Small & Large Intestine Flashcards
Name two congenital conditions of intestines.
- Meckel Diverticulum
- Hirschsprung Disease
What is the pathogenesis of Hirschsprung Disease?
Absence of neural crest derived ganglion cells within the colon - lacking Meissner Submucosal and Auerbach Myenteric plexus
Hence absence of co-ordinated peristalsis leading to functional obstruction of the affected bowel and proximal dilation
What is the initial sign of Hirschsprung Disease?
Failure to pass meconium in immediate postnatal period
- constipation, abdominal distension, bilous vomiting
What are the complications of Hirschsprung Disease?
Megacolon –> Perforation –> Peritonitis –> Sepsis
Enterocolitis
Fluid/Electrolyte Disturbances
How can Hirschsprung Disease be treated?
Surgical Removal Of Aganglionic Segment
In Ischemic Bowel Disease, infarction may be ___, ___, or _____. What are the underlying causes of each?
Transmural (acute vascular obstruction), Mural or Mucosal (secondary to hypoperfusion)
Which part of the bowel epithelium is most vulnerable to damaghe in ischemic bowel disease?
Surface epithelium. Patterns of intestinal microvessels: intestinal capillaries run alongside glands from crypt to surface before U-turning to empty into post-capillary venules
How does ischemic colitis appear?
Surface epithelial necrosis and normal crypts
State some predisposing conditions for ischemia.
- Arterial Thrombosis
- Arterial Embolism
- Venous Thrombosis
- Non-Occulsive Ischemia
- Misc. (Volvulus, Herniation, Adhesions)
How does malabsorption present normally?
Chronic Diarrhoea
Name 3 common chronic malabsorptive disorders.
Pancreatic Insufficiency
Celiac Disease
Crohn’s Disease
What is the pathogenesis of Celiac Disease?
Immune-mediated enteropathy triggered by ingestion of gluten
3 morphological features seen in Celiac Disease
- Intraepithelial CD8+ T lymphocytes
- Crypt Hyperplasia
- Villous Atrophy
Name some
a) Bacteria
b) Viruses
c) Fungi
d) Protozoa and Parasites
that cause Infectious Enterocolitis
a) E. Coli, Salmonella, Shigella, V. Cholerae, Campylobacter
b) Rotavirus, Norovirus, CMV, HSV
c) Candida, Aspergillus, Mucormycosis, Histoplasma
d) Entameba histolytica, Giardia lambila, Cryptosporidia Ascaris, Trichuris, Enterobius, Strongyloides, Schistosomiasis
What bacteria causes pseudomembranous colitis?
Clostridium Difficile
What are the histological presentations of pseudomembranous colitis?
Pseudomembranes composed of an adherent layer of inflammatory cells and debris at sites of colonic mucosal injury, where damaged crypts spew out mucopurulent exudates
What are the clinical presentations of pseudomembranous colitis?
Fever, Leukocytosis, Abdominal pain/cramps, watery diarrhoea
How is diagnosis of pseudomembranous colitis done?
Detection of C. Difficule Toxin
Histopathology
Where is the commonest site of intestinal TB?
Ileocecal region
What can intestinal TB cause?
Circumferential ulcers (in the direction of lymphatics to mesentery)
Thickening of walls, strictures
How can intestinal TB spread?
Miliary Spread
How does amebiasis present endoscopically?
Flask-shaped ulcers with shaggy edges, napkin-like constrictive mass (granulation tissue)
Name a complication of amebiasis.
Liver Abscesses via portal circulation
What is the pathogenesis of acute appendicitis?
Lumen Obstruction (fecolith, foreign matter, lymphoid hyperplasia) –> Luminal bacteria multiplication, invasion of mucosa and wall, acute inflammation, necrosis and ulceration –> Perforation (peritonitis, pelvic abscess, subphrenic abscess)
What are the histological features in acute appendicitis?
Edema and Turgidity
Congestion and Hemorrhage
Fibrinopurulent Exudate
Necrosis, Ulceration
What is the pathogenesis of IBD
Dysfunctions of gut microbiome
Intestinal epithelial dysfunction\
Aberrant mucosal immune responses
Two types of IBD?
Crohn’s
Ulcerative Colitis
How is IBD treated?
Immunosuppression
4 features of Crohn’s
Transmural Chronic Inflammation with Lymphoid FOllicles
Non-Caseating Granulomas
Discrete Deep Ulcers
Fibrosis
4 complications of Crohn’s
Stricture
Fissues/Fistulas
Perforation/Peritonitis
malignancy
Features of UC?
Limited to mucosal surface
Only affects rectum and distal colon (only affects Small intestine if ‘backwash ileitis’)
Inflammatory pseudopolyps
Complications of UC?
Malignancy
Toxic Megacolon - inflammatory mediators damage muscularis propria and disturb neuromuscular function such that there is massive dilation and perforation risk
Compare and COntrast Crohn’s and UC. Divisions are macroscopic, microscopic, clinical.
What is diverticular disease?
Mucosa outpiuching surrounded by fibrous tissue
Who usually gets diverticular disease?
Elderly due to weakening of muscle wall
What are 2 complications of diverticular disease?
Acute inflammation (diverticulitis)
- pericolic abscess
- pericolic fibrosis and adhesions
- colovesical fistula
- strictures
- perforation/peritonitis
Erosion of blood vessels
- rectal bleeding
-anemia
Name some obstructive lesions of the GIT
Name some causes of lower GI bleeds.
What is angiodysplasia? Where does it occur? When does it occur?
Malformed submucosal or mucosal blood vessels
Cecum or right colon
After sixth decade
