Polyps and Bowel Cancer
Sessile polyp Pedunculated polyp Large polyp
Polyp (left) and early cancer (right)
Your bowel consists of 2 specialised parts, namely the colon and the rectum. The colon is broadly referred to as having 2 halves, the right colon (or right hemicolon) and the left colon (or left hemicolon). The rectum is broadly divided into three parts, the upper, middle and lower thirds. Various parts of the colon have specific names, as shown in the diagram below. Doctors refer to parts of the bowel sometimes according to whether it is the upstream portion ("proximal") or the downstream portion ("distal"). The colon is very variable in its length and in the number of convolutions or bends in the tubing.
What is a polyp?
A polyp is a fleshy growth on the inside of the bowel. Polyps appear because the genes in the cells forming the inner bowel lining (called the mucosa) which usually control the cell's lifecycle, fail to do so. This results in unregulated cell multiplication until eventually enough cells are visible to the naked eye as a growth. These growths may be broad-based ("sessile") or have a stalk ("pedunculated") resembling a toadstool. They appear in a variety of sub-types and sizes, with different risks of future harm from them based on these two sets of characteristics. Polyps tend to be slightly more common in men than women and increase in incidence as we grow older. Polyps are very common - one in four people will have a polyp at some time in their life, but most of us will be oblivious to them and remain in good health despite their presence.
Polyps are benign growths, but they have the potential to transform into bowel cancer. This process of growth and transformation is believed to occur over several years. Only 1 in 10 polyps turns cancerous. Most polyps occur sporadically i.e. there is no obvious genetic abnormality or syndrome behind their emergence. Rare family genetic syndromes exist in which abnormal bowel genes are identifiable. These conditions include Familial Adenomatous Polyposis, Gardner's Syndrome and Peutz-Jegher's Syndrome (amongst others) and such persons have increased risks of both polyps and cancers due to their genetic pedigree.
Where do bowel polyps occur?
Polyps occur in the large bowel, which consists of the colon and the rectum (back passage). They are commonest in the lower colon and rectum i.e. towards the exit, and 80% will be found within 1 foot of the anus. If a polyp is encountered, there is a 20% chance that there will be more polyps higher up in the colon and a 5% chance that there will be a cancer somewhere in the bowel. For this reason, your whole bowel length will need to be inspected to ensure that all the polyps are identified and removed to prevent them turning cancerous.
What symptoms might occur?
Polyps may produce excess mucus (slime) and may bleed as faeces is passed over them. Blood and/or mucus passage when opening your bowels could indicate an underlying polyp. If the polyp is nearer the anus, such symptoms will be more likely. If it is situated high up in the bowel, the only indication may be vague symptoms related to anaemia from long-standing bleeding, such as fatigue, lethargy, shortness of breath with exertion, palpitations or light-headedness. Polyps can cause a looseness or increased frequency of stool passage, but only very rarely will they grow large enough to cause colonic obstruction. Please remember that the vast majority of polyps never grow and thus most polyp bearers will have no symptoms from the polyp at all.
Investigations for polyps?
Polyps can be detected either by direct inspection of the bowel lining, called an endoscopy, or indirectly through radiological scans. Endoscopy implies a camera procedure and this takes the form of either a flexible sigmoidoscopy (partial examination, of the lower colon and rectum) or a colonoscopy (complete examination, of the entire colon and rectum). Radiological scans include a barium enema, a CT scan or a hybrid of the two called a CT colonography scan. See the menu bar for further information on these procedures.
How are polyps treated?
Typical polyps are managed through endoscopy procedures. This usually comprises the painless removing of the polyp flush with the bowel lining by passing a wire noose around the polyp and applying electrical current to it to burn it off. This is termed a "polypectomy". Tiny polyps that are too small to be snared are simply cauterised in a procure called "hot biopsy". Don't worry - you cannot feel this occurring inside you as there are no nerves in the bowel that can sense heat or electricity or pain from cutting! Larger polyps may need to be removed by an extension of the polypectomy technique called EMR. Before the polyp is snared, a fluid is injected (again painlessly) between the mucosal lining and the muscular tube of the bowel, which acts as a cushion or buffer for the heat of removing it. Very large polyps may necessitate surgery: if the polyp is near your anus, it may be reachable via the anus whilst you are anaesthetised. This is a specialised technique called "Transanal Resection" or "Transanal Endoscopic Micro-Surgery" (TEMS). If the large polyp is far away from the anus, or there is doubt that it is benign, more radical surgical procedures are required (see under "cancer" below and "learn about your surgery" in the menu).
What do we mean by the term “cancer”?
Doctors are notorious for using jargon and may speak euphemistically, whilst some patients have selective memory and misinterpret things that they heard. So let’s get some terminology clear:
A Growth = something that is growing that shouldn’t be; this could be harmless or harmful, but generally the word implies something which a doctor doesn’t like the look of and is somewhat anxious about.
