Lower GI pathology Flashcards
How can lower GI pathology be categorised?
Congenital
Acquired:
* Mechanical
* Infection
* Inflammation
* Ischaemia
* Tumour
What are 5 “general effects” of large bowel pathology?
Disturbance of normal function (diarrhoea, constipation)
Bleeding
Perforation/ fistula formation
Obstruction
+/- Systemic illness
What are congenital diseases of the large bowel?
Atresia/ stenosis
Duplication
What are atresias of the GI tract?
no communication between duodenum + latter small bowel
(can happen in large bowel)
What is Hirschsprung’s Disease? Describe the epidemiology and associations
- Absence of ganglion cells in submucosal + myenteric plexus
- Distal colon fails to dilate
- 80% male
- A/w Down’s syndrome (2%)
- RET proto-oncogene Cr10 + others
Describe the presentation of Hirshsprung’s disease (4)
Constipation: failure to pass meconium
Abdominal distension
Vomiting
‘overflow’ diarrhoea
What initial investigation may be performed in Hirshsprung’s Disease? What will be seen?
Abdo XR
Dilated colon
Air fluid levels
What is the initial management for Hirschprungs disease?
Bowel irrigation
AKA
Rectal washouts
What is the gold standard appropriate investigation for Hirschsprung’s Disease?
What is the definitive treatment for Hirschsprung’s Disease?
Biopsy of affected segment: Hypertrophied nerve fibers but no ganglia.
Tx: Resection of affected (constricted) segment with frozen section to assess extent of disease.
“Anorectal pull through”
What is seen here?
Blue: mucosa
Yellow: Muscularis mucosa
Green: Ganglion cells
(If Hirschsprung’s these would be absent)
What are mechanical diseases of the large bowel?
Obstruction:
*Adhesions
*Herniation
*Extrinsic mass
*Volvulus
Diverticular disease
What is a volvulus? What does it lead to? Which parts of the bowel are involved?
Complete twisting of a loop of bowel at mesenteric base, around vascular pedicle.
Leads to intestinal obstruction +/- infarction
Bowel with mesentery:
Small bowel (infants)
Sigmoid colon (elderly)
What is the pathogenesis of diverticular disease?
High incidence in West
Low fibre diet
High intraluminal pressure has to be generated
High pressure pushes mucosa through “Weak points” in wall of bowel
90% occur in left colon (Sigmoid)
What is seen here?
Blue: Lumen
Yellow: Diverticulum
Why is diverticular disease a misnomer?
Actually pseudodiverticula: just mucosa + submucosa protrude through muscular wall
(True diverticuli contain all layers of bowel wall)
What types of imaging can be used to diagnose diverticular disease?
Diverticular disease: Sigmoidoscopy/ Colonoscopy to r/o malignancy
Diverticulitis: Contrast CT
What are 5 complications associated with diverticular disease?
Pain
Diverticulitis
Gross perforation
Fistula (bowel, bladder, vagina)
Obstruction
What is the difference between diverticulosis, diverticular disease, and diverticulitis?
Diverticulosis: Presence of diverticuli
Diverticular disease: Symptomatic
Diverticulitis: inflammation +/- infection due to obstruction of material, causing more severe Sx
What are inflammatory diseases of the bowel?
Acute colitis:
* Infection (bacterial, viral, protozoal etc.)
* Drug/ toxin (esp. abx)
* Chemotherapy
* Radiation
Chronic colitis:
* Crohn’s
* Ulcerative colitis
* TB
Give 4 examples of species and a pathogen causing infectious colitis
Viral e.g. CMV esp. immunosuppressed
Bacterial e.g. Salmonella
Protozoal e.g. Entamoeba hystolytica
Fungal e.g. candida
What is pseudomembranous colitis?
Abx associated colitis
Acute colitis with pseudomembrane formation
Caused by protein exotoxins of C.difficile
Why is pseudomembranous colitis called so?
Membrane is inflammatory tissue
Not a true membrane (true membrane would be epithelial)
List 4 effects of infectious colitis
Secretory diarrhoea (toxin)
Exudative diarrhoea (invasion + mucosal damage)
Severe tissue damage + perforation
Systemic illness
Describe the histology of pseudomembranous colitis
Yellow-white mucosal plaques or pseudomembranes
May resemble polyps or aphthoid ulcers of Crohn’s disease.
Mucopurulent exudate erupts out of crypts to form a mushroom-like cloud with a linear configuration of karyorrhectic debris + neutrophils that adheres to surface.
How is pseudomembranous colitis diagnosed and treated?
Laboratory: C. difficile toxin stool assay.
Therapy: Metronidazole or Vancomycin.
What is ischaemic colitis/infarction?
Acute or chronic.
