The symptoms from a bowel cancer depend on the size, position and stage of the cancer. If the cancer is near the anus, then symptoms of bleeding and change in bowel habit (diarrhoea or constipation, not typical for the patient) are common. Sometimes the patient may feel that they are not able to empty their bowel fully; this is a symptom known as tenesmus.
For cancers located further round the bowel (on the right hand side of the tummy), there may be few symptoms. These cancers might also bleed, though the patient will often not be able to see the blood in the stools. The first symptoms might be of breathlessness and tiredness from anaemia, secondary to chronic blood loss.
About one in five patients with a bowel cancer present with a blockage or obstruction. This commonly gives symptoms of abdominal distension, pain, constipation and vomiting.
Many of the symptoms of bowel cancer such as diarrhoea and bleeding are non-specific and most patients with these symptoms do not have cancer. However, if you have any of these symptoms and are worried, then you should see your doctor.