Neoplasm = the correct term for a growth of any kind, whether benign or cancerous
Lesion = an abnormality that is visible or palpable; it’s something we cannot yet give a name to e.g. we see an abnormality on a scan but can't interpret exactly what it is; sometimes doctors use this word in an obtuse reference to something specific e.g. “the growth in his appendix was indeed cancerous but I removed the lesion in time”
Benign = a neoplasm or growth that is growing, but it is not transgressing the membrane from which it first arose; it is thus not cancerous and will not spread and cause your death; though it is benign, it may still be undesirable and need to be removed, but it is not usually of immediate concern to your health
Cancer = a growth that arose from a particular cell type in the tissue of an organ, but which has developed characteristics indicating that it has invaded through to the next layer of cells in the adjacent tissue. Because it has invaded, this growth has the potential to spread locally or remotely elsewhere in the body so it may ultimately cause your death if not treated
Malignant = same as cancer
Polyp = a benign accumulation or growth of cells in a membrane layer. True polyps are growths, but sometimes doctors use the word `pseudo-polyp’ or `inflammatory polyp’ to refer to bowel lining that looks like a polyp but which is merely a heaped up membrane caused by inflammation. `Hyperplastic’ and `metaplastic’ polyps are similar, but the expression “polyp” in that context is a misnomer.
Dysplasia = a term used to describe the histological changes seen under the microscope in a benign growth that indicates that the growth is becoming unstable or pre-cancerous; terms like `mildly’, `moderately’ and `highly’ are all prefixed to dysplasia , indicating growing instability and thus increased concern that it may turn cancerous soon.
Metastases = a term used to describe tumour deposits that have appeared in remote places from where the tumour originated i.e. it indicates spread beyond the immediate vicinity of the primary tumour.
Bowel cancer in the opened bowel tube Bowel cancer seen during colonoscopy
What is Bowel Cancer and what causes it?
Each year, 35,000 people in Britain are diagnosed with cancer of the colon and rectum. For most of us, the lifetime risk of developing colorectal cancer is approximately 1:30. The vast majority of bowel cancer occurs sporadically i.e. by pure chance. The earlier the bowel cancer is diagnosed, the greater the likelihood of cure since growth and spread are usually time-dependent. Most bowel cancer occurs due to progression of polyps through dysplastic stages until they transform into cancer, so removing polyps as soon as they are detected is vital to preventing most bowel cancer. A small minority of cancers arise immediately i.e. without a polyp appearing first. Rarely, some chronic inflammatory conditions in the bowel, like Ulcerative Colitis, predispose to bowel cancer developing. Unlike some malignant tumours, bowel cancer can often be cured by surgery, or surgery in combination with additional modalities like radiotherapy or chemotherapy.
Less than 10% of bowel cancer has identifiable genetic causes. Two important genetic conditions predominate in the 10% whose genes are at fault:
Familial Adenomatous Polyposis (FAP) – this is an autosomal dominant inherited condition in which a faulty gene called APC is passed from one parent to the next generation. The risk of this transmission to the progeny is 50:50. Bowel cancer is usually prevalent in successive generations of the extended family. This condition is usually recognised in a family tree and a Clinical Geneticist can test family members for the APC gene. In this syndrome victims develop hundreds of polyps whilst still in their teenage years and with time 100% of carriers will develop a cancer of the bowel, often in early adulthood.
Hereditary Non-Polyposis Colorectal Cancer (HNPCC) – This is also known as Lynch Syndrome and is also an autosomal dominant inherited syndrome, yielding a 50:50 chance that the progeny of a carrier will carry the gene too. More than 5 genes have been implicated and can be tested for in suitable family members. The mutations of HNPCC genes cause a variety of other organ cancers, so there may be an unusually large number of other family members across several generations with cancer in the family tree. In this syndrome, patients may develop a few polyps, despite its name. The risk of a genuine HNPCC person developing colorectal cancer is approximately 1:4 with most cancers appearing in middle adulthood.
Not all patients fulfil the so-called Amsterdam-II criteria for HNPCC. Similarly, in FAP the condition sometimes skips a generation and is referred to as “Attenuated FAP”. If you are in doubt about your genetic risk, speak to your specialist colorectal surgeon or gastroenterologist.
What are the symptoms or signs of bowel cancer?
Bowel cancer can be very difficult to recognise. The symptoms may be broadly classified as follows:
1. Constitutional symptoms ("something's not quite right") - these symptoms are vague and non-specific, meaning that other everyday things can also cause them. These symptoms include fatigue, tiredness, loss of appetite, loss of weight, weakness, lethargy and malaise.
2. Symptoms of spread to other remote parts of the body - this is an extremely unlikely scenario in the first instance! Most individuals are found to have bowel cancer before it has spread to other organs. Even when it has done so, it is unusual for it to cause symptoms from that organ. Examples can include: breathlessness (lungs), jaundice (liver), bone pain (skeleton), neurological events like strokes or convulsions (brain) or abdominal distension with fluid (peritoneal or ovarian spread).
3. Bowel symptoms - this is the predominant manner in which bowel cancer manifests. The most important of these are:
- a change in bowel pattern (usually towards increased looseness, increased frequency and urgency, rather than towards constipation)
- loss of blood from the bowel (usually blood that is mixed with the stool, older in colour or clotted, but not usually blood that is on tissue paper only, or bright red and separate from the stools or associated with anal pain)
- a feeling of not clearing the back passage after doing so (a sensation that you have to go again when you've just been, or a feeling that there is something to shift which despite straining doesn't emerge)
(A) (B) (C)
Bowel tube and its mesocolon (A), with the bowel wall window opened (B) and the mesocolon opened (C) to show the lymph glands and blood vessels into which cancer may spread.