Clinical Manifestations

Question 1

RIGHT-sided / ascending colon cancers are associated with what types of symptoms?

Answer 1

• Iron-deficiency anaemia
• Fatigue

Thus, it is a clinical maxim that the underlying cause of iron deficiency anemia in an older man or postmenopausal woman is GI cancer until proven otherwise.

Question 2

LEFT-sided / descending colon cancers are associated with what types of symptoms?

Answer 2

• Left lower quadrant pain
• Altered bowel habits (e.g. overflow diarrhoea)
• Cramping
• Bowel obstruction (due to napkin-ring constriction)
• Occult bleeding

Question 3

What is the most common type of GI malignancy?

Answer 3

Adenocarcinoma (affects the mucous-producing glandular cells)

Question 4

What is responsible for the majority of precursors to colorectal carcinoma?

Answer 4

Polyps

Question 5

Adenomatous polyps have a normal appearance. What types of mutations are they generally caused by, and where do they typically occur?

Answer 5

Adenomatous polyps: APC gene mutation

Location: RIGHT / ascending colon

Question 6

Serrated polyps have a saw-tooth appearance. What types of mutations are they generally caused by, and where do they typically occur?

Answer 6

Serrated polyps: Mutations in DNA mismatch repair genes

Location: LEFT / descending colon

Question 7

What is the most common site of metastases for colon cancers?

Answer 7

LIVER (due to portal drainage of the colon)

Question 8

What is the most common site of metastases for rectal cancers?

Answer 8

LUNGS

Question 9

What are the 2 categories of bowel obstruction?

Answer 9

1. Mechanical

2. Pseudoobstruction

Question 10

List 4 causes of mechanical bowel obstruction and briefly explain their cause(s).

Answer 10

• Adhesions: 2 parts of the bowel connected to each other by a fibrous band (e.g. post-operative adhesions)
• Tumour:
• Intussusception: invagination of the bowel into itself (common site: ileocaecal valve)
• Hernia: protrusion of a structure through the body wall that normally contains it
• Volvulus: twisting of the bowel

Question 11

List 2 causes of pseudoobbstruction and briefly explain their cause(s).

Answer 11

• Myopathy: no movement / peristaltic contractions

- Neuropathy: no innervation –> abnormal movement

Question 12

Bowel obstruction is the presenting symptom of CRC in up to 30% of cases.

List 3 signs/symptoms of large bowel obstruction.

Answer 12

• Bloating
• Abdominal pain
• Obstipation
• Nausea & vomiting (but this is more likely with more proximal obstructions, which can mimic small bowel obstruction)

Question 13

A blood sample from a patient with considerable blood loss due to colorectal cancer will be likely to show an abnormally large number of what type of RBC?

Answer 13

Reticulocytes (immature RBCs)

Question 14

In a patient with carcinoma of the sigmoid colon which has spread to lymph nodes in the sigmoid mesocolon, lymph will drain to which nodes?

Answer 14

Inferior mesenteric nodes