Usually occurs in segments in “watershed” zones, e.g. splenic flexure (SMA + IMA) + the rectosigmoid (IMA + internal iliac artery).
Degree of damage is variable: Mucosal, mural, transmural, perforation.
What is the aetiology of ischaemic colitis? (5)
Arterial Occlusion: Atheroma, thrombosis, embolism
Venous Occlusion: Thrombus, hypercoagulable states
Small Vessel Disease: DM, cholesterol emboli, vasculitis
Low Flow States: CCF, haemorrhage, shock
Obstruction: Hernia, intussusception, volvulus, adhesions
What are the two forms of inflammatory bowel disease?
Crohn’s disease
Ulcerative colitis
What are the causes of inflammatory bowel disease?
Aetiology unclear.
- Genetic predisposition (familial aggregation, twin studies, HLA)
- Infection (Mycobacteria, Measles etc)
- Abnormal host immunoreactivity
- Microbiome
What are 7 signs and symptoms of inflammatory bowel disease?
- Diarrhoea +/- blood
- Fever
- Abdominal pain
- Acute abdomen
- Anaemia
- Weight loss
- Extra-intestinal manifestations
What is the epidemiology of Crohn’s Disease?
Western populations
Occurs at any age but peak onset in teens/ 20s
White 2-5x > non-white
Higher incidence in Jewish population
Smoking
What are 5 features of Crohn’s disease in the GIT?
- Whole of GIT can be affected (mouth to anus)
- ‘Skip lesions’
- Transmural inflammation
- Non-caseating granulomas
- Fissures/ Sinus/ Fistula formation
Give 6 descriptive features of the appearance of Crohn’s microscopically/ macroscopically
- ‘Fat wrapping’
- Thick ‘rubber-hose’ like wall
- Narrow lumen
- ‘Cobblestone mucosa’
- Linear ulcers
- Abscesses
What are 4 extra-intestinal manifestations of Crohn’s Disease?
Arthritis
Uveitis
Stomatitis/cheilitis
Skin lesions:
* Pyoderma gangrenosum
* Erythema multiforme
* Erythema nodosum
What is the epidemiology of ulcerative colitis?
Slightly more common than Crohn’s
Whites > non-whites
Peak 20-25y but can affect any age
What are clinical features of ulcerative colitis?
Involves rectum + colon in contiguous fashion.
May see mild ‘backwash ileitis’ + appendiceal involvement but small bowel + proximal GIT not affected.
Inflammation confined to mucosa
Bowel wall normal thickness
Shallow ulcers
What are 3 complications associated with ulcerative colitis?
Severe haemorrhage
Toxic megacolon
Adenocarcinoma (20-30x risk)
What are 5 extra-intestinal manifestations of ulcerative colitis?
Arthritis
Myositis
Uveitis/iritis
Erythema nodosum, pyoderma gangrenosum
Primary Sclerosing Cholangitis (5.5% in pancolitis). Important RF for cholangiocarcinoma
What are different tumours of the colon and rectum?
Non-neoplastic polyps
Neoplastic epithelial lesions:
* Adenoma
* Adenocarcinoma
* Carcinoid tumour
Mesenchymal lesions:
* Lipoma
* Sarcoma
Lymphoma
What is a polyp?
Any protrusion into the lumen of an organ
What are the 3 types of non-neoplastic polyps of the colon and rectum?
Hyperplastic (subtype: sessile serrated lesions)
Inflammatory (“pseudo-polyps”)
Hamartomatous (juvenile, Peutz Jeghers)
What is shown here?
Hyperplastic polyp
Small, translucent, v common
What is shown here?
LHS: normal mucosa, testube shaped glands
RHS: hyperplastic polyp, sawtooth “serrations’, tissue overgrowth
What is shown here?
Sessile serrated lesion
Hyperplastic polyp with architectural abnormalities
Dysplasia (darker glands at base)
May give rise to cancer
What are the 3 types of neoplastic polyps of the colon and rectum?
Tubular adenoma
Tubulovillous adenoma
Villous adenoma
What are adenomas of the colon and rectum and how can they be grouped?
Excess epithelial proliferation + dysplasia
20-30% prevalence <40y
40-50% prev. >60y
Types:
* Tubular
* Villous
* Tubulovillous
Describe the appearance of adenomas of the colon and rectum?
Dark because nuclei are dark, nuclei are bigger in adenomas + Rise in nuclear to cytoplasmic ratio.
Thus, look darker than normal tissue
What is this?
Tubular adenoma
Rounded with glands running straight
Long stalk
What is this?
Tubular adenoma
Yellow: normal glands
Red: adenoma- flat surface, glands coming down. Much darker as higher N:C ratio
What shape can polyps be?
