Symptoms of colorectal cancer

The doubling time of colorectal cancer is about 620 days. That means that it is a slow growing type of cancer and it may be present for as long as five years before symptoms appear.

Unfortunately, the symptoms are often so insignificant that they are ignored. The symptoms depend on where the cancer is. The more distal cancers in the rectum and the sigmoid (the part of the bowel above the rectum) may present with red blood in the stool. Many people may think they have haemorrhoids (piles) and ignore it because the blood can come and go. When the tumour grows, it can cause bowel obstruction or grow into the pelvic bones and cause local pain. The left side of the colon is narrower that the right, so you may have colicky abdominal pain after meals or changed bowel habits as well.

Tumours in the right colon (the caecum – where the small bowel attaches itself to the colon –, the ascending colon – the part on the right side of the abdomen – and the transverse colon – the part that is situated between the left and right side) may also cause obstruction, but often present only with anaemia, because the tumour does not bleed enough at a time for blood to be noted.

Common complaints are:

• A change in bowel habits
• Blood in the stool (red or tarry)
• Foul-smelling stool
• Abdominal discomfort such as colic, bloating or fullness
• Fatigue
• Weight loss
• A feeling that one wants to pass stool, but nothing comes out

Colorectal cancer is often misdiagnosed as irritable bowel syndrome (the so-called spastic colon), diverticular disease (balloon-like structures mostly on the left side of the colon) or haemorrhoids. It is for this reason that if you develop new abdominal symptoms, they must be fully investigated. All patients with blood in their stool should have a colonoscopy.

Reviewed by Dr C R Jacobs, Clinical Oncologist, August 2008.

Reviewed by Dr Estelle Wilken, Senior Specialist, Internal Medicine and Gastroenterology, University of Stellenbosch and Tygerberg Hospital, August 2010