Bowel polyps: causes, colonoscopy and removal

The NHS describes bowel polyps as small growths on the lining of the large intestine (colon) or rectum, also called colonic or colorectal polyps. It says the exact cause is not known but they are thought to arise because the body produces too many cells in the lining of the bowel, and the extra cells form a bump.

The NHS says you may be more likely to develop polyps if:

• A member of your family has had bowel polyps or bowel cancer.

• You are over 50; around 1 in 4 people over 50 will have at least 1 polyp.

• You have inflammatory bowel disease, which includes ulcerative colitis and Crohn's disease.

• You are overweight or smoke.

Most polyps are discovered by chance, for example during a colonoscopy for another bowel condition. The NHS says that rarely, larger polyps can cause a small amount of mucus or blood in the poo, bleeding from the bottom, a change in normal bowel habit such as diarrhoea or constipation, or weight loss without trying.

The NHS advises seeing a GP if you have mucus or blood in your poo for 3 weeks or more, your bowel habit is different from normal, constipation is not improving with treatment or lasts a long time, or you have lost a noticeable amount of weight without trying. It advises an urgent GP appointment or NHS 111 for diarrhoea lasting more than 7 days, black or dark red poo, or bloody diarrhoea, and A&E or 999 for non-stop bleeding from the bottom or a lot of blood.

The NHS says most polyps are harmless and do not become cancerous, but a small number can change over many years. Bowel cancer screening can help find polyps that are more likely to develop into bowel cancer so they can be removed. Cancer Research UK lists screening, high-risk surveillance and follow-up after bowel cancer treatment among the reasons for a colonoscopy.

The NHS says a GP who thinks symptoms could be caused by polyps may recommend a colonoscopy or a CT colonography. In a colonoscopy, a long, thin flexible tube with a camera (a colonoscope) is passed into the bottom and guided up the bowel; the NHS says it should not be painful but can feel uncomfortable. CT colonography uses X-rays and a computer to create a detailed image of the bowel after you have been given a special liquid so the bowel can be seen clearly.

Cancer Research UK says a colonoscopy can take between 15 and 60 minutes, that you need an empty bowel and take laxatives the day before, that you may be offered painkillers and sedation or gas and air, and that during the test the endoscopist can take photographs and tissue samples and remove growths using a wire loop. If you have sedation you need someone to take you home and stay with you overnight, and for 24 hours you should not drive, drink alcohol, operate heavy machinery or sign legally binding documents.

The NHS says polyps are usually removed during colonoscopy: a wire loop that is part of the colonoscope cuts off (snares) or burns off (cauterises) the polyp. This is called a polypectomy and is painless. Rarely, when there are lots of polyps or a polyp is very large, surgery may be needed to remove part of the bowel.

The polyps are then sent to a laboratory to check whether the polyp has been completely removed, whether there is any risk of it regrowing and whether there are cancerous changes. If there are, you may need further treatment and your specialist will advise. Ask at the end of the procedure when and how you will receive the result, and whether follow-up colonoscopies are recommended and when, since the sources reviewed here do not specify intervals.

Cancer Research UK calls colonoscopy a very safe procedure but lists possible tummy cramping or pain after the test because of gas put into the bowel, some bleeding after a biopsy or polyp removal that usually stops on its own within a couple of days, very rarely a tear in the bowel wall that would likely need surgery, and a rare reaction to sedation causing breathing difficulty. Contact the endoscopy unit or the hospital advice line if bleeding continues or is heavy, and call 999 for severe pain, heavy bleeding or feeling faint.

Polyps are found through NHS screening, symptom investigation or follow-up of other bowel conditions. Private colonoscopy offers quicker access if symptoms are not on an urgent pathway, but symptoms such as persistent blood in the poo or a change in bowel habit should still go through your GP so that cancer is not overlooked. Ask who will review the pathology and who is responsible for recall if surveillance is advised.