Colorectal Carcinoma

Question 1

Definition

Answer 1

Malignant adenocarcinoma of the large bowel

Question 2

Distribution

Answer 2

· 60% - rectum and sigmoid
· 30% - descending colon
· 10% - rest of colon

Question 3

Aetiology

Answer 3

· Environmental and genetic

· There is a sequence of genetic changes that go from normal bowel epithelium to cancer (e.g. APC, K-Ras)

Question 4

Risk factors

Answer 4

o Western diet (e.g. red meat, alcohol)
o Colorectal polyps
o Previous colorectal cancer
o Family history
o IBD

Question 5

Epidemiology

Answer 5

· SECOND MOST COMMON cause of cancer death in the West

· UK: 20,000 deaths per year

· Average age of diagnosis: 60-65 yrs

Question 6

Presenting symptoms (left-sided colon and rectum)

Answer 6

Depends on size and location of the tumour

o Change in bowel habit
o Rectal bleeding (blood or mucus mixed with the stools)
o Tenesmus (due to a space-occupying tumour in the rectum)

Question 7

Presenting symptoms (right-sided colon)

Answer 7

Depends on size and location of the tumour

o Presents later
o Anaemia symptoms (lethargy)
o Weight loss
o Non-specific malaise
o Lower abdominal pain (rare)

Question 8

Presenting symptoms (emergency)

Answer 8

20% of tumours will present as an EMERGENCY with pain and distension due to:

o Large bowel obstruction
o Haemorrhage or peritonitis due to perforation

Question 9

Signs on physical examination

Answer 9

· Anaemia

· Abdominal mass

· If metastatic:
o Hepatomegaly
o Ascites (shifting dullness)

· Low-lying rectal tumours may be palpable on DRE

Question 10

Investigations

Answer 10

· Bloods
o FBC - anaemia
o LFTs
o Tumour markers (CEA)

· Stools
o FOBT - used as a screening test

· Endoscopy
o Sigmoidoscopy
o Colonoscopy
o This can be used to biopsy the tumour

· Double-Contrast Barium Enema
o May show ‘apple core’ strictures

· Contrast CT
o For staging (Duke’s staging)