Histopath - Lower GI Flashcards
What is Hirschprung’s disease caused by?
Absence of ganglion cells of the myenteric plexus
- distal colon fails to dilate
What presentation is Hirschsprung disease associated with?
Failure to pass meconium within 48h
Which genetic syndrome is Hirschsprung associated with?
Down’s syndrome (2%)
Two types of acute cholitis
Pseudomembranous colitis and ischaemic colitis
*What cause is pseudomembranous colitis associated with?
Clostridium difficile
caused by 3C antibx: Cephalosporins, ciprofloxacin & clindamycin
*Histology for pseudomembranous colitis
Pseudomembrane (membrane like material) formation
Ix for diagnosing pseudomembranous colitis
Toxin stool assay (for exotoxins)
Mx for pseudomembranous colitis
Side room, metronidazole
*What is ischaemic colitis?
Bowel is hypoperfused
oedematous thickening bowel wall, areas necrotic ulceration confined to mucosal layers
Where does ischaemic colitis usually occur?
Watershed zones -
splenic flexure and rectosigmoid
*Causes of ischaemic colitis
Occlusive
- Arterial/venous occlusion
- Small vessel disease: DM, vasculitides
- Obstruction: hernia, volvulus
Hypoperfusion
- CHF
- Haemorrhage
- Shock
Two types of Inflammatory bowel diseases
Crohn’s disease and ulcerative colitis
What part of GI tract is affected in Crohn’s?
Entire GI tract: mouth to anus
(skip lesions)
Inflammation depth for Crohn’s disease
Transmural inflammation
Bowel wall thickness in Crohn’s
Thick bowel wall, narrow lumen
*What feature is pathognomonic of Crohn’s disease?
Non-caseating granulomas
What part of GI tract is affected in Ulcerative colitis?
Rectum and colon
(continuous)
*Inflammation depth for UC?
Inflammation confined to mucosa (superficial)
Bowel wall thickness in UC?
Normal thickness
*Complication of UC
Toxic megacolon
+ (20-30x) increased risk colonic adenocarcinoma
Extra-intestinal manifestations of UC
- Uveitis
- Erythema nodosum
- Pyoderma gangrenosum (shallow, weeping, angry break in skin)
- Arthritis
- Stomatitis
What are GI polyps?
Benign dysplastic lesions
(precursor to adenocarcinomas)
What 3 polyp types have increased risk of becoming malignant?
- Tubular
- Tubulovillous
- Villous
Histopathology of tubular polyps
>75% has tubular appearance
Histopathology of tubovillous polyps
25-75% villous
Histopathology of villous polyps
>75% villous
Which polyp type has highest risk of malignancy?
Villous
How does polyp progress to adenocarcinoma?
Normal -(APC)-> Early adenoma -> late adenoma -(KRAS + p53)-> adenocarcinoma
What type of ca is majority of colorectal ca?
Adenocarcinoma
RFs of colorectal ca
- Low fibre
- High fat diet
- No exercise
- Obesity
- Chronic IBD
Staging used for colorectal ca
Duke’s staging
Duke’s staging
A - confined to mucosa
B1 - extending into muscularis propria
B2 - transmural invasion
C1 - extending to muscularis propria with LN involvement
C2 - transmural invasion with LN involvement
D - distant metastasis
*Colonic carcinoma presentation
- Rectal bleeding
- New onset constipation
- Recent weight loss
- Previous dx polyps in colon
3 inherited lower GI conditions
Familial adenomatous polyposis, Gardner’s syndrome, Hereditary non-polyposis colorectal cancer/Lynch syndrome
Hereditary pattern for FAP
AD
What is FAP?
Lots of polyps! (~1000)
What is the mutation for FAP?
Adenomatous polyposis coli (APC) tumour suppressor gene mutation on Cr 5q21
Hereditary pattern for Gardner’s syndrome
AD
What is Gardner’s syndrome?
Subtype of FAP with extra-intestinal manifestations
What are extra-intestinal manifestations of Garnder’s syndrome?
- Osteomas of skull and mandible
- Epidermoid cyst
- Dental caries
What is hereditary non-polyposis colorectal ca/ lynch syndrome caused by?
Defective DNA mismatch repair
What is a presenting feature of hereditary non-polyposis colorectal ca/lynch syndrome?
Other extra-colonic ca at the same time
Hereditary pattern for hereditary non-polyposis colorectal ca/lynch syndrome
AD
Lower GI inherited conditions Mx
Monitoring + total coelctomy (and stoma)
*Histopathology of Diverticular disease
pouches of mucosa extruding through the muscle layer
What is the name given to areas of regenerating mucosa which project into the lumen of the bowel, which may be visualised during a colonoscopy of a patient with ulcerative colitis?
Pseudopolyp
*3 cancers associated w coeliac
- enteropathy-associated T-cell lymphoma (EATL)
- non-Hodgkin’s lymphoma
- adenocarcinoma of the small intestine
Non caseating granulomas
Crohn’s
(And Sarcoidosis!)
