What is Crohn’s disease? What causes Crohn’s disease?


MNT Knowledge CenterCrohn’s disease is an ongoing condition that causes inflammation of the digestive tract, or the GI (gastrointestinal) tract (the gut). Crohn’s disease may also be called ileitis or enteritis.

Crohn’s disease can affect any part of the gut, from the mouth all the way down to the anus. In the majority of cases the lower part of the small intestine – the ileum – is affected. Patients with Crohn’s disease experience several unpleasant symptoms, including intestinal ulcers, fatigue, inflammation, discomfort and pain; the condition makes the intestines empty frequently, resulting in diarrhea.

In the UK about 1 in 1,500 people have Crohn’s disease, according to the National Health Service (NHS), (another study1 says 1 in 800). It is slightly more prevalent among women than men according to UK sources (NHS), while US sources state that it affects both sexes equally (NIH). Although Crohn’s disease typically starts between the ages of 15 to 40, it can start at any age.

As the symptoms of Crohn’s disease are similar to other disorders, such as IBS (irritable bowel syndrome) and ulcerative colitis, it can be tricky to diagnose initially. While ulcerative colitis causes inflammation and ulcers in the top layer of the lining of the large intestine, all layers of the intestine may be inflamed and with ulcers in Crohn’s disease. The Crohn’s disease patient’s bowels can have normal healthy sections in between the diseased parts.

Approximately one fifth of all people with Crohn’s disease have a close relative with some type of inflammatory bowel disease. People of Jewish descent have a higher chance of developing Crohn’s disease.

What are the causes of Crohn’s disease?

Experts are not completely sure, although several theories do exist. Unfortunately, none of these theories has yet been scientifically proven. Most experts agree that the immune system of people with Crohn’s disease reacts abnormally – it treats good bacteria, foods, and other substances that are good for us as foreign unwanted substances. In other words, the immune system:

  • Attacks foods and beneficial substances
  • During the attack white blood cells build up in the lining of the gut
  • The accumulation of white blood cells in the lining of the gut triggers inflammation
  • The inflammation leads to ulcerations and bowel injury

However, we are not sure whether the abnormal immune system is the cause or the result of Crohn’s disease. In other words, does Crohn’s disease cause an abnormal immune system response, or does an abnormal immune system response cause Crohn’s disease?

Studies indicate that the inflammation seen in the gut of Crohn’s disease patients is linked to several factors:

  • The patient’s genes (a study has identified a gene2)
  • The patient’s immune system itself
  • The environment

The way a Crohn’s disease patient’s body reacts to antigens may cause the inflammation, or the antigens themselves may be the cause. Antigens are substances our immune system attacks – foreign substances. Many experts believe that TNF (anti-tumor necrosis factor), a protein our immune system produces, may be one possible cause for inflammation linked to Crohn’s disease.

According to the National Health Service (NHS), UK, about 10% of Crohn’s disease patients have a relative with the same condition.

Some experts believe a bacterium or virus may be a factor in causing Crohn’s disease to occur. E. coli Bacteria Linked To Crohn’s Disease3.

Enteroviruses may be linked to Crohn’s disease4 – researchers from Uppsala University Hospital, Sweden, reported in the journal Clinical and Translational Gastroenterology (June 2013 issue) that children with Crohn’s disease have considerably higher numbers of enteroviruses in their intestines compared to other kids.

A higher percentage of smokers and/or women who use the combined oral contraceptive pill develop Crohn’s disease, compared to non-smokers and/or women who do not use the combined oral contraceptive pill. A study found that smoking may determine which part of the gut is attacked among patients with Crohn’s disease5.

What are the symptoms of Crohn’s disease?

Crohn’s disease symptoms will often vary depending on which part of the gut is affected. When the wall of the affected part of the gut is inflamed, the patient may experience the following symptoms:

  • Pain – the level of pain varies according to the patient, and where the inflammation is in the gut. Most commonly, pain will be felt at the lower-right side of the abdomen; because the majority of inflammations are locate in the ileum (lower end of the small intestine).
  • Ulcers in the gut – ulcers are raw areas in the gut that may bleed. If they do bleed the patient may notice blood in his/her stools.
  • Mouth ulcers – mouth ulcers are commonly experienced by people with Crohn’s disease.
  • Diarrhea – can be mild to very severe. Sometimes there may be mucus, blood or pus. The patient may keep wanting to go and find there is nothing to pass.
  • Fatigue – patients with Crohn’s disease may sometimes feel extremely tired. Fever is also possible during fatigue.
  • Altered appetite – generally, people with Crohn’s disease have periods when their appetite is very low.
  • Weight loss – this is common, especially when the patient experiences loss of appetite.
  • Anemia – if the patient is losing blood there is a risk of anemia.
  • Rectal bleeding and anal fissures – when the skin of the anus becomes cracked there will be anal fissures. These may become painful and can bleed.

