HISTO: Lower GI Disease Flashcards
What are the general effects of pathology of the large bowel?
- Disturbance of normal function (diarrhoea, constipation)
- Bleeding
- Perforation/fistula formation
- Obstruction
- Systemic illness
Name 4 congenital disorders of the large bowel. What is the most common?
- · Atresia/stenosis (e.g. duodenal atresia)
- · Duplication
- · Imperforate anus
- · Hirschsprung’s Disease (MOST COMMON CONGENITAL ABNORMALITY)
What is the cause of Hirschsprung’s disease? Who is most affected? What other conditions/genetics is it associated with?
- Caused by absence of ganglion cells of the myenteric plexus –> distal colon fails to dilate
- 80% of cases occur in male babies
- Associated with Down syndrome
- Associated genetic abnormality: RET proto-oncogene Cr10
How does Hirschsprung’s disease present? How is it diagnosed and treated?
Presentation: constipation, abdominal distension, vomiting, overflow diarrhoea
Diagnosis
- Clinical impression
- Full thickness biopsy of affected segment
- Hypertrophied nerve fibres but NO ganglia
Treatment
- Resection of affected (constricted) segment
What are the types of mechanical disorders of the large bowel?
- Obstruction
- · Adhesions
- · Herniation
- · Extrinsic mass
- · Volvulus
- Diverticular disease
What is volvulus and which part of the bowel is affected in different age groups?
- Complete twisting of a loop of bowel at the mesenteric base, around a vascular pedicle –> can lead to intestinal obstruction and infarction
- Affects the small bowel in CHILDREN
- Affects the sigmoid colon in the ELDERLY
What is the pathophysiology and complications of diverticular disease? Which side of the colon is most affected?
High intraluminal pressure leads to herniation of the bowel mucosa through weak points in the bowel wall (usually at points of entry of nutrient vessels)
90% occur in the left side of the colon
Complications
- Pain
- Diverticulitis
- Perforation
- Fistula (bowel, bladder, vagina)
- Obstruction
What are the risk factors for diverticular disease?
High incidence in the WEST
Associated with a low fibre diet
What are the causes of acute colitis?
Acute Colitis
- Infection (bacterial, viral, protozoal, fungal)
- Drug/toxin (especially antibiotics)
- Chemotherapy
- Radiotherapy
What are the causes of chronic colitis?
Chronic Colitis
- Crohn’s disease
- Ulcerative colitis
- TB
What are the effects of infection in the colon?
Effects of Infection in the Colon
- Secretory diarrhoea (caused by toxin)
- Exudative diarrhoea (invasion and mucosal damage)
- Severe tissue damage and perforation
- Systemic illness
What is shown? What are the causes?
Pseudomembraneous colitis
- · Antibiotic-associated colitis
- · Acute colitis with pseudomembrane formation
- · Caused by protein exotoxins of C. difficile
- · Characteristic microscopic appearance on biopsy
What is shown?
Pseudomembraneous colitis -
- Looks a bit like volcanoes exploding onto the surface
- The bits on the surface are the necrotic pseudomembranous regions full of pus and inflammatory cells
- C diff may be detected on a toxin stool assay
How do you treat pseudomembranous colitis?
Metronidazole or vancomycin
What is shown? Where does it usually occur?
Ischaemic colitis/infarction
- Acute or chronic
- Most common vascular disorder of the GI tract
- Usually occurs in segments in watershed zones (e.g. splenic flexure and the rectosigmoid)
- Extend can be mucosal, mural or transmural (leading to perforation)
What is the aetiology of ischaemic colitis?
- Arterial occlusion: atheroma, thrombosis, embolism
- Venous occlusion: thrombus, hypercoagulable states
- Small vessel disease: diabetes mellitus, cholesterol, vasculitis
- Low flow states: CCF, haemorrhage, shock
- Obstruction: hernia, intussusception, volvulus, adhesions
What is the aetiology of idiopathic chronic IBD?
- Uncertain
- Potential genetic predisposition
- Possibly infectious contribution (e.g. Mycobacteria, Measles)
- Possibly due to abnormal immunoreactivity
What are the features of chronic IBD?
- Diarrhoea with or without blood
- Fever
- Abdominal pain
- Acute abdomen
- Anaemia
- Weight loss
- Extra-intestinal manifestations
What is shown? Who is most affected/what are the risks?
CROHN’S DISEASE
More common in Western populations; peak onset in early 20s; more common in White people; can affect the entire GI tract from mouth to anus
Description:
- Skip lesions
- Transmural inflammation
- Non-caseating granulomas
- Sinus/fistula formation
- Most commonly affects the large bowel and terminal ileum
- Fat wrapping of the bowel
- Thick rubber-hose like wall
- Narrow lumen
- Cobblestone mucosa
- Linear ulcers
- Fissures
- Abscesses
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What are the extra intestinal features of Crohn’s disease?
