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Changes in your bowels

Updated: May 27, 2021

With a 5% chance of developing colorectal cancer within your lifetime and it is the 2nd most common cancer in the UK, this week we’re looking into how it can be treated.

Colorectal cancers are adenocarcinomas as they derive from glandular tissue. Often symptoms are not noticed until a late stage, often presenting with a change in bowel habit such as increased frequency and loose stools, caused by overflow diarrhoea. Right-sided bowel cancers can present with a mass on the right side of the abdomen and more commonly iron deficiency anaemia. There are many causes of iron deficiency anaemia so testing to identify the cause should always be carried out to rule out treatable conditions such as bowel cancer. Blood is sometimes seen within the stool of patients with bowel cancer; this can be fresh red blood or black tar-like substance. These differences in the appearance of blood in the stool are based upon where in the bowel the bleed is occurring. The higher the gastrointestinal tract the blood will appear darker and tar-like, mixed in with the stool whereas bleeding from the rectum produces fresh red blood that is not mixed with the stool.

The UK has a screening programme in which a simple faecal occult test (tests for any blood in a stool sample) is performed at home in those aged 60-74years old and this is done twice a year. Whereas over 55-year-olds are invited to a one-off bowel scope screening test. These screening tests are in place to pick up any bowel cancers early as the lack of symptoms can often leave them undetected until cancer has progressed further. The earlier intervention is made the better the outcome.

Surgical treatment is used in most cases of colorectal cancer and this functions to remove the area of the colon affected, often removing 5cm of the colon above and below the mass. To prevent spread the lymphatic drainage of that area of the colon is also removed. This runs along the arteries that supply that area of the colon so the blood vessels are also removed. Therefore, knowing the vasculature supply to the gastrointestinal tract is extremely important.

If the cancer is present on the ascending or transverse colon then a right hemicolectomy is performed and removal of the ileocaecal and right colic branches of the superior mesenteric artery (SMA). The whole of the superior mesenteric artery is not removed as it has jejunal and ileal artery branches that supply the small bowel, removal of these would result in small bowel ischaemia and is fatal. A cancerous mass in the descending or sigmoid colon can be removed by various procedures like a left hemicolectomy or a Hartman’s procedure (emergency operation). The inferior mesenteric artery (IMA) will also be removed to remove the draining lymph nodes. This artery only supplies the large intestine so can be entirely removed. The marginal artery runs around the whole of the large intestine so can provide blood to any remaining descending colon.


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