Crohn’s disease is a
long-term condition that causes inflammation of the lining of the digestive
system. Inflammation can
affect any part of the digestive system, from the mouth to the anus (back passage),
but most commonly occurs in the last section of the small intestine (ileum) or
the large intestine (colon). Common symptoms of Crohn's disease include:
- diarrhoea
- abdominal pain
- fatigue (extreme tiredness)
- unintended weight loss
- blood and mucus in your
faeces (stools).
People with Crohn’s
disease sometimes go for long periods without symptoms, or with very mild
symptoms. This is known as remission. Remission can be followed by periods
where symptoms flare up and become particularly troublesome.
The exact cause of
Crohn’s disease is unknown. However, research suggests that a combination of
factors may be responsible. These include:
- genetics -
genes that you inherit from your parents may increase your risk of
developing Crohn’s disease
- the immune system -
the inflammation may be caused by a problem with the immune system
(the body’s defence against infection and illness) that causes it
to attack healthy bacteria in the gut
- previous infection - a
previous infection may trigger an abnormal response from the immune system
- smoking - smokers
with Crohn’s disease usually have more severe symptoms than non-smokers
- environmental factors -
Crohn’s disease is most common in westernised countries, such as the UK,
and least common in poorer parts of the world, such as Africa, which
suggests the environment (particularly sanitation) has a part to play.
There is currently no
cure for Crohn’s disease so the aims of treatment are to stop the inflammatory
process, relieve symptoms (induce and maintain remission), and avoid surgery
wherever possible.
The first treatment
offered to reduce symptoms is usually steroid medication (corticosteroids).
If this doesn't help, medication to suppress the immune system
(immunosuppressants) and medication to reduce inflammation may be used. In some cases,
surgery may be needed to remove the inflamed section of intestine. Once your symptoms
are under control (in remission), further medication may be needed to help
maintain this.
Schematic diagram showing how Crohn's disease can affect the last part of the small intestine, (known as the terminal ileum), causing terminal iliitis.
Crohn’s disease is a
relatively uncommon condition. There are currently at least 115,000 people
living with Crohn’s disease in the UK. Crohn's
disease can affect people of all ages, including children. However, most
cases first develop between the ages of 16 and 30. A large number of
cases also develop between the ages of 60 and 80.
It affects
slightly more women than men, but in children more boys are affected than
girls. Crohn’s disease is
more common in white people than in black or Asian people. It is most
prevalent among Jewish people of European descent.
Over time,
inflammation can damage sections of the digestive system, resulting in
additional complications, such as narrowing of the intestine (stricture)
and a channel that develops between the end of the bowel and the
skin near the anus or vagina (fistula). These problems
usually require surgical treatment.
Causes
The exact cause of
Crohn’s disease is unknown. Most researchers think that it is caused
by a combination of factors. These are thought to
be:
- genetics
- the immune system
- smoking
- previous infection
- environmental factors.
There is no evidence
to suggest a particular diet can cause Crohn’s disease, although changes to
your diet can be helpful to control certain symptoms and maybe recommended by
your specialist or dietitian.
There is evidence to
suggest that genetics plays a role in the development of Crohn’s disease. Researchers have
identified over 200 different genes that are more common in people with
Crohn’s disease than in the general population. There is also
evidence that Crohn’s disease can run in families.
About 3 in 20 people
with the condition have a close relative (mother, father, sister or brother)
who also has Crohn’s disease. If you have an identical twin with Crohn’s
disease, you have a 70% chance of also developing it. The fact that Crohn’s
disease is more common in some ethnic groups than in others also suggests that
genetics plays an important role.
The immune system
provides protection against harmful bacteria that could potentially find their
way into the digestive system. The digestive system
is also home to many different types of so-called "friendly
bacteria" that help to digest food. The immune system usually
recognises these bacteria and lets them do their job without attacking them.
However, in Crohn’s
disease, it seems that something disrupts the immune system, which sends a
special protein, known as tumour necrosis factor alpha (TNF-alpha), to
kill all bacteria, regardless of whether they are friendly or not. This
causes most of the inflammation associated with Crohn’s disease.
