How the digestive system works
To understand the various operations, it can help to get to know the main features of the gastrointestinal (digestive) system and the way it works. As you can see from the diagram below, the gastrointestinal tract, which is also known as the gut, is like a long tube that starts at the mouth and ends at the anus.
The main purpose of the gut is to break down the food we eat so that our body can absorb its nutrients. This begins as we chew and swallow food, and it passes down the oesophagus (gullet) into the stomach where digestive juices break it down further over 2-4 hours.
The stomach then empties the food into the small intestine (also known as the small bowel). Here the food is broken down into even smaller particles and the useful nutrients are absorbed through the wall of the intestine into the blood stream.
The waste products from this process, which include liquid and undigested parts of food, are then pushed into the large intestine or large bowel. The colon – which together with the rectum makes up the large bowel - has four main sections: the ascending colon, the transverse colon, the descending or distal colon, and the sigmoid colon which connects to the rectum.
The colon absorbs some vitamins and minerals and the water from the liquid waste. The left over waste becomes solid faeces (stools). These collect in the rectum and are passed out of the body through the anus in a bowel movement.
How does Ulcerative Colitis affect the gut?
Ulcerative Colitis (UC) causes inflammation and ulceration of the mucosa (inner lining) of the large bowel. Raw areas or ulcers develop on the surface of the lining, and these may bleed and produce pus. The colon is less able to absorb water or hold as much waste and tends to produce more mucus (a natural lubricant). This leads to more frequent and looser bowel actions, experienced as urgency and diarrhoea.
Other common UC symptoms include crampy abdominal pain, blood and mucus in stools, a lack of energy, and weight loss. If you lose a lot of blood you may develop anaemia (a reduced number of red blood cells), which can also make you feel very tired.
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| Types of Colitis |
UC sometimes affects just the rectum, in which case it is called proctitis. It may also involve part or all of the colon, as shown below. UC affecting the rectum and the sigmoid colon is known as proctosigmoiditis. When the descending colon is involved it is called distal colitis, and when it affects most of the colon or the entire colon, extensive or pancolitis (total colitis). Exact symptoms tend to vary with the extent of the disease. For more details see our booklet Ulcerative Colitis.
When is surgery necessary?
About one in four people with UC will require surgery at some time during their illness. Surgery is seldom necessary for people with proctitis, but if you have extensive or total colitis it becomes more likely that you might need to have an operation to remove all or part of your colon. Some of the most common reasons for surgery are outlined below.
Poor response to long term medical treatment
UC is often well treated with drugs, but sometimes medical therapies fail to control the inflammation. If you have repeated flare ups with symptoms such as urgency and diarrhoea that seriously affect your quality of life, you may wish to consider surgery.
Emergency problems
Surgery may also be recommended for people with acute symptoms, for example, severe diarrhoea with bleeding, dehydration and a raised temperature, if they do not respond to intensive medical treatment once admitted to hospital. Rare complications such as acute toxic dilation (distension) of the colon, or a perforated colon also require urgent surgery.
Cancer of the large bowel
UC is not a form of cancer. However, if you have had severe Ulcerative Colitis affecting all or most of the colon and this has lasted for at least 8-10 years, there is a slightly increased risk of bowel cancer, which may require surgery. For more information on this see our leaflet Bowel Cancer and IBD.
Involvement of other organs
Inflammation in other parts of the body, such as the eyes, skin, or joints, can sometimes be associated with extensive or total UC. Rarely, surgery may be suggested if medication fails to control these symptoms.
Coming up in Part 2 - Which are the most common operations?
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