Colorectal cancer symptoms can be easy to dismiss, because many of them, such as a change in bowel habit or mild abdominal discomfort, are also caused by far more common and less serious conditions. That overlap is exactly why it helps to know which signs are worth paying attention to and when a check is sensible.
This article outlines the colorectal cancer symptoms that warrant an assessment, in a factual and non-alarmist way. Most people with these symptoms will not have cancer, but a timely conversation with a GP, polyclinic doctor or specialist allows any concern to be investigated properly and put into context.
Quick answer
- A persistent change in bowel habit (constipation/diarrhoea) lasting more than a few weeks is worth checking.
- Blood in the stool, whether bright red or dark, should be assessed rather than assumed to be piles.
- Unexplained weight loss, tiredness or ongoing abdominal discomfort can be relevant.
- A feeling that the bowel does not empty fully may be significant.
- Screening can detect changes before symptoms appear, so it matters even if you feel well.
Changes in bowel habit
One of the more commonly discussed colorectal cancer symptoms is a lasting change in how your bowels work. This might mean looser stools, constipation, or an alternating pattern that persists for several weeks rather than settling after a day or two. Stools that become noticeably narrower or changes in shape and size than usual can also be worth mentioning to a doctor.
Occasional changes tied to diet, travel, stress or a passing infection are common and usually settle. The signal to take note of is persistence: a new pattern that continues, or one that is accompanied by other symptoms below, is a reasonable reason to arrange a check.
Bleeding and changes in the stool
Blood in the stool is a symptom that should always be assessed, even though it frequently has a harmless cause such as haemorrhoids (piles) or an anal fissure (small tear in the anus). Bleeding linked to colorectal conditions can appear as:
- Bright red blood on the stool or the toilet paper
- Darker blood mixed into the stool
- Black, tarry stools, which can indicate bleeding higher in the digestive tract
Because piles and cancer can both cause visible bleeding, it is not safe to assume the cause without an examination. A doctor can distinguish between them and advise whether further tests, such as a colonoscopy, are appropriate.
Abdominal symptoms and other warning signs
Colorectal cancer can also produce more general symptoms that are easy to attribute to everyday causes. These include:
- Persistent abdominal discomfort, cramping or bloating
- A sensation that the bowel has not fully emptied after going to the toilet
- Unexplained tiredness, which can result from slow blood loss and anaemia
- Unintended weight loss without a clear reason
Any single one of these is usually not caused by cancer. What raises the value of a check is when a symptom persists, when several occur together, or when they appear alongside bleeding or a change in bowel habit. Ongoing digestive symptoms are among the situations where seeing a surgical oncologist or cancer specialist can help clarify what is going on.
Why symptoms are easy to overlook
Colorectal cancer often develops slowly, and early changes may cause no symptoms at all. When symptoms do appear, they tend to be mild and intermittent at first, which is why they are commonly put down to diet, stress, ageing or piles. This is not a reason for alarm, but it is a reason to take persistent symptoms seriously rather than waiting for them to become severe.
Age and family history can influence risk, and it can be helpful to understand how family history affects gastrointestinal cancer risk when deciding how vigilant to be. Sharing relevant family history with your doctor helps them advise on the most appropriate checks for you.
The role of screening
Screening is designed to detect changes before any symptoms are present, which is one of its main strengths. In Singapore, the faecal immunochemical test (FIT) is widely used to check for hidden blood in the stool, and colonoscopy allows the bowel lining to be examined directly and any growths, such as polyps, to be removed or sampled. Removing all polyps in the colon which can be precursors of cancer will prevent some cancers from developing.
Screening is generally recommended to start for anyone aged 50, and sometimes earlier for those with a family history or other risk factors. Your GP or a specialist can advise on timing based on your circumstances. Even if you feel well, screening remains worthwhile, because it can identify changes that symptoms alone would not reveal.
When to arrange a check
It is reasonable to see a doctor if you have a persistent change in bowel habit, any bleeding from the back passage, ongoing abdominal discomfort, unexplained weight loss or unusual tiredness. Most of these symptoms turn out to have non-cancerous causes, but the purpose of a check is to investigate and reassure, or to identify anything that needs treatment early.
If you would like to discuss your symptoms or arrange an assessment, you can contact the clinic to speak with the team. Acting on symptoms in a timely way keeps the greatest number of options open.
This article is for general information only and is not a substitute for medical advice. Please consult a qualified doctor or relevant specialist in Singapore for advice specific to your situation.