Sessile: flat on mucosa
Pedunculated: with a stalk
What is a tubular adenoma?
most common type of adenoma in the colon/ rectum
Considered benign, or noncancerous.
What is a villous carcinoma?
Sessile growths lined by dysplastic glandular epithelium, whose risk of malignancy is esp. high up to 50%.
What are risk factors for lower GI cancer?
Size of polyp (>1cm start to worry)
Proportion of villous component: the more villous the greater the risk of cancer
Degree of dysplastic change within polyp
What is the evidence that adenomas are precursors of carcinomas? (6)
High prevalence of adenoma = High prevalence of carcinoma.
Colonic distribution similar.
Peak incidence of adenomas 10y before peak for Ca.
Residual adenoma near invasive Ca.
Risk proportional to no. of adenomas.
Screening + removal of adenomas reduce Ca.
Where is the most common site of colon cancer?
Rectum + sigmoid
Sigmoidoscopy can detect
What are symptoms of adenomas?
Usually none
Bleeding/ anaemia
What are 4 familial syndromes which can result in an increased risk of adenomas in lower GI?
(Peutz Jeghers- hamartomatous polyps can give rise to cancer but not always)
Familial adenomatous polyposis:
* Gardner’s
* Turcot
Hereditary non polyposis colon cancer
Summarise the epidemiology of FAP.
- Autosomal dominant: average onset 25y
- Adenomatous polyps, mostly colorectal
- Min. 100 polyps, average ~1,000 polyps
- Chr 5q21, APC tumour suppressor gene
- Virtually 100% will develop cancer within 10-15y;
- 5% periampullary Ca.
What is Gardner’s Syndrome?
FAP
+
Extra-intestinal manifestations:
- Osteomas of skull + mandible
- Desmoid tumors
What is Turcot’s syndrome?
FAP + brain tumours
What is hereditary non-polyposis colorectal cancer (HNPCC)?
Autosomal dominant
May have polyps
3-5% of all colorectal cancers
Atl least 1 of 4 DNA mismatch repair genes involved (mutation- if oncogenic mutations arise, they can’t be repaired)
Numerous DNA replication errors (RER)
What are 5 features of HNPCC?
Onset of colorectal cancer at an early age
High freq. of carcinomas proximal to splenic flexure
Poorly differentiated + mucinous carcinoma more frequent
Multiple synchronous cancers
Presence of extracolonic cancers (endometrium, prostate, breast, stomach)
Where are cancers in HNPCC most likely to occur? Why does this make them harder to diagnose?
Caecum
Need full colonoscopy
What is the epidemiology of colorectal cancer? (4)
98% are adenocarcinoma
Age: 60-79y
If < 50y consider familial syndrome
Western population
What is the aetiology of colorectal cancer? (4)
- Diet (low fibre, high fat etc)
- Lack of exercise
- Obesity
- Familial
Give 2 predisposing factors to colorectal cancer
- Chronic Inflammatory bowel disease, esp. UC
- Adenomas
What are 5 symptoms of colorectal cancer?
Bleeding
Change of bowel habit
Anaemia
Weight loss
Pain
What is grading and staging of colorectal cancer?
Staging: TNM
Grading: degree of differentiation.
Which system is used to stage colorectal cancers?
Dukes’ staging = old
TNM (tumour, nodes, metastases)
What sort of colon polyps most commonly predispose to adenocarcinoma of the colon?
Villous adenoma
A 76M presents with rectal bleeding. What diagnosis must be excluded first?
Colorectal cancer
What is this?
Volvulus
What is this?
Hirschsprung’s Disease
What is this?
Diverticular disease - barium enema
What is this?
Diverticular disease endoscopy
What is this?
Diverticular disease histology
What is this?
Diverticular disease
What is this?
Pseudomembranous colitis
What is this?
Pseudomembranous colitis histology
What is this?
Ischaemic bowel
What is this?
Ischaemic bowel histology
What is this?
Ischaemic bowel histology
What is this?
Crohn’s Disease
What is this?
Crohn’s Disease
What is this?
Crohn’s Disease histology
What is this?
Crohn’s Disease histology
What is this?
Ulcerative colitis
What is this?
Ulcerative colitis
What is this?
Ulcerative colitis histology
What is this?
Ulcerative colitis histology
What is this?
Polyps
What is this?
Adenoma
Big fleshy lesion
What is this?
Villous adenoma histology
Blood vessels running in core
What is this?
Villous adenoma
Finger like projections
Irregular surface
What is this?
Villous adenoma histology
What is this?
FAP
What is this?
Colorectal cancer
What is this?
Colorectal cancer
What is this?
Adenocarcinoma
Secreting mucous + forming glands
