Colorectal cancer

Question 1

Define

Answer 1

DEFINITION: malignant adenocarcinoma of the large bowel

Distribution:

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

Question 2

Causes

Answer 2

Environmental and genetic

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

Question 3

Risk factors

Answer 3

Western diet (e.g. red meat, alcohol)

Colorectal polyps

Previous colorectal cancer

Family history

IBD

Question 4

Epidemiology

Answer 4

SECOND MOST COMMON cause of cancer death in the West

UK: 20,000 deaths per year

Average age of diagnosis: 60-65 yrs

Question 5

Symptoms

Answer 5

Depends on the size and location of the tumour

Left-Sided Colon and Rectum

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

Right-Sided Colon

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

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

• Large bowel obstruction
• Haemorrhage or peritonitis due to perforation

Question 6

Signs

Answer 6

Anaemia

Abdominal mass

If metastatic:

• Hepatomegaly
• Ascites (shifting dullness)

Low-lying rectal tumours may be palpable on DRE

Question 7

Investigations

Answer 7

Bloods

• FBC - anaemia
• LFTs
• Tumour markers (CEA)

Stools

• FOBT - used as a screening test

Endoscopy

• Sigmoidoscopy
• Colonoscopy
• This can be used to biopsy the tumour

Double-Contrast Barium Enema

• May show ‘apple core’ strictures

Contrast CT

• For staging (Duke’s staging)