Lower GI Flashcards
- List some congenital disorders of the GI tract.
Atresia/stenosis
Duplication
Imperforate anus
Hirschsprung disease (MOST COMMON)
- What is Hirschsprung disease?
Caused by the absence of ganglion cells of the myenteric plexus results in failure of dilatation of the distal colon
Presents with constipation, abdominal distension, vomiting and overflow diarrhoea
- List some genetic associations of Hirschsprung disease.
Down syndrome
RET proto-oncogene Cr10
- How is Hirschsprung disease diagnosed?
Clinical impression
Full thickness rectal biopsy
Shows hypertrophied nerve fibres but no ganglia
- How is Hirschsprung disease treated?
Resection of affected (constricted) segment
- What is a volvulus?
twisting of a loop of bowel at the mesenteric base around a vascular pedicle
- Which part of the intestines tend to be affected by volvulus in children and the eldery?
Children – small bowel
Elderly – sigmoid colon
- Describe the pathophysiology of diverticular disease.
High intraluminal pressure (e.g. due to poor diet) leads to herniation of the bowel mucosa through weak points in the bowel wall (usually sites of entry of nutrient vessels)
- List some causes of acute colitis.
Infection
Drugs/toxins
Chemotherapy
Radiotherapy
- 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 can cause pseudomembranous colitis?
Exotoxins by C. difficile
- How can C. difficile colitis be diagnosed?
Toxin stool assay
- How is pseudomembranous colitis treated?
Metronidazole or vancomycin
- Where in the intestines does ischaemic colitis tend to occur?
Watershed zones (e.g. splenic flexure, rectosigmoid)
- List some causes of ischaemic colitis.
Arterial occlusion (e.g. embolism)
Venous occlusion (e.g. thrombus)
Small vessel disease (e.g. diabetes mellitus)
Low flow states (e.g. CCF)
Obstruction (e.g. hernia, intussusception)
- List some characteristic features of Crohn’s disease.
Can occur anywhere from mouth to anus Skip lesions Transmural inflammation Non-caseating granulomas Sinus/fistula formation Mostly affects large bowel and terminal ileum Thick rubber hose-like wall Cobblestone mucosa Narrow lumen
- List some extra-intestinal features of inflammatory bowel disease.
Arthritis
Uveitis
Stomatitis/cheilitis
Skin lesions (pyoderma gangrenosum, erythema multiforme, erythema nodosum)
- List some characteristic features of ulcerative colitis.
Involves rectum and colon in a continuous fashion
May see backwash ileitis (involvement of the terminal ileum)
Inflammation is confined to the mucosa
Bowel wall is normal thickness
- List some complications of ulcerative colitis.
Severe haemorrhage
Toxic megacolon
Adenocarcinoma (20-30 x increased risk)
- Which liver condition is associated with UC?
Primary sclerosing cholangitis
- List some types of neoplastic epithelial lesions that occur in the GI tract.
Adenoma
Adenocarcinoma
Carcinoid tumour
- List some types of stromal lesions that occur in the GI tract.
Stromal tumours
Lipoma
Sarcoma
Other: lymphoma
- List three types of non-neoplastic polyp.
Hyperplastic
Inflammatory (pseudopolyp)
Haemartomatous (juvenile, Peutz-Jeghers)
- List three types of neoplastic polyp.
Tubular adenoma
Tubulovillous adenoma
Villous adenoma
- What is an adenoma?
Excess epithelial proliferation with dysplasia
- List some features of an adenoma that are associated with increased risk of becoming a carcinoma.
Size of polyp (> 4 cm = 45%)
Proportion of villous component
Degree of dysplastic change within a polyp
- List some observations that have given rise to the 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
- List some familial syndromes that are characterised by intestinal polyps.
Peutz-Jegher’s syndrome
FAP (Gardner’s, Turcot)
HNPCC
- Which gene is mutated in FAP?
APC gene – chromosome 5q21
- What is Gardner’s syndrome?
Same features of FAP but with extra-intestinal manifestations: multiple osteomas of the skull and mandible, epidermoid cysts, desmoid tumours and supernumerary teeth
- Where do carcinomas in HNPCC tend to occur?
Proximal to the splenic flexure
NOTE: poorly differentiated and mucinous cancers are more common. Polyps do not necessarily precede the cancer
- Outline Dukes’ staging of colorectal cancer.
A – confined to bowel wall
B – through the bowel wall
C – lymph node metastases
D – distant metastases