These symptoms are also possible:

  • Arthritis
  • Uveitis (eye inflammation)
  • Skin rash
  • Liver inflammation

How is Crohn’s disease diagnosed?

A doctor will check through the list of signs and symptoms. There may also be some physical signs – if loops of inflamed bowels are stuck together a lump can be felt in the abdomen.

The following tests may help in the diagnosis:

  • Stool tests.
  • Blood tests
  • Biopsy.
  • Sigmoidoscopy – a short, flexible telescope (sigmoidoscope) is used to investigate the lower bowel.
  • Colonoscopy – a long, flexible telescope (colonoscope) is used to investigate the colon.
  • Endoscopy – this can be used if the patient has symptoms in the upper part of his/her gut. A long, thin, flexible telescope (endoscope) goes down through the esophagus into the stomach.
  • Barium enema X-ray – this involves placing a fluid containing barium (a substance which shows up on X-rays) into the bowel via the rectum. X-ray pictures of the abdomen then show the inside of the bowel more clearly. Barium appears white on X-rays.
  • Barium meal X-ray – for the small intestine a barium meal will be used – the patient will drink barium, a chalky solution that coats the lining of the small intestine, before x rays are taken. The barium appears white on X-rays. The doctor can then see which part of the gut is affected.
  • CT scans – X-rays are used to make a 3-dimensional picture of the bowel. The molecular imaging power of PET/CT is invaluable in noninvasively monitoring Crohn’s disease6, a study reported.

None of these tests require a general anesthetic, and they are generally carried out as out-patient procedures – the patient does not need to stay in hospital overnight.

What is the treatment for Crohn’s disease?

Treatment may involve medication, surgery, and/or nutritional supplements. The doctor’s goal is to control inflammation, correct nutritional problems, and relieve symptoms. There is no current cure for Crohn’s disease, although there are treatments that can help control the disease by reducing the number of times a patient experiences recurrences.

Crohn’s disease treatment depends on:

  • Where the inflammation is (location)
  • The severity of the disease
  • Complications
  • The patient’s response to previous treatment for recurring symptoms

Some patients can have long periods without any symptoms (remission). However, there will generally be recurrences. Some people may spend years without a recurrence. As periods of remission vary so much, it can be hard to know how effective treatment has been. It is impossible to predict how long a period of remission is going to be.

Medication for Crohn’s disease

  • Anti-Inflammation Drugs – the doctor will most likely start with mesalamine (Sulfasalazine), which helps control inflammation. Some patients may be prescribed 5-ASA agents, such as Asacol, Dipentum, or Pentasa if they cannot tolerate Slufasalazine,or derived no benefit from it.
  • Cortisone or Steroids – corticosteroids are drugs containing cortisone and steroids. During the initial stages of Crohn’s disease prednisone is commonly prescribed, usually in quite a large dose. The dosage is then lowered when symptoms are controlled. Corticosteroids can make patients more susceptible to infection.
  • Immunosuppressant drugs – these drugs reduce the patient’s immune response. The doctor may prescribe 6-mercaptopurine or a related drug, azathioprine. Immunosuppressive agents block the immune reaction that is thought to cause inflammation. Side effects include vomiting, nausea, and a weaker resistance to infection. If a patient is given both corticosteroids and immunosuppressant medications, the corticosteroid dose may eventually be lowered.
  • Infliximab (Remicade) – this blocks the body’s inflammation response. In the USA Remicade is indicated for patients with moderate to severe Crohn’s disease who have not responded to standard therapies (mesalamine substances, corticosteroids, immunosuppressive agents). It is also indicated for the treatment of open, draining fistulas (A fistula is an abnormal tunnel connecting two body cavities, such as the rectum and the vagina, or a body cavity to the skin, such as the rectum to the outside of the body).
  • Antibiotics – fistulas, stricture, or prior surgery may cause bacterial overgrowth. Doctors will generally treat this by prescribing ampicillin, sulfonamide, cephalosporin, tetracycline, or metronidazole.
  • Anti-Diarrheal and Fluid Replacements – when the inflammation subsides diarrhea usually becomes less of a problem. However, sometimes the patient may need something for diarrhea and abdominal pain. The following medications are commonly prescribed for this: diphenoxylate, loperamide, and codeine. If the diarrhea causes dehydration the patient may be treated with fluids and electrolytes.

