Bowel polyps

A bowel polyp is a growth on the lining of the large bowel or the rectum. It is a very common finding: after the age of fifty, at least one polyp turns up in roughly one person in four. Almost always it is benign. But some polyps are precisely the tissue from which bowel cancer grows over the years, and that is the whole point of the story: a polyp removed in good time is a tumour that will now never exist.

Why polyps usually give nothing away

The lining of the bowel does not register touch and stretch the way skin does. A polyp does not hurt, grows slowly, gets in the way of nothing and stays silent until it becomes large. That is why the overwhelming majority are found by chance — during a colonoscopy arranged for something else entirely, or when someone with no complaints is examined.

Hence the most useful rule of all: waiting for symptoms makes no sense. Symptoms appearing means the polyp is already big or has already changed. This is the reason for examining people who feel perfectly well: a stool test for hidden blood at set intervals, and colonoscopy according to age and family history. The schedule is chosen by a doctor.

The types, and why the type matters

Polyps are not all the same, and the type determines quite literally everything that follows.

• Hyperplastic polyps are small and mostly sit in the last part of the bowel. They practically never turn cancerous.
• Adenomas are the commonest of the ones that count. Risk rises with size: a polyp over a centimetre calls for different attention than a two-millimetre one. The architecture of the tissue and the degree of cell change matter too.
• Serrated lesions are the most treacherous. They are flat, pale, blend into the lining and often lie under a film of mucus, so they are easy to miss even on a careful examination. They grow in the far, right-hand parts of the bowel and can turn cancerous faster than adenomas.
• Inflammatory pseudopolyps appear in long-standing colitis. They do not become cancer, but they make the examination harder.

An ordinary adenoma needs around ten years to become a cancer — the margin is generous, and it works entirely in favour of anyone who gets checked. Serrated lesions shorten that margin.

What raises the odds

The exact cause is unknown: cells in the lining start dividing faster than they should and form the growth. What makes it more likely, though, is well established.

• age — from forty-five or fifty onwards polyps are found more and more often;
• polyps or bowel cancer in a parent, brother, sister or child;
• long-standing ulcerative colitis and Crohn's disease;
• smoking and regular drinking;
• excess weight, a sedentary life, type 2 diabetes;
• a diet heavy in red and processed meat and light on vegetables, fruit and wholegrains.

When heredity is the answer

In a small proportion of people polyps are not a matter of chance but the expression of an inherited syndrome. Such patients are few, but they are exactly the ones for whom follow-up by the general rules is wrong, and recognising them matters more than anything.

Familial adenomatous polyposis: polyps run into the hundreds and thousands and start appearing in the teenage years. Without treatment, bowel cancer develops almost inevitably and early, so in such families surveillance begins in childhood and preventive removal of the large bowel is often discussed.

Lynch syndrome: here polyps are few, but they turn into cancer quickly and at a young age. The raised risk is not confined to the bowel — it extends to the womb, the ovaries, the stomach and the urinary tract.

There are rarer variants too, such as the syndrome in which polyps of the small bowel go together with dark pigmented spots on the lips and the lining of the mouth.

It is worth asking your doctor about a genetics assessment if there is:

• bowel cancer in a close relative diagnosed before the age of fifty;
• several relatives with bowel or womb tumours;
• ten or more polyps found over a lifetime;
• polyps detected at a young age.

What should bring you to a doctor

Book an appointment if the following appear and last more than three weeks:

• blood or mucus in the stool;
• a change in your bowel habit that does not settle back to normal;
• constipation that does not yield to the usual measures, or keeps coming back;
• a feeling of incomplete emptying and false urges;
• weight loss you were not working towards.

A low haemoglobin deserves a separate mention. Iron-deficiency anaemia in a man, or in a woman past the menopause, is almost always a reason to look for the source of blood loss in the bowel, even when there is no visible blood in the stool and no other complaint at all. Simply taking iron and leaving it there is not acceptable.

Seek emergency care if bleeding from the back passage does not stop, the amount of blood is large, there are big clots, or weakness, dizziness, pallor and a racing heart appear alongside it.

One more thing: do not put the blood down to haemorrhoids yourself. Plenty of people have haemorrhoids, and having them does nothing to rule out that something higher up is the source.

How they are found

Colonoscopy is the only method that both finds a polyp and allows it to be taken away in the same sitting. A flexible instrument with a camera examines the bowel from the inside; the procedure should not be painful and is usually done with pain relief or sedation.

There is a detail here that is very often underrated: how well the bowel is prepared. If the preparation is not finished or not taken as instructed, the doctor is looking at the wall through leftover contents and will simply not see small flat lesions. Preparation is half the result.

A CT scan of the bowel is an option when a colonoscopy cannot be done or cannot be completed. It shows polyps but does not remove them: if one is found, a colonoscopy will be needed anyway. A stool test for hidden blood is a screening tool, not a diagnosis — a polyp does not bleed continuously, and a negative result does not rule one out.

How they are removed, and what comes next

Usually the polyp is taken off during the colonoscopy itself with a wire loop, sometimes with cautery. The lining has no pain endings, so it does not hurt. Large flat lesions are removed in layers, after lifting the lining with an injected solution, occasionally over several sessions. Surgery is rarely reached — only with very large or very numerous polyps.

Everything removed goes to the laboratory, which answers three questions: whether the polyp came out completely, what type it is, and whether there are signs of malignant change. If there are, treatment continues, and its extent is decided by a specialist.

For a week or two after removal there remains a small risk of bleeding from the raw area. See a doctor if heavy bleeding, severe abdominal pain or a fever appears.

And the most important part is the date you are given for the next colonoscopy. It depends on the number, size and type of the polyps removed and can be anything from a year to several years. Missing that follow-up undoes everything achieved so far, because new polyps do appear, and the entire point was to meet them in good time. What lowers the chance of new ones is the same as everywhere else: stopping smoking, moderating alcohol, keeping to a healthy weight, moving, and eating enough fibre.

Online consultation

In an online appointment the doctor will go through your symptoms and test results, judge whether anything calls for urgent investigation, help you set out the family history and decide whether a genetics assessment is warranted, explain how to prepare properly for a colonoscopy and what the laboratory report means, and tell you when to be checked again.

This material is for information only and does not replace medical advice.