Symptoms & Diagnosis of Colorectal Cancer

Colorectal cancer is one of the most common form of cancer internationally, and the number one form of cancer in Singapore for both men and women. In our series of four-part articles, we will be looking at: What causes colorectal cancer How to prevent colorectal cancer Symptoms & Diagnosis of colorectal cancer Treatment for colorectal […]

Colorectal cancer is one of the most common form of cancer internationally, and the number one form of cancer in Singapore for both men and women. In our series of four-part articles, we will be looking at:

Do read on to find out more about one of the greatest threats to your life, and be equipped with the knowledge to prevent it from causing you your life. In this article, we will be discussing about the symptoms of colorectal cancer and the types of screening to go for to help you to detect it as early as possible.

Symptoms of Colorectal Cancer

While it is important that you consistently go for your routine screenings, it is also very beneficial for you to recognize the symptoms of colorectal cancer so that you will know that you have to go for a screening, and seek necessary treatments before the problem escalates.

Take note of the following common symptoms of colorectal cancer:

  • Changes in bowel habits and consistency
  • Constipation or Diarrhoea
  • Experience the feeling that the bowel has not been completely emptied after a bowel movement
  • Stools appearing narrower than usual
  • Rectal bleeding causing bright red blood to appear when passing motion
  • Blood in your stool causing the stools to look black
  • Persistent abdominal pain and cramps
  • Feeling bloated or full in the abdomen, even if you did not eat
  • Chronic tiredness or weakness
  • unexplained weight loss
  • Nausea or vomiting
  • Lump in the abdomen or the back passage discovered by your doctor

However, do note that in early stages of colorectal cancer, most people usually do not experience any symptoms. When the symptoms appear, they may also vary according to the size of the cancer cells and their locations in the large intestine. Hence, it is still the safest to go for your routine screenings especially if you are above the age of 50.

Most of these symptoms may also be caused by other health problems and not colorectal cancer. However, if the symptoms persist for more than 4 weeks, then it is important to see a doctor immediately to be screened for colorectal cancer.

Types of Diagnosis For Colon Cancer

Apart from doing your routine screening, screening should also be done if you are suffering from the previously mentioned symptoms for more than a month. Early screening can detect polyps when they are still benign, or colorectal cancer during its early stages. This greatly increase the chance of successful treatment.

The following are some of the common screening and diagnostic procedures for colorectal cancer that you can choose from.


Colonoscopy makes use of a colonoscope to examine the whole of the colon and rectum for signs of colorectal cancer. A colonoscope is a long, flexible, thin tube with a video camera attached, and the footage recorded is viewed on a screen monitor. Tissue samples found in suspicious areas are taken for analysis. Should there be Polyps discovered during the colonoscopy process, they can also be removed immediately during the procedure by surgical tools through the tube.

Colonoscopy is a painless procedure, but some patients may request for mild sedative to help calm them down. Before the examination, patients may be given laxative fluid to clear the colon as much as possible. Bleeding of the colon wall is an extremely rare, but possible complications.

Image 1.1: Colonoscope and how it is used Source Medicine Net


Sigmoidoscopy is similar to colonoscopy except that only the rectum and the lower part of the colon can be examined. If the doctor detects polyps or colon cancer, a colonoscopy have to be used to examine the entire colon and to remove any polyps present.

Sigmoidoscopy is a very short process and although it is not painful, it might be uncomfortable. There is also a small risk of bleeding of the colon wall.

Image 1.2: Sigmoidoscopy and how it is used Source: Hopkins Medicine

Virtual Colonoscopy

X-ray equipment can be used to capture images of the colon and rectum, after they have been cleared. The results are then examined on a computer to look out for signs of like polyps and tumours. This procedure offers a less-invasive alternative to colonoscopy, without compromising the accuracy of diagnosis.

Barium enema X-ray

The colon and rectum are filled with a white liquid (barium) in order to improve the X-ray pictures. Polyps and anything foreign can then be seen clearly in the scans. In the case of a double-contrast barium enema, air is added as well.

A sigmoidoscopy may also be done to ensure that small polyps are not missed by the barium enema X-ray process. A colonoscopy may also need to be done if the barium enema X-ray detects anything abnormal.

Barium Enema
Image 1.3: Analysis of results after Barium Enema X-ray Source: Very Well Health

Faecal Occult Blood Test (FOBT)

FOBT is a kind of test that examines a sample of the patient’s stool for any presence of blood. FOBT can be done at clinics or even at home, with a kit. If there is blood found in the stools, further tests are conducted to find the source of the blood. However, FOBT is not completely accurate, as you may not necessarily bleed all the time. Blood found in stool may also be caused by other benign conditions and illnesses like haemorrhoids. The appearance of blood in stool may also be caused by certain food.

Image 1.4: Animation depiction of FOBT Source: Laboratory Info

DNA test on stool

DNA tests can be conducted on stools to analyse for DNA indicators that colorectal cancer or precancerous Polyps cells are present. These tests can be conducted in clinics, and stools are sent to a laboratory.

DNA tests is more accurate in detecting colorectal cancer rather than signs of polyps.

Written by: Lim Jun Tian

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