In certain
genetically susceptible individuals, a previous childhood infection may lead to
an abnormal immune response, causing the symptoms of Crohn’s disease. One possible source
of this infection is a bacterium called Mycobacterium avium subspecies
paratuberculosis (MAP). MAP is commonly found in cows, sheep and goats.
Research has found
that people with Crohn’s disease are seven times more likely to have traces of
MAP in their blood compared with the general population. MAP has been known to
survive the pasteurisation process (where milk is treated with heat to kill
bacteria), so it is possible that people have become infected with MAP by
drinking milk from contaminated animals. However, the exact
role that MAP may play in the development of Crohn’s disease is uncertain and
some researchers dispute this theory.
Aside from family
history and ethnic background, smoking is the most important risk factor for
Crohn’s disease. Smokers are twice as likely to develop Crohn’s disease
compared with non-smokers. Furthermore, people
with Crohn’s disease who smoke usually experience more severe symptoms compared
with those with the condition who do not smoke.
There are two unusual
aspects of Crohn’s disease that have led many researchers to believe that
environmental factors may play a part. These are explained below.
- Crohn’s disease is a
"disease of the rich". The highest number of cases occurs in
developed parts of the world, such as the UK and US, and the lowest
number in developing parts of the world, such as Africa and Asia.
- Crohn’s disease became much
more widespread from the 1950s onwards.
This suggests that
there is something associated with modern, western lifestyles that
increases a person’s risk of developing Crohn’s disease. One theory to explain
this is known as the hygiene hypothesis. It suggests that as children grow up
in increasingly germ-free environments, their immune system does not fully
develop due to a lack of exposure to childhood infections. However, there is
little in the way of hard, scientific evidence to support this theory.
An alternative theory
is the cold-chain hypothesis, which suggests that the increase in the number of
cases of Crohn’s disease might be linked to the increased use of refrigerators
after the Second World War.
Symptoms of Crohn's disease
The symptoms of
Crohn’s vary depending on which part of the digestive system is
inflamed.
Common symptoms
include:
- recurring diarrhoea
- abdominal pain and
cramping, which is usually worse after eating
- extreme tiredness (fatigue)
- unintended weight loss
- blood and mucus in your
faeces (stools).
You may find that you
experience all or only one of the above. Some people experience severe
symptoms, but others only have mild problems. There may be long
periods that last for weeks or months where you have very mild or no
symptoms (known as remission), followed by periods where the symptoms are
particularly troublesome (known as flare ups or relapses). Less common symptoms
include:
- high temperature (fever) of
38°C (100°F) or above
- feeling sick (nausea)
- being sick (vomiting)
- joint pain and swelling
(arthritis)
- inflammation and irritation
of the eyes (uveitis)
- areas of painful, red and
swollen skin - most often of the legs
- mouth ulcers.
Children with Crohn's
disease may grow at a slower rate than expected because the inflammation can
prevent the body absorbing nutrients from food.
You should contact
your doctor if you have:
- persistent diarrhoea
- persistent abdominal pain
- unexplained weight loss
- blood in your faeces (stools).
You should also see
your doctor if you are concerned about your child's development.
Diagnosing Crohn's disease
A number of different
tests may be needed to diagnose Crohn's disease, as it has similar symptoms to
several other conditions.
During your initial
assessment, it is likely that your doctor will ask you about the pattern of your
symptoms and check whether there may be any contributing causes, such as:
- diet
- recent travel - for example,
you may have developed travellers' diarrhoea while travelling abroad
- whether you are taking any
medication, including any over-the-counter (OTC) medicines
- whether you have a family
history of Crohn’s disease.
Your doctor may also
carry out a series of standard tests to assess your general state of health.
For example, they may:
- check your pulse
- check your blood pressure
- measure your weight and
height
- measure your temperature
- examine your abdomen (tummy).
Your doctor may then
arrange a series of blood tests. These can be used to assess:
- the levels of inflammation
in your body
- whether you have an
infection
- whether
you are anaemic (have low levels of red blood cells), which
could suggest you are malnourished.
