Crohn’s Disease

Knowing more about Crohn’s Disease can help you to feel better informed and able to take a more active part in decisions about your treatment.

We hope this booklet will give you and your family and friends a better understanding of Crohn’s and how it is treated.

Crohn’s Disease is a condition that causes inflammation of the digestive system (also known as the gastrointestinal tract or gut). Inflammation is the body’s reaction to injury or irritation, and can cause redness, swelling and pain.

Crohn’s Disease is one of the two main forms of Inflammatory Bowel Disease (IBD). The other main form of IBD is a condition known as Ulcerative Colitis. Crohn’s is sometimes described as a chronic condition. This means that it is ongoing and life-long, although you may have periods of good health (remission) as well as times when symptoms are more active (relapses or flare-ups). In many people the disease runs a benign course with few flare-ups, while other people may have more severe disease. Crohn’s Disease is not infectious.

At present there is no cure for Crohn’s, but drugs, and sometimes surgery, can give long periods of relief from symptoms.

As you can see from the diagram, the gut (digestive system) is like a long tube that starts at the mouth and ends at the anus.

When we eat, the food goes down the oesophagus into the stomach, where gastric (digestive) juices break it down to a porridge-like consistency. The partly digested food then moves through the small intestine (also known as the small bowel). Here it is broken down even further so that the nutrients (useful parts of the food) can be absorbed into the bloodstream.

The waste products from this process – liquid and non- digestible parts of food – then pass into the colon (also known as the large intestine or large bowel). The colon absorbs the liquid, and the leftover waste forms solid faeces (stools). These collect in the last part of the colon and the rectum until they are passed out of the body in a bowel movement.

Crohn’s Disease causes ulceration and inflammation, which affects the body’s ability to digest food, absorb nutrients and eliminate waste, in a healthy way.

Crohn’s can affect any part of the gut, but is most likely to develop in the ileum (the last part of the small intestine) or 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 across, or extend quite a distance along part of the gut. As well as affecting the lining of the bowel, Crohn’s may also penetrate deeper into the bowel wall causing abscesses and fistulas (abnormal tracts or passages between organs such as between two sections of bowel, or the bowel and skin).

Crohn’s Disease symptoms may range from mild to severe, and will vary from person to person.

They may also change over time, with periods of good health when you have few or no symptoms (remission), alternating with times when your symptoms are more active (relapses or ‘flare-ups’). Crohn’s is a very individual condition and some people may remain well for a long time, even for many years, while others may have more frequent flare-ups.

Your symptoms may also vary depending on where in your gut you have Crohn’s. However, the most common symptoms during a flare-up are:

• Abdominal pain and diarrhoea. Sometimes mucus, pus or blood is mixed with the diarrhoea.
• Tiredness and fatigue. This can be due to the illness itself, from the weight loss associated with flare-ups or surgery, from anaemia (see below) or to a lack of sleep if you have to keep getting up in the night
with pain or diarrhoea.
• Feeling generally unwell. Some people may have a raised temperature and feel feverish.
• Mouth ulcers
• Loss of appetite and weight loss. Weight loss can also be due to the body not absorbing nutrients from the food you eat because of the inflammation in the gut.
• Anaemia (a reduced level of red blood cells). You are more likely to develop anaemia if you are losing blood, are not eating much, or your body is not fully absorbing the nutrients from the food you do eat. Anaemia can make you feel very tired.

There is no single answer to this question because everyone is different and people’s experiences vary greatly. Also, much depends on the severity of your condition and whether your disease is in a quiet or active phase.

With medication, many people with Crohn’s have mild and infrequent symptoms of diarrhoea and pain, and their illness may not affect their lives very much. Most people follow a course of intermittent relapses (flare-ups) with periods of well-being (remission) in between, when they are able to lead a full and complete working and social life. Less commonly, some people have more frequent or continuous symptoms in spite of medical and surgical treatment, and have to adapt their lifestyle considerably.

Our booklet Living with Crohn’s or Colitis looks at some of the challenges of day-to-day life with Crohn’s. We also have information on Bloating and Wind, Diarrhoea and Constipation, Managing Bowel Incontinence in IBD and Fatigue and IBD.

You are likely to see your GP, and perhaps also your hospital IBD team, on a fairly regular basis if you have Crohn’s Disease. So, it can be very helpful if you build up a good relationship with them. Living With Crohn’s or Colitis has some suggestions on how to get the most from your time with health professionals.

