Lower GI disease Flashcards
Summarise the ‘general effects’ of pathology in large bowel
- Disturbance of normal function (diarrhoea, constipation)
- Bleeding
- Perforation/fistula formation
- Obstruction
- +/- Systemic illness
Name some congenital disorders of the lower bowel
- Atresia/stenosis
- Duplication
- Imperforate anus
What are congenital atresias?
Congenital atresias is the absence or abnormal narrowing of an opening or passage in the body.
- What is Hirchsprung’s disease?
- Epidemiology?
- Signs and symptoms
- Underlying genetics
- Hirchsprung’s disease is a congenital condition where there is an absence of ganglion cells in the myenteric plexus, causing the distal colon to fails to dilate
- 80% are male, normaly diagnosed before the age of 5 years
- Constipation, abdominal distension, vomiting, ‘overflow’ diarrhoea
- Associated with Down’s syndrome
Underlying genetics - RET proto-oncogene Cr10+ others
What does this image show?
Hirchsprung’s disease
- How is Hirchsprung’s disease is diagnosed?
- What is the treatment?
- Diagnosis:
- Clinical impression
- Biopsy of affected segment
- Hypertrophied nerve fibers but no ganglia
- Treatment
* Resection of affected (constricted) segment with a frozen section
Name some mechanical disorders that cause obstruction
–Adhesions
–Herniation
–Extrinsic mass
–Volvulus
Define the mechanical disorder of Volvulus
Where does it occur in adults and infants?
Volvulus is a complete twisting of a loop of bowel at mesenteric base, around vascular pedicle. Causes intestinal obstruction +/- infarction
Infants: small bowel
Elderly: Sigmoid colon
Describe the pathogenesis of diverticular disease
–High incidence in West
–Low fibre diet
–High intraluminal pressure
–‘Weak points’ in wall of bowel
–90% occur in left colon
What does this barium enema show?
Diverticular disease
What are the complications of diverticular disease?
- Pain
- Diverticulitis
- Gross perforation
- Fistula (bowel, bladder, vagina)
- Obstruction
- Name some of the causes of Acute colitis
- Name some causes of Chronic colitis
- Acute colitis
- Infection - bacterial, viral, protozoal
- Drug/toxin esp. antibiotic
- Chemotherapy
- Radiation
2.Chronic colitis
- Crohn’s
- Ulcerative colitis
- TB
What are the effects of infection on the lower GI system?
- Secretory diarrhoea (toxin)
- Exudative diarrhoea (invasion and mucosal damage)
- Severe tissue damage + perforation
- Systemic illness
- What is pseudomembranous colitis?
- How is it diagnosed?
- What is the therapy/treatment?
1.
- Antibiotic associated colitis
- Acute colitis with pseudomembrane formation
- Caused by protein exotoxins of C.difficile
2.
- Histology: Characteristic microscopic features on biopsy
- Laboratory: C.difficile toxin stool assay
- Therapy:
* Metronidazole or Vancomycin
What does this image show?
Pseudomembranous colitis
Describe ischaemia colitis/infarction of the large bowel
–Acute or chronic
–Most common vascular disorder of the intestinal tract
–Usually occurs in segments in “watershed” zones, e.g. splenic flexure (SMA and IMA) and the rectosigmoid (IMA and internal iliac artery)
–Mucosal, mural, transmural (perforation)
Describe the aetiology of the different causes of ischaemia colitis
- Arterial occlusion
- Venous occlusion
- Small vessel disease
- Low flow states
- Obstruction
- Arterial Occlusion: atheroma, thrombosis, embolism
- Venous Occlusion: thrombus, hypercoagulable states
- Small Vessel Disease: DM, cholesterol emboli, vasculitis
- Low Flow States: CCF, haemorrhage, shock
- Obstruction: hernia, intussusception, volvulus, adhesions
What are the two main types of chronic inflammatory bowel disease?
- Crohn’s disease
- Ulcerative colitis
- Is usually a diagnosis of exclusion
What is the possible aetiology of chronic inflammatory bowel disease?
- Genetic predisposition (familial aggregation, twin studies, HLA )
- Infection (Mycobacteria, Measles etc)
- Abnormal host immunoreactivity
- ->Inflammation
What are the clinical features of chronic inflammatory bowel disease?
- Diarrhoea +/- blood
- Fever
- Abdominal pain
- Acute abdomen
- Anaemia
- Weight loss
- Extra-intestinal manifestations
Describe the epidemiology of Crohn’s disease
- Western populations
- Occurs at any age but peak onset in teens/twenties
- White 2-5x > non-white
- Higher incidence in Jewish population
- Smoking
What are the characteristic features in the bowel for Crohn’s disease?
- Whole of GI tract can be affected (mouth to anus)
- ‘Skip lesions’
- Transmural inflammation
- Non-caseating granulomas
- Sinus/fistula formation
Describe some of the histopathological features of crohn’s disease
- ‘Fat wrapping’
- Thick ‘rubber-hose’ like wall
- Narrow lumen
- ‘cobblestone mucosa’
- Linear ulcers
- Fissures
- abscesses
Describe some of the extra-intestinal conditions associated with Crohn’s disease
- Arthritis
- Uveitis
- Stomatitis/cheilitis
- Skin lesions
–Pyoderma gangrenosum
–Erythema multiforme
–Erythema nodosum
What does this image show?
