Lower GI disease Flashcards by Adya Rao

Examples of congenital disorders affecting the large bowel

atresia/stenosis
hirschsprung’s
duplication
imperforate anus

most common hirschsprung’s

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What is the congenital abnormality in hirschsprung’s disease?

absence of ganglionic cells in the myenteric plexus

causes failure of dilatation of the distal colon

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Which patient group does hirshcsprung’s affect?

80% affects male babies

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Presentation of hirschsprung’s disease

constipation with overflow diarrhoea

abdominal distension

vomiting

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Associations of hirschsprung’s disease

down’s syndrome
RET proto-oncogene

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Diagnosis of hirschsprung’s disease

full thickness biopsy

hypertrophy of nerve cells but absence of ganglion cells

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Treatment of hirschsprung’s disease

Resection of affected (constricted) segment

Ano-rectal pull through

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Which parts of the bowel are affected by volvulus? (small intestine vs large intestine)

Children: small intestine: Midgut volvulus

Elderly and pregnant women: sigmoid colon (sigmoid > caecal)

*think children are younger; more proximal part is affected

NOTE: psychiatric patients also get this (?medication related)

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3 types of volvulus

caecal
midgut
sigmoid

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AXR findings of sigmoid vs caecal volvulus

sigmoid: coffee bean sign
caecal: embryo sign

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Associated factors for diverticular disease

Age (>60 years)

Chronic Constipation

Diet:

Low Fibre

Rich in fatty food or red meat

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Difference between pseudodiverticulum and true diverticulum

pseudodiverticulum: caused by high intraluminal pressure eg due to straining –> causes outpouchings. does not involve all layers of the bowel wall

true diverticulum: caused by traction/pulling forces –> involves all layers of the bowel wall

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Which side of the colon is most affected by diverticular disease?

90% are left sided

**maybe because constipation commonly causes faecal impaction on the left side??

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Diagnosis of diverticular disease

CT with contrast

colonoscopy is contraindicated in acute diverticulitis due to risk of perforation

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Which drugs can cause c diff colitis?

4Cs:

cephalosporins

ciprofloxacin

clindamycin

co-amoxiclav

can also be precipitated by antacids/PPIs, cytotoxic drugs and non-surgical procedures eg NG tubes

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Histological appearance of c difficile colitis

pseudomembraneous colitis

looks like volcano exploding - bits on the surface are necrotic pseudomembranous regions full of pus and inflammatory cells

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CRP in C difficile colitis

CRP may be low

even though WCC is high

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C difficile treatment

moderate severity: metronidazole –> vancomycin if no response
severe: vancomycin first, can add on metronidazole

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Which ribotype of c difficile is associated with increased toxicity?

Ribotype 027

caused an outbreak in June 2005

as it produces more toxins

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Which genetic mutation can predispose to crohn’s?

NOD2 mutation

present in 30% of people with crohn’s

**NOD2 is expressed in myeloid cells

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Characteristic features of crohn’s disease

Crow’s NESTS

N: no blood or mucous

E: entire GI tract can be affected (most common in terminal ileum and large bowel- caecum)

S: skip lesions

T: transmural inflammation

S: smoking is a risk factor

Histological features:

non-caseating granulomas
rose thorn ulcers

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Management of Crohn’s disease

Inducing remission:

1st line: corticosteroids (PO–>IV)

2nd line: immunosuppressants

Maintaining remission:

immunosuppressants

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Which is more common: crohn’s or UC?

UC is slightly more common

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Key features of ulcerative colilitis

Extends proximally from rectum
Continuous inflammation
Inflammation confined to the mucosa → bowel wall is normal thickness
Usually does not affect the small intestine unless severe pancolitis causes backwash ileitis
Extensive superficial broad ulcers
No granulomas/ fissures/ fistulae/ strictures
Islands of regenerating mucosa bulge into lumen → pseudopolyps
- can fuse to form mucosal bridges
May see appendiceal involvement

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Extraintestinal manifestations of ulcerative colitis

Arthritis Myositis Uveitis/ iritis Erythema nodosum pyoderma gangrenosum Primary sclerosing cholangitis \*\*pretty much the same as crohn's disease except PSC

Management of ulcerative colitis

**Inducing remission**: **1) Mild:** * prednisolone * mesalazine (5-ASA) **2) Moderate:** * prednisolone * 5-ASA mesalazine * steroid enema bd **3) Severe:** * Admit * NBM * IV fluids * IV hydrocortisone * rectal steroids * Maintain remission: * 1st line: 5-ASA - mesalazine * 2nd line: azathioprine **Maintain remission** * 5-ASA * immunosuppressants

What is the most common vascular disorder of the GI tract?

