Histo: Lower GI Disease Flashcards
(51 cards)
List some congenital disorders of the GI tract.
- Atresia/stenosis (e.g. duodenal atresia)
- 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
Epidemiology of hirschsprung disease
80% of cases occur in male babies
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
Types of GI Mechanical Disorders
- Obstruction
o Adhesions
o Herniation
o Extrinsic mass
o Volvulus - Diverticular disease
What is a volvulus?
Complete Twisting of a loop of bowel at the mesenteric base around a vascular pedicle
What can Volvulus lead to?
intestinal obstruction and infarction
Which part of the intestines tend to be affected by volvulus in children and the elderly?
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)
What is diverticulular disease associated with?
- High incidence in the WEST
- Associated with a low fibre diet
90% of diverticular disease occur on what side of the colon?
left side of the colon
List some causes of acute colitis.
*Infection (bacterial, viral, protozoal, fungal)
*Drug/toxin (especially antibiotics)
*Chemotherapy
*Radiotherapy
List some causes of chronic gastritis?
*Chronic Colitis
*Crohn’s disease *Ulcerative colitis
*TB
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?
*Antibiotic-associated colitis
*Acute colitis with pseudomembrane formation
*Caused by protein exotoxins of C. difficile
What is the Characteristic microscopic appearance of pseudomembranous colitis on biopsy?
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
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?
Occurs in segments In Watershed zones (e.g. splenic flexure, rectosigmoid)
Types of ischaemic colitis /infarction
Acute or chronic
Most common vascular disorder of the GI tract
Ischaemic colitis/infarction
Where can ischaemic colitis extend?
Extend can be mucosal, mural or transmural (leading to perforation)
