Crohn's disease is a chronic inflammatory illness that can affect the entire digestive
tract, but most commonly is localized to the end portion of small intestine (terminal
ileum) and to large intestine (colon). The disease is complex and can affect other
extraintestinal sites, such as skin, joints, liver, gallbladder, eyes and kidneys.
Crohn's disease belongs to a group of intestinal diseases, called inflammatory bowel
disease. Another illness in this group is ulcerative colitis which is sometimes difficult
to distinguish from Crohn's disease.
Crohn's disease starts within the lining (mucosa) of the small and/or large intestine
causing inflammation and ulcers (sores) that can affect the entire wall. Upon reparative
(healing) phase of the disease, marked thickening of the bowel wall occurs that can lead
to the narrowing of the bowel resulting in obstruction. The inflammation is most
characteristically patchy involving some parts of the intestine while leaving other
segments unharmed. In time, if left untreated or in the refractory cases (defined as
patients that not respond to treatment) severe complications may occur
Crohn's disease affects approximately 7 out of 100,000 people in the United States each
year.
The disease may occur in people of all ages, but it is primarily a disease of older
children and young adults (ages between 15 and 35 years). A second peak of disease occurs
in the 5th and 6th decade. Men and women are equally affected.
Crohn's disease has a strong genetic background. If a person has a first-degree
relative with the disease, he/she has a risk of developing the illness that is 20-30 times
higher than the general population. Although no single gene is responsible for the
disease, recent studies have pointed to a mutation in the gene Nod2 that is twice as
common in the patients with Crohn's disease than in general population. This gene
alteration affects the body's ability of killing bacteria.
None of the theories about what causes Crohn's disease has been proved. One of the most
recent theories is that the body's defense system (immune system) abnormally reacts to a
bacterium (Mycobacterium paratuberculosis), producing antibodies (defense molecules) that
inadvertently attack the target organs, causing ongoing inflammation and damage.
People with Crohn's disease may have various signs and symptoms depending on the
severity of the disease and the segment of the intestine (or organ) affected.
The most common symptom is abdominal pain in the right lower quadrant followed by
diarrhea. Other symptoms may include rectal bleeding, weight loss and fever.
When the predominant intestinal segment affected by Crohn's disease is the large
intestine, in addition to rectal bleeding in diarrhea, patients may develop anal pain due
to disease around the anus (abscess, fistulas and ulcers).
Crohn's disease may affect the upper digestive system (stomach and duodenum) causing
nausea, vomiting, loss of appetite and weight loss.
Children with Crohn's disease may have impaired growth and development.
The diagnosis of Crohn's disease requires a complex approach with emphasis on accurate
history of the symptoms, complete physical examination, exclusion of other possible causes
(infectious, functional), blood tests to evaluate for the presence of anemia, colonoscopy
with biopsies, barium enema, and other.
Depending on the duration of the disease and on how well it responds to treatment,
Crohn's disease may have a long, chronic course complicated by:
- Severe anemia due to chronic bleeding.
- Intestinal obstruction due to marked narrowing of the intestine, thin
ring-like narrowing (strictures), fusion between two bowel loops due to inflammation, all
leading to blockage of the intestinal flow. Some of these complications cannot be resolved
endoscopically and may need surgical treatment
- Fistulas are abnormal connections between two neighboring bowel loops
or between bowel and neighboring organs (skin, bladder, internal genital organs) that
occur as a result of severe inflammation and ulceration involving the entire thickness of
intestinal wall. When fistulas form between bowel and skin or bladder, fecal material and
gas will be expressed onto skin or when urinating.
- Anal fissures are clefts into anus or perianal skin (skin around anus)
that occur as a result of chronic inflammation. These lesions may become infected leading
to abscesses (collections of pus).
- Malnutrition may develop as a result of loss of absorptive function of
the small bowel lining due to chronic inflammation and scarring. The patient becomes
deficient in proteins, calories and vitamins, most of which can be supplemented by
injectable compounds.
- Cancer. Patients with longstanding Crohn's disease (more than 10 years)
are at risk to develop carcinoma, either small intestinal or colonic. Therefore, routine
ileocolonoscopy surveillance is recommended for patients with severe disease.
The goal of the treatment is to decrease the inflammation responsible for the symptoms
and to prevent the development of complications. The initial treatment is medical and
includes antiinflammatory drugs, immune suppressors, antibiotics and novel therapies. Once
the complications developed, surgical treatment may become necessary.
1. Medical treatment. The antiinflammatory drugs are used routinely as
first line treatment for mild to moderate symptoms at the onset of disease. They include
aminosalicylates (sulfasalazine, mesalamine, balsalazide, known under the commercial name
of Asacol, Pentasa, Dipentum, Colazal). Corticosteroids are another class of
antiinflammatory drugs that non-specifically suppress the immune system. These drugs are
recommended for patients with moderate to severe symptoms, and include prednisone and
methylprednisolone. They act fast in reducing the inflammation in some patients with
Crohn's disease (particularly those that do not respond to standard treatment), but have
significant side effects. Therefore, these drugs should not be used long term. A newer
steroid with fewer side effects is budesonide (Entocort).
Immune suppressors are drugs that also decrease the inflammation, but they target the
immune system (that brings the inflammation about) rather than the inflammation itself.
These drugs are used to decrease the dose of steroids and can be used as maintenance
therapy (long term treatment). They are also used in the medical treatment of fistulas.
This group includes azathioprine (Imuran), infliximab (Remicade), methotrexate
(Rheumatrex) and cyclosporine (Neoral, Sandimmune).
Antibiotics are used for treating fistulas and abscesses and include metronidazole,
ampicillin, ciprofloxacin and others.
2. Surgical treatment. Surgery may become necessary when the medical
treatment fails to heal the diseased segment of bowel, and the symptoms can no longer be
controlled. Approximately two thirds of patients with Crohn's disease will need surgical
treatment during their disease course. Surgery is not a definitive treatment, since the
disease may re-occur (relapse) in previously healthy segment of bowel.
Surgery is indicated to remove a segment of bowel that is narrowed or strictured, and to
resect and close fistulas between neighboring bowel loops, or between bowel loops and
neighboring organs. It is also indicated to remove perianal skin abscesses that do not
respond to antibiotic treatment.
3. The role of nutrition. Certain foods and beverages can aggravate
the symptoms of Crohn's disease especially during the acute episodes
("flare-ups"). Reducing the intake of milk and other dairy foods, alcoholic
beverages, spicy foods, coffee, fruit and fruit juices (especially citrus fruits) and
vegetables or beans that produce gas, may substantially reduce the symptoms.
During the acute episodes eating small meals and drinking plenty of fluids (to replace
those lost due to diarrhea) are beneficial diet changes.
Due to the loss of nutrients caused by deficient absorption by the inflamed bowel,
multivitamin and mineral supplements may be indicated.
Mayo Clinic
National
Institute of Diabetes and Digestive and Kidney Diseases
Crohn's and Colitis Foundation of
America
