, folate, calcium
- obesity
- alcohol
- NSAIDs & aspirin
- HRT and oral contraceptives
- schistosomiasis
- pelvic radiation
- UC and Crohn’s
What is FAP?
- autosomal domianant familial adenotomatous polyposis
- associated with multiple benign adenomatous polyps in the colon
FAP is due to a mutation in which gene?
APC tumour suppressor gene
What is Lynch syndrome?
- autosomal dominant
- 60% lifetime risk of small bowel cancer
- due to mutations in DNA mismatch repair genes
- increased risk of endometrial, ovarian, gastric, small bowel, urinary tract and biliary tract cancer
Where do 2/3rds of colorectal cancers occur?
left colon between splenic flexure and rectum
what type of tumour are 95% of colorectal cancers?
adenocarcinoma (glandular/ producing mucin)
What are the 4 stages of Dukes staging of colorectal cancer?
Stage A: adenocarcinoma confined to the bowel wall with no lymph node metastasis
Stage B: adenocarcinoma invading through the bowel wall with no lymph node metastasis
Stage C: adenocarcinoma with regional lymph node metastasis regardless of depth of invasion
Stage D: distant mets present