You may be asked to
provide a stool sample that can be checked for blood and mucus. It can
also be used to determine whether your symptoms are being caused by a parasitic
infection such as roundworm, or other infections.
After you have
provided a stool and blood sample, you will probably be referred a
gastroenterologist (a specialist in conditions of the digestive system) who can
discuss the results with you and can carry out the tests described below
if they are necessary.
A colonoscopy is
a test used to examine the inside of your colon. It involves inserting a long
flexible tube, known as an endoscope, into your colon through your back
passage (rectum).
The endoscope has a
light and a camera on the end. The camera can be used to send images to a
television screen. These will show the level and extent of inflammation
inside your colon.
The endoscope can
also be fitted with surgical tools that can be used to take a number of small
tissue samples from different sections of your digestive system. This is known
as a biopsy. The procedure may feel uncomfortable but it is not painful. These tissue samples
will be examined under a microscope for the cell changes known to occur in
cases of Crohn’s disease.
Schematic diagram showing a colonoscope advanced all the way to the caecum, including various colonoscopic pathologies that can de detected during a colonoscopy (a camera test through the back passage).
A wireless capsule
endoscopy is a new type of test that involves swallowing a small capsule (about
the size of a large vitamin tablet). The capsule works its way down to your
small intestines where it transmits images to a recording device worn on a belt
or in a small shoulder bag.
A few days after the
test, the capsule passes out of your body in a stool. The capsule is disposable
so you do not have to worry about retrieving it from your stools.
As this is a
relatively new test, availability may be limited. In some cases, scans called
MRE or CTE may be used instead of a capsule endoscopy.
Scans
called magnetic resonance enterography/enteroclysis (MRE) or
computerised tomography enterography/enteroclysis (CTE) may be
used to examine the small intestine in people with suspected Crohn's
disease. Before having these
scans you will either need to drink a harmless liquid called a contrast agent
(enterography), or a contrast agent may be placed through a tube in your nose
that leads to your small intestine (enteroclysis). These contrast agents allow
your small intestine to show up more clearly during the scans.
During an MRE scan,
magnetic fields and radio waves are used to produce detailed images of your
small intestines. During CTE scans, several X-rays are taken and assembled by
computer to create a detailed image. These tests
are increasingly used instead of a small bowel enema or small bowel
follow-through (see below) because they allow more detailed examination of
the small intestine and MRE scans also avoid any exposure to X-ray
radiation.
A small
bowel enema (SBE) and small bowel follow through (SBFT) are two
similar tests that have traditionally been used to examine the whole of the
inside of the small intestine, usually at the point where it meets the colon.
Thay are sometimes used because only about the last 20 cm is usually seen
during colonoscopy.
During an SBE/SBFT,
a local anaesthetic spray is used to numb the inside of your nose and
throat. A tube is passed down your nose and into your throat, before being
threaded into your small intestines. This can feel unpleasant at first, but
most people find that they get used to the sensation after a few minutes.
A harmless liquid
called barium is passed down the tube. The barium coats the lining of your
small intestines so that they show up clearly on X-rays. A series of X-ray
images will then be taken. The images can often highlight the areas of
narrowing and inflammation that are caused by Crohn’s disease.
After the test, you
will be advised to drink plenty of fluid to help wash the barium out of your
body. You may notice that your stools look white for the first few days after
having an SBE/SBFT. This is perfectly normal and it is nothing to worry about.
Treating Crohn's disease
There is currently no
cure for Crohn’s disease, but treatment can help improve the symptoms. The main aims of
treatment are to:
- reduce symptoms -
known as inducing remission (remission is a period without symptoms)
- maintain remission.
In children,
treatment also aims to promote healthy growth and development. Your treatment will
usually be provided by a range of healthcare professionals, including
specialist doctors (such as gastroenterologists or surgeons), family doctors (e.g. GPs) and
specialist nurses.
If you have Crohn's
disease and it's causing moderate or severe symptoms, this is known as
"active disease". Treatment for active Crohn's disease usually
involves medication, but surgery is sometimes the best option.
