Lower GI tract pathology

Question 1

which congenital GI condition is associated with Down’s syndrome (2%) ?

Answer 1

Hirschsprung’s disease

Question 2

how does Hirschsprung’s disease present? aetiology?

Answer 2

Constipation, abdominal distension, vomiting, ‘overflow’ diarrhoea

Mostly Male

Aetiology;
Absence of ganglion cells in myenteric plexus - means neurological function of bowel is lost means perristalsis malfunctions
Distal colon fails to dilate - AXR: narrow bowel

RET proto-oncogene Cr10 + others

Question 3

how do we diagnose and manage Hirschsprung’s disease ?

Answer 3

clinical impression
biopsy of affected segment.

hypertrophied nerve fibers but no ganglia.
Treatment: resection of affected (constricted) segment. (frozen section)

Question 4

list some mechanical disorders of the GI tract?

Answer 4

1. Obstruction:
Adhesions
Herniation
Extrinsic mass
Volvulus

2. Diverticular disease

Question 5

what is a volvulus and what does it lead to?

Answer 5

complete twisting of a loop of bowel at mesenteric base, around vascular pedicle - A volvulus occurs when bowel twists on its own mesentery

intestinal obstruction +/- infarction

Question 6

what are common sites of volvulus by age?

Answer 6

small bowel (infants)

sigmoid colon (elderly)

Question 7

how would voluvulus present?

Answer 7

With clinical features of bowel obstruction;

As the sigmoid colon is located distally in the GI tract, vomiting is usually a late sign, whilst the colicky pain, abdominal distension, and absolute constipation occur earlier on in the clinical course.

Particularly noteworthy in cases of volvulus, compared to other causes of bowel obstruction, is the rapidity of onset (over a few hours) and degree of abdominal distension

Question 8

what is the pathogenesis of diverticular disease?

Answer 8

is the formation of numerous tiny pockets, or diverticula, in the lining of the bowel - food etc. can get. stuck inside -> inflammatio, perforation* etc

VERY COMMON

Low fibre diet
High intraluminal pressure
‘Weak points’ in wall of bowel
90% occur in left colon

• can lead to diverticulitis

Question 9

how does diverticular disease present?

Answer 9

often asymptomatic

Pain - If out-pouches become inflamed
Diverticulitis
Gross perforation
Fistula (bowel, bladder, vagina)
Obstruction

Question 10

how would you investigate diverticular disease?

Answer 10

Barium enema

Question 11

list causes of acute colitis

Answer 11

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

Question 12

what is Pseudomembranous colitis?

Answer 12

Antibiotic associated colitis
aka C. diff colitis

Acute colitis with pseudomembrane formation
Caused by protein exotoxins of C.difficile

Question 13

what findings on ivx might suggest a Pseudomembranous colitis ?

Answer 13

C. difficile toxin stool assay

gross: wet cornflakes on bowel

histology; crypts look. like inflammed

Question 14

how can Pseudomembranous colitis be treated?

Answer 14

Metronidazole or Vancomycin

Question 15

what is the Most common vascular disorder of the intestinal tract ? sites?

Answer 15

Ischaemic Colitis/ Infarction

commonly. occures at watershed areas - where vessels meet;
splenic flexure (SMA and IMA*) and the rectosigmoid (IMA and internal iliac artery)

• inferior mesenteric artery

Question 16

what are causes of ischaemic colitis?

Answer 16

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

Question 17

how is ischaemic colitis treated ?

how does it kill?

Answer 17

resect area of bowel

kills because - ischaemic bowel can lead to infection

Question 18

what are the features of chrons disease that help differentiate. it from other IBD?

Answer 18

Whole of GI tract can be affected (mouth to anus) - likes terminal ileum

‘Skip lesions’
Transmural inflammation

Non-caseating granulomas
Sinus/fistula formation

‘cobblestone mucosa’
Linear ulcers
Fissures

Extra-intestinal manifestations!

Question 19

what are the extra-intestinal manifestations of Chrons?

Answer 19

Arthritis
Uveitis
Stomatitis/cheilitis
Skin lesions
  - Pyoderma gangrenosum
   - Erythema multiforme
   - Erythema nodosum

Question 20

which is more common UC or Chrons?

Answer 20

UC

Question 21

what are the features of Ulcerative colitis - UC that help differentiate. it from other IBD?

Answer 21

Involves rectum and colon in contiguous fashion.

May see mild ‘backwash ileitis’ (involvement of ileum - small bowel) and appendiceal involvement but small bowel and proximal GI tract not affected.

contiguos spread

Inflammation confined to mucosa
Bowel wall normal thickness
Shallow ulcers

associated with Primary Sclerosing Cholangitis

Question 22

which inflammatory bowel disease is associated with the following;

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

Answer 22

Ulcerative colitis - UC

Question 23

lead pipe colon on xray. is seen. in UC or Chrons?

Answer 23

UC

Question 24

String sign on xray. is seen. in UC or Chrons?

Answer 24

chrons

Question 25

how do the complications of chrons and UC differ?

Answer 25

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

Chrons;
obstruction
fistula
abscess

Question 26

bloody diarrhoea is seen. in UC or Chrons?

Answer 26

UC

Question 27

UC has similar extraintestinal manifestations as Chrons execpt for?

Answer 27

UC can invovle eyes and muscles;

Myositis
Uveitis/iritis

Question 28

are the following polyps cancerous ;

Tubular adenoma
Tubulovillous adenoma
Villous adenoma

Answer 28

no are neolplastic, associated with iincreased risk of cancer ;

Adenomas are precursors of carcinoma

Question 29

what is the difference between a hyperplastic polyp and an adenoma?

Answer 29

adenoma = excess epithelial proliferation AND dysplasia

Question 30

what. factors increase risk of polyp being cancerous?

Answer 30

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

Question 31

how might an adenoma present?

Answer 31

Usually none

Bleeding/anaemia

Question 32

what are the details of Familial Adenomatous polyposis (FAP/APC) ?

prognosis?

Answer 32

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

Question 33

how is Familial Adenomatous polyposis (FAP/APC) treated?

Answer 33

prophylactic resection of colon to prevent cancer

Question 34

what is Gardner’s Syndrome?

Answer 34

same as FAP but higher risk of cancer

Distinctive extra-intestinal manifestations eg cysts and tumours

Question 35

what causes Hereditary Non-polyposis Colorectal Cancer (HNPCC)?

Answer 35

Uncommon autosomal dominant disease
3-5% of all colorectal cancers

1 of 4 DNA mismatch repair genes involved (mutated)
Numerous DNA replication errors (RER)

Question 36

what is the progression and prognosis of Hereditary Non-polyposis Colorectal Cancer (HNPCC)?

Answer 36

Onset of colorectal cancer at an early age - 35 year olds

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)

Question 37

most Colorectal carcinoma are of which type?

Answer 37

98% are adenocarcinoma

Question 38

what Grading and Staging is used in Colorectal carcinoma?

Answer 38

Grade = level of differentiation

Dukes’ staging:
A = confined to wall of bowel
B = through wall of bowel
C = lymph node metastases
D = distant metastases

TNM (tumour, nodes, metastases)

Question 39

what age is expected for diffirent colon cancers

Answer 39

normal one (non familial) - age 65 approx

FAP - 25

HNPCC - 35 / 40