Living with a chronic condition can have both an emotional and practical impact. It can help to have the understanding and support of those around you – your family, friends, work colleagues and employers.

We have information that may be useful, such as IBD and Employment: a guide for employers, and IBD and Employment: a guide for employees. There is also information for students and universities.

For me, it’s really important to listen to my body and know when to take it easy and rest, because when I’m stressed and tired, that’s when my symptoms flare. It is a bit like being on a rollercoaster, sometimes being well, sometimes being poorly, but you can live your life to the full.

Claire, 43
Diagnosed with Crohn's in 2005

It is estimated that Crohn's Disease affects about one in every 650 people in the UK.

Crohn’s is more common in urban than rural areas, and in northern, developed countries such as Northern Europe and North America, although the numbers are beginning to increase in developing nations. Crohn’s is also more common in white people of European descent, especially those descended from Ashkenazi Jews (those who lived in Eastern Europe and Russia).

Crohn’s can start at any age, but usually appears for the first time between the ages of 10 and 40, although there is a small peak in the number of people diagnosed over the age of 60.

Recent surveys suggest that new cases of Crohn’s are being diagnosed more often, particularly among teenagers and children. The reason for this is not clear. Crohn’s appears to be slightly more common in women than in men. It is also more common in smokers.

Although there has been much research, we still do not know exactly what causes Crohn’s Disease. However major advances have been made over the past few years, particularly in genetics.

Researchers now believe that Crohn's is caused by a combination of factors:

Viruses, bacteria, diet, smoking, certain medications, and stress have all been suggested as environmental triggers, but there is no definite evidence that any one of these is the cause of Crohn’s.

Crohn’s is often categorised according to which part or parts of the gut are most affected. Sometimes it can affect more than one part of the gut. The main types are as follows:

Terminal ileal and ileocaecal
Crohn’s in the ileum (the last part of the small intestine) may be called ileal or sometimes ‘terminal ileal’ Crohn’s – because it is affecting the terminus or end of the ileum. If it also affects the beginning  of the large bowel it is known as ileocaecal Crohn’s. This is one of the most common forms of
Crohn’s Disease. 

Typical symptoms are pain in the lower right side of the abdomen, especially after eating, diarrhoea and weight loss. Any bleeding is unlikely to be visible in stools, but stools may appear black and blood tests may show that you are anaemic.

Small bowel
This type of Crohn’s is also referred to as ileitis or jejunoileitis, depending on the part of the small bowel affected. Abdominal pain and diarrhoea are also typical symptoms of Crohn’s in the small bowel, along with nutrient deficiencies. Again, the diarrhoea is unlikely to be blood-stained, but you may still have anaemia, and also weight loss. The small bowel is commonly affected in children and young people.

Crohn’s Disease in the colon (large intestine or large bowel) is often called Crohn’s Colitis. This is also a common form of Crohn’s Disease, but is not the same as Ulcerative Colitis. The main symptom tends to be diarrhoea, with blood and mucus. Because
of the inflammation, the colon cannot hold as much waste as normal and you may have very frequent bowel movements, especially if your rectum is inflamed. You may also have urgency to pass stools, and tenesmus (feeling the need to pass a stool although the rectum is empty). 

Crohn’s in the upper gut – the oesophagus, stomach or duodenum – is much less common, but may occur on its own or alongside Crohn’s in other parts of the digestive system. Key symptoms include indigestion- like pain, nausea with or without vomiting, loss of appetite, and weight loss and anaemia.

Crohn’s in the area around the anus (back passage) can occur on its own or at the same time as inflammation in other parts of the body. It is quite common, and some people notice perianal symptoms before they develop intestinal symptoms. It causes a number of symptoms, such as:
• Fissures – these are tears or splits in the lining of the anal canal (back passage), which can cause pain and bleeding, especially during bowel movements.
• Skin tags – small fleshy growths around the anus.
• Haemorrhoids (piles) – swollen blood vessels in or around the anus and rectum.
• Abscesses – collections of pus that can become swollen and painful. They are often found in the area around the anus and can cause a fever or lead to a fistula.
• Fistulas – these are narrow tunnels or passageways between the gut and the skin or another organ. See Living with a Fistula.

Oral Crohn’s
Crohn’s can occasionally affect the mouth.True oral Crohn’s is often referred to as ‘orofacial granulomatosis’ and is more likely to affect children, although it is rare. It typically causes swollen lips and mouth fissures. Some people with Crohn’s may develop mouth ulcers during flare-ups. This can sometimes be due to nutritional deficiencies such as vitamin B12, folate and iron.

