Histo: Lower GI Disease Pt.1 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
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)