- Arthritis
- Uveitis
- Stomatitis/cheilitis
- Skin lesions
- Pyoderma gangrenosum
- Erythema multiforme
- Erythema nodosum
What is shown? Who is most affected/what are the risk factors?
ULCERATIVE COLITIS
Slightly more common than Crohn’s disease; peak age 20-25 years; More common in White people
Description:
- Involves the rectum and colon in a contiguous fashion
- May see mild backwash ileitis (where the terminal ileum also gets inflamed)
- May see appendiceal involvement
- Small bowel and proximal GI tract is not affected
- Inflammation is confined to the mucosa
- Bowel wall is normal thickness
- Shallow ulcers
What are the complications of UC?
Severe haemorrhage
Toxic megacolon
Adenocarcinoma (20-30 x increased risk)
What are the extra-intestinal complications of UC?
Arthritis
Myositis
Uveitis/iritis
Erythema nodosum, pyoderma gangrenosum
Primary sclerosing cholangitis
List the tumours of the colon and rectum.
Non-neoplastic polyps
Neoplastic epithelial lesions
- Adenoma
- Adenocarcinoma
- Carcinoid tumour
Mesenchymal lesions
- Stromal tumours
- Lipoma
- Sarcoma
Lymphoma
What is this?
Type of non-neoplastic polym - hyperplastic
What are the types of polyps?
Non-neoplastic polyps
- Hyperplastic
- Inflammatory (pseudopolyps)
- Hamartomatous (juvenile, Peutz-Jeghers)
Neoplastic Polyps
- Tubular adenoma
- Tubulovillous adenoma
- Villous adenoma
What is this? What are the three types? Who is most affected?
Excess epithelial proliferation with dysplasia (this is abnormal growth that is moving towards cancer)
40-50% prevalence > 60 years
THREE types:
- Tubular
- Villous
- Tubulovillous
What is this?
tubular adenoma
What is this?
Villous adenoma
What are the risk factors for cancer from a polyp?
Size of polyp (> 4 cm = 45% invasive risk)
Proportion of villous component
Degree of dysplastic change within a polyp
What are the reasons for adenoma-carcinoma sequence?
- Areas that have a high prevalence of adenomas also have a high prevalence of carcinomas
- The distribution within the colon is similar
- Adenomas tend to appear about 10 years before carcinoma
- Residual adenomas may be found near a carcinoma
- Risk of cancer is proportions to the number of adenomas
- Screening and removal of adenoma reduces the risk of cancer
What are the symptoms of adenoma?
Aymptomatic or may bleed and cause anaemia
Name 3 familial syndromes characterised by polyps.
Peutz-Jeghers syndrome
Familial adenomatous polyposis (FAP)
- Gardner’s
- Turcot
Hereditary non-polyposis colorectal cancer (HNPCC)
What genetics causes FAP? What is the age of onset? What is the risk of cancer?
Autosomal DOMINANT
Genetics: APC tumour suppressor gene on chromosome 5q21
Average age of onset is 25 years
Characterised by large numbers of adenomatous polyps (mostly colorectal)
Minimum 100 polyps
Virtually 100% will develop cancer within 10-15 years
What is Gardner’s syndrome? What are the extra-intestinal manifestations?
Same clinical, pathological and aetiological features of FAP with high cancer risk
There are distinctive extra-intestinal manifestations:
- Multiple osteomas of the skull and mandible
- Epidermoid cysts
- Desmoid tumours
- Dental caries, unerrupted supernumerary teeth
- Post-surgical mesenteric fibromatoses
What is HNPCC? What are the genetics? What type of cancers are most common here and where are they usually found? What may NOT be found?
- Uncommon autosomal DOMINANT condition
- 3-5% of colorectal cancers
- 1 of 4 DNA mismatch repair genes are mutated
- Numerous DNA replication errors
- Onset of colorectal cancer at an early age
- High frequency of carcinomas proximal to the splenic flexure
- Poorly differentiated and mucinous carcinoma are more frequent
- Multiple synchronous cancers
- Presence of extra-colonic cancers (e.g. endometrium, prostate, breast, stomach)
- NOTE: you do NOT necessarily get polyps in this condition
What is shown?
Dark purple is bad
Colorectal carcinoma
What type are most colorectal carcinomas?
98% are adenocarcinomas
What are the risk factors for colorectal adenocarcinoma?
- Age 60-80 years (if < 50 years consider familial syndrome)
- More common in Western populations
- Diet (low fibre, high fat)
- Lack of exercise
- Obesity
- Familial
- Chronic inflammatory bowel disease
What are the symptoms of colorectal carcinoma?
- Bleeding
- Change in bowel habit
- Anaemia
- Weight loss
- Pain
- Fistula
What is grade? How are colorectal carcinomas staged?
Grade = extent of differentiation
Dukes’ Staging
- A = confined to bowel wall
- B = through bowel wall
- C = lymph node metastases
- D = distant metastases
TNM staging is used now
Why is staging of colorectal carcinoma important?
The staging determines the (1) treatment and also gives an idea of (2) prognosis