Crohn’s can sometimes cause additional problems in the gut. These complications include strictures, perforations and fistulas.

Ongoing inflammation and then healing in the bowel may cause scar tissue to form, which can create a narrow section of the bowel. This is known as a stricture. A stricture can make it difficult for food
to pass through and, if severe, may cause a blockage (obstruction). Symptoms include severe cramping abdominal pain, nausea, vomiting and constipation. The abdomen may become bloated and distended, and the gut may make loud noises. Strictures are usually treated surgically, often with an operation known as a stricturoplasty. However, in some cases it may be possible to treat them endoscopically with balloon dilatation (see Surgery for Crohn’s Disease). Some people have ‘inflammatory strictures’, where inflammation, not scar tissue, narrows the intestines. Often, medication can reduce this inflammation.

Although rare, inflammation deep in the bowel wall or a severe blockage caused by a stricture may lead to a perforation or rupture of the bowel, making a hole. The contents of the bowel can leak through the hole. This complication is a medical emergency. Symptoms include severe abdominal pain, fever, nausea and vomiting. In some cases, the leak will form an abscess.

A fistula is a narrow tunnel or passageway between the gut and the skin or another organ. See Living with a Fistula.

Crohn’s Disease can also cause problems outside the gut. Some people with Crohn’s develop conditions affecting the joints, eyes or skin. These can be known as extraintestinal manifestations (EIMs) and often occur during active disease, but they can develop before any signs of bowel disease or during times of remission.
Many of these are not very common.

Inflammation of the joints, often known as arthritis, is a common complication of Crohn’s Disease. For detailed information, see Joints.

Crohn’s can also cause skin problems. The most common skin problem is erythema nodosum, which affects about one in seven people with Crohn’s, and is more common in women than men. It consists of raised tender red or violet swellings 1.5cm in diameter, usually on the legs. This condition tends to occur during flare-ups and generally improves with treatment for Crohn’s.

More rarely, a condition called pyoderma gangrenosum affects people with Crohn’s Disease. This starts as small tender blisters or pustules, which become painful, deep ulcers. These can occur anywhere on the skin, but most commonly appear on the shins or near stomas. This condition is sometimes, but not always, linked to an IBD flare- up. It is often treated by a dermatologist with topical therapy, but may need drug therapy with steroids, immunosuppressants or biological therapy.

Another skin condition associated with Crohn’s Disease is Sweet’s Syndrome, where tender red nodules appear on the upper limbs, face and neck, sometimes with a fever. It is generally associated with active Crohn’s Disease, and can be treated by steroids or immunosuppressants.

Eye problems affect some people with Crohn’s. The most common condition is episcleritis, which affects the layer of tissue covering the sclera, the white outer coating of the eye, making it red, sore and inflamed. Episcleritis tends to flare up at the same time as IBD, and may need anti-inflammatory treatment; sometimes steroid drops are prescribed.

The two other eye conditions linked with Crohn’s are scleritis (inflammation of the sclera itself) and uveitis (inflammation of the iris). These conditions are a lot more serious and can lead to loss of vision if not treated. If you get any kind of eye irritation, redness or inflammation, always mention it to your doctor, who may refer you to an eye specialist. Scleritis and uveitis can usually be treated with steroid drops, although sometimes immunosuppressants or biological drugs are needed.

People with Crohn’s are more at risk of developing thinner and weaker bones. For detailed information, see Bones.

People with Crohn’s Disease have an increased risk of developing kidney stones. This can be due to inflammation in the small bowel causing fat malabsorption, so the fat binds to calcium, leaving a molecule called oxalate free to be absorbed and deposited in the kidneys where it can form stones. Another cause of kidney stones is dehydration, which can be caused by fluid loss from diarrhoea. More concentrated urine results from dehydration, which can lead to kidney stones. Symptoms of kidney stones include pain, nausea, vomiting and blood in the urine.

Inflammation in the small bowel can affect the ureters (tubes which carry urine from the kidneys to the bladder) by pressing on the tubes and blocking them, preventing the urine from draining.
This makes the kidney swell up, and surgery may be needed to remove the inflamed section of tissue so the urine can flow again.