In most cases, the
first treatment offered is steroid medication (corticosteroids) to reduce the
inflammation. Examples of corticosteroids used for Crohn's disease include
prednisolone tablets or hydrocortisone injections. These medications are
often effective in reducing the symptoms of Crohn's disease, but they can have
significant side effects - such as:
- weight gain
- swelling of the face
- increased vulnerability to
infections
- thinning and weakening of
the bones (osteopenia and osteoporosis).
Due to these possible
side effects, your dose will be gradually reduced when your symptoms start to
improve. If you prefer, you
may be able to choose to have a milder steroid called budesonide, or a type of
medication called a 5-aminosalicylate (such as mesalazine), as an alternative
initial treatment. These medications have fewer side effects, but they are less
effective.
In children or young
people where there are concerns about growth and development, a special liquid
diet may be recommended as an initial treatment. This is known as an elemental
or polymeric diet and it can help to reduce inflammation by allowing your
digestive system to recover, while ensuring that they get all the nutrients
they need.
If your
symptoms flare up twice or more during 12 months, or if your
symptoms return when your steroid dose is reduced, further treatment may
be necessary. In these cases,
medicines to suppress your immune system (immunosuppressants) may be
combined with your initial medication. Medicines called azathioprine
or mercaptopurine are most commonly used.
These medicines
aren't suitable for everyone, so a blood test should be carried out to
check if you can use them. If they are not suitable, an alternative
immunosuppressant medication called methotrexate may be used. Side effects of these
immunosuppressants can include:
- nausea and vomiting
- increased vulnerability to
infection
- feeling tired, breathless
and weak, which is caused by anaemia (a decrease in the number of red
blood cells)
- liver problems.
During the course of
medication you will have regular blood tests to check for serious side effects. The
immunosuppressants azathioprine and mercaptopurine are considered safe in
pregnancy and breast feeding. They can continue to be used when trying to
start a family and during pregnancy.
However, methotrexate
must not be taken for at least six months before trying for a baby (applies to
both males and females) as this drug is know to cause birth defects. It
must also be avoided while you are breastfeeding. It's important to
speak to your doctor if you are planning a pregnancy or if you become pregnant
during your course of treatment for Crohn’s disease.
For people
in poor general health with severe symptoms of Crohn's disease, medicines
called biological therapies may be used to reduce your symptoms if
corticosteroids and immunosuppressants are unsuitable or ineffective. Biological therapies
are a type of powerful immunosuppressant medication created using naturally
occurring biological substances, such as antibodies and enzymes.
The two medicines
used to treat Crohn's disease in the UK are called infliximab and adalimumab.
They work by targeting a protein called TNF-alpha (tumour necrosis
factor-alpha), which is believed to be responsible for the inflammation
associated with Crohn's disease. Infliximab can be
used for children over six years old and adults, but adalimumab should
only be used for adults.
Infliximab is given
as a drip into a vein in your arm (known as infusion) in hospital. Adalimumab
is given as an injection and it may be possible for you, a family member or a
friend to be taught how to give it so you don't need to visit hospital for
every treatment.
Treatment will
usually last at least 12 months, unless they stop being effective sooner than
this. After this time, your condition will be assessed to determine if further
treatment is necessary. There is a risk of
these medicines causing an allergic reaction, which can cause symptoms
such as:
- itchy skin
- high temperature
- joint and muscle pain
- swelling of the hands or
lips
- problems swallowing.
You should seek
immediate medical assistance if you experience these symptoms. Reactions can
occur immediately after treatment, although they have been known to occur
months later, even after treatment stops.
Surgery may
be recommended to reduce your symptoms if your healthcare team feel
the benefits outweigh the risks. In many cases, a type
of surgery called a resection is used. This involves removing the inflamed area
of the intestine and stitching the healthy sections together.
In some cases, your
doctor may recommend a procedure called an ileostomy to temporarily
divert digestive waste away from the inflamed colon (large intestine) to give
it a chance to heal. During this operation, the end of the small intestine
(the ileum) is disconnected from the colon and re-routed through a hole
made in the abdomen, which is known as a stoma. An external bag is attached to
the opening to collect waste products.
