What is bowel cancer?
The body is made up of billions of tiny cells, which are constantly growing, dying and reforming. If the cells become abnormal for any reason, this turnover cycle can lose control. The abnormal cells start dividing and growing faster than normal, forming a growth of abnormal cells (cancer). Cancers cause problems because they replace normal cells with abnormal non-functioning cells, destroying nearby areas as they grow.
A benign bowel growth is one that forms a lump, but is not dangerous. A pre-malignant bowel growth is one that has the potential to turn into a cancer, but has not done so yet. A malignant growth is a bowel cancer that has the potential to spread elsewhere.
What problems can bowel cancer cause?
'Small bowel' cancers do exist, but are very rare. The commonest place for bowel cancers is in the large bowel, in particular the rectal area.
The symptoms are influenced by where the tumour is, but generally large bowel cancer can cause bleeding from the back passage, weight loss, loss of energy and constipation alternating with diarrhoea. Sometimes bleeding may be the only symptom and people may think they only have piles. For this reason, any bleeding from the back passage should be reported to your doctor to exclude cancer as a cause.
Eventually the cancer can cause serious problems such as bowel obstruction (blockage) or perforation (hole in the bowel), which can be immediately life threatening. The cancer can spread to other areas such as the liver, which often carries a poor prognosis.
What causes bowel cancer?
The exact causes of bowel cancer are generally unknown, although a high-fat, low-fibre diet seems to increase risks. Risks may also be higher if a close relative has had bowel cancer.
Most bowel cancers arise from pre-existing polyps - these are swellings that hang from the bowel wall, and may cause bleeding and mucus discharge from the back passage. Whilst benign, they have the potential to turn cancerous. If you are found to have polyps, therefore, you may need to be regularly checked by endoscopy to ensure no cancers have arisen.
Occasionally bowel cancer can arise from other conditions such as ulcerative colitis or Crohn's disease.
What tests can be done for bowel cancer?
If your doctor suspects bowel cancer, then they may arrange for an endoscopy to examine the bowel from the inside. Special x-rays and scans may also be required, as are blood tests.
If you are at risk of possibly developing bowel cancer (for example having a close relative affected), then simple stool tests can be performed to check for microscopic evidence of blood. Presence of blood may mean that you have a condition that could one day lead to cancer, so regular check-ups may be employed to keep careful watch.
What treatment is available for bowel cancer?
The main treatment option is surgery. The operation will aim to remove the cancer with the affected portion of bowel; the bowel can usually then be reattached, although a stoma may occasionally be required (the bowel is sewn to the tummy skin and a bag is sealed over the opening to collect bowel contents). The surgery may often be curative, although the cancer can occasionally return or spread elsewhere.
Depending on the type of bowel cancer, radiotherapy and/or chemotherapy may be used to help shrink the tumour or help prevent recurrences and spread.
Overall, early treatment is definitely beneficial and gives the best prognosis. For this reason, you should consult a doctor as soon as possible if you have any concerns.
What are the risks of surgery for bowel cancer?
Hernia - if the deep tummy muscles do not heal well after the surgery, the underlying bowel could push through the muscle, being seen or felt as a lump. Hernias may need to be treated by surgery.
Infection - this may require antibiotics, or rarely further surgery.
Injury to other structures - injury to bowel, nerves or blood vessels is rare but can occur, which may need further surgery.
Bowel leakage - after the bowel ends are joined together there is a small risk that a leak may occur, allowing bowel contents to escape into the abdomen. This can make you feel very unwell and often needs further surgery to seal the leak.
Adhesions - surgery in the abdomen will lead to scar tissue forming. This can stick to nearby bowel, which may cause problems such as obstruction. This can require further surgery.
Difficulty passing urine - if this happens you may need a tube (catheter) for a day or two to help you pass water.
Recurrence - the cancer could return after surgery, needing further operations or radiotherapy and chemotherapy.
Blood clots in the legs - clots in the calf (deep vein thrombosis/DVT) can usually be treated with medication, but a DVT can (rarely) move to the lungs. This can cause breathing difficulty, or even be life threatening.
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You may also be interested to read our articles on Crohn's disease, Diverticulitis or Ulcerative Colitis
Any procedure involving skin incision can also result in unfavourable scarring, wound infection, or bleeding. This list of risks is not exhaustive, and you should discuss possible complications with your specialist. Whilst these risks will seem very worrysome, and indeed can be serious, it should also be borne in mind that many people have no postoperative problems whatsoever.
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