Friday, November 20, 2009

Colon Cancer - Q & A

What are the risk factors?
Age > 45 yrs
Lack of dietary fibers & High protein diet (meat)
Alcoholism, Smoking
Cholecystectomy - increased bile acid secretion

Explain briefly the pathology.
Histologically - columnar cell neoplasm
Macroscopically, it's divided into 4 types : annular, tubular, ulcerative and cauliflower type.
Annular type causes predominantly obstructive symptoms, whilst others causes bleeding more often.

Enumerate some common sites involved.
Rectum (most common)
Sigmoid colon
Descending colon

Explain the clinical features.

a) Carcinoma of caecum + ascending colon

Patient presents mostly with features of anaemia, weight lost or sometimes abdominal mass. Abdominal pain is not a usual symptoms, however if present, usually is dull aching, or colicky in nature, over the right lower quadrant.

On examination, the patient is usually pale and appears wasted.
If the patient is thin enough, a mass may be visible over the RIF or the right lumbar region, confirmed by palpation, which is usually hard, mobile/fixed.
Percussion over the mass - dull note.
Normal bowel sounds are usually heard.

It's possible that CA caecum can triggers episode of acute appendicitis in such patients. More importantly, there's no difference in the clinical features from the usual ones. Hence, any patient, >45 yrs of age, presented with acute appendicitis, CA caecum should also be suspected. The other differential diagnosis includes :

Caecal diverticulum
Ileocaecal tuberculosis
Crohn's disease

b) Carcinoma involving the left sided colon

The age of the patient is usually >45yrs old.
However, if it involves younger patients (20-30), suspect familial polyposis/or it can even occurs as a complication of long-standing ulcerative colitis.
There's no sexual predilection.
The first complaint is usually altered bowel habits.
There's usually a period of constipation, interpersed in between periods of explosive diarrhoea.
The constipation is obviously caused by obstruction, and diarrhoea is caused by liquefaction of the stools above the obstruction.
Sometimes, the diarrhoea can be worsened by passing mucuos, as when the surrounding colonic mucosa gets inflammed.
Per rectal bleeding is also an important symptom.
The blood is usually dark-plum coloured, sometimes accompanied by some amount of clots.
Especially when the tumour involves sites such as the rectosigmoid junction, it can easily prolapsed into the rectum, causing tenesmus.
Tenesmus is defined as intense desire to evacuate the bowel, but however, nothing passes out (or scanty amount of loose stools) when the patient tried to pass motion.
Commonly associated with sensation of incomplete bowel evacuation.
Lastly, pain is again not a usual feature.
Some amount of dull-aching, or colicky pain may be appreciated over the left lower quadrant of abdomen.
Weight lost usually occurs before anorexia develops.

On examination, patient is wasted.
Mass may be visible/felt over the left iliac fossa or the left lumbar region.
In can be tender when associated with areas of inflammation around the mass.
Indentation of the abdomen at proximal sites may be possible - stool collection
Dull note on percussion over the mass.
Normal bowel sounds are usually heard.

However, if the patient neglects the above symptoms, it can complicates as bowel perforation, that surprisingly, occurs at the caecum instead of the site of malignancy.
Patient can presents with severe generalised abdominal pain, with features of shock.

What are the mode of spreading for CA colon?

1) Direct spread

Longituidinal, transverse or radial.
It usually involves the surrounding bowel wall causing obstruction before invading the adjacent structures.
Sometimes, fistulas are formed when the tumour invades to adjacent structures (vesico-enteric fistula)
Radial spread involving the adjacent organ determines the prognosis.

2) Lymphatic spread

Lymph nodes draining the colon :

L1 -> Nodes located within the vicinity of the colon
L2 -> Right, left colic, mid-colic and ileocolic nodes
L3 -> Nodes originating from the abdominal aorta, close to the superior mesenteric vessels

3) Hematogenous spread

Via the portal system, it spreads to the liver.
Rarely to the skin, lungs, brain

4) Transcoelomic spread

What are the investigations to be done?

Currently, colonscopy is the investigation of choice, provided that the patient is fit enough to undergo bowel preparation.
The advantage is, not only the primary tumour can be clealy visible, but any polyps or other synchronous tumour.
However, it carries a small risk of bowel perforation.

If colonoscopy is contraindicated, Double contrast barium studies can be done.
On abdominal X-ray, we'll be looking for a filling-defect.
Or flexible sigmoidoscopy can be done.

Ultrasound of the liver to look for secondaries.
CT abdomen, thorax as for staging of the malignancy.

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