Histo: Lower GI Disease Flashcards
What are the general effects of bowel pathology?
- Disturbance of of normal function
- Bleeding
- Perforation / Fistula
- Obstruction
- Systemic illness
List some congenital disorders of the GI tract.
- Atresia/stenosis
- Duplication
- Imperforate anus
- Hirschsprung disease (MOST COMMON)
What is atresia?
Lack of connection between two parts of bowel
What is Hirschsprung disease?
How does it present?
The absence of ganglion cells of the myenteric plexus resulting in failure of dilatation of the distal colon
Presents with:
- Delayed passage of meconium
- Constipation
- Abdominal distension
- Vomiting
- Overflow diarrhoea
List some genetic associations of Hirschsprung disease.
- Down syndrome (2%)
- RET proto-oncogene mutation (chr 10)
How is Hirschsprung disease diagnosed?
Clinical impression from history and examination
Full thickness rectal biopsy (gold standard)
- Shows hypertrophied nerve fibres but no ganglia
- if ganglion cells seen = not Hirschprungs
How is Hirschsprung disease treated?
Resection of affected (constricted) segment (anorectal pull-through precedure)
Causes of Mechanical obstruction
- Adhesion
- Herniation
- Cancer
- Volvulus
What is a volvulus? What complications does it cause
Twisting of a loop of bowel at the mesenteric base around a vascular pedicle
Causes bowel obtruction +/- infarction
Which part of the intestines tend to be affected by volvulus in infants and the elderly?
Infant - small bowel
Elderly - sigmoid colon
Describe the pathophysiology of diverticular disease
Which part of bowel is most commonly affected?
What is a risk factor for developing diverticular disease?
- High intraluminal pressure leads to herniation of the bowel mucosa through weak points in the bowel wall (usually sites of entry of nutrient vessels)
- 90% in left colon (specifically sigmoid)
- Associated with low-fibre diet
What are some complications of diverticular disease?
- Pain
- Diverticulitis
- Perforation
- Fistula
- Obstruction
List some causes of acute colitis.
- Infection
- Drugs/toxins (especially antibiotics)
- Chemotherapy
- Radiation
List some causes of chronic colitis
- Crohn’s
- Ulcerative colitis
- TB
List some infectious causes of colitis
- Viral e.g. CMV
- Bacterial e.g. Salmonella
- Protozoal e.g. Entamoeba histolytica
- Fungal e.g. Candida
List the effects of infection on the colon.
- Secretory diarrhoea (due to toxin)
- Exudative diarrhoea (due to invasion and mucosal damage)
- Severe tissue damage and perforation
- Systemic illness
What is pseudomembranous colitis?
Antibiotic-associated colitis characterised by acute colitis with pseudomembrane formation
Caused by C. difficile exotoxins
pseudomembrane = membrane formed by inflammatory tissue
How can C. difficile colitis be diagnosed?
- Lab - toxin stool assay
- Histology - characteristic features on biopsy
Always considered in hospital - precipitated by ABx
(Clindamycin, Cephalosporins)
How is pseudomembranous colitis treated?
Vancomycin
What can causes both acute and chronic colitis?
Ischaemia
IBD
Where in the intestines does ischaemic colitis tend to occur? Give 2 examples.
Watershed zones - areas that receive dual blood supply from the most distal branches of two large arteries
- Splenic flexure - SMA and IMA
- Rectosigmoid - IMA and internal iliac
How can ischaemic colitis be classified?
- Mucosal
- Mural
- Transmural (perforation)
List the potential causes of ischaemic colitis.
- Arterial occlusion - atheroma, embolism
- Venous occlusion - thrombus
- Small vessel disease - diabetes mellitus, vasculitis
- Low flow states - CHF, shock, haemorrhage
- Obstruction - hernia, intussusception, volvulus, adhesions
What are some clinical features of IBD?
- Diarrhoea (bloody in UC)
- Fever
- Abdominal pain
- Anaemia
- Weight loss
- Perforation
- Extra-intestinal manifestations
Describe the epidemiology of Crohn’s
- Mainly affects white people
- Onset typically late teens - 20s
List some characteristic features of Crohn’s disease.
- Can affect whole GI tract (mouth to anus)
- Skip lesions with cobblestone mucosa
- Transmural inflammation
- Non-caseating granulomas
- Fissure/sinus/fistula formation
- Bowel wall is thickened
- Mostly affects large bowel and terminal ileum
List some extra-intestinal features of Crohn’s.