Crohn’s disease - inflammatory cells, and ceasating granulomas that can occur anywhere within the bowel
Describe the epidemiology of ulcerative colitis
- Slightly more common than Crohn’s
- Whites > non-whites
- Peak 20-25 years but can affect any age
Describe what is affected in UC and how it presents on endoscopy
- Involves rectum and colon in contiguous fashion.
- May see mild ‘backwash ileitis’ and appendiceal involvement but small bowel and proximal GI tract not affected.
- Inflammation confined to mucosa
- Bowel wall normal thickness
- Shallow ulcers
What are the complications of ulcerative colitis?
–Severe haemorrhage
–Toxic megacolon
–Adenocarcinoma (20-30 x risk)
What are some of the extraintestinal problems associated with Ulcerative colitis?
- Arthritis
- Myositis
- Uveitis/iritis
- Erythema nodosum, pyoderma gangrenosum
- Primary Sclerosing Cholangitis (5.5% in pancolitis)
Name the different groups of tumors in the colon and rectum
- Non-neoplastic polyps
- Neoplastic epithelial lesions
–Adenoma
–Adenocarcinoma
–Carcinoid tumour
•Mesenchymal lesions
–Stromal tumours
–Lipoma
–Sarcoma
•Lymphoma
Name some non-neoplastic polyps
–(Hyperplastic)
–Inflammatory (“pseudo-polyps”)
–Hamartomatous (juvenile, Peutz Jeghers)
Name some neoplastic polyps
–Tubular adenoma
–Tubulovillous adenoma
–Villous adenoma
What do these images show?
Hyperplastic polyp - non-neoplastic
- What is an adenoma?
- What is the epidemiology?
- What are the three main types?
- Excess epithelial proliferation + dysplasia
- 20-30% prevalance before age 40, 40-50% prev. after age 60
- 3 types:
- Tubular
- Villous
- Tubulovillous
What does this image show?
Tubular adenoma
What does this image show?
Villous adenoma
What are the risk factors for bowel cancer?
–Size of polyp (> 4 cm approx 45% have invasive malignancy)
–Proportion of villous component
–Degree of dysplastic change within polyp
What is the evidence for adenomas being precursors for a carcinoma?
- High prevalence of adenoma = high prevalence of carcinoma
- Colonic distribution similar
- Peak incidence of adenomas 10 years before peak for Ca.
- Residual adenoma near invasive Ca.
- Risk proportional to no. of adenomas
- Screening + removal of adenomas reduce Ca.
What are the symptoms of adenomas?
- Usually none
- Bleeding/anaemia
Name some familial syndromes that lead to the development of polyps
- Peutz Jeghers - is an autosomal dominant genetic disorder characterized by the development of benign hamartomatous polyps in the gastrointestinal tract and hyperpigmented macules on the lips and oral mucosa (melanosis)
- Familial adenomatous polyposis
–Gardner’s
–Turcot
•Hereditary non polyposis colon cancer
- What is Familial adenomatous polyposis (FAP/APC)?
- Epidemiology
- What happens?
- What are the underlying genetics?
- Autosomal dominant condition-
- Average onset is 25 years old
3.
- Adenomatous polyps, mostly colorectal
- Minimum 100 polyps, average ~1,000 polyps
- virtually 100% will develop cancer within 10 to 15 years; 5% periampullary Ca
- chromosome 5q21, APC tumour suppressor gene
Describe Gardner’s syndrome
- Same clinical, pathological, and etiologic features as FAP, with high Ca risk
- Distinctive extra-intestinal manifestations:
–multiple osteomas of skull & mandible
–epidermoid cysts
–desmoid tumors
–dental caries, unerrupted supernumery teeth
–post-surgical mesenteric fibromatoses
Describe Hereditary non-polyposis Colorectal cancer (HNPCC)
- Uncommon autosomal dominant disease
- 3-5% of all colorectal cancers
- 1 of 4 DNA mismatch repair genes involved (mutation)
- Numerous DNA replication errors (RER)
- Onset of colorectal cancer at an early age
- High frequency of carcinomas proximal to splenic flexure
- Poorly differentiated and mucinous carcinoma more frequent
- Multiple synchronous cancers
- Presence of extracolonic cancers (endometrium, prostate, breast, stomach)
- What are the majority of colorectal carcinomas?
- What is the epidemiology for colorectal carcinomas?
- Aetiology of colorectal carcinoma
- 98% are adenocarcinoma
2.
- Age: 60-79 years
- If < 50yrs consider familial syndrome
- Western population
- Aetiology:
- Diet (low fibre, high fat etc)
- Lack of exercise
- Obesity
- Familial
- Chronic Inflammatory bowel disease
What are the signs and symptoms of colorectal carcinoma?
- Bleeding
- Change of bowel habit
- Anaemia
- Weight loss
- Pain
- Fistula
Describe how colorectal carcinoma is graded and staged
- Grade = level of differentiation
- Stage = amount of invasion
•Dukes’ staging
–A = confined to wall of bowel
–B = through wall of bowel
–C = lymph node metastases
–D = distant metastases
•TNM (tumour, nodes, metastases)