Once the colon has
sufficiently recovered - usually after several months - a second operation
will be needed to close the stoma and re-attach the small intestine to the colon.
Remission is a period
when you don't have any symptoms, or your symptoms are mild. During these
periods, you can choose whether or not to use medication to help maintain
this. If you decide not to
have further treatment, you should be advised about attending regular
follow-up appointments, and which symptoms to look out for. These include
unintended weight loss, abdominal pain and diarrhoea. If you
choose treatment, this will usually involve immunosuppressants.
Corticosteroids are not recommended for maintaining remission.
Complications
If you develop
complications of Crohn's disease, such as fistulas (channels that develop
between two sections of the digestive system), or intestinal narrowing
(stricture), these will also need to be treated. In most of these cases,
surgery will be necessary.
Complications of Crohn's disease
People with Crohn's
disease are at risk of developing a number of complications. The two most common
problems associated with Crohn’s disease are discussed in more detail below.
The inflammation of
the bowel (intestines) in Crohn's disease can cause scar tissue to form,
leading to the affected areas becoming narrowed. This is known as stricture. If this happens,
there is a risk of digestive waste causing an
obstruction, This means you will not be able to pass any stools,
or you will only be able to pass watery stools. Other symptoms of
bowel obstruction include:
- abdominal pain and cramping
- being sick (vomiting)
- bloating
- an uncomfortable feeling of
fullness in your abdomen.
Left untreated, there
is a risk that the bowel should split (rupture). This creates a hole
that the contents of the bowel can leak from. Therefore, you should
contact your family doctor as soon as possible if you suspect that your bowel is
obstructed. If this is not possible, you should go to your nearest A&E department.
Intestinal stricture
is usually treated with surgery to widen the affected section of intestine. In
some cases, this may be achieved using a procedure called balloon dilation
which is performed during colonoscopy. During balloon dilation, a colonoscope
is passed up your back passage (rectum) and a balloon inserted through the
colonoscope. This is then inflated to open up the affected area.
If this does not work
or is unsuitable, a surgical procedure known as a stricturoplasty may be needed
to widen the affected area. During this operation, the surgeon widens the
narrowed part of the intestine by opening it, reshaping it and sewing it back
together.
If your digestive
system becomes scarred due to excessive inflammation, ulcers can develop. Over time the ulcers
develop into tunnels, or passageways, that run from one part of your digestive
system to another or, in some cases, to the bladder, vagina, anus or skin.
These passageways are known as fistulas. Small fistulas do not
usually cause symptoms. However, larger fistulas can become infected and cause
symptoms such as:
- a constant, throbbing pain
- a high temperature (fever) of
38°C (100°F) or above
- blood or pus in your faeces
(stools)
- leakage of stools or mucus
into your underwear.
Schematic diagram showing the presence of an anal fistula (an abnormal communication between the large bowel and the skin).
If a fistula develops
on your skin (usually on, or near, the anus) it may release a foul-smelling
discharge. A type of medication
called biological medication is usually used to treat fistulas, when these are
not effective surgery is usually required.
Other complications
People with Crohn's
disease are also at an increased risk of other complications, such as:
- osteoporosis -
weakening of the bones caused by the intestines not absorbing nutrients
and by the use of steroid medication to treat Crohn's disease
- iron deficiency
anaemia - a condition that can occur in people with Crohn’s
disease due to bleeding in the digestive tract; common symptoms include
tiredness, shortness of breath and a pale complexion
- vitamin B12 or folate
deficiency anaemia - a condition caused by a lack of vitamin B12
or folate being absorbed by the body; common symptoms include tiredness
and lack of energy
- pyoderma gangrenosum -
a rare skin reaction that causes painful skin ulcers.
Children with Crohn's
disease may also experience problems with their growth and development, due to
a lack of nutrients being absorbed by the body.
Source: NHS Choices.
Source: NHS Choices.