Lower GI pathology Flashcards by Kat Qiao

How can lower GI pathology be categorised?

Congenital

Acquired:

Mechanical
Infection
Inflammation
Ischaemia
Tumour

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What are “general effects” of large bowel pathology?

Disturbance of normal function (diarrhoea, constipation)

Bleeding

Perforation/fistula formation

Obstruction

+/- Systemic illness

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What are congenital diseases of the large bowel?

Atresia/stenosis

Duplication

Imperforate anus

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What is Hirschsprung’s Disease?

Absence of ganglion cells in myenteric plexus,
Distal colon fails to dilate
80% male
Constipation, abdominal distension, vomiting, ‘overflow’ diarrhoea
Associated with Down’s syndrome (2%)
RET proto-oncogene Cr10 + other

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What are appropriate investigations for Hirschsprung’s Disease?

What is the treatment for Hirschsprung’s Disease?

Clinical impression

Biopsy of affected segment: Hypertrophied nerve fibers but no ganglia.

Treatment: Resection of affected (constricted) segment (frozen section).

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What are mechanical diseases of the large bowel?

Obstruction

Adhesions

Herniation

Extrinsic mass

Volvulus

Diverticular disease

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What is a volvulus?

Complete twisting of a loop of bowel at mesenteric base, around vascular pedicle.

Intestinal obstruction +/- infarction

Small bowel (infants)

Sigmoid colon (elderly)

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What is the pathogenesis of diverticular disease?

High incidence in West

Low fibre diet

High intraluminal pressure

“Weak points” in wall of bowel

90% occur in left colon

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What types of imaging can be used to diagnose diverticular disease?

Barium enema

Endoscopy

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What are complications associated with diverticular disease?

Pain

Diverticulitis

Gross perforation

Fistula (bowel, bladder, vagina)

Obstruction

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What are inflammatory diseases of the bowel?

Acute colitis:

Infection (bacterial, viral, protozoal etc.)
Drug/toxin (esp.antibiotic)
Chemotherapy
Radiation

Chronic colitis:

Crohn’s
Ulcerative colitis
TB

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What are the effects of infection?

Secretory diarrhoea (toxin)

Exudative diarrhoea (invasion and mucosal damage)

Severe tissue damage + perforation

Systemic illness

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What is pseudomembranous colitis?

Antibiotic associated colitis

Acute colitis with pseudomembrane formation

Caused by protein exotoxins of C.difficile

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How is pseudomembranous colitis diagnosed and treated?

Histology: 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 and neutrophils that adheres to surface.

Laboratory: C. difficile toxin stool assay.

Therapy: Metronidazole or Vancomycin.

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What is ischaemic colitis/infarction?

Acute or chronic.

Most common vascular disorder of the intestinal tract.

Usually occurs in segments in “watershed” zones, e.g. splenic flexure (SMA and IMA) and the rectosigmoid (IMA and internal iliac artery).

Mucosal, mural, transmural (perforation).

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What is the aetiology of ischaemic colitis?

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

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What are the two forms of inflammatory bowel disease?

Crohn’s disease

Ulcerative colitis

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What are the causes of inflammatory bowel disease?

Aetiology unclear.

Genetic predisposition (familial aggregation, twin studies, HLA)
Infection (Mycobacteria, Measles etc)
Abnormal host immunoreactivity

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What are the signs and symptoms of inflammatory bowel disease?

Diarrhoea +/- blood
Fever
Abdominal pain
Acute abdomen
Anaemia
Weight loss
Extra-intestinal manifestations

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What is the epidemiology of Crohn’s Disease?

Western populations

Occurs at any age but peak onset in teens/twenties

White 2-5x > non-white

Higher incidence in Jewish population

Smoking

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What are the clinical features of Crohn’s?

Whole of GI tract can be affected (mouth to anus)
‘Skip lesions’
Transmural inflammation
Non-caseating granulomas
Sinus/fistula formation
‘Fat wrapping’
Thick ‘rubber-hose’ like wall
Narrow lumen
‘Cobblestone mucosa’
Linear ulcers
Fissures
Abscesses

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What are extra-intestinal manifestations of Crohn’s Disease?

Arthritis

Uveitis

Stomatitis/cheilitis

Skin lesions:

Pyoderma gangrenosum
Erythema multiforme
Erythema nodosum

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What is the epidemiology of ulcerative colitis?

Slightly more common than Crohn’s

Whites > non-whites

Peak 20-25 years but can affect any age

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What are clinical features of ulcerative colitis?

Involves rectum and colon in contiguous fashion.

May see mild ‘backwash ileitis’ and appendiceal involvement but small bowel and proximal GI tract not affected.

