Week 6 - Lower Gastrointestinal Disease Flashcards
What is the function of the large intestine and rectum?
- part of the digestive tract
- most digestion and absorption already done at this stage
- mainly absorbs water and electrolytes to form a solid stool
What is acute appendicitis?
- sudden onset inflammation of the appendix
- acute bacterial infection of the appendix precipitated by the obstruction of the lumen (fecalith, calculus, tumour or worms) causing increased intraluminal pressure
What are the clinical signs and symptoms of appendicitis?
- classically pain begins in the umbilical region of the abdomen which migrates to the right lower abdomen
- on examination there is often tenderness in the right quadrant, with involuntary guarding on palpating, due to localised peritonitis
Visceral vs. parietal pain
- the sensory innervation of abdominal viscera is much less than that of other parts of the body such as skin, linings of the abdominal and thoracic cavities (parietal)
- visceral pain = referred pain - pain is felt in a different location to where the pathology is
- parietal pain = much more localised
What is the difference between localised and generalised peritonitis?
- peritoneum is the lining of the abdominal cavity and the lining of the organs within the abdominal cavity
- peritonitis is inflammation of this cavity due to a variety of causes, most commonly infection
- in appendicitis the inflamed appendix on coming in contact with the abdominal wall causes localised peritonitis
How is acute appendicitis treated?
Surgery and/or antibiotics
What is pseudomembranous colitis?
- antibiotic associated colitis
- acute inflammation of the colon characterised by the formation of plaque like fibrinous exudate (pseudomembranes) overlying the sites of mucosal injury/parts of the large intestinal mucosa
What is pseudomembranous colitis caused by?
A toxin produced by an overgrowth of C.diff, replacing the normal intestinal flora
-usually happens because the competing bowel organisms were eliminated by broad spectrum antibiotics
What are the symptoms of pseudomembranous colitis?
- typically develops in patients treated with broad spectrum antibiotics
- fever and lower abdominal tenderness
How is pseudomembranous colitis treated?
- discontinuation of abx
- hydration
- specifical antibacterial therapy
What is inflammatory bowel disease?
-chronic inflammatory conditions of unknown aetiology affecting the GI tract
What are the two main forms of idiopathic IBD (inflammatory bowel disease)?
- Crohn’s disease
- ulcerative colitis
What is the pathogenesis of idiopathic inflammatory bowel disease?
- genetics
- environment
- constitutional susceptibility
What does Crohn’s disease affect?
- affects from mouth to anus: particularly terminal ilium (30%), colon alone (20%), and ilium and colon (50%)
- skip lesions (not continuous) - intervening uninvolved areas
- often perianal skin involvement (75%)
What is the pathology of Crohn’s disease?
- mucosal ulceration - typically fissuring
- oedema of adjacent epithelium (cobblestone)
- pseudopolyp formation regeneration
- transmural inflammation:
- active chronic inflammation with non-ceseating epithelioid granulomas
- can have fistula formation
What are the complications of Crohn’s disease?
- anaemia (megaloblastic from B12 deficiency, hypo chromic microcytic from iron deficiency)
- malabsorption - fat, vitamins A, D, E, K, bile salts
- fistulas
- extra-intestinal - skin, eyes, joints (ankylosing spondylitis)
- increased risk of bowel carcinoma
- bowel obstruction and perforation
Describe ulcerative colitis
- colon only
- starts in rectum - spreads proximally
- continuous disease (no skip lesions)
- mucosal disease (no transmural involvement)
- may involve whole colon, also appendix
What are the complications of ulcerative colitis?
- anaemia - iron deficiency from blood loss
- electrolyte loss from diarrhoea
- extra-intestinal disease: skin, eyes, joints, bile ducts (PSC)
- increased risk of carcinoma: related to duration and severity of disease
- need for surveillance for dysplasia
What are the mimics of IBD?
- ischaemic colitis
- radiation colitis
- Behçet’s disease
- pouchitis
- diversion colitis
- microscopic (lymphocytic/collagenous) colitis
- infectious colitis
- latrogenic colitis
Name the types of neoplasia that can occur in the lower GI tract
- benign polyps - adenomas
- malignant adenocarcinoma (cancer)
-different stages/grades of adenocarcinoma affect prognosis and treatment
What are the factors that could trigger colorectal carcinoma?
Genetic factors - (familial adenomatous polyposis, lynch syndrome (hereditary non-polyposis colorectal cancer)
Chronic inflammation - IBD - UC, Crohn’s
Dietary factors (?low fibre, ? Bile aerobes, ?rdped meat, ?lack of vitamins, antioxidants)
What is the national bowel cancer screening (NBCSP) programme?
- all population 60-75 years
- faecal occult blood test (FOBT)
- if +ve - refer to colonoscopy
- look for polyps (adenomas) and carcinomas
- refer for definitive treatment
What are the signs and symptoms of colorectal carcinoma?
- depends of the site of the lesion
- altered bowel habit
- blood PR
- iron deficiency anaemia
- weight loss
- disease can be advanced at the time of the presentation
What can colorectal carcinomas be (gross)?
- ulcerating
- polypoid/fungating
What is an adenoma?
Benign tumour of glandular epithelium
What do almost all carcinomas arise from?
- benign adenomas - polyps
- the more polyps the greater the risk
Describe the spread of colorectal carcinoma
- dukes stage A (above muscle layer - 5yr survival 95%)
- dukes stage B (into serosal fat, LN negative - 5 yr survival 66%)
- dukes stage C (LN involvement - 33% 5yr survival)
Describe the T (primary tumour) part of the TNM system for colorectal carcinoma
Primary tumour Tx - not assessable T0 - no primary tumour Tis in situ - intraepithelial or intra-mucosal T1 - submucosa T2 - muscularis propria T3 - subserosa, perirectal tissues T4 - perforated visceral peritoneum (a) or invades other organs (b)
Describe the N (regional lymph nodes) part of the TNM system for colorectal carcinoma
NX - not assessable
N0 - no LN metastases
N1 - 1-3 LN+
N2 - >4 LN+
Describe the M (distant metastases) part of the TNM system for colorectal carcinoma
MX - not assessable
M0 - no distant metastases
M1 - distant metastases
Name the parts of the lower GI tract
Large intestine
- ascending colon
- transverse colon
- sigmoid colon
- rectum
- anus
- appendix
