Polyps and Bowel Cancer

BOWEL TERMINOLOGY

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.

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)
4. Emergency symptoms – the commonest example is bowel obstruction in which case the abdomen is likely to distend, you are likely to feel naseous and to vomit, you may develop cramping abdominal pain and the bowels may stop working. Other examples include the rare events of bowel perforation (in which you will rapidly develop severe abdominal pain with peritonitis), massive bowel haemorrhage or an abscess around the bowel.

5. Symptoms of spread to adjacent parts of the body – cancer of the bowel may lead to communication between the bowel and the bladder (causing you to pass bubbles and waste in the urine, or get recurring urinary infections) or between the bowel and the vagina (causing a female to lose stool via the vagina).

Bowel cancer hardly ever causes abdominal pain! Also, in only 1% of cases of isolated constipation is bowel cancer the cause of the constipation.

One of the commonest incidental ways in which bowel cancer is detected is when blood tests discover the presence of anaemia caused through iron deficiency. Though cancer of the bowels is a minority cause in such cases, iron deficiency anaemia has the strongest association with bowel cancer of any other symptoms or signs.

Clearly, the more symptoms you have from categories 1-5, the greater the prospect that you have bowel cancer. However, there are often many other simple or less serious explanations for your symptoms. The most typical scenario that prompts a referral to a specialist is the change in bowel pattern or the rectal bleeding. The commonest cause of rectal bleeding (something experienced by 85% of individuals in their lifetime) is haemorrhoids or piles. Bowel pattern change is very difficult to quantify, as most people don’t discuss each other’s bowel behaviour! “Normal” bowel pattern ranges from 3 times per day to going only once every 3 days, and “normal” stool consistency can vary from solid formed stool to sloppy porridge consistency. All of us experience variation in our bowel behaviour or stool consistency, depending on what we eat, what we drink, what medication we take, where we have travelled and even what our levels of stress are. Thus, if your bowels have changed in some way, discuss it with your GP.

HOW IS BOWEL CANCER DIAGNOSED?

This begins by the doctor taking a detailed history from you and examining you thoroughly. This must include an internal rectal examination by finger. Additional tests are often required. Blood is analysed for evidence of iron deficiency anaemia and to exclude other possible causes for your symptoms. Some doctors test for a blood chemical called Carcinoembryonic Antigen (CEA), but this is useless as a diagnostic test for cancer as it can be both falsely negative or falsely positive. Investigations of your bowel itself usually necessitate referral to a specialist.

Your specialist will usually repeat the consultation, perhaps in more detail, and may often perform a limited rectal inspection with a short telescope called a sigmoidoscopy. Thereafter, further direct bowel investigations may include a flexible sigmoidoscopy or a colonoscopy. These two procedures allow direct inspection of the bowel and an opportunity for the specialist to take biopsies or remove polyps. For details of these two tests, please see the main menu. Other bowel tests that provide indirect inspection include a barium enema, a plain CT scan or a CT colonography test.

Increasingly, patients of a suitable age or with a worrying pedigree of cancer in the family will be offered screening tests. These tests occasionally reveal bowel cancers that were not causing any symptoms. Similarly, some doctors and businesses offer screening tests of general health and this may include a Faecal Occult Blood Test (FOBT). The FOBT is a rather non-specific test i.e. things other than blood can cause a positive test result and the FOBT often is positive due to non-cancerous bleeding in the stool (particularly bleeding from piles).

HOW IS BOWEL CANCER CATEGORISED OR STAGED?

Many different classification systems are used to describe bowel cancer. The obvious first categorisation is an anatomical one that divides bowel cancer (a.k.a. colorectal cancer) into COLON cancer and RECTAL cancer. The colon consists of the remainder of the large intestine: starting in the lower right side of the abdomen as the CAECUM, then running upwards to the right ribcage as the ASCENDING colon, then running across the upper abdomen as the TRANSVERSE colon, then running downwards from the left ribcage as the DESCENDING colon and then finally running as a convoluted s-shaped coil known as the SIGMOID colon. The RECTUM is the last 6 inches (or 15cm or so) of the bowel, before it reaches the ANUS.

Cancer specialists categorise, or “stage”, cancer on oncological grounds to indicate the extent of the problem. The simplest such staging system is the Stage I, Stage II and Stage III system:
Stage I – disease is confined to the organ of origin
Stage II – disease has spread to local or regional lymph glands
Stage III – disease has reached an adjacent organ or a distant organ

The Dukes staging system categorises patients into those with tumour confined to within the bowel muscular tube (Dukes A), those with tumour involving the muscular tube without the lymph nodes (Dukes B) and those with tumour involving the lymph nodes (Dukes C). This sytem was modified subsequently into sub-groups of B and C and a group D was added to indicate those with tumour spreading to another organ. The Stage I, II, III and the Dukes systems tend to over-simplify things, since there is enormous variation within these stages and sometimes even Stage III cancer can still be cured.

Instead, cancer specialists rely on information about the Tumour in the bowel wall itself (T), the lymph Nodes (N) and Metastases (M) in what is called the TNM staging system. Subcategories of the T, N and M categories break each category down further, and even newer symbols are added, for instance Vascular involvement (V) and the success of complete Removal (R). This system is the most widely used system internationally and it allows doctors to more accurately predict the future for a group of patients or to compare “like for like” when assessing the success of a particular treatment.

Your specialist will arrange “staging tests” as soon as your cancer is suspected. For colon cancer this involves a CT scan of the chest, abdomen and pelvis. For rectal cancer, a similar CT scan is required, but an additional MRI scan of the pelvis is required. It is unusual for additional tests to be required, but occasionally the CT scan or MRI scan throw up additional information that needs clarification. Tests such as a Positron Emission Tomography (PET) CT scan or a bone scan or an MRI scan of the liver may be required. These tests all give the specialist information about the stage your disease is found to be at prior to treatment and it informs the team about which is the best way to address the cancer. Upon removing the cancer, the surgeon has further information about what was seen at operation – as some things might not be picked up on scans beforehand or the disease may have been better/worse than anticipated from the staging tests. The pathologists will analyse the removed organ(s) and cancer to give a microscopic report to add to the existing knowledge of the tumour stage. This finally informs the team as to whether the patient needs additional treatment e.g. chemotherapy and what the prognosis for the patient is.

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.