Inflammation confined to mucosa

Bowel wall normal thickness

Shallow ulcers

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What are complications associated with ulcerative colitis?

Severe haemorrhage Toxic megacolon Adenocarcinoma (20-30x risk)

What are the extra-intestinal manifestations of ulcerative colitis?

Arthritis Myositis Uveitis/iritis Erythema nodosum, pyoderma gangrenosum Primary Sclerosing Cholangitis (5.5% in pancolitis)

What are different tumours of the colon and rectum?

**Non-neoplastic polyps** **Neoplastic epithelial lesions:** * Adenoma * Adenocarcinoma * Carcinoid tumour **Mesenchymal lesions:** * Stromal tumours * Lipoma * Sarcoma **Lymphoma**

What are non-neoplastic polyps of the colon and rectum?

Hyperplastic Inflammatory (“pseudo-polyps”) Hamartomatous (juvenile, Peutz Jeghers)

What are 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 before age 40 40-50% prev. after age 60 **Types:** * Tubular * Villous * Tubulovillous

What is a tubular adenoma?

Tubular adenomas are the most common type. They're considered benign, or noncancerous.

What is a villous carcinoma?

Villous adenomas are sessile growths lined by dysplastic glandular epithelium, whose risk of malignancy is especially high up to 50%. Looks like a cauliflower.

What are risk factors for lower GI cancer?

Size of polyp (\> 4 cm approx 45% have invasive malignancy) Proportion of villous component Degree of dysplastic change within polyp

What is the evidence that adenomas are precursors of carcinomas?

**High prevalence of adenoma:** High prevalence of carcinoma. Colonic distribution similar. Peak incidence of adenomas 10 years before peak for Ca. Residual adenoma near invasive Ca. Risk proportional to no. of adenomas. Screening + removal of adenomas reduce Ca.

What are symptoms of adenomas?

Usually none Bleeding/anaemia

What are familial syndromes which can result in an increased risk of adenomas in lower GI?

Peutz Jeghers **Familial adenomatous polyposis** * Gardner’s * Turcot Hereditary non polyposis colon cancer

Summarise the epidemiology of FAP.

* Autosomal dominant - average onset is 25 years old * Adenomatous polyps, mostly colorectal * Minimum 100 polyps, average ~1,000 polyps * Chromosome 5q21, APC tumour suppressor gene * Virtually 100% will develop cancer within 10 to 15 years; 5% periampullary Ca.

What is Gardner's Syndrome?

Same clinical, pathological, and etiologic features as FAP, with high Ca risk. Distinctive extra-intestinal manifestations: * Multiple osteomas of skull & mandible * Epidermoid cysts * Desmoid tumors * Dental caries, unerrupted supernumery teeth * Post-surgical mesenteric fibromatoses

What is hereditary non-polyposis colorectal cancer (HNPCC)?

Uncommon autosomal dominant disease 3-5% of all colorectal cancers 1 of 4 DNA mismatch repair genes involved (mutation) Numerous DNA replication errors (RER)

What are features of HNPCC?

Onset of colorectal cancer at an early age High frequency of carcinomas proximal to splenic flexure Poorly differentiated and mucinous carcinoma more frequent Multiple synchronous cancers Presence of extracolonic cancers (endometrium, prostate, breast, stomach)

What is the epidemiology of colorectal cancer?

98% are adenocarcinoma Age: 60-79 years If \< 50yrs consider familial syndrome Western population

What is the aetiology of colorectal cancer?

* Diet (low fibre, high fat etc) * Lack of exercise * Obesity * Familial * Chronic Inflammatory bowel disease

What are symptoms of colorectal cancer?

Bleeding Change of bowel habit Anaemia Weight loss Pain Fistula

What is grading and staging of colorectal cancer?

Staging means how big the cancer is and whether it has spread. Grading means how abnormal the cancer cells look under a microscope/level of differentiation.

Which system is used to stage colorectal cancers?

Dukes’ staging TNM (tumour, nodes, metastases)

What is Duke's staging?

**A:** Confined to wall of bowel **B:** Through wall of bowel **C:** Lymph node metastases **D:** Distant metastases

What do the different stages of Duke's mean for survival?

**A:** Limited to mucosa, 5y survival: \>95% **B1:** Extending into muscularis propria, 5y survival: 67% **B2:** Transmural invasion, no lymph nodes involved, 5y survival: 54% **C1:** Extending into muscularis propria, but with involved lymph nodes, 5y survival: 43% **C2:** Transmural invasion, with involved lymph nodes, 5y survival: 23% **D:** Distant metastases, 5y survival: \<10%

What is this?