If someone whose bowels are normally regular starts getting diarrhoea, constipation or a mixture of the two, then doctors call this an 'altered bowel habit'. There are many different causes for this and most of these are completely benign (non-cancerous). Having said this, sometimes an altered bowel habit can be caused by cancer and if there is a cancer it is important to get it diagnosed and treated as soon as possible. So you should never ignore an altered bowel habit that has gone on for a few weeks.
This means that you should go to see your family doctor so that he or she can take all the details and give you a proper examination.
The Department of Health has recently given clear advice to general practitioners suggesting they should arrange an urgent hospital appointment with a specialist in diseases of the digestive system (a gastroenterologist) for anyone who is over 60 and has been having more frequent or looser bowel movements going on for more than six weeks. Actually many doctors do not think this guidance goes far enough and feel that people younger than 60 who have this problem should also be urgently referred.
An urgent appointment usually means the specialist will see you within about two weeks.
When the bowel specialist sees you they will usually take a full medical history and carry out a thorough examination, including a rectal examination. This involves putting a gloved finger into your back passage and feeling it gently for lumps or other abnormalities - it may uncomfortable but not painful. You may also have a proctoscopy or sigmoidoscopy where a small metal tube or a narrow flexible telescope is passed into the back passage so that the specialist can look at the lining of your bowel.
These examinations may show the cause of the diarrhoea but if not then other tests may be necessary - like blood tests, a barium enema may or a colonoscopy (which looks at the whole of the large bowel with a long flexible telescope).
If there is a cancer then you will usually need an operation to remove it and there may also be some radiotherapy and/or chemotherapy involved as part of your treatment.
Do remember that these days bowel cancer is a very curable condition, especially if it is caught early, so if you have noticed some bleeding from the back passage don't delay - see your doctor!