Some complications are related to the liver and its function. About one in three people with Crohn’s develop gallstones. These are small stones made of cholesterol which may get trapped in the gallbladder, just beneath the liver, and can be very painful. Several factors linked with Crohn’s can make gallstones more likely – for example, removal of the end of the small intestine or severe inflammation in this area, which can lead to poor absorption of bile salts (which help to digest fat in the gut).

Some of the drugs used to treat Crohn’s (for example, azathioprine and methotrexate) may affect the liver. Changes in treatment may help to reduce this type of complication.

Primary Sclerosing Cholangitis (PSC) is a rare disease that affects up to one in 50 people with Crohn’s. It causes inflammation of the bile ducts and can eventually damage the liver. Symptoms include fatigue, itching, jaundice, and weight loss.

Blood circulation
People with Crohn’s are more than twice as likely to develop blood clots, including DVT (deep vein thrombosis) in the legs, and pulmonary embolisms in the lungs. You may be particularly at risk during a flare-up or if you are confined to bed, for example in hospital. If you get pain, swelling and tenderness in your leg, or chest pains and shortness of breath, contact your doctor straight away. You can reduce your risk by not smoking, by keeping as mobile as possible, drinking plenty of fluids, and wearing support stockings. Precautions like these can be especially helpful when travelling by air, which increases the risk of blood clots for everyone. For more details see Travel and Crohn's and Colitis.

Anaemia is one of the most common complications of IBD. If you are anaemic it means you have fewer red blood cells than normal and/or lower levels of haemoglobin in your blood (haemoglobin is a protein found in red blood cells and carries oxygen around the body). There are several different types of anaemia. People with IBD are most likely to develop iron deficiency anaemia. This can be caused by a lack of iron in the diet, poor absorption of iron from food, or ongoing blood loss. Blood loss from the bowel commonly causes anaemia in people with Crohn’s, even if the blood loss is not visible. It is important to try and ensure a good intake of foods containing iron to help prevent anaemia.

Another type of anaemia is vitamin deficiency anaemia, caused by a low intake or poor absorption of certain vitamins, such as vitamin B12 or folic acid. This may particularly affect people with Crohn’s who have had sections of the small intestine removed. Some of the drugs used for IBD (for example, sulphasalazine and azathioprine) can also cause anaemia.

If the anaemia is very mild, there may be few or no symptoms. With more severe anaemia, the main symptoms are chronic (ongoing) tiredness and fatigue. You might also develop shortness of breath, headaches and general weakness. How anaemia
is treated will depend on its cause. For iron deficiency anaemia you may be prescribed iron supplements as tablets or as IV (intravenous) iron, which is given by injection or in an infusion through a drip. Some people with IBD find that they cannot tolerate iron by mouth, so are given IV iron which can be more effective. For vitamin deficiency anaemia you may be given extra B12 or folic acid, as tablets or by injection.

IBS stands for Irritable Bowel Syndrome. This is a different condition from IBD, although some of the symptoms are similar. Like IBD, IBS can cause abdominal pain, bloating and bouts of diarrhoea or constipation. However, it does not cause the type of inflammation typical of Crohn’s or Colitis, and there is no blood loss with IBS.

However, some people with Crohn’s may develop IBS-like symptoms. They may, for example, get diarrhoea even when their IBD is inactive. IBS is more common in people with IBD than in the general population.

If you develop diarrhoea, abdominal pain, and weight loss lasting for several weeks or longer, or have blood in your stools, your doctor may suspect that you have Crohn’s, particularly if you are a young adult or have a family history of IBD. You’ll then need a combination of tests and physical examinations to confirm a diagnosis. See Tests and Investigations for Crohn's and Colitis.

You may need to have the tests repeated from time to time to check on your condition and how your treatment is working. Some drug treatments may also require a series of blood tests and, occasionally, x-rays or scans, to check for potential side effects. However, your specialist will avoid giving you any unnecessary tests or investigations.

Drug treatment for Crohn’s usually aims to reduce symptoms, control flare-ups and achieve remission, and then to prevent a relapse (maintain remission) once the disease is under control. This can mean that you need to take your medication on an on-going basis, sometimes for many years.

Or, you may need only a short course of drugs.

The main aim of drug treatment for Crohn’s Disease is to reduce inflammation. The main types of drugs are:

Aminosalicylates (5-ASAs) reduce inflammation in the lining of the intestine. Examples include mesalazine, olsalazine, sulphalazine and balsalazide.

Corticosteroids (steroids) work by blocking the substances that trigger allergic and inflammatory responses in your body. They include prednisolone, prednisone, methylprednisolone, budesonide, hydrocortisone, and beclometasone dipropionate.