- Arthritis
- Uveitis
- Stomatitis/cheilitis
- Skin lesions - pyoderma gangrenosum, erythema multiforme, erythema nodosum
Describe the epidemiology of UC
- Slightly more common that Crohn’s
- Mainly affects white people
- Onset typically 20-25 years
List some characteristic features of ulcerative colitis.
- Involves rectum and colon in a continuous fashion (starts at rectum)
- May see backwash ileitis (involvement of the terminal ileum)
- Inflammation is confined to the mucosa
- Shallow ulceration
- Bowel wall is normal thickness
List some complications of ulcerative colitis.
- Severe haemorrhage
- Toxic megacolon
- Adenocarcinoma (20-30x increased risk)
List some extra-intestinal manifestation of UC
- Arthritis
- Myositis
- Uveitis/iritis
- Skin lesion - erythema nodosum, pyoderma gangrenosum
- Primary sclerosing cholangitis
Which hepatobiliary condition is associated with UC?
Primary sclerosing cholangitis
NOTE: PSC is big risk factor for cholangiocarcinoma
List some types of tumour affecting the of colon and rectum
Non-neoplastic polyps
Neoplastic Epithelial Tumours
- Adenoma
- Adenocarcinoma
- Neuro-endocrine tumours - carcinoid (mainly affects small bowel)
Mesenchymal lesions
- Lipoma
- Leiomyoma
Lymphoma
What is a polyp?
A growth that protrudes into the lumen of an organ
List some non-neoplastic and neoplastic polyps of the colon and rectum
Non-neoplastic
- Hyperplastic and sessile serrated lesions
- Inflammatory pseudopolyps seen in UC
- Hamartomatous polyps (Peutz-Jeghers)
Neoplastic
- Adenoma
- Adenocarcinoma
What are sessile serrated lesions?
Type of hyperplastic polyp with architectual abnormalitis that may be premalignant and show dyplasia
What are adenomas? What are the types of adenoma?
Benign tumours that characterised by excessive epithelial proliferation and may be dysplastic
- Tubular
- Tubulovillous
- Villous (highest risk of carcinoma)
What are the risk factors for cancer in an individual adenoma polyp?
- Size (>4cm = 45%)
- Proportion of villous component (finger-like projections)
- Degree of dysplasia
List some observations that have given rise to adenoma-carcinoma sequence theory.
- Areas with a high prevalence of adenomas have a high prevalence of carcinoma
- Adenomas tend to appear 10 years before a carcinoma
- Risk of cancer is proportional to the number of adenomas
What are some genetic causes of colon cancer?
Familial adenomatous polyposis
- Gardner’s
- Turcot
Hereditary non-polyposis colon cancer (Lynch syndrome)
All are autosomal dominant
What is Lynch syndrome (HNPCC)?
- Autosomal dominant condition
- Affects DNA mismatch repair genes - MSH2 most commonly affected
- Associated with increased risk of colorectal, endometrial, gastric, and ovarian cancers
What is familial andeomatous polyposis?
- Autosomal dominant condition
- Caused by mutation in APC tumour supressor gene (chr 5)
- Characterised by numerous (average 1000) colorectal polyps
- Virtually 100% will develop colorectal cancer within 10-15 years
What is Gardner’s syndrome?
FAP plus extra-intestinal manifestations e.g.
- Cranial osteomas
- Desmoid tumours
- Epidermoid cysts
Where does colon cancer typically arise in HNPCC?
Colon cancer typically arises proximal to splenic flexture (proximal colon) and is typically poorly differentiated
Describe the epidemiology of colorectal cancer?
- 98% are adenocarcinoma
- Average age affected is 60-79
- If <50 years consider familial syndrome
- Primarily affects western population
List some risk factors for colorectal cancer
- Familial
- Diet (low fibre, high fat)
- Lack of exercise
- Obesity
List some prediposing conditions to colorectal cancer
- Adenomas
- IBD
What are the symptoms of CRC?
- Change in bowel habit
- Blood in stool
- Anaemia
- Weight loss
- Pain
Describe the grading and staging of CRC?
- Grade - degree of differentiation
- Staging - TMN
List some types of stromal lesions that occur in the GI tract.
- Stromal tumours
- Lipoma
- Sarcoma
- Other: lymphoma
