Bowel cancer: signs and symptoms

Bowel cancer is the fourth most common cancer in the UK. However, over half of cases are diagnosed at a late stage, which reduces the chances of successful treatment. Early signs of bowel cancer are not always noticeable, which is why many people don’t seek treatment until later when the symptoms are more obvious. It’s really important to screen for bowel cancer, especially in people aged over 50 who are more likely to develop the condition.

What is bowel cancer?

Bowel cancer covers cancers that start in the large bowel or back passage (rectum). It’s sometimes called colon cancer or rectal cancer depending on where it begins. Both types of cancer can have very similar symptoms and are usually diagnosed in the same way. 

Colon cancer

Colon cancer can start anywhere in the colon, which is a large organ at one and a half metres long. 

Rectal cancer

Rectal cancer refers to cancer that starts in the rectum, which is approximately the last 12cm of the colon and is located near the bladder and reproductive organs. 

Signs and symptoms

Many of the signs of bowel cancer are easy to mistake for other problems such as irritable bowel syndrome (IBS) or piles (haemorrhoids). If you notice any of the signs below, it’s always a good idea to talk to your GP even if you don’t think it is something to worry about. They can advise you on whether it needs investigating further.

Early warning signs

Bowel cancer often starts with small growths called polyps. These are not always cancerous but can change over time. The polyp, or tumour, can cause bleeding in your colon and make your stools become narrow and ribbon-like. 

Bleeding in the colon isn’t always noticeable but you might notice your stools have become very dark in colour or you may spot some blood or a black tar-like substance. Even when bleeding is not noticeable, it can cause anaemia, which can make you feel tired and weak. 

Unexplained weight loss and pain in your tummy that won’t go away can also be early signs of cancer but these also apply to many other health problems.

Signs of intermediate or advanced cancer

As cancer grows and advances it can spread, affecting other parts of the body and causing more noticeable symptoms. Signs that affect your whole body can include fatigue, loss of appetite, unexplained weight loss, and nausea or vomiting. Other signs of bowel cancer include:

• A feeling that you haven’t fully emptied your bowels
• A lump or pain in your back passage
• Changes in your bowel habits including constipation, diarrhoea or needing to go more often than usual
• Cramps, a bloated feeling or discomfort in your tummy

Differences in the symptoms of colon and rectal cancer

While many symptoms of colon and rectal cancer are the same, there can be a few differences. Colon cancer is more likely to cause pain in your tummy and changes to your bowel movements while rectal cancer can cause changes in the size and shape of your stools and visible blood in your stools. 

Causes of bowel cancer and risk factors

It isn’t always possible to know the cause of bowel cancer but there are a number of risk factors that increase the likelihood of developing it. Age is the biggest factor, with most people diagnosed with bowel cancer being aged over 60. If you already have a bowel condition such as polyps, Crohn’s disease or ulcerative colitis, you have a higher risk of developing bowel cancer. 

Lifestyle and diet can also increase your risk of getting bowel cancer. If you smoke, are overweight, have an inactive lifestyle, or eat a lot of processed foods and red meat and not enough fibre, you are more at risk too. 

Family history is a factor in a small number of cases. If a close family member had bowel cancer when they were aged under 50, you might be more at risk and may be offered early screening. 

Detecting bowel cancer

While there is no definitive way to prevent bowel cancer, there are things you can do to lessen your risk. Screening is one of the most important things you can do if you are aged 55 or over. As so many cases do not show symptoms in the early stages, screening is the best way to detect it. There are two types of screening — a bowel scope or sigmoidoscopy, where a thin, flexible tube with a camera on the end is used to look inside your bowel and a home testing kit, where you collect a small stool sample and send it off to be tested. 

Leading a healthy lifestyle is a good way to lower your risk of bowel cancer and other types of cancer.

Talk to your GP

If you think you may have symptoms of bowel cancer or there are any signs that worry you, talk to your GP. They can assess your symptoms and send you for screening if necessary. Most people with the symptoms above do not have bowel cancer, but it’s important to get them checked.