Immunosuppressants suppress the immune system, and reduce levels of inflammation. The main immunosupressants used in IBD are:
Azathioprine and Mercaptopurine
Mycophenolate mofetil, ciclosporin, and tacrolimus are also used.

Biological drugs are the newest group of drugs used to treat Crohn’s. These include:

Other medications may be used to help ease the symptoms of Crohn’s, such as antibiotics, antidiarrhoeals and painkillers. You should always check with your IBD team before using them. For detailed information, see Other treatments for IBD.

Some people with Crohn's or Colitis may be prescribed exclusive enteral nutrition (a special liquid-only diet), usually for 2-8 weeks. People on this diet do not eat ordinary food or drink because the liquid diet provides them with all the nutrients they need.

Not everyone likes the taste of these specialised feeds, but they do come in a range of flavours. Some people have found that taking the liquid ice-cold or through a straw makes it easier to drink. An alternative may be to take the feed overnight through a naso- gastric tube (a fine tube passed through the nose down into the stomach).

It is commonly used in children because it can improve growth by providing easily digested nutrients. It may also make it less likely that steroids are needed, by helping to ‘rest’ the bowel and allow it to heal. Adults are less likely to need exclusive enteral nutrition, but this can be an option for treating flares. Diets such as this are usually supervised by a dietitian.

Some people may find it helpful to have supplemental drinks alongside normal food, in order to obtain more nutrients. This may also be useful for children.

People with Crohn’s are now much less likely to need surgery than they were in the past. However, surgery remains an important and life-changing treatment option for many. For detailed information, see Surgery for Crohn’s Disease.

Crohn’s does tend to run in families, and parents with Crohn's are slightly more likely to have a child with Crohn's or Colitis. However, studies show for most people the actual risk is still relatively low.

If one parent has Crohn’s, the risk of their child developing Crohn's or Colitis is generally thought to be between 5% and 10% – that is, for every 100 people with Crohn’s having a child, 5 to 10 of the children may develop Crohn's. However, we still cannot predict exactly how Crohn’s is passed on. Even with genetic predisposition – that is, an increased risk because of a person’s genes – additional factors are needed to trigger Crohn's.

As many as a quarter of people with Crohn's or Colitis are diagnosed when under the age of sixteen. 

For information on Crohn’s and Colitis in children, see IBD in Children: A parent’s guide, or find out how we support young people and families.

Living with Crohn’s may mean you have to make some changes. But you can still get the most out of life. And we’re here to help, every step of the way.

You can find out more about:
Living with Crohn’s or Colitis (link to ‘living with’ menu drop down)
Or see our full range of information

We offer more than 50 publications on many aspects of Crohn’s Disease, Ulcerative Colitis and other forms of Inflammatory Bowel Disease. You may be interested in our comprehensive booklets on each disease, as well as the following publications:

Living With Crohn's or Colitis
Taking Medicines
Managing Bowel Incontinence
Living With a Stoma

Health professionals can order some publications in bulk by using our online ordering system. If you would like a printed copy of a booklet or information sheet, please contact our helpline.

Our helpline is a confidential service providing information and support to anyone affected by Crohn's or Colitis. Our team can:
• help you understand more about Crohn's or Colitis, diagnosis and treatment options
• provide information to help you to live well with your condition
• help you understand and access disability benefits
• be there to listen if you need someone to talk to
• help you to find support from others living with the condition

Call us on 0300 222 5700 
Use our LiveChat 

Crohn’s & Colitis UK Forum
This closed-group community on Facebook is for everyone affected by Crohn's or Colitis. You can share your experiences and receive support from others.

Crohn’s & Colitis UK Patient Panels
IBD Patient Panels, which are supported by Crohn’s & Colitis UK, are groups of people with Crohn's or Colitis who use their perspective as a patient to work with their IBD healthcare team to help improve their hospital services. For more information on patient panels, please read our information leaflet or contact our Patient Engagement Team.

Crohn’s & Colitis UK Local Networks
Our Local Networks of volunteers across the UK organise events and provide opportunities to get to know other people in an informal setting, as well as to get involved with educational, awareness-raising and fundraising activities. You may find just being with other people and realising that you are not alone can be reassuring. Families and relatives may also find it useful to meet other people with Crohn's or Colitis. All events are open to members of Crohn’s & Colitis UK

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Last reviewed: October 2016