Ischaemic colitis/ifarction \*\*can be acute or chronic

Where do diverticulae usually form?

At points where nutrient arteries penetrate the GI tract --\> taenia coli

Which areas of the bowel does ischaemic colitis affect?

Watershed areas - receive dual blood supply. a) rectosigmoid b) splenic flexure

Small bowel vs large bowel ischaemia

Histological findings of ischaemic colitis

* thickening of bowel wall * necrotic ulceration confined to mucosal layers

Types of non-neoplastic polyps in. the bowel

1. hyperplastic - most common - rectosigmoid - rare- malignant potential 2. hamartomous - isolated or as part of syndromes eg peutz-jeghers, juvenile 3. inflammatory - associated with inflammatory bowel disease - aka pseudopolyps (ulcerative colitis)

Definition of adenoma

Excess epithelial proliferation with dysplasia

3 types of adenoma

1. tubular - lowest malignant potential 2. villous - highest malignant potential (V for violent) 3. tubulovillous - intermediate malignant potential

Description of villous adenoma

sessile cauliflower-like mass covered by dysplastic columnar epithelium in the rectum

Risk factors for adenoma progressing to cancer

1. size 2. villous content 3. degree of dysplastic changes

Adenoma carcinoma sequence

What electrolyte abnormality may be seen in colorectal adenoma?

hypokalaemia \*\*because the adenoma leaks potassium \*\*also causes hypoproteinaemia

Which area of the bowel is most commonly affected by adenocarcinoma?

rectosigmoid

Left vs right colon cancer presentation

left: obstruction right: anaemia

What staging is used for colorectal adenocarcinoma?

Duke's staging ## Footnote A = confined to bowel wall B = through bowel wall C = lymph node metastases D = distant metastases

Name 3 familial syndromes characterised by intestinal polyps

1. peutz jeghers 2. HNPCC 3. FAP

Which type of polyps in peutz jegher's?

Hamartomous polyps

Which genes are mutated in HNPCC? Mode of inheritance?

MSH2 and MLH1 Autosomal dominant rare

Where do you get tumours in HNPCC? Type?

Proximal to splenic flexure Tend to be mucinous adenocarcinomas

Which other type of tumour does HNPCC predispose to?

Ovarian tumours --\>endometroid and mucinous (think mucinous - tend to form mucinous tumours in the GIT also) (early onset- more bc of HNPCC than BRCA)

Mode of inheritance of FAP Which gene is affected?

autosomal dominant Mutation in APC tumour suppressor gene on chromosome 5q21

Two forms of FAP

1. Gardener's * bony and soft tissue tumours 2. Turcots * gliomas * medulloblastoma

Between crohn's and UC which one has higher monozygotic twin concordancy?

Crohns: 50%

Which cells does carcinoid syndrome originate from?

Enterochromaffin cells produce 5-HT (serotonin)

Where do carcinoid tumours arise from?

Commonly in bowel but also lung, ovaries and testes

Carcinoid syndrome vs carcinoid crisis

Ivx and treatment of carcinoid tumours

Investigation: 24hr urine 5-HIAA (main metabolite of serotonin) Treatment: Octreotide (somatostatin analogue

Juvenile vs peut-jeghers syndrome

2nd commonest cause of cancer deaths in UK

colorectal cancer

What drug is protective against colorectal cancer?

NSAIDS - as a lot of tumours express COX-2

Tumour marker of colorectal carcinoma

Carcinoembryonic antigen

What is gardner's syndrome?

– like FAP with extra intestinal features eg: osteoma’s, dental caries

complciations of diverticular disease

* Pain * Diverticul**_itis_** * Perforation \>\>\> peritonitis * Fistula (bowel, bladder, vagina) * Obstruction