Extracorporeal photopheresis (ECP) may be effective for patients with clinically active (or symptomatic) Crohn’s disease who cannot tolerate or are refractory to immunosuppressants and/or anti-TNF agents7, a study found.

Vedolizumab may help patients with Crohn’s and ulcerative colitis8 – investigational drug, vedolizumab, showed promise in two international Phase III clinical trains (GEMINI I and GEMINI II) for patients suffering from Crohn’s disease and ulcerative colitis.

Nutritional supplementation

Children with Crohn’s disease may need high-calorie liquid formulas, especially if their growth is being affected. Sometimes patients may be fed intravenously for a short period (rarely). Feeding a patient intravenously, through a drip, may help those whose intestines need to rest, or patients whose intestines are not absorbing enough nutrition from the food they eat. Most patients with Crohn’s disease say that the following foods may increase diarrhea and cramping: bulky grains, dairy products, spicy foods, and alcohol.

Stem cell therapy

Replacing the cells of damaged tissue with other new cells from the same patient is already a reality9.


The majority of Crohn’s disease patients will need surgery at some time. When medications no longer control symptoms the only solution sometimes is to operate. Surgery can relieve symptoms that did not respond to medication, or to correct complications, such as abscess, perforation, bleeding, and blockage.

Removing part of the intestine can help, but it does not cure Crohn’s disease. Inflammation often returns to the area next to where the affected part of the gut was removed. Some Crohn’s disease patients may require more than one operation during their lives.

In some cases a colectomy is needed – the whole colon is removed. During the procedure the surgeon will make a small opening in front of the abdominal wall, and the tip of the ileum is brought to the skin’s surface – this opening is called a stoma. Feces exit the body through the stoma. The stoma is generally located near the beltline, on the right side of the body. A pouch collects the feces. Doctors say that a patient who has a stoma can carry on leading a normal and active life.

If the surgeon can remove the diseased section of the intestine and then connect the intestine again, no stoma is needed.

The patient and his/her doctor need to consider surgery very carefully. It is not appropriate for everybody. The patient has to bear in mind that after the operation the disease will recur.

“Side-to-side isoperistaltic stricturoplasty”10 procedure can alleviate the pain of Crohn’s disease while sparing the intestine and safeguarding patients from developing malnutrition.

Post-operative Crohn’s disease recurrence may be prevented by Infliximab11.

The majority of Crohn’s disease patients are able to live normal and active lives, hold jobs, raise families, and function successfully.

Recent developments on Crohn’s disease from MNT news

New Crohn’s disease treatment may result from ‘bodyguard protein’ discovery

The exact cause of Crohn’s disease is unknown. However, scientists agree it likely results when certain gene variants combine with an abnormal immune reaction triggered by something in the environment. Now a new study by two researchers sheds light on one of the genetic factors, namely how a bodyguard protein helps to stabilize a protein known to be linked to Crohn’s disease.

Inflammatory bowel disease may be treatable with gel-delivered drugs

According to research in Science Translational Medicine, using hydrogel to precisely target and deliver drugs to affected tissue shows promise as a treatment for inflammatory bowel disease.


If symptoms are severe and frequent the likelihood of complications is higher. The following complications may require surgery:

  • Internal bleeding
  • Stricture – a part of the gut narrows, causing build up of scar tissue, and partial or complete blockage of the intestine
  • Perforation – a small hole develops in the wall of the gut. Contents leak out of this hole and cause infections or abscesses to develop.
  • Fistulas – a channel forms between two parts of the gut. (Recommended treatments for fistulas in Crohn’s disease12)
  • Iron deficiency
  • Food absorption problems
  • Slightly higher risk of developing bowel cancer
  • People with Crohn’s disease are at a greater risk of suffering from asthma13, a study found

In this video below, Peter Higgins, M.D., Ph.D., MSc., a physician specialist in the Crohn’s and Colitis Program at the University of Michigan Health System, talks about IBD and Crohn’s disease