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 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). This has 3 sections: the duodenum, jejunum and ileum. 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 colon (large intestine or large bowel).
Finally, the colon absorbs the liquid and the left over waste becomes solid faeces (stools). These collect in the rectum and are passed out through the anus in a bowel movement.
How does Crohn’s Disease affect the gut?
Crohn’s Disease causes inflammation and can affect any part of the gut, although it is most commonly found in the ileum (the lower end of the small intestine) or in the colon. The areas of inflammation are often patchy, with sections of normal gut in between. A patch of inflammation may be small, only a few centimetres, or spread quite a distance along part of the gut. As well as affecting the lining of the bowel, Crohn’s may also go deeper into the bowel wall and cause abscesses or a fistula (see below).
The type of treatment recommended for Crohn’s will depend on the part(s) of the gut affected and on the severity of the symptoms. It may be medical or surgical or a combination of both. For some people, especially children, nutritional therapy (the use of an exclusive liquid diet to treat or reduce inflammation) can be a useful option.
When is surgery necessary?
Over the last decade advances such as the development of biological drugs have produced increasingly effective medical therapies for Crohn’s Disease. There have also been changes in the way surgery for Crohn’s is now managed, for example extensive resections (removal of diseased sections of the intestine) are now less common. Nevertheless, surgery remains an important treatment option, often in combination with medical therapies, and it is estimated that about 70% of people with Crohn’s will still need surgery at some
point in their lives.
Some of the most common reasons for surgery are outlined below.
Poor response to drug or nutritional treatment
Sometimes drug and/or nutritional therapies fail to control the inflammation and you may continue to experience symptoms such as diarrhoea, pain, poor appetite, and weight loss. Your doctor may then recommend surgery to remove any irreversibly damaged sections of intestine.
Strictures in the intestine
The inflammation from Crohn’s may cause scarring, and this can lead to a stricture, or narrowing of the space in the intestine, especially in the small intestine. This can make it difficult for food or waste matter to pass through and may cause a blockage. Symptoms of a stricture include cramping pains, distension or bloating, and, if there is a serious blockage, nausea, vomiting and constipation. You may need surgery to
overcome the narrowing or blockage.
Abscesses or fistulas
Sometimes the inflammation spreads through the full thickness of the bowel wall and forms an abscess (a collection of pus). As the abscess develops it may ‘hollow out’ a chamber or hole. This then becomes a fistula - a channel or passageway linking the bowel to another loop of bowel, another organ such as the bladder or vagina, or the outside skin. About a third of people with Crohn’s develop fistulas (or fistulae), most commonly perianal fistulas linking the anal canal (back passage) to the skin near the anus. Fistula symptoms vary but often include leaks of faecal matter, and can be very distressing. (For more information on fistulas, see our information sheet, Living with a Fistula.) Abscesses can cause pain, fever and feeling generally unwell. Surgery can be used to treat both abscesses and fistulas.
Delayed growth in children
Poor absorption of nutrients combined with steroid treatment can lead to delayed growth in children with Crohn’s Disease. While this is most likely to be managed with nutritional treatment and drug therapy, it can also be helpful to remove any severely damaged sections of the intestine.
Cancer
If you have severe Crohn’s Disease 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. (For more details on this, see our information sheet, Bowel Cancer and IBD.) This may require surgery.
Emergency problems
Emergency surgery is not often required for Crohn’s Disease, but may be needed if there is severe bleeding from the bowel, a perforation (a hole or tear in the wall of the bowel), for toxic megacolon (very severe disease of the colon), or to treat a bowel obstruction.
Coming up in Part 2: Which are